diff --git a/lua/barbar.lua b/lua/barbar.lua
index ec02e263..9db667fc 100644
--- a/lua/barbar.lua
+++ b/lua/barbar.lua
@@ -6,19 +6,19 @@ local command = vim.api.nvim_command --- @type function
 local create_user_command = vim.api.nvim_create_user_command --- @type function
 local set_option = vim.api.nvim_set_option --- @type function
 
-local api = require'barbar.api'
-local bbye = require'barbar.bbye'
-local events = require'barbar.events'
-local notify = require'barbar.utils'.notify
-local render = require'barbar.ui.render'
-local state = require'barbar.state'
-local utils = require'barbar.utils'
+local api = require('barbar.api')
+local bbye = require('barbar.bbye')
+local events = require('barbar.events')
+local markdown_inline_code = require('barbar.utils').markdown_inline_code
+local notify = require('barbar.utils').notify
+local scroll = require('barbar.ui.render').scroll
+local state = require('barbar.state')
 
 -------------------------------
 -- Section: `barbar` module
 -------------------------------
 
---- @class barbar
+--- @class Barbar
 local barbar = {}
 
 --- Setup this plugin.
@@ -47,7 +47,7 @@ function barbar.setup(options)
       local index = tonumber(tbl.args)
       if not index then
         return notify(
-          'Invalid argument to ' .. utils.markdown_inline_code':BufferGoto',
+          'Invalid argument to ' .. markdown_inline_code':BufferGoto',
           vim.log.levels.ERROR
         )
       end
@@ -59,7 +59,7 @@ function barbar.setup(options)
         local buffers = state.buffers
         local buffer_indices = {}
 
-        for i = 1, #buffers do
+        for i in ipairs(buffers) do
           table_insert(buffer_indices, tostring(i))
         end
 
@@ -82,7 +82,7 @@ function barbar.setup(options)
     vim.api.nvim_cmd and
       function(tbl) vim.cmd.BufferMovePrevious {count = tbl.count} end or
       function(tbl) command('BufferMovePrevious ' .. tbl.count) end,
-    {count = true, desc = 'Synonym for ' .. utils.markdown_inline_code':BufferMovePrevious'}
+    {count = true, desc = 'Synonym for ' .. markdown_inline_code':BufferMovePrevious'}
   )
 
   create_user_command(
@@ -188,13 +188,13 @@ function barbar.setup(options)
 
   create_user_command(
     'BufferScrollLeft',
-    function(tbl) render.scroll(-max(1, tbl.count)) end,
+    function(tbl) scroll(-max(1, tbl.count)) end,
     {count = true, desc = 'Scroll the bufferline left'}
   )
 
   create_user_command(
     'BufferScrollRight',
-    function(tbl) render.scroll(max(1, tbl.count)) end,
+    function(tbl) scroll(max(1, tbl.count)) end,
     {count = true, desc = 'Scroll the bufferline right'}
   )
 
diff --git a/lua/barbar/animate.lua b/lua/barbar/animate.lua
index 9ba4603c..43b1418d 100644
--- a/lua/barbar/animate.lua
+++ b/lua/barbar/animate.lua
@@ -17,7 +17,7 @@ local schedule_wrap = vim.schedule_wrap
 --- @field timer userdata
 --- @field type unknown
 
---- @class barbar.animate
+--- @class barbar.Animate
 local animate = {}
 
 --- The amount of time between rendering the next part of the animation.
diff --git a/lua/barbar/api.lua b/lua/barbar/api.lua
index baf6d046..6191dda2 100644
--- a/lua/barbar/api.lua
+++ b/lua/barbar/api.lua
@@ -16,15 +16,17 @@ local set_current_buf = vim.api.nvim_set_current_buf --- @type function
 -- TODO: remove `vim.fs and` after 0.8 release
 local normalize = vim.fs and vim.fs.normalize
 
-local animate = require'barbar.animate'
-local bbye = require'barbar.bbye'
-local Buffer = require'barbar.buffer'
-local config = require'barbar.config'
-local JumpMode = require'barbar.jump_mode'
-local Layout = require'barbar.ui.layout'
-local render = require'barbar.ui.render'
-local state = require'barbar.state'
-local utils = require'barbar.utils'
+local animate = require('barbar.animate')
+local bdelete = require('barbar.bbye').bdelete
+local buffer = require('barbar.buffer')
+local config = require('barbar.config')
+local index_of = require('barbar.utils.list').index_of
+local is_relative_path = require('barbar.fs').is_relative_path
+local jump_mode = require('barbar.jump_mode')
+local layout = require('barbar.ui.layout')
+local notify = require('barbar.utils').notify
+local render = require('barbar.ui.render')
+local state = require('barbar.state')
 
 local ESC = vim.api.nvim_replace_termcodes('<Esc>', true, false, true)
 
@@ -32,8 +34,8 @@ local ESC = vim.api.nvim_replace_termcodes('<Esc>', true, false, true)
 --- @param fn fun()
 --- @return nil
 local function pick_buffer_wrap(fn)
-  if JumpMode.reinitialize then
-    JumpMode.initialize_indexes()
+  if jump_mode.reinitialize then
+    jump_mode.initialize_indexes()
   end
 
   state.is_picking_buffer = true
@@ -49,7 +51,7 @@ end
 --- @param buffer_number integer
 --- @return nil
 local function notify_buffer_not_found(buffer_number)
-  utils.notify(
+  notify(
     'Current buffer (' .. buffer_number .. ") not found in barbar.nvim's list of buffers: " .. vim.inspect(state.buffers),
     vim.log.levels.ERROR
   )
@@ -73,7 +75,7 @@ local function with_pin_order(order_func)
   end
 end
 
---- @class barbar.api
+--- @class barbar.Api
 local api = {}
 
 --- Close all open buffers, except the current one.
@@ -83,7 +85,7 @@ function api.close_all_but_current()
 
   for _, buffer_number in ipairs(state.buffers) do
     if buffer_number ~= current_bufnr then
-      bbye.bdelete(false, buffer_number)
+      bdelete(false, buffer_number)
     end
   end
 
@@ -93,10 +95,10 @@ end
 --- Close all open buffers, except those in visible windows.
 --- @return nil
 function api.close_all_but_visible()
-  local visible = Buffer.activities.Visible
+  local visible = buffer.activities.Visible
   for _, buffer_number in ipairs(state.buffers) do
-    if Buffer.get_activity(buffer_number) < visible then
-      bbye.bdelete(false, buffer_number)
+    if buffer.get_activity(buffer_number) < visible then
+      bdelete(false, buffer_number)
     end
   end
 
@@ -108,7 +110,7 @@ end
 function api.close_all_but_pinned()
   for _, buffer_number in ipairs(state.buffers) do
     if not state.is_pinned(buffer_number) then
-      bbye.bdelete(false, buffer_number)
+      bdelete(false, buffer_number)
     end
   end
 
@@ -122,7 +124,7 @@ function api.close_all_but_current_or_pinned()
 
   for _, buffer_number in ipairs(state.buffers) do
     if not state.is_pinned(buffer_number) and buffer_number ~= current_bufnr then
-      bbye.bdelete(false, buffer_number)
+      bdelete(false, buffer_number)
     end
   end
 
@@ -132,13 +134,13 @@ end
 --- Close all buffers which are visually left of the current buffer.
 --- @return nil
 function api.close_buffers_left()
-  local idx = utils.index_of(state.buffers, get_current_buf())
+  local idx = index_of(state.buffers, get_current_buf())
   if idx == nil or idx == 1 then
     return
   end
 
   for i = idx - 1, 1, -1 do
-    bbye.bdelete(false, state.buffers[i])
+    bdelete(false, state.buffers[i])
   end
 
   render.update()
@@ -147,13 +149,13 @@ end
 --- Close all buffers which are visually right of the current buffer.
 --- @return nil
 function api.close_buffers_right()
-  local idx = utils.index_of(state.buffers, get_current_buf())
+  local idx = index_of(state.buffers, get_current_buf())
   if idx == nil then
     return
   end
 
   for i = #state.buffers, idx + 1, -1 do
-    bbye.bdelete(false, state.buffers[i])
+    bdelete(false, state.buffers[i])
   end
 
   render.update()
@@ -180,7 +182,7 @@ function api.goto_buffer(index)
   if buffer_number then
     set_current_buf(buffer_number)
   else
-    utils.notify(
+    notify(
       'E86: buffer at index ' .. index .. ' in list ' .. vim.inspect(state.buffers) .. ' does not exist.',
       vim.log.levels.ERROR
     )
@@ -195,15 +197,15 @@ function api.goto_buffer_relative(steps)
   render.get_updated_buffers()
 
   if #state.buffers < 1 then
-    return utils.notify('E85: There is no listed buffer', vim.log.levels.ERROR)
+    return notify('E85: There is no listed buffer', vim.log.levels.ERROR)
   end
 
   local current_bufnr = render.set_current_win_listed_buffer()
-  local idx = utils.index_of(state.buffers, current_bufnr)
+  local idx = index_of(state.buffers, current_bufnr)
 
   if not idx then -- fall back to: 1. the alternate buffer, 2. the first buffer
-    idx = utils.index_of(state.buffers, bufnr'#') or 1
-    utils.notify(
+    idx = index_of(state.buffers, bufnr'#') or 1
+    notify(
       "Couldn't find buffer #" .. current_bufnr .. ' in the list: ' .. vim.inspect(state.buffers) ..
         '. Falling back to buffer #' .. state.buffers[idx],
       vim.log.levels.INFO
@@ -222,7 +224,7 @@ local move_animation_data = {
 --- An incremental animation for `move_buffer_animated`.
 --- @return nil
 local function move_buffer_animated_tick(ratio, current_animation)
-  for _, current_number in ipairs(Layout.buffers) do
+  for _, current_number in ipairs(layout.buffers) do
     local current_data = state.get_buffer_data(current_number)
 
     if current_animation.running == true then
@@ -263,7 +265,7 @@ local function move_buffer(from_idx, to_idx)
 
   local previous_positions
   if animation == true then
-    previous_positions = Layout.calculate_buffers_position_by_buffer_number()
+    previous_positions = layout.calculate_buffers_position_by_buffer_number()
   end
 
   table_remove(state.buffers, from_idx)
@@ -271,7 +273,7 @@ local function move_buffer(from_idx, to_idx)
   state.sort_pins_to_left()
 
   if animation == true then
-    local current_index = utils.index_of(Layout.buffers, buffer_number)
+    local current_index = index_of(layout.buffers, buffer_number)
     local start_index = min(from_idx, current_index)
     local end_index   = max(from_idx, current_index)
 
@@ -281,9 +283,9 @@ local function move_buffer(from_idx, to_idx)
       animate.stop(move_animation)
     end
 
-    local next_positions = Layout.calculate_buffers_position_by_buffer_number()
+    local next_positions = layout.calculate_buffers_position_by_buffer_number()
 
-    for _, layout_bufnr  in ipairs(Layout.buffers) do
+    for _, layout_bufnr  in ipairs(layout.buffers) do
       local current_data = state.get_buffer_data(layout_bufnr)
 
       local previous_position = previous_positions[layout_bufnr]
@@ -319,7 +321,7 @@ function api.move_current_buffer_to(idx)
   end
 
   local current_bufnr = get_current_buf()
-  local from_idx = utils.index_of(state.buffers, current_bufnr)
+  local from_idx = index_of(state.buffers, current_bufnr)
 
   if from_idx == nil then
     return notify_buffer_not_found(current_bufnr)
@@ -335,7 +337,7 @@ function api.move_current_buffer(steps)
   render.update()
 
   local current_bufnr = get_current_buf()
-  local idx = utils.index_of(state.buffers, current_bufnr)
+  local idx = index_of(state.buffers, current_bufnr)
 
   if idx == nil then
     return notify_buffer_not_found(current_bufnr)
@@ -361,8 +363,8 @@ function api.order_by_directory()
 
     -- TODO: remove this block after 0.8 releases
     if not normalize then
-      local a_is_relative = utils.is_relative_path(name_of_a)
-      if a_is_relative and utils.is_relative_path(name_of_b) then
+      local a_is_relative = is_relative_path(name_of_a)
+      if a_is_relative and is_relative_path(name_of_b) then
         return a_less_than_b
       end
 
@@ -408,13 +410,13 @@ function api.pick_buffer()
   pick_buffer_wrap(function()
     local ok, letter = pcall(function() return char(getchar()) end)
     if ok and letter ~= '' then
-      if JumpMode.buffer_by_letter[letter] ~= nil then
-        set_current_buf(JumpMode.buffer_by_letter[letter])
+      if jump_mode.buffer_by_letter[letter] ~= nil then
+        set_current_buf(jump_mode.buffer_by_letter[letter])
       else
-        utils.notify("Couldn't find buffer", vim.log.levels.WARN)
+        notify("Couldn't find buffer", vim.log.levels.WARN)
       end
     else
-      utils.notify('Invalid input', vim.log.levels.WARN)
+      notify('Invalid input', vim.log.levels.WARN)
     end
   end)
 end
@@ -426,15 +428,15 @@ function api.pick_buffer_delete()
     while true do
       local ok, letter = pcall(function() return char(getchar()) end)
       if ok and letter ~= '' then
-        if JumpMode.buffer_by_letter[letter] ~= nil then
-          bbye.bdelete(false, JumpMode.buffer_by_letter[letter])
+        if jump_mode.buffer_by_letter[letter] ~= nil then
+          bdelete(false, jump_mode.buffer_by_letter[letter])
         elseif letter == ESC then
           break
         else
-          utils.notify("Couldn't find buffer with letter '" .. letter .. "'", vim.log.levels.WARN)
+          notify("Couldn't find buffer with letter '" .. letter .. "'", vim.log.levels.WARN)
         end
       else
-        utils.notify('Invalid input', vim.log.levels.WARN)
+        notify('Invalid input', vim.log.levels.WARN)
       end
 
       render.update()
@@ -446,7 +448,7 @@ end
 --- @param width integer the amount to offset
 --- @param text? string text to put in the offset
 --- @param hl? string
---- @param side? 'left'|'right'
+--- @param side? side
 --- @return nil
 function api.set_offset(width, text, hl, side)
   if side == nil then
diff --git a/lua/barbar/bbye.lua b/lua/barbar/bbye.lua
index 52c428f5..9f539db1 100644
--- a/lua/barbar/bbye.lua
+++ b/lua/barbar/bbye.lua
@@ -41,9 +41,10 @@ local set_current_win = vim.api.nvim_set_current_win --- @type function
 local win_get_buf = vim.api.nvim_win_get_buf --- @type function
 local win_is_valid = vim.api.nvim_win_is_valid --- @type function
 
-local config = require'barbar.config'
-local state = require'barbar.state'
-local utils = require'barbar.utils'
+local config = require('barbar.config')
+local list = require('barbar.utils.list')
+local markdown_inline_code = require('barbar.utils').markdown_inline_code
+local state = require('barbar.state')
 
 -------------------
 -- Section: helpers
@@ -100,10 +101,10 @@ local function get_focus_on_close(closing_number)
   end
 
   if focus_on_close == 'right' then
-    state_bufnrs = utils.list_reverse(state.buffers)
+    state_bufnrs = list.reverse(state.buffers)
   end
 
-  local index = utils.index_of(state_bufnrs, closing_number)
+  local index = list.index_of(state_bufnrs, closing_number)
   if index then
     index = index - 1
 
@@ -158,7 +159,7 @@ end
 -- Section: module
 ------------------
 
---- @class bbye
+--- @class barbar.Bbye
 local bbye = {}
 
 --- Delete a buffer
@@ -249,7 +250,7 @@ function bbye.delete(action, force, buffer, mods)
           return err(msg)
         end
       else
-          return err('Could not delete buffer ' .. buffer_number .. ' with ' .. utils.markdown_inline_code(action))
+          return err('Could not delete buffer ' .. buffer_number .. ' with ' .. markdown_inline_code(action))
       end
     end
   end
diff --git a/lua/barbar/buffer.lua b/lua/barbar/buffer.lua
index ef889553..e84789b8 100644
--- a/lua/barbar/buffer.lua
+++ b/lua/barbar/buffer.lua
@@ -7,27 +7,29 @@ local min = math.min
 local table_concat = table.concat
 local table_insert = table.insert
 
-local bufnr = vim.fn.bufnr --- @type function
 local buf_get_name = vim.api.nvim_buf_get_name --- @type function
 local buf_get_option = vim.api.nvim_buf_get_option --- @type function
 local buf_is_valid = vim.api.nvim_buf_is_valid --- @type function
+local bufnr = vim.fn.bufnr --- @type function
 local bufwinnr = vim.fn.bufwinnr --- @type function
-local ERROR = vim.diagnostic.severity.ERROR --- @type integer
 local get_current_buf = vim.api.nvim_get_current_buf --- @type function
 local get_diagnostics = vim.diagnostic.get --- @type fun(bufnr: integer): {severity: integer}[]
-local HINT = vim.diagnostic.severity.HINT --- @type integer
-local INFO = vim.diagnostic.severity.INFO --- @type integer
 local matchlist = vim.fn.matchlist --- @type function
+local severity = vim.diagnostic.severity
 local split = vim.split
 local strcharpart = vim.fn.strcharpart --- @type function
 local strwidth = vim.api.nvim_strwidth --- @type function
-local WARN = vim.diagnostic.severity.WARN --- @type integer
 
-local config = require'barbar.config'
-local utils = require'barbar.utils'
+local basename = require('barbar.fs').basename
+local config = require('barbar.config')
+local slice_from_end = require('barbar.utils.list').slice_from_end
 
 local ELLIPSIS = '…'
 local ELLIPSIS_LEN = strwidth(ELLIPSIS)
+local ERROR = severity.ERROR
+local HINT = severity.HINT
+local INFO = severity.INFO
+local WARN = severity.WARN
 
 --- @alias barbar.buffer.activity 1|2|3|4
 
@@ -51,9 +53,45 @@ local function terminalname(name)
   end
 end
 
+--- @class barbar.Buffer
+local buffer = { activities = activities }
+
+--- @param buffer_number integer
+--- @return integer[] # indexed on `vim.diagnostic.severity`
+function buffer.count_diagnostics(buffer_number)
+  local count = {[ERROR] = 0, [HINT] = 0, [INFO] = 0, [WARN] = 0}
+
+  for _, diagnostic in ipairs(get_diagnostics(buffer_number)) do
+    count[diagnostic.severity] = count[diagnostic.severity] + 1
+  end
+
+  return count
+end
+
+--- For each severity in `diagnostics`: if it is enabled, and there are diagnostics associated with it in the `buffer_number` provided, call `f`.
+--- @param buffer_number integer the buffer number to count diagnostics in
+--- @param diagnostics barbar.config.options.icons.buffer.diagnostics the user configuration for diagnostics
+--- @param f fun(count: integer, severity_idx: integer, option: barbar.config.options.icons.diagnostics.severity) the function to run when diagnostics of a specific severity are enabled and present in the `buffer_number`
+--- @return nil
+function buffer.for_each_counted_enabled_diagnostic(buffer_number, diagnostics, f)
+  local count
+  for i in ipairs(severity) do
+    local option = diagnostics[i]
+    if option.enabled then
+      if count == nil then
+        count = buffer.count_diagnostics(buffer_number)
+      end
+
+      if count[i] > 0 then
+        f(count[i], i, option)
+      end
+    end
+  end
+end
+
 --- @param buffer_number integer
 --- @return barbar.buffer.activity # whether `bufnr` is inactive, the alternate file, visible, or currently selected (in that order).
-local function get_activity(buffer_number)
+function buffer.get_activity(buffer_number)
   if get_current_buf() == buffer_number then
     return activities.Current
   elseif config.options.highlight_alternate and bufnr('#') == buffer_number then
@@ -65,138 +103,97 @@ local function get_activity(buffer_number)
   return activities.Inactive
 end
 
---- @param buffer_number integer
---- @return integer[] # indexed on `vim.diagnostic.severity`
-local function count_diagnostics(buffer_number)
-  local count = {[ERROR] = 0, [HINT] = 0, [INFO] = 0, [WARN] = 0}
-
-  for _, diagnostic in ipairs(get_diagnostics(buffer_number)) do
-    count[diagnostic.severity] = count[diagnostic.severity] + 1
+--- @param activity barbar.buffer.activity.name
+--- @param modified boolean
+--- @param pinned boolean
+--- @return barbar.config.options.icons.buffer
+function buffer.get_icons(activity, modified, pinned)
+  local icons_option = config.options.icons[activity:lower()]
+  if pinned then
+    icons_option = icons_option.pinned
+  elseif modified then
+    icons_option = icons_option.modified
   end
 
-  return count
+  return icons_option
 end
 
---- @class barbar.buffer
-local buffer = {
-  activities = activities,
-
-  count_diagnostics = count_diagnostics,
-
-  --- For each severity in `diagnostics`: if it is enabled, and there are diagnostics associated with it in the `buffer_number` provided, call `f`.
-  --- @param buffer_number integer the buffer number to count diagnostics in
-  --- @param diagnostics barbar.config.options.icons.buffer.diagnostics the user configuration for diagnostics
-  --- @param f fun(count: integer, severity_idx: integer, option: barbar.config.options.icons.diagnostics.severity) the function to run when diagnostics of a specific severity are enabled and present in the `buffer_number`
-  --- @return nil
-  for_each_counted_enabled_diagnostic = function(buffer_number, diagnostics, f)
-    local count
-    for severity_idx, severity_option in ipairs(diagnostics) do
-      if severity_option.enabled then
-        if count == nil then
-          count = count_diagnostics(buffer_number)
-        end
-
-        if count[severity_idx] > 0 then
-          f(count[severity_idx], severity_idx, severity_option)
-        end
-      end
-    end
-  end,
-
-  get_activity = get_activity,
-
-  --- @param activity barbar.buffer.activity.name
-  --- @param modified boolean
-  --- @param pinned boolean
-  --- @return barbar.config.options.icons.buffer
-  get_icons = function(activity, modified, pinned)
-    local icons_option = config.options.icons[activity:lower()]
-    if pinned then
-      icons_option = icons_option.pinned
-    elseif modified then
-      icons_option = icons_option.modified
-    end
-
-    return icons_option
-  end,
-
-  --- @param buffer_number integer
-  --- @param hide_extensions boolean? if `true`, exclude the extension of the file
-  --- @return string name
-  get_name = function(buffer_number, hide_extensions)
-    --- @type string
-    local name = buf_is_valid(buffer_number) and buf_get_name(buffer_number) or ''
+--- @param buffer_number integer
+--- @param hide_extensions boolean? if `true`, exclude the extension of the file
+--- @return string name
+function buffer.get_name(buffer_number, hide_extensions)
+  --- @type string
+  local name = buf_is_valid(buffer_number) and buf_get_name(buffer_number) or ''
+
+  local no_name_title = config.options.no_name_title
+  local maximum_length = config.options.maximum_length
+
+  if name ~= '' then
+    name = buf_get_option(buffer_number, 'buftype') == 'terminal' and terminalname(name) or basename(name, hide_extensions)
+  elseif no_name_title ~= nil and no_name_title ~= vim.NIL then
+    name = no_name_title
+  end
 
-    local no_name_title = config.options.no_name_title
-    local maximum_length = config.options.maximum_length
+  if name == '' then
+    name = '[buffer ' .. buffer_number .. ']'
+  end
 
-    if name ~= '' then
-      name = buf_get_option(buffer_number, 'buftype') == 'terminal' and terminalname(name) or utils.basename(name, hide_extensions)
-    elseif no_name_title ~= nil and no_name_title ~= vim.NIL then
-      name = no_name_title
-    end
+  if strwidth(name) > maximum_length then
+    local ext_index = name:reverse():find('%.')
 
-    if name == '' then
-      name = '[buffer ' .. buffer_number .. ']'
+    if ext_index ~= nil and (ext_index < maximum_length - ELLIPSIS_LEN) then
+      local extension = name:sub(-ext_index)
+      name = strcharpart(name, 0, maximum_length - ELLIPSIS_LEN - #extension) .. ELLIPSIS .. extension
+    else
+      name = strcharpart(name, 0, maximum_length - ELLIPSIS_LEN) .. ELLIPSIS
     end
+  end
 
-    if strwidth(name) > maximum_length then
-      local ext_index = name:reverse():find('%.')
+  return name
+end
 
-      if ext_index ~= nil and (ext_index < maximum_length - ELLIPSIS_LEN) then
-        local extension = name:sub(-ext_index)
-        name = strcharpart(name, 0, maximum_length - ELLIPSIS_LEN - #extension) .. ELLIPSIS .. extension
-      else
-        name = strcharpart(name, 0, maximum_length - ELLIPSIS_LEN) .. ELLIPSIS
-      end
-    end
+--- @param first string
+--- @param second string
+--- @return string, string
+function buffer.get_unique_name(first, second)
+  local first_parts  = split(first,  separator)
+  local second_parts = split(second, separator)
+
+  local length = 1
+  local first_result  = table_concat(slice_from_end(first_parts, length),  separator)
+  local second_result = table_concat(slice_from_end(second_parts, length), separator)
+
+  while first_result == second_result and
+        length < max(#first_parts, #second_parts)
+  do
+    length = length + 1
+    first_result  = table_concat(slice_from_end(first_parts,  min(#first_parts, length)),  separator)
+    second_result = table_concat(slice_from_end(second_parts, min(#second_parts, length)), separator)
+  end
 
-    return name
-  end,
-
-  --- @param first string
-  --- @param second string
-  --- @return string, string
-  get_unique_name = function(first, second)
-    local first_parts  = split(first,  separator)
-    local second_parts = split(second, separator)
-
-    local length = 1
-    local first_result  = table_concat(utils.list_slice_from_end(first_parts, length),  separator)
-    local second_result = table_concat(utils.list_slice_from_end(second_parts, length), separator)
-
-    while first_result == second_result and
-          length < max(#first_parts, #second_parts)
-    do
-      length = length + 1
-      first_result  = table_concat(utils.list_slice_from_end(first_parts,  min(#first_parts, length)),  separator)
-      second_result = table_concat(utils.list_slice_from_end(second_parts, min(#second_parts, length)), separator)
-    end
+  return first_result, second_result
+end
 
-    return first_result, second_result
-  end,
-
-  --- Filter buffer numbers which are not to be shown during the render process.
-  --- Does **not** mutate `bufnrs`.
-  --- @param bufnrs integer[]
-  --- @return integer[] bufnrs the shown buffers
-  hide = function(bufnrs)
-    local hide = config.options.hide
-    if hide.alternate or hide.current or hide.inactive or hide.visible then
-      local shown = {}
-
-      for _, buffer_number in ipairs(bufnrs) do
-        local activity = activities[get_activity(buffer_number)]
-        if not hide[activity:lower()] then
-          table_insert(shown, buffer_number)
-        end
+--- Filter buffer numbers which are not to be shown during the render process.
+--- Does **not** mutate `bufnrs`.
+--- @param bufnrs integer[]
+--- @return integer[] bufnrs the shown buffers
+function buffer.hide(bufnrs)
+  local hide = config.options.hide
+  if hide.alternate or hide.current or hide.inactive or hide.visible then
+    local shown = {}
+
+    for _, buffer_number in ipairs(bufnrs) do
+      local activity = activities[buffer.get_activity(buffer_number)]
+      if not hide[activity:lower()] then
+        table_insert(shown, buffer_number)
       end
-
-      bufnrs = shown
     end
 
-    return bufnrs
-  end,
-}
+    bufnrs = shown
+  end
+
+  return bufnrs
+end
 
 return buffer
diff --git a/lua/barbar/config.lua b/lua/barbar/config.lua
index a5e37a1e..cef171d5 100644
--- a/lua/barbar/config.lua
+++ b/lua/barbar/config.lua
@@ -1,8 +1,11 @@
 local deepcopy = vim.deepcopy
+local get_sign = vim.fn.sign_getdefined --- @type function
+local severity = vim.diagnostic.severity
 local table_concat = table.concat
 local tbl_deep_extend = vim.tbl_deep_extend
 
-local utils = require'barbar.utils'
+local table_set = require('barbar.utils.table').set
+local utils = require('barbar.utils')
 
 --- The prefix used for `utils.deprecate`
 local DEPRECATE_PREFIX = '\nThe barbar.nvim option '
@@ -31,6 +34,10 @@ local DEFAULT_OPTIONS = {
   tabpages = true,
 }
 
+--- A cache for `sign_getdefined`
+--- @type string[]
+local diagnostic_sign_cache = {}
+
 --- @class barbar.config.options.hide
 --- @field alternate? boolean
 --- @field current? boolean
@@ -47,43 +54,66 @@ local DEFAULT_OPTIONS = {
 --- @field [2] barbar.config.options.icons.diagnostics.severity
 --- @field [3] barbar.config.options.icons.diagnostics.severity
 --- @field [4] barbar.config.options.icons.diagnostics.severity
-local DEFAULT_DIAGNOSTIC_ICONS = {
-  [vim.diagnostic.severity.ERROR] = { enabled = false, icon = 'Ⓧ ' },
-  [vim.diagnostic.severity.HINT] = { enabled = false, icon = '💡' },
-  [vim.diagnostic.severity.INFO] = { enabled = false, icon = 'ⓘ ' },
-  [vim.diagnostic.severity.WARN] = { enabled = false, icon = '⚠️ ' },
-}
+
+--- Deeply extend `icons` to include the `DEFAULT_DIAGNOSTIC_ICONS`
+--- HACK: required because `vim.tbl_deep_extend` does not deep extend lists.
+--- @param icons table
+--- @see vim.tbl_deep_extend
+local function tbl_deep_extend_diagnostic_icons(icons)
+  for i, name in ipairs(severity) do
+    local diagnostic_severity_icons = icons.diagnostics[i]
+    if diagnostic_severity_icons == nil then
+      diagnostic_severity_icons = {}
+      icons.diagnostics[i] = diagnostic_severity_icons
+    end
+
+    if diagnostic_severity_icons.enabled == nil then
+      diagnostic_severity_icons.enabled = false
+    end
+
+    if diagnostic_severity_icons.icon == nil then
+      local cached = diagnostic_sign_cache[i]
+      if cached then
+        diagnostic_severity_icons.icon = cached
+      else
+        local sign = get_sign('DiagnosticSign' .. name:sub(1, 1) .. name:sub(2):lower())
+        diagnostic_severity_icons.icon = sign
+        diagnostic_sign_cache[i] = sign
+      end
+    end
+  end
+end
 
 --- @class barbar.config.options.icons.buffer.filetype
 --- @field custom_colors? boolean if present, this color will be used for ALL filetype icons
---- @field enabled? boolean iff `true`, show the `devicons` for the associated buffer's `filetype`.
+--- @field enabled boolean iff `true`, show the `devicons` for the associated buffer's `filetype`.
 
 --- @class barbar.config.options.icons.buffer.separator
---- @field left? string a buffer's left separator
---- @field right? string a buffer's right separator
+--- @field left string a buffer's left separator
+--- @field right string a buffer's right separator
 
 --- @class barbar.config.options.icons.scroll
 --- @field left string
 --- @field right string
 
 --- @class barbar.config.options.icons.buffer
---- @field buffer_index? boolean iff `true`, show the index of the associated buffer with respect to the ordering of the buffers in the tabline.
---- @field buffer_number? boolean iff `true`, show the `bufnr` for the associated buffer.
---- @field filename? boolean iff `true`, show the filename
---- @field button? false|string the button which is clicked to close / save a buffer, or indicate that it is pinned.
---- @field diagnostics? barbar.config.options.icons.buffer.diagnostics the diagnostic icons
---- @field filetype? barbar.config.options.icons.buffer.filetype filetype icon options
---- @field separator? barbar.config.options.icons.buffer.separator the left-hand separator between buffers in the tabline
+--- @field buffer_index boolean iff `true`, show the index of the associated buffer with respect to the ordering of the buffers in the tabline.
+--- @field buffer_number boolean iff `true`, show the `bufnr` for the associated buffer.
+--- @field filename boolean iff `true`, show the filename
+--- @field button false|string the button which is clicked to close / save a buffer, or indicate that it is pinned.
+--- @field diagnostics barbar.config.options.icons.buffer.diagnostics the diagnostic icons
+--- @field filetype barbar.config.options.icons.buffer.filetype filetype icon options
+--- @field separator barbar.config.options.icons.buffer.separator the separators between buffers in the tabline
 
 --- @class barbar.config.options.icons.state: barbar.config.options.icons.buffer
---- @field modified? barbar.config.options.icons.buffer the icons used for an modified buffer
---- @field pinned? barbar.config.options.icons.buffer the icons used for a pinned buffer
+--- @field modified barbar.config.options.icons.buffer the icons used for an modified buffer
+--- @field pinned barbar.config.options.icons.buffer the icons used for a pinned buffer
 
 --- @class barbar.config.options.icons: barbar.config.options.icons.state
---- @field alternate? barbar.config.options.icons.state the icons used for an alternate buffer
---- @field current? barbar.config.options.icons.state the icons for the current buffer
+--- @field alternate barbar.config.options.icons.state the icons used for an alternate buffer
+--- @field current barbar.config.options.icons.state the icons for the current buffer
 --- @field inactive barbar.config.options.icons.state the icons for inactive buffers
---- @field visible? barbar.config.options.icons.state the icons for visible buffers
+--- @field visible barbar.config.options.icons.state the icons for visible buffers
 --- @field scroll barbar.config.options.icons.scroll the scroll arrows
 local DEFAULT_ICONS = {
   buffer_index = false,
@@ -157,7 +187,7 @@ local DEPRECATED_OPTIONS = {
 --- @field clickable boolean
 --- @field exclude_ft string[]
 --- @field exclude_name string[]
---- @field focus_on_close 'left'|'right'
+--- @field focus_on_close side
 --- @field hide barbar.config.options.hide
 --- @field highlight_alternate boolean
 --- @field highlight_inactive_file_icons boolean
@@ -174,7 +204,7 @@ local DEPRECATED_OPTIONS = {
 --- @field sidebar_filetypes {[string]: nil|barbar.config.options.sidebar_filetype}
 --- @field tabpages boolean
 
---- @class barbar.config
+--- @class barbar.Config
 --- @field options barbar.config.options
 local config = { options = {} }
 
@@ -206,7 +236,7 @@ function config.setup(options)
   for deprecated_option, new_option in pairs(DEPRECATED_OPTIONS) do
     local user_setting = options[deprecated_option]
     if user_setting then
-      utils.tbl_set(options, new_option, user_setting)
+      table_set(options, new_option, user_setting)
       utils.deprecate(
         DEPRECATE_PREFIX .. utils.markdown_inline_code(deprecated_option),
         utils.markdown_inline_code(table_concat(new_option, '.'))
@@ -219,8 +249,8 @@ function config.setup(options)
   -- TODO: remove after v2
   -- Edge case deprecated option
   if options.closable == false then
-    utils.tbl_set(options, { 'icons', 'button' }, false)
-    utils.tbl_set(options, { 'icons', 'modified', 'button' }, false)
+    table_set(options, { 'icons', 'button' }, false)
+    table_set(options, { 'icons', 'modified', 'button' }, false)
     utils.deprecate(
       DEPRECATE_PREFIX .. utils.markdown_inline_code'closable',
       utils.markdown_inline_code'icons.button' ..
@@ -252,50 +282,39 @@ function config.setup(options)
 
   config.options = tbl_deep_extend('keep', options, DEFAULT_OPTIONS, { icons = default_icons })
 
-  -- NOTE: we do this because `vim.tbl_deep_extend` doesn't deep copy lists
-  for i, default_diagnostic_severity_icons in ipairs(DEFAULT_DIAGNOSTIC_ICONS) do
-    local diagnostic_severity_icons = config.options.icons.diagnostics[i] or {}
+  do
+    local icons = config.options.icons
 
-    if diagnostic_severity_icons.enabled == nil then
-      diagnostic_severity_icons.enabled = default_diagnostic_severity_icons.enabled
-    end
+    --- `config.options.icons` without the recursive structure
+    --- @type barbar.config.options.icons.buffer
+    local base_options = {
+      buffer_index = icons.buffer_index,
+      buffer_number = icons.buffer_number,
+      filename = icons.filename,
+      button = icons.button,
+      diagnostics = icons.diagnostics,
+      filetype = icons.filetype,
+      separator = icons.separator,
+    }
 
-    if diagnostic_severity_icons.icon == nil then
-      diagnostic_severity_icons.icon = default_diagnostic_severity_icons.icon
-    end
-  end
+    local modified_icons = icons.modified or {}
+    local pinned_icons = icons.pinned or {}
 
-  local icons = config.options.icons
-
-  --- `config.options.icons` without the recursive structure
-  --- @type barbar.config.options.icons.buffer
-  local base_options = {
-    buffer_index = icons.buffer_index,
-    buffer_number = icons.buffer_number,
-    filename = icons.filename,
-    button = icons.button,
-    diagnostics = icons.diagnostics,
-    filetype = icons.filetype,
-    separator = icons.separator,
-  }
-
-  -- resolve all of the icons for the activities
-  for _, activity in ipairs { 'alternate', 'current', 'inactive', 'visible' } do
-    local activity_options = tbl_deep_extend('keep', config.options.icons[activity] or {}, base_options)
-    config.options.icons[activity] = activity_options
-    config.options.icons[activity].modified = tbl_deep_extend(
-      'keep',
-      config.options.icons[activity].modified or {},
-      config.options.icons.modified or {},
-      activity_options
-    )
+    diagnostic_sign_cache = {}
 
-    config.options.icons[activity].pinned = tbl_deep_extend(
-      'keep',
-      config.options.icons[activity].pinned or {},
-      config.options.icons.pinned or {},
-      activity_options
-    )
+    -- resolve all of the icons for the activities
+    for _, activity in ipairs { 'alternate', 'current', 'inactive', 'visible' } do
+      local activity_icons = tbl_deep_extend('keep', config.options.icons[activity] or {}, base_options)
+      tbl_deep_extend_diagnostic_icons(activity_icons)
+
+      activity_icons.pinned = tbl_deep_extend('keep', activity_icons.pinned or {}, pinned_icons, activity_icons)
+      tbl_deep_extend_diagnostic_icons(activity_icons.pinned)
+
+      activity_icons.modified = tbl_deep_extend('keep', activity_icons.modified or {}, modified_icons, activity_icons)
+      tbl_deep_extend_diagnostic_icons(activity_icons.modified)
+
+      icons[activity] = activity_icons
+    end
   end
 end
 
diff --git a/lua/barbar/events.lua b/lua/barbar/events.lua
index 47858d1a..b92fe263 100644
--- a/lua/barbar/events.lua
+++ b/lua/barbar/events.lua
@@ -21,14 +21,15 @@ local tbl_isempty = vim.tbl_isempty
 local win_get_position = vim.api.nvim_win_get_position --- @type function
 local win_get_width = vim.api.nvim_win_get_width --- @type function
 
-local api = require'barbar.api'
-local bbye = require'barbar.bbye'
-local config = require'barbar.config'
-local highlight = require'barbar.highlight'
-local JumpMode = require'barbar.jump_mode'
-local render = require'barbar.ui.render'
-local state = require'barbar.state'
-local utils = require'barbar.utils'
+local bdelete = require('barbar.bbye').bdelete
+local config = require('barbar.config')
+local highlight_reset_cache = require('barbar.utils.highlight').reset_cache
+local highlight_setup = require('barbar.highlight').setup
+local jump_mode = require('barbar.jump_mode')
+local relative = require('barbar.fs').relative
+local render = require('barbar.ui.render')
+local set_offset = require('barbar.api').set_offset
+local state = require('barbar.state')
 
 --- The `<mods>` used for the close click handler
 local CLOSE_CLICK_MODS = vim.api.nvim_cmd and { confirm = true } or 'confirm'
@@ -36,7 +37,7 @@ local CLOSE_CLICK_MODS = vim.api.nvim_cmd and { confirm = true } or 'confirm'
 --- Whether barbar is currently set up to render.
 local enabled = false
 
---- @class barbar.events
+--- @class barbar.Events
 local events = {}
 
 --- Create and reset autocommand groups associated with this plugin.
@@ -60,7 +61,7 @@ function events.close_click_handler(buffer)
     buf_call(buffer, function() command('w') end)
     exec_autocmds('BufModifiedSet', {buffer = buffer})
   else
-    bbye.bdelete(false, buffer, CLOSE_CLICK_MODS)
+    bdelete(false, buffer, CLOSE_CLICK_MODS)
   end
 end
 
@@ -81,13 +82,13 @@ function events.enable()
   create_autocmd({'VimLeave'}, { callback = state.save_recently_closed, group = augroup_misc })
 
   create_autocmd({'BufNewFile', 'BufReadPost'}, {
-    callback = function(tbl) JumpMode.assign_next_letter(tbl.buf) end,
+    callback = function(tbl) jump_mode.assign_next_letter(tbl.buf) end,
     group = augroup_misc,
   })
 
   create_autocmd({'BufDelete', 'BufWipeout'}, {
-    callback = vim.schedule_wrap(function(tbl)
-      JumpMode.unassign_letter_for(tbl.buf)
+    callback = schedule_wrap(function(tbl)
+      jump_mode.unassign_letter_for(tbl.buf)
       state.push_recently_closed(tbl.file)
       render.update()
     end),
@@ -96,8 +97,8 @@ function events.enable()
 
   create_autocmd('ColorScheme', {
     callback = function()
-      utils.hl.reset_cache()
-      highlight.setup()
+      highlight_reset_cache()
+      highlight_setup()
     end,
     group = augroup_misc,
   })
@@ -150,7 +151,7 @@ function events.enable()
       right = {}, --- @type {[string]: nil|integer}
     }
 
-    --- @param side 'left'|'right'
+    --- @param side side
     --- @return integer total_width
     local function total_widths(side)
       local offset = 0
@@ -168,7 +169,7 @@ function events.enable()
       create_autocmd('FileType', {
         callback = function(tbl)
           local bufwinid --- @type nil|integer
-          local side --- @type 'left'|'right'
+          local side --- @type side
           local autocmd = create_autocmd({'BufWinEnter', 'WinScrolled'}, {
             callback = function()
               if bufwinid == nil then
@@ -187,7 +188,7 @@ function events.enable()
               if width ~= widths[ft] then
                 widths[side][ft] = width
                 widths[other_side][ft] = nil
-                api.set_offset(total_widths(side), option.text, nil, side)
+                set_offset(total_widths(side), option.text, nil, side)
               end
             end,
             group = augroup_render,
@@ -197,7 +198,7 @@ function events.enable()
             buffer = tbl.buf,
             callback = function()
               widths[side][ft] = nil
-              api.set_offset(total_widths(side), nil, nil, side)
+              set_offset(total_widths(side), nil, nil, side)
               del_autocmd(autocmd)
             end,
             group = augroup_render,
@@ -265,14 +266,14 @@ function events.enable()
       for _, bufnr in ipairs(state.buffers) do
         local name = buf_get_name(bufnr)
         if use_relative_file_paths then
-          name = utils.relative(name)
+          name = relative(name)
         end
 
         -- escape quotes
         table_insert(buffers, {name = name, pinned = state.is_pinned(bufnr)})
       end
 
-      vim.g.Bufferline__session_restore = "lua require'barbar.state'.restore_buffers " ..
+      vim.g.Bufferline__session_restore = "lua require('barbar.state').restore_buffers " ..
         vim.inspect(buffers, {newline = ' ', indent = ''})
     end,
     group = augroup_misc,
@@ -318,7 +319,7 @@ function events.main_click_handler(bufnr, _, btn, _)
 
   -- NOTE: in Vimscript this was not `==`, it was a regex compare `=~`
   if btn == 'm' then
-    bbye.bdelete(false, bufnr)
+    bdelete(false, bufnr)
   else
     render.set_current_win_listed_buffer()
     set_current_buf(bufnr)
@@ -331,8 +332,8 @@ end
 --- @return nil
 function events.on_option_changed(user_config)
   config.setup(user_config) -- NOTE: must be first `setup` called here
-  highlight.setup()
-  JumpMode.set_letters(config.options.letters)
+  highlight_setup()
+  jump_mode.set_letters(config.options.letters)
 
   -- Don't jump-start barbar if it is disabled
   if enabled then
diff --git a/lua/barbar/fs.lua b/lua/barbar/fs.lua
index 021066a6..b3b95695 100644
--- a/lua/barbar/fs.lua
+++ b/lua/barbar/fs.lua
@@ -2,33 +2,87 @@
 -- fs.lua
 --
 
+local fnamemodify = vim.fn.fnamemodify --- @type function
 
+--- @class barbar.Fs
 local fs = {}
 
+--- Get
+--- @param path string
+--- @param hide_extension? boolean if `true`, exclude the extension of the file in the basename
+--- @return string basename
+function fs.basename(path, hide_extension)
+  return fnamemodify(path, hide_extension and ':t:r' or ':t')
+end
+
+--- @param path string
+--- @return boolean is_relative `true` if `path` is relative to the CWD
+function fs.is_relative_path(path)
+  return fs.relative(path) == path
+end
+
+--- @param filepath string
+--- @param mode? openmode
+--- @return string|nil error_message, any content
+function fs.read(filepath, mode)
+  local file, open_err = io.open(filepath, mode or 'r')
+
+  -- Ignore if the file doesn't exist or isn't readable
+  if open_err ~= nil then
+    return
+  elseif file == nil then
+    return
+  end
+
+  local content, read_err = file:read('*a')
+  if read_err ~= nil then
+    return read_err
+  end
+
+  do
+    local success, close_err = file:close()
+    if close_err ~= nil then
+      return close_err
+    elseif success == false then
+      return 'Error while closing ' .. filepath
+    end
+  end
+
+  return nil, content
+end
+
+--- @param path string
+--- @return string relative_path
+function fs.relative(path)
+  return fnamemodify(path, ':~:.')
+end
+
 --- @param filepath string
 --- @param content string
---- @param mode string
---- @return string | nil err
+--- @param mode? openmode
+--- @return string|nil error_message
 function fs.write(filepath, content, mode)
-  mode = mode or 'w'
-  local file, open_err = io.open(filepath, mode)
+  local file, open_err = io.open(filepath, mode or 'w')
+
   if open_err ~= nil then
     return open_err
   elseif file == nil then
-    return 'Error while opening file'
+    return 'Error while opening ' .. filepath
   end
-  local _, write_err = file:write(content)
-  if write_err ~= nil then
-    return write_err
+
+  do
+    local _, write_err = file:write(content)
+    if write_err ~= nil then
+      return write_err
+    end
   end
 
   local success, close_err = file:close()
   if close_err ~= nil then
     return close_err
   elseif success == false then
-    return 'Error while closing file'
+    return 'Error while closing ' .. filepath
   end
-  return nil
 end
 
 return fs
diff --git a/lua/barbar/highlight.lua b/lua/barbar/highlight.lua
index 541435f4..a8e8e180 100644
--- a/lua/barbar/highlight.lua
+++ b/lua/barbar/highlight.lua
@@ -1,8 +1,8 @@
 -- !::exe [So]
 
-local config = require 'barbar.config'
-local hl = require'barbar.utils'.hl
-local icons = require 'barbar.icons'
+local config = require('barbar.config')
+local hl = require('barbar.utils.highlight')
+local icons = require('barbar.icons')
 
 -- Setup the highlight groups used by the plugin.
 hl.set_default_link('BufferAlternate', 'BufferDefaultAlternate')
@@ -70,93 +70,93 @@ hl.set_default_link('BufferDefaultOffset', 'BufferTabpageFill')
 hl.set_default_link('BufferDefaultVisibleIcon', 'BufferVisible')
 hl.set_default_link('BufferDefaultVisibleNumber', 'BufferVisibleIndex')
 
---- @class barbar.highlight
-local highlight = {
-  --- Setup the highlight groups for this plugin.
-  --- @return nil
-  setup = function()
-    local fg_current = hl.fg_or_default({'Normal'}, '#efefef', 255)
-    local fg_inactive = hl.fg_or_default({'TabLineFill'}, '#888888', 102)
-    local fg_target = {gui = 'red'} --- @type barbar.utils.hl.color
-    fg_target.cterm = fg_target.gui
-
-    local fg_error = hl.fg_or_default({'ErrorMsg'}, '#A80000', 124)
-    local fg_hint = hl.fg_or_default({'HintMsg'}, '#D5508F', 168)
-    local fg_info = hl.fg_or_default({'InfoMsg'}, '#FFB7B7', 217)
-    local fg_warn = hl.fg_or_default({'WarningMsg'}, '#FF8900', 208)
-
-    local fg_modified = hl.fg_or_default({'WarningMsg'}, '#E5AB0E', 178)
-    local fg_special = hl.fg_or_default({'Special'}, '#599eff', 75)
-    local fg_subtle = hl.fg_or_default({'NonText', 'Comment'}, '#555555', 240)
-
-    local bg_current = hl.bg_or_default({'Normal'}, 'none')
-    local bg_inactive = hl.bg_or_default({'TabLineFill', 'StatusLine'}, 'none')
-
-    --    Alternate: alternate buffer
-    --      Current: current buffer
-    --      Visible: visible but not current buffer
-    --     Inactive: invisible but not current buffer
-    --        -Icon: filetype icon
-    --       -Index: buffer index
-    --      -Number: buffer number
-    --         -Mod: when modified
-    --        -Sign: the separator between buffers
-    --      -Target: letter in buffer-picking mode
-    if config.options.highlight_alternate then
-      local fg_alternate = hl.fg_or_default({'TabLineFill'}, '#ead0a0', 223)
-      local bg_alternate = hl.bg_or_default({'TabLineSel', 'Normal'}, 'none')
-
-      hl.set('BufferDefaultAlternate',        bg_alternate, fg_alternate)
-      hl.set('BufferDefaultAlternateERROR',   bg_alternate, fg_error)
-      hl.set('BufferDefaultAlternateHINT',    bg_alternate, fg_hint)
-      hl.set('BufferDefaultAlternateIndex',   bg_alternate, fg_special)
-      hl.set('BufferDefaultAlternateINFO',    bg_alternate, fg_info)
-      hl.set('BufferDefaultAlternateMod',     bg_alternate, fg_modified)
-      hl.set('BufferDefaultAlternateSign',    bg_alternate, fg_special)
-      hl.set('BufferDefaultAlternateTarget',  bg_alternate, fg_target, nil, {bold = true})
-      hl.set('BufferDefaultAlternateWARN',    bg_alternate, fg_warn)
-    end
-
-    hl.set('BufferDefaultCurrent',        bg_current, fg_current)
-    hl.set('BufferDefaultCurrentERROR',   bg_current, fg_error)
-    hl.set('BufferDefaultCurrentHINT',    bg_current, fg_hint)
-    hl.set('BufferDefaultCurrentIndex',   bg_current, fg_special)
-    hl.set('BufferDefaultCurrentINFO',    bg_current, fg_info)
-    hl.set('BufferDefaultCurrentMod',     bg_current, fg_modified)
-    hl.set('BufferDefaultCurrentSign',    bg_current, fg_special)
-    hl.set('BufferDefaultCurrentTarget',  bg_current, fg_target, nil, {bold = true})
-    hl.set('BufferDefaultCurrentWARN',    bg_current, fg_warn)
-
-    hl.set('BufferDefaultInactive',       bg_inactive, fg_inactive)
-    hl.set('BufferDefaultInactiveERROR',  bg_inactive, fg_error)
-    hl.set('BufferDefaultInactiveHINT',   bg_inactive, fg_hint)
-    hl.set('BufferDefaultInactiveIndex',  bg_inactive, fg_subtle)
-    hl.set('BufferDefaultInactiveINFO',   bg_inactive, fg_info)
-    hl.set('BufferDefaultInactiveMod',    bg_inactive, fg_modified)
-    hl.set('BufferDefaultInactiveSign',   bg_inactive, fg_subtle)
-    hl.set('BufferDefaultInactiveTarget', bg_inactive, fg_target, nil, {bold = true})
-    hl.set('BufferDefaultInactiveWARN',   bg_inactive, fg_warn)
-
-    hl.set('BufferDefaultTabpageFill',    bg_inactive, fg_inactive)
-    hl.set('BufferDefaultTabpages',       bg_inactive, fg_special, nil, {bold = true})
-
-    if config.options.highlight_visible then
-      local fg_visible = hl.fg_or_default({'TabLineSel'}, '#efefef', 255)
-      local bg_visible = hl.bg_or_default({'TabLineSel', 'Normal'}, 'none')
-
-      hl.set('BufferDefaultVisible',        bg_visible, fg_visible)
-      hl.set('BufferDefaultVisibleERROR',   bg_visible, fg_error)
-      hl.set('BufferDefaultVisibleHINT',    bg_visible, fg_hint)
-      hl.set('BufferDefaultVisibleIndex',   bg_visible, fg_visible)
-      hl.set('BufferDefaultVisibleINFO',    bg_visible, fg_info)
-      hl.set('BufferDefaultVisibleMod',     bg_visible, fg_modified)
-      hl.set('BufferDefaultVisibleSign',    bg_visible, fg_visible)
-      hl.set('BufferDefaultVisibleTarget',  bg_visible, fg_target, nil, {bold = true})
-      hl.set('BufferDefaultVisibleWARN',    bg_visible, fg_warn)
-    end
-
-    icons.set_highlights()
+--- @class barbar.Highlight
+local highlight = {}
+
+--- Setup the highlight groups for this plugin.
+--- @return nil
+function highlight.setup()
+  local fg_current = hl.fg_or_default({'Normal'}, '#efefef', 255)
+  local fg_inactive = hl.fg_or_default({'TabLineFill'}, '#888888', 102)
+  local fg_target = {gui = 'red'} --- @type barbar.utils.hl.color
+  fg_target.cterm = fg_target.gui
+
+  local fg_error = hl.fg_or_default({'ErrorMsg'}, '#A80000', 124)
+  local fg_hint = hl.fg_or_default({'HintMsg'}, '#D5508F', 168)
+  local fg_info = hl.fg_or_default({'InfoMsg'}, '#FFB7B7', 217)
+  local fg_warn = hl.fg_or_default({'WarningMsg'}, '#FF8900', 208)
+
+  local fg_modified = hl.fg_or_default({'WarningMsg'}, '#E5AB0E', 178)
+  local fg_special = hl.fg_or_default({'Special'}, '#599eff', 75)
+  local fg_subtle = hl.fg_or_default({'NonText', 'Comment'}, '#555555', 240)
+
+  local bg_current = hl.bg_or_default({'Normal'}, 'none')
+  local bg_inactive = hl.bg_or_default({'TabLineFill', 'StatusLine'}, 'none')
+
+  --    Alternate: alternate buffer
+  --      Current: current buffer
+  --      Visible: visible but not current buffer
+  --     Inactive: invisible but not current buffer
+  --        -Icon: filetype icon
+  --       -Index: buffer index
+  --      -Number: buffer number
+  --         -Mod: when modified
+  --        -Sign: the separator between buffers
+  --      -Target: letter in buffer-picking mode
+  if config.options.highlight_alternate then
+    local fg_alternate = hl.fg_or_default({'TabLineFill'}, '#ead0a0', 223)
+    local bg_alternate = hl.bg_or_default({'TabLineSel', 'Normal'}, 'none')
+
+    hl.set('BufferDefaultAlternate',        bg_alternate, fg_alternate)
+    hl.set('BufferDefaultAlternateERROR',   bg_alternate, fg_error)
+    hl.set('BufferDefaultAlternateHINT',    bg_alternate, fg_hint)
+    hl.set('BufferDefaultAlternateIndex',   bg_alternate, fg_special)
+    hl.set('BufferDefaultAlternateINFO',    bg_alternate, fg_info)
+    hl.set('BufferDefaultAlternateMod',     bg_alternate, fg_modified)
+    hl.set('BufferDefaultAlternateSign',    bg_alternate, fg_special)
+    hl.set('BufferDefaultAlternateTarget',  bg_alternate, fg_target, nil, {bold = true})
+    hl.set('BufferDefaultAlternateWARN',    bg_alternate, fg_warn)
   end
-}
+
+  hl.set('BufferDefaultCurrent',        bg_current, fg_current)
+  hl.set('BufferDefaultCurrentERROR',   bg_current, fg_error)
+  hl.set('BufferDefaultCurrentHINT',    bg_current, fg_hint)
+  hl.set('BufferDefaultCurrentIndex',   bg_current, fg_special)
+  hl.set('BufferDefaultCurrentINFO',    bg_current, fg_info)
+  hl.set('BufferDefaultCurrentMod',     bg_current, fg_modified)
+  hl.set('BufferDefaultCurrentSign',    bg_current, fg_special)
+  hl.set('BufferDefaultCurrentTarget',  bg_current, fg_target, nil, {bold = true})
+  hl.set('BufferDefaultCurrentWARN',    bg_current, fg_warn)
+
+  hl.set('BufferDefaultInactive',       bg_inactive, fg_inactive)
+  hl.set('BufferDefaultInactiveERROR',  bg_inactive, fg_error)
+  hl.set('BufferDefaultInactiveHINT',   bg_inactive, fg_hint)
+  hl.set('BufferDefaultInactiveIndex',  bg_inactive, fg_subtle)
+  hl.set('BufferDefaultInactiveINFO',   bg_inactive, fg_info)
+  hl.set('BufferDefaultInactiveMod',    bg_inactive, fg_modified)
+  hl.set('BufferDefaultInactiveSign',   bg_inactive, fg_subtle)
+  hl.set('BufferDefaultInactiveTarget', bg_inactive, fg_target, nil, {bold = true})
+  hl.set('BufferDefaultInactiveWARN',   bg_inactive, fg_warn)
+
+  hl.set('BufferDefaultTabpageFill',    bg_inactive, fg_inactive)
+  hl.set('BufferDefaultTabpages',       bg_inactive, fg_special, nil, {bold = true})
+
+  if config.options.highlight_visible then
+    local fg_visible = hl.fg_or_default({'TabLineSel'}, '#efefef', 255)
+    local bg_visible = hl.bg_or_default({'TabLineSel', 'Normal'}, 'none')
+
+    hl.set('BufferDefaultVisible',        bg_visible, fg_visible)
+    hl.set('BufferDefaultVisibleERROR',   bg_visible, fg_error)
+    hl.set('BufferDefaultVisibleHINT',    bg_visible, fg_hint)
+    hl.set('BufferDefaultVisibleIndex',   bg_visible, fg_visible)
+    hl.set('BufferDefaultVisibleINFO',    bg_visible, fg_info)
+    hl.set('BufferDefaultVisibleMod',     bg_visible, fg_modified)
+    hl.set('BufferDefaultVisibleSign',    bg_visible, fg_visible)
+    hl.set('BufferDefaultVisibleTarget',  bg_visible, fg_target, nil, {bold = true})
+    hl.set('BufferDefaultVisibleWARN',    bg_visible, fg_warn)
+  end
+
+  icons.set_highlights()
+end
 
 return highlight
diff --git a/lua/barbar/icons.lua b/lua/barbar/icons.lua
index 2eaece27..95cfa7c8 100644
--- a/lua/barbar/icons.lua
+++ b/lua/barbar/icons.lua
@@ -9,8 +9,8 @@ local buf_get_option = vim.api.nvim_buf_get_option --- @type function
 local fnamemodify = vim.fn.fnamemodify --- @type function
 local hlexists = vim.fn.hlexists --- @type function
 
-local utils = require'barbar.utils'
-local hl = utils.hl
+local hl = require('barbar.utils.highlight')
+local utils = require('barbar.utils')
 
 --- @type boolean, {get_icon: fun(name: string, ext?: string, opts?: {default: nil|boolean}): string, string}
 local ok, web = pcall(require, 'nvim-web-devicons')
@@ -37,62 +37,60 @@ end
 --- @type barbar.icons.group[]
 local hl_groups = {}
 
---- @class barbar.icons
-local icons = {
-  --- Re-highlight all of the groups which have been set before. Checks for updated highlight groups.
-  --- @return nil
-  set_highlights = vim.schedule_wrap(function()
-    for _, group in ipairs(hl_groups) do
-      hl_buffer_icon(group.buffer_status, group.icon_hl)
-    end
-  end),
-
-  get_icon = ok and
-    --- @param bufnr integer
-    --- @param buffer_activity barbar.buffer.activity.name
-    --- @return string icon, string highlight_group
-    function(bufnr, buffer_activity)
-      local basename, extension = '', ''
-      local filetype = buf_get_option(bufnr, 'filetype')
-      local icon_char, icon_hl = '', ''
-
-      -- nvim-web-devicon only handles filetype icons, not other types (eg directory)
-      -- thus we need to do some work here
-      if filetype == 'netrw' or filetype == 'LuaTree' then
-        icon_char, icon_hl = '', 'Directory'
+--- @class barbar.Icons
+local icons = {}
+
+icons.get_icon = ok and
+  --- @param bufnr integer
+  --- @param buffer_activity barbar.buffer.activity.name
+  --- @return string icon, string highlight_group
+  function(bufnr, buffer_activity)
+    local basename, extension = '', ''
+    local filetype = buf_get_option(bufnr, 'filetype')
+    local icon_char, icon_hl = '', ''
+
+    -- nvim-web-devicon only handles filetype icons, not other types (eg directory)
+    -- thus we need to do some work here
+    if filetype == 'netrw' or filetype == 'LuaTree' then
+      icon_char, icon_hl = '', 'Directory'
+    else
+      if filetype == 'fugitive' or filetype == 'gitcommit' then
+        basename, extension = 'git', 'git'
       else
-        if filetype == 'fugitive' or filetype == 'gitcommit' then
-          basename, extension = 'git', 'git'
-        else
-          basename = fnamemodify(buf_get_name(bufnr), ':t')
-          extension = fnamemodify(basename, ':e')
-        end
-
-        icon_char, icon_hl = web.get_icon(basename, extension, { default = true })
+        basename = fnamemodify(buf_get_name(bufnr), ':t')
+        extension = fnamemodify(basename, ':e')
       end
 
-      if icon_hl and hlexists(icon_hl .. buffer_activity) < 1 then
-        hl_buffer_icon(buffer_activity, icon_hl)
-        table_insert(hl_groups, {buffer_status = buffer_activity, icon_hl = icon_hl})
-      end
+      icon_char, icon_hl = web.get_icon(basename, extension, { default = true })
+    end
 
-      return icon_char, icon_hl .. buffer_activity
-    end or
-    --- @param buffer_activity barbar.buffer.activity.name
-    --- @return string icon, string highlight_group
-    function(_, buffer_activity)
-      local invalid_option = utils.markdown_inline_code'icons.filetype.enabled'
-      utils.notify_once(
-        'barbar.nvim: ' .. invalid_option .. ' is set to ' .. utils.markdown_inline_code'true' ..
-          ' but ' .. utils.markdown_inline_code'nvim-dev-icons' .. ' was not found.' ..
-          '\nbarbar.nvim: icons have been disabled. Set ' .. invalid_option .. ' to ' ..
-          utils.markdown_inline_code'false' .. ' or ' .. 'install ' ..
-          utils.markdown_inline_code'nvim-dev-icons' .. 'to disable this message.',
-        vim.log.levels.WARN
-      )
-
-      return '', 'Buffer' .. buffer_activity .. 'Icon'
-    end,
-}
+    if icon_hl and hlexists(icon_hl .. buffer_activity) < 1 then
+      hl_buffer_icon(buffer_activity, icon_hl)
+      table_insert(hl_groups, {buffer_status = buffer_activity, icon_hl = icon_hl})
+    end
+
+    return icon_char, icon_hl .. buffer_activity
+  end or
+  function(_, buffer_activity)
+    local invalid_option = utils.markdown_inline_code'icons.filetype.enabled'
+    utils.notify_once(
+      'barbar.nvim: ' .. invalid_option .. ' is set to ' .. utils.markdown_inline_code'true' ..
+        ' but ' .. utils.markdown_inline_code'nvim-dev-icons' .. ' was not found.' ..
+        '\nbarbar.nvim: icons have been disabled. Set ' .. invalid_option .. ' to ' ..
+        utils.markdown_inline_code'false' .. ' or ' .. 'install ' ..
+        utils.markdown_inline_code'nvim-dev-icons' .. 'to disable this message.',
+      vim.log.levels.WARN
+    )
+
+    return '', 'Buffer' .. buffer_activity .. 'Icon'
+  end
+
+--- Re-highlight all of the groups which have been set before. Checks for updated highlight groups.
+--- @return nil
+icons.set_highlights = vim.schedule_wrap(function()
+  for _, group in ipairs(hl_groups) do
+    hl_buffer_icon(group.buffer_status, group.icon_hl)
+  end
+end)
 
 return icons
diff --git a/lua/barbar/jump_mode.lua b/lua/barbar/jump_mode.lua
index 34c4987f..df6e090d 100644
--- a/lua/barbar/jump_mode.lua
+++ b/lua/barbar/jump_mode.lua
@@ -8,7 +8,7 @@ local split = vim.fn.split --- @type function
 local strcharpart = vim.fn.strcharpart --- @type function
 local strwidth = vim.api.nvim_strwidth --- @type function
 
-local config = require'barbar.config'
+local config = require('barbar.config')
 
 ----------------------------------------
 -- Section: Buffer-picking mode state --
@@ -24,36 +24,36 @@ local letters = {}
 --- @field private letter_by_buffer {[integer]: string} a bi-directional map of buffer integers and their letters.
 --- @field private letter_status {[integer]: boolean}
 --- @field reinitialize boolean whether an `initialize_indexes` operation has been queued.
-local JumpMode = {}
+local jump_mode = {}
 
 --- Reset the module to a valid default state
 --- @return nil
-function JumpMode.initialize_indexes()
-  JumpMode.buffer_by_letter = {}
-  JumpMode.index_by_letter = {}
-  JumpMode.letter_by_buffer = {}
-  JumpMode.letter_status = {}
+function jump_mode.initialize_indexes()
+  jump_mode.buffer_by_letter = {}
+  jump_mode.index_by_letter = {}
+  jump_mode.letter_by_buffer = {}
+  jump_mode.letter_status = {}
 
   for index, letter in ipairs(letters) do
-    JumpMode.index_by_letter[letter] = index
-    JumpMode.letter_status[index] = false
+    jump_mode.index_by_letter[letter] = index
+    jump_mode.letter_status[index] = false
   end
 
-  JumpMode.reinitialize = false
+  jump_mode.reinitialize = false
 end
 
 --- Set the letters which can be used by jump mode.
 --- @param chars string
 --- @return nil
-function JumpMode.set_letters(chars)
+function jump_mode.set_letters(chars)
   letters = split(chars, [[\zs]])
-  JumpMode.initialize_indexes()
+  jump_mode.initialize_indexes()
 end
 
 --- @param bufnr integer
 --- @return nil|string assigned
-function JumpMode.assign_next_letter(bufnr)
-  if JumpMode.letter_by_buffer[bufnr] ~= nil then
+function jump_mode.assign_next_letter(bufnr)
+  if jump_mode.letter_by_buffer[bufnr] ~= nil then
     return
   end
 
@@ -64,14 +64,14 @@ function JumpMode.assign_next_letter(bufnr)
     for i = 1, strwidth(name) do
       local letter = strcharpart(name, i - 1, 1):lower()
 
-      if JumpMode.index_by_letter[letter] ~= nil then
-        local index = JumpMode.index_by_letter[letter]
-        local status = JumpMode.letter_status[index]
+      if jump_mode.index_by_letter[letter] ~= nil then
+        local index = jump_mode.index_by_letter[letter]
+        local status = jump_mode.letter_status[index]
         if status == false then
-          JumpMode.letter_status[index] = true
+          jump_mode.letter_status[index] = true
           -- letter = m.letters[index]
-          JumpMode.buffer_by_letter[letter] = bufnr
-          JumpMode.letter_by_buffer[bufnr] = letter
+          jump_mode.buffer_by_letter[letter] = bufnr
+          jump_mode.letter_by_buffer[bufnr] = letter
           return letter
         end
       end
@@ -79,12 +79,12 @@ function JumpMode.assign_next_letter(bufnr)
   end
 
   -- Otherwise, assign a letter by usable order
-  for i, status in ipairs(JumpMode.letter_status) do
+  for i, status in ipairs(jump_mode.letter_status) do
     if status == false then
       local letter = letters[i]
-      JumpMode.letter_status[i] = true
-      JumpMode.buffer_by_letter[letter] = bufnr
-      JumpMode.letter_by_buffer[bufnr] = letter
+      jump_mode.letter_status[i] = true
+      jump_mode.buffer_by_letter[letter] = bufnr
+      jump_mode.letter_by_buffer[bufnr] = letter
       return letter
     end
   end
@@ -92,35 +92,35 @@ end
 
 --- @param bufnr integer
 --- @return string letter assiegned to `bufnr`
-function JumpMode.get_letter(bufnr)
-  return JumpMode.letter_by_buffer[bufnr] or JumpMode.assign_next_letter(bufnr)
+function jump_mode.get_letter(bufnr)
+  return jump_mode.letter_by_buffer[bufnr] or jump_mode.assign_next_letter(bufnr)
 end
 
 --- @param letter string
 --- @return nil
-function JumpMode.unassign_letter(letter)
+function jump_mode.unassign_letter(letter)
   if letter == '' or letter == nil then
     return
   end
 
-  local index = JumpMode.index_by_letter[letter]
+  local index = jump_mode.index_by_letter[letter]
 
-  JumpMode.letter_status[index] = false
+  jump_mode.letter_status[index] = false
 
-  if JumpMode.buffer_by_letter[letter] ~= nil then
-    local bufnr = JumpMode.buffer_by_letter[letter]
-    JumpMode.buffer_by_letter[letter] = nil
-    JumpMode.letter_by_buffer[bufnr] = nil
+  if jump_mode.buffer_by_letter[letter] ~= nil then
+    local bufnr = jump_mode.buffer_by_letter[letter]
+    jump_mode.buffer_by_letter[letter] = nil
+    jump_mode.letter_by_buffer[bufnr] = nil
   end
 
-  JumpMode.reinitialize = true
+  jump_mode.reinitialize = true
 end
 
 --- Unassign the letter which is assigned to `bufnr.`
 --- @param bufnr integer
 --- @return nil
-function JumpMode.unassign_letter_for(bufnr)
-  JumpMode.unassign_letter(JumpMode.letter_by_buffer[bufnr])
+function jump_mode.unassign_letter_for(bufnr)
+  jump_mode.unassign_letter(jump_mode.letter_by_buffer[bufnr])
 end
 
-return JumpMode
+return jump_mode
diff --git a/lua/barbar/state.lua b/lua/barbar/state.lua
index 404e21d2..bc4ae752 100644
--- a/lua/barbar/state.lua
+++ b/lua/barbar/state.lua
@@ -20,9 +20,10 @@ local tbl_contains = vim.tbl_contains
 local tbl_filter = vim.tbl_filter
 local tbl_map = vim.tbl_map
 
-local Buffer = require'barbar.buffer'
-local config = require'barbar.config'
-local utils = require'barbar.utils'
+local buffer = require('barbar.buffer')
+local config = require('barbar.config')
+local fs = require('barbar.fs')
+local utils = require('barbar.utils')
 
 local CACHE_PATH = vim.fn.stdpath('cache') .. '/barbar.json'
 
@@ -48,7 +49,7 @@ local CACHE_PATH = vim.fn.stdpath('cache') .. '/barbar.json'
 --- @field left barbar.state.offset.side
 --- @field right barbar.state.offset.side
 
---- @class barbar.state
+--- @class barbar.State
 --- @field buffers integer[] the open buffers, in visual order.
 --- @field data_by_bufnr {[integer]: barbar.state.data} the buffer data indexed on buffer number
 --- @field is_picking_buffer boolean whether the user is currently in jump-mode
@@ -98,7 +99,7 @@ function state.get_buffer_list()
       not tbl_contains(exclude_ft, buf_get_option(bufnr, 'filetype'))
     then
       local name = buf_get_name(bufnr)
-      if not tbl_contains(exclude_name, utils.basename(name, hide_extensions)) then
+      if not tbl_contains(exclude_name, fs.basename(name, hide_extensions)) then
         table_insert(result, bufnr)
       end
     end
@@ -196,7 +197,7 @@ function state.update_names()
 
   -- Compute names
   for i, buffer_n in ipairs(state.buffers) do
-    local name = Buffer.get_name(buffer_n, hide_extensions)
+    local name = buffer.get_name(buffer_n, hide_extensions)
 
     if buffer_index_by_name[name] == nil then
       buffer_index_by_name[name] = i
@@ -205,7 +206,7 @@ function state.update_names()
       local other_i = buffer_index_by_name[name]
       local other_n = state.buffers[other_i]
       local new_name, new_other_name =
-        Buffer.get_unique_name(
+        buffer.get_unique_name(
           buf_get_name(buffer_n),
           buf_get_name(state.buffers[other_i]))
 
@@ -230,7 +231,7 @@ function state.set_offset(width, text, hl)
     utils.markdown_inline_code'barbar.api.set_offset'
   )
 
-  require'barbar.api'.set_offset(width, text, hl)
+  require('barbar.api').set_offset(width, text, hl)
 end
 
 --- Restore the buffers
@@ -269,50 +270,18 @@ end
 --- Save recently_closed list
 --- @return nil
 function state.save_recently_closed()
-  local file, open_err = io.open(CACHE_PATH, 'w')
-  if open_err ~= nil then
-    return utils.notify(open_err, vim.log.levels.ERROR)
-  elseif file == nil then
-    return utils.notify('Could not open ' .. CACHE_PATH, vim.log.levels.ERROR)
-  end
-  do
-    local _, write_err = file:write(json_encode({
-      recently_closed = state.recently_closed,
-    }))
-    if write_err ~= nil then
-      return utils.notify(write_err, vim.log.levels.ERROR)
-    end
-  end
-  local success, close_err = file:close()
-  if close_err ~= nil then
-    return utils.notify(close_err, vim.log.levels.ERROR)
-  elseif success == false then
-    return utils.notify('Could not close ' .. CACHE_PATH, vim.log.levels.ERROR)
+  local err_msg = fs.write(CACHE_PATH, json_encode({ recently_closed = state.recently_closed }))
+  if err_msg then
+    utils.notify(err_msg, vim.log.levels.WARN)
   end
 end
 
 --- Save recently_closed list
 --- @return nil
 function state.load_recently_closed()
-  local file, open_err = io.open(CACHE_PATH, 'r')
-
-  -- Ignore if the file doesn't exist or isn't readable
-  if open_err ~= nil then
-    return
-  elseif file == nil then
-    return
-  end
-
-  local content, read_err = file:read('*a')
-  if read_err ~= nil then
-    return utils.notify(read_err, vim.log.levels.ERROR)
-  end
-
-  local success, close_err = file:close()
-  if close_err ~= nil then
-    return
-  elseif success == false then
-    return
+  local err_msg, content = fs.read(CACHE_PATH)
+  if err_msg then
+    utils.notify(err_msg, vim.log.levels.WARN)
   end
 
   local ok, result = pcall(json_decode, content, {luanil = {array = true, object = true}})
diff --git a/lua/barbar/types.lua b/lua/barbar/types.lua
new file mode 100644
index 00000000..c3534fcd
--- /dev/null
+++ b/lua/barbar/types.lua
@@ -0,0 +1,3 @@
+--- @meta
+
+--- @alias side 'left'|'right'
diff --git a/lua/barbar/ui/layout.lua b/lua/barbar/ui/layout.lua
index c05af191..e97637c7 100644
--- a/lua/barbar/ui/layout.lua
+++ b/lua/barbar/ui/layout.lua
@@ -12,10 +12,10 @@ local get_option = vim.api.nvim_get_option --- @type function
 local strwidth = vim.api.nvim_strwidth --- @type function
 local tabpagenr = vim.fn.tabpagenr --- @type function
 
-local Buffer = require'barbar.buffer'
-local config = require'barbar.config'
-local icons = require'barbar.icons'
-local state = require'barbar.state'
+local buffer = require('barbar.buffer')
+local config = require('barbar.config')
+local get_icon = require('barbar.icons').get_icon
+local state = require('barbar.state')
 
 --- The number of sides of each buffer in the tabline.
 local SIDES_OF_BUFFER = 2
@@ -49,23 +49,21 @@ local SPACE_LEN = #' '
 --- @class barbar.ui.layout.data.tabpages
 --- @field width integer the amount of space allocated to the tabpage indicator
 
-
---- @class barbar.ui.layout
+--- @class barbar.ui.Layout
 --- @field buffers integer[] different from `state.buffers` in that the `hide` option is respected. Only updated when calling `calculate_buffers_width`.
-local Layout = { buffers = {} }
+local layout = { buffers = {} }
 
 --- Calculate the current layout of the bufferline.
 --- @return barbar.ui.layout.data
-function Layout.calculate()
-
+function layout.calculate()
   local total_width = get_option('columns')
 
   local left_width  = state.offset.left.width
   local right_width = state.offset.right.width
-  local tabpages_width = Layout.calculate_tabpages_width()
+  local tabpages_width = layout.calculate_tabpages_width()
   local buffers_width = total_width - state.offset.left.width - state.offset.right.width - tabpages_width
 
-  local pinned_count, pinned_sum, unpinned_sum, widths = Layout.calculate_buffers_width()
+  local pinned_count, pinned_sum, unpinned_sum, widths = layout.calculate_buffers_width()
   local pinned_width = pinned_sum + (pinned_count * config.options.minimum_padding * SIDES_OF_BUFFER)
 
   local unpinned_allocated_width = buffers_width - pinned_width
@@ -113,22 +111,20 @@ end
 --- @param bufnr integer the buffer to calculate the width of
 --- @param index integer the buffer's numerical index
 --- @return integer width
-function Layout.calculate_buffer_width(bufnr, index)
+function layout.calculate_buffer_width(bufnr, index)
   local buffer_data = state.get_buffer_data(bufnr)
   if buffer_data.closing then
     return buffer_data.width or buffer_data.computed_width or 0
   end
 
-  local buffer_activity = Buffer.activities[Buffer.get_activity(bufnr)]
-  local buffer_name = buffer_data.name or '[no name]'
-
-  local icons_option = Buffer.get_icons(buffer_activity, buf_get_option(bufnr, 'modified'), buffer_data.pinned)
+  local buffer_activity = buffer.activities[buffer.get_activity(bufnr)]
+  local icons_option = buffer.get_icons(buffer_activity, buf_get_option(bufnr, 'modified'), buffer_data.pinned)
 
   local width = strwidth(icons_option.separator.left)
 
   local filename_enabled = icons_option.filename
   if filename_enabled then
-    width = width + strwidth(buffer_name)
+    width = width + strwidth(buffer_data.name or '[no name]')
   end
 
   if icons_option.buffer_index then
@@ -140,7 +136,7 @@ function Layout.calculate_buffer_width(bufnr, index)
   end
 
   if icons_option.filetype.enabled then
-    local file_icon = icons.get_icon(bufnr, buffer_activity)
+    local file_icon = get_icon(bufnr, buffer_activity)
     width = width + strwidth(file_icon)
 
     if filename_enabled then
@@ -148,7 +144,7 @@ function Layout.calculate_buffer_width(bufnr, index)
     end
   end
 
-  Buffer.for_each_counted_enabled_diagnostic(bufnr, icons_option.diagnostics, function(count, _, option)
+  buffer.for_each_counted_enabled_diagnostic(bufnr, icons_option.diagnostics, function(count, _, option)
     width = width + SPACE_LEN + strwidth(option.icon) + #tostring(count)
   end)
 
@@ -161,25 +157,25 @@ function Layout.calculate_buffer_width(bufnr, index)
 end
 
 --- @return {[integer]: integer} position_by_bufnr
-function Layout.calculate_buffers_position_by_buffer_number()
-  local layout = Layout.calculate()
+function layout.calculate_buffers_position_by_buffer_number()
+  local data = layout.calculate()
   local positions = {}
 
   local pinned_position = 0
-  local unpinned_position = layout.buffers.pinned_width
+  local unpinned_position = data.buffers.pinned_width
 
-  for i, buffer_number in ipairs(Layout.buffers) do
+  for i, buffer_number in ipairs(layout.buffers) do
     if state.is_pinned(buffer_number) then
       positions[buffer_number] = pinned_position
-      pinned_position = pinned_position + Layout.calculate_width(
-        layout.buffers.base_widths[i],
+      pinned_position = pinned_position + layout.calculate_width(
+        data.buffers.base_widths[i],
         config.options.minimum_padding
       )
     else
       positions[buffer_number] = unpinned_position
-      unpinned_position = unpinned_position + Layout.calculate_width(
-        layout.buffers.base_widths[i],
-        layout.buffers.padding
+      unpinned_position = unpinned_position + layout.calculate_width(
+        data.buffers.base_widths[i],
+        data.buffers.padding
       )
     end
   end
@@ -189,16 +185,16 @@ end
 
 --- Calculate the width of the buffers
 --- @return integer pinned_count, integer pinned_sum, integer unpinned_sum, integer[] widths
-function Layout.calculate_buffers_width()
-  Layout.buffers = Buffer.hide(state.buffers)
+function layout.calculate_buffers_width()
+  layout.buffers = buffer.hide(state.buffers)
 
   local pinned_count = 0
   local pinned_sum = 0
   local unpinned_sum = 0
   local widths = {}
 
-  for i, bufnr in ipairs(Layout.buffers) do
-    local width = Layout.calculate_buffer_width(bufnr, i)
+  for i, bufnr in ipairs(layout.buffers) do
+    local width = layout.calculate_buffer_width(bufnr, i)
     if state.is_pinned(bufnr) then
       pinned_count = pinned_count + 1
       pinned_sum = pinned_sum + width
@@ -214,7 +210,7 @@ end
 
 --- The number of characters needed to represent the tabpages.
 --- @return integer width
-function Layout.calculate_tabpages_width()
+function layout.calculate_tabpages_width()
   if not config.options.tabpages then
     return 0
   end
@@ -231,8 +227,8 @@ end
 --- @param base_width integer
 --- @param padding_width integer
 --- @return integer width
-function Layout.calculate_width(base_width, padding_width)
+function layout.calculate_width(base_width, padding_width)
   return base_width + (padding_width * SIDES_OF_BUFFER)
 end
 
-return Layout
+return layout
diff --git a/lua/barbar/ui/nodes.lua b/lua/barbar/ui/nodes.lua
index ca1ab3af..fb2f0ad5 100644
--- a/lua/barbar/ui/nodes.lua
+++ b/lua/barbar/ui/nodes.lua
@@ -1,34 +1,34 @@
 --
--- nodes.lua
+-- node_list.lua
 --
 
 local table_insert = table.insert
 local strcharpart = vim.fn.strcharpart --- @type function
 local strwidth = vim.api.nvim_strwidth --- @type function
 
---- @class barbar.ui.Nodes
---- @see barbar.ui.node
 --- Operations on `node`s.
-local Nodes = {}
+--- @see barbar.ui.node
+--- @class barbar.ui.Nodes
+local nodes = {}
 
---- Sums the width of the nodes
---- @param nodes barbar.ui.node[]
+--- Sums the width of the node_list
+--- @param node_list barbar.ui.node[]
 --- @return integer
-function Nodes.width(nodes)
+function nodes.width(node_list)
   local result = 0
-  for _, node in ipairs(nodes) do
+  for _, node in ipairs(node_list) do
     result = result + strwidth(node.text)
   end
   return result
 end
 
---- Concatenates some `nodes` into a valid tabline string.
---- @param nodes barbar.ui.node[]
+--- Concatenates some `node_list` into a valid tabline string.
+--- @param node_list barbar.ui.node[]
 --- @return string
-function Nodes.to_string(nodes)
+function nodes.to_string(node_list)
   local result = ''
 
-  for _, node in ipairs(nodes) do
+  for _, node in ipairs(node_list) do
     -- NOTE: We have to escape the text in case it contains '%', which is a special character to the
     --       tabline.
     --       To escape '%', we make it '%%'. It just so happens that '%' is also a special character
@@ -39,46 +39,46 @@ function Nodes.to_string(nodes)
   return result
 end
 
---- Concatenates some `nodes` into a raw string.
---- @param nodes barbar.ui.node[]
+--- Concatenates some `node_list` into a raw string.
+--- @param node_list barbar.ui.node[]
 --- For debugging purposes.
 --- @return string
-function Nodes.to_raw_string(nodes)
+function nodes.to_raw_string(node_list)
   local result = ''
 
-  for _, node in ipairs(nodes) do
+  for _, node in ipairs(node_list) do
     result = result .. node.text
   end
 
   return result
 end
 
---- Insert `other` into `nodes` at the `position`.
---- @param nodes barbar.ui.node[]
+--- Insert `other` into `node_list` at the `position`.
+--- @param node_list barbar.ui.node[]
 --- @param position integer
 --- @return barbar.ui.node[] with_insertions
-function Nodes.insert(nodes, position, node)
-  return Nodes.insert_many(nodes, position, { node })
+function nodes.insert(node_list, position, node)
+  return nodes.insert_many(node_list, position, { node })
 end
 
---- Insert `others` into `nodes` at the `position`.
---- @param nodes barbar.ui.node[]
+--- Insert `others` into `node_list` at the `position`.
+--- @param node_list barbar.ui.node[]
 --- @param position integer
 --- @param others barbar.ui.node[]
 --- @return barbar.ui.node[] with_insertions
-function Nodes.insert_many(nodes, position, others)
+function nodes.insert_many(node_list, position, others)
   if position < 0 then
-    local others_width = Nodes.width(others)
+    local others_width = nodes.width(others)
     local others_end = position + others_width
 
     if others_end < 0 then
-      return nodes
+      return node_list
     end
 
     local available_width = others_end
 
     position = 0
-    others = Nodes.slice_left(others, available_width)
+    others = nodes.slice_left(others, available_width)
   end
 
 
@@ -87,8 +87,8 @@ function Nodes.insert_many(nodes, position, others)
   local new_nodes = {}
 
   local i = 1
-  while i <= #nodes do
-    local node = nodes[i]
+  while i <= #node_list do
+    local node = node_list[i]
     local node_width = strwidth(node.text)
 
     -- While we haven't found the position...
@@ -109,7 +109,7 @@ function Nodes.insert_many(nodes, position, others)
         })
       end
 
-      -- Add new other nodes
+      -- Add new other node_list
       local others_width = 0
       for _, other in ipairs(others) do
         local other_width = strwidth(other.text)
@@ -119,10 +119,10 @@ function Nodes.insert_many(nodes, position, others)
 
       local end_position = position + others_width
 
-      -- Then, resume adding previous nodes
+      -- Then, resume adding previous node_list
       -- table.insert(new_nodes, 'then')
-      while i <= #nodes do
-        local previous_node = nodes[i]
+      while i <= #node_list do
+        local previous_node = node_list[i]
         local previous_node_width = strwidth(previous_node.text)
         local previous_node_start_position = current_position
         local previous_node_end_position   = current_position + previous_node_width
@@ -150,15 +150,15 @@ function Nodes.insert_many(nodes, position, others)
   return new_nodes
 end
 
---- Select from `nodes` while fitting within the provided `width`, discarding all indices larger than the last index that fits.
+--- Select from `node_list` while fitting within the provided `width`, discarding all indices larger than the last index that fits.
 --- @param width integer
 --- @return barbar.ui.node[] sliced
-function Nodes.slice_right(nodes, width)
+function nodes.slice_right(node_list, width)
   local accumulated_width = 0
 
   local new_nodes = {}
 
-  for _, node in ipairs(nodes) do
+  for _, node in ipairs(node_list) do
     local text_width = strwidth(node.text)
     accumulated_width = accumulated_width + text_width
 
@@ -174,17 +174,17 @@ function Nodes.slice_right(nodes, width)
   return new_nodes
 end
 
---- Select from `nodes` in reverse while fitting within the provided `width`, discarding all indices less than the last index that fits.
---- @param nodes barbar.ui.node[]
+--- Select from `node_list` in reverse while fitting within the provided `width`, discarding all indices less than the last index that fits.
+--- @param node_list barbar.ui.node[]
 --- @param width integer
 --- @return barbar.ui.node[] sliced
-function Nodes.slice_left(nodes, width)
+function nodes.slice_left(node_list, width)
   local accumulated_width = 0
 
   local new_nodes = {}
 
-  for i = #nodes, 1, -1 do
-    local node = nodes[i] --- @type barbar.ui.node (it cannot be `nil`)
+  for i = #node_list, 1, -1 do
+    local node = node_list[i] --- @type barbar.ui.node (it cannot be `nil`)
     local text_width = strwidth(node.text)
     accumulated_width = accumulated_width + text_width
 
@@ -201,4 +201,4 @@ function Nodes.slice_left(nodes, width)
   return new_nodes
 end
 
-return Nodes
+return nodes
diff --git a/lua/barbar/ui/render.lua b/lua/barbar/ui/render.lua
index fd32fe74..e0bd41ae 100644
--- a/lua/barbar/ui/render.lua
+++ b/lua/barbar/ui/render.lua
@@ -5,6 +5,7 @@
 local max = math.max
 local min = math.min
 local table_insert = table.insert
+local table_remove = table.remove
 
 local buf_get_option = vim.api.nvim_buf_get_option --- @type function
 local buf_is_valid = vim.api.nvim_buf_is_valid --- @type function
@@ -26,16 +27,17 @@ local tbl_contains = vim.tbl_contains
 local tbl_filter = vim.tbl_filter
 local win_get_buf = vim.api.nvim_win_get_buf --- @type function
 
-local animate = require'barbar.animate'
-local Buffer = require'barbar.buffer'
-local config = require'barbar.config'
--- local fs = require'barbar.fs' -- For debugging purposes
-local Nodes = require'barbar.ui.nodes'
-local icons = require'barbar.icons'
-local JumpMode = require'barbar.jump_mode'
-local Layout = require'barbar.ui.layout'
-local state = require'barbar.state'
-local utils = require'barbar.utils'
+local animate = require('barbar.animate')
+local buffer = require('barbar.buffer')
+local config = require('barbar.config')
+-- local fs = require('barbar.fs') -- For debugging purposes
+local get_icon = require('barbar.icons').get_icon
+local get_letter = require('barbar.jump_mode').get_letter
+local index_of = require('barbar.utils.list').index_of
+local layout = require('barbar.ui.layout')
+local nodes = require('barbar.ui.nodes')
+local notify = require('barbar.utils').notify
+local state = require('barbar.state')
 
 --- Last value for tabline
 --- @type string
@@ -65,7 +67,7 @@ local ANIMATION = {
 --- @field target integer the place where the bufferline is scrolled/wants to scroll to.
 local scroll = { current = 0, target = 0 }
 
---- @class barbar.ui.render
+--- @class barbar.ui.Render
 local render = {}
 
 --- An incremental animation for `close_buffer_animated`.
@@ -127,15 +129,15 @@ end
 
 --- Opens a buffer with animation.
 --- @param bufnr integer
---- @param layout barbar.ui.layout.data
+--- @param data barbar.ui.layout.data
 --- @return nil
-local function open_buffer_start_animation(layout, bufnr)
+local function open_buffer_start_animation(data, bufnr)
   local buffer_data = state.get_buffer_data(bufnr)
-  local index = utils.index_of(Layout.buffers, bufnr)
+  local index = index_of(layout.buffers, bufnr)
 
-  buffer_data.computed_width = Layout.calculate_width(
-    layout.buffers.base_widths[index] or Layout.calculate_buffer_width(bufnr, #Layout.buffers + 1),
-    layout.buffers.padding
+  buffer_data.computed_width = layout.calculate_width(
+    data.buffers.base_widths[index] or layout.calculate_buffer_width(bufnr, #layout.buffers + 1),
+    data.buffers.padding
   )
 
   local target_width = buffer_data.computed_width or 0
@@ -158,7 +160,7 @@ local function open_buffers(new_buffers)
 
   -- Open next to the currently opened tab
   -- Find the new index where the tab will be inserted
-  local new_index = utils.index_of(state.buffers, state.last_current_buffer)
+  local new_index = index_of(state.buffers, state.last_current_buffer)
   if new_index ~= nil then
     new_index = new_index + 1
   else
@@ -169,7 +171,7 @@ local function open_buffers(new_buffers)
 
   -- Insert the buffers where they go
   for _, new_buffer in ipairs(new_buffers) do
-    if utils.index_of(state.buffers, new_buffer) == nil then
+    if index_of(state.buffers, new_buffer) == nil then
       local actual_index = new_index
 
       local should_insert_at_end = config.options.insert_at_end or
@@ -208,10 +210,10 @@ local function open_buffers(new_buffers)
   -- Update names because they affect the layout
   state.update_names()
 
-  local layout = Layout.calculate()
+  local data = layout.calculate()
 
   for _, buffer_number in ipairs(new_buffers) do
-    open_buffer_start_animation(layout, buffer_number)
+    open_buffer_start_animation(data, buffer_number)
   end
 end
 
@@ -303,6 +305,7 @@ local function set_scroll_tick(new_scroll, animation)
   if animation.running == false then
     scroll_animation = nil
   end
+
   render.update(nil, false)
 end
 
@@ -330,7 +333,10 @@ end
 --- @param s? string
 --- @return nil
 function render.set_tabline(s)
-  s = s or ''
+  if s == nil then
+    s = ''
+  end
+
   if last_tabline ~= s then
     last_tabline = s
     set_option('tabline', s)
@@ -339,54 +345,54 @@ function render.set_tabline(s)
 end
 
 --- Compute the buffer hl-groups
---- @param layout barbar.ui.layout.data
+--- @param data barbar.ui.layout.data
 --- @param bufnrs integer[]
 --- @param refocus? boolean
---- @return barbar.ui.container[] pinned_groups, barbar.ui.container[] clumps
-local function get_bufferline_containers(layout, bufnrs, refocus)
+--- @return barbar.ui.container[] pinend, barbar.ui.container[] unpinned, nil|{[1]: integer, pinned: boolean} current_buffer_index
+local function get_bufferline_containers(data, bufnrs, refocus)
   local click_enabled = has('tablineat') and config.options.clickable
 
   local accumulated_pinned_width = 0 --- the width of pinned buffers accumulated while iterating
   local accumulated_unpinned_width = 0 --- the width of buffers accumulated while iterating
-  local current_buffer_index = nil --- @type nil|integer
+  local current_buffer_index = nil --- @type nil|{[1]: integer, pinned: boolean}
   local done = false --- if all of the visible buffers have been clumped
   local containers = {} --- @type barbar.ui.container[]
   local pinned_containers = {} --- @type barbar.ui.container[]
 
   local pinned_pad_text   = (' '):rep(config.options.minimum_padding)
-  local unpinned_pad_text = (' '):rep(layout.buffers.padding)
+  local unpinned_pad_text = (' '):rep(data.buffers.padding)
 
   for i, bufnr in ipairs(bufnrs) do
-    local activity = Buffer.get_activity(bufnr)
-    local activity_name = Buffer.activities[activity]
+    local activity = buffer.get_activity(bufnr)
+    local activity_name = buffer.activities[activity]
     local buffer_data = state.get_buffer_data(bufnr)
     local modified = buf_get_option(bufnr, 'modified')
     local pinned = buffer_data.pinned
 
     if pinned then
       buffer_data.computed_position = accumulated_pinned_width
-      buffer_data.computed_width    = Layout.calculate_width(layout.buffers.base_widths[i], config.options.minimum_padding)
+      buffer_data.computed_width    = layout.calculate_width(data.buffers.base_widths[i], config.options.minimum_padding)
     else
-      buffer_data.computed_position = accumulated_unpinned_width + layout.buffers.pinned_width
-      buffer_data.computed_width    = Layout.calculate_width(layout.buffers.base_widths[i], layout.buffers.padding)
+      buffer_data.computed_position = accumulated_unpinned_width + data.buffers.pinned_width
+      buffer_data.computed_width    = layout.calculate_width(data.buffers.base_widths[i], data.buffers.padding)
     end
 
     local container_width = buffer_data.width or buffer_data.computed_width
 
-    if activity == Buffer.activities.Current and refocus ~= false then
-      current_buffer_index = i
+    if activity == buffer.activities.Current and refocus ~= false then
+      current_buffer_index = {i, pinned = pinned}
 
       local start = accumulated_unpinned_width
       local end_  = accumulated_unpinned_width + container_width
 
       if scroll.target > start then
         render.set_scroll(start)
-      elseif scroll.target + layout.buffers.unpinned_allocated_width < end_ then
-        render.set_scroll(scroll.target + (end_ - (scroll.target + layout.buffers.unpinned_allocated_width)))
+      elseif scroll.target + data.buffers.unpinned_allocated_width < end_ then
+        render.set_scroll(scroll.target + (end_ - (scroll.target + data.buffers.unpinned_allocated_width)))
       end
     end
 
-    local scroll_current = min(scroll.current, layout.buffers.scroll_max)
+    local scroll_current = min(scroll.current, data.buffers.scroll_max)
 
     if pinned then
       accumulated_pinned_width = accumulated_pinned_width + container_width
@@ -396,7 +402,7 @@ local function get_bufferline_containers(layout, bufnrs, refocus)
       if accumulated_unpinned_width < scroll_current  then
         goto continue -- HACK: there is no `continue` keyword
       elseif (refocus == false or (refocus ~= false and current_buffer_index ~= nil)) and
-        accumulated_unpinned_width - scroll_current > layout.buffers.unpinned_allocated_width
+        accumulated_unpinned_width - scroll_current > data.buffers.unpinned_allocated_width
       then
         done = true
       end
@@ -405,7 +411,7 @@ local function get_bufferline_containers(layout, bufnrs, refocus)
     local buffer_name = buffer_data.name or '[no name]'
     local buffer_hl = wrap_hl('Buffer' .. activity_name .. (modified and 'Mod' or ''))
 
-    local icons_option = Buffer.get_icons(activity_name, modified, pinned)
+    local icons_option = buffer.get_icons(activity_name, modified, pinned)
 
     --- Prefix this value to allow an element to be clicked
     local clickable = click_enabled and ('%' .. bufnr .. '@barbar#events#main_click_handler@') or ''
@@ -452,7 +458,7 @@ local function get_bufferline_containers(layout, bufnrs, refocus)
     local icon = { hl = clickable, text = '' }
 
     if state.is_picking_buffer then
-      local letter = JumpMode.get_letter(bufnr)
+      local letter = get_letter(bufnr)
 
       -- Replace first character of buf name with jump letter
       if letter and not icons_option.filetype.enabled then
@@ -469,7 +475,7 @@ local function get_bufferline_containers(layout, bufnrs, refocus)
         jump_letter.text = '  '
       end
     elseif icons_option.filetype.enabled then
-      local iconChar, iconHl = icons.get_icon(bufnr, activity_name)
+      local iconChar, iconHl = get_icon(bufnr, activity_name)
       local hlName = (activity_name == 'Inactive' and not config.options.highlight_inactive_file_icons)
         and 'BufferInactive'
         or iconHl
@@ -489,7 +495,6 @@ local function get_bufferline_containers(layout, bufnrs, refocus)
     local padding = { hl = buffer_hl, text = pinned and pinned_pad_text or unpinned_pad_text }
 
     local container = { --- @type barbar.ui.container
-      activity = activity,
       nodes = { left_separator, padding, buffer_index, buffer_number, icon, jump_letter, name },
       --- @diagnostic disable-next-line:assign-type-mismatch it is assigned just earlier
       position = buffer_data.position or buffer_data.computed_position,
@@ -497,7 +502,7 @@ local function get_bufferline_containers(layout, bufnrs, refocus)
       width = container_width,
     }
 
-    Buffer.for_each_counted_enabled_diagnostic(bufnr, icons_option.diagnostics, function(count, idx, option)
+    buffer.for_each_counted_enabled_diagnostic(bufnr, icons_option.diagnostics, function(count, idx, option)
       table_insert(container.nodes, {
         hl = wrap_hl('Buffer' .. activity_name .. severity[idx]),
         text = ' ' .. option.icon .. count,
@@ -517,7 +522,7 @@ local function get_bufferline_containers(layout, bufnrs, refocus)
     ::continue::
   end
 
-  return pinned_containers, containers
+  return pinned_containers, containers, current_buffer_index
 end
 
 local HL = {
@@ -532,8 +537,8 @@ local HL = {
 --- @param refocus? boolean if `true`, the bufferline will be refocused on the current buffer (default: `true`)
 --- @return nil|string syntax
 local function generate_tabline(bufnrs, refocus)
-  local layout = Layout.calculate()
-  local pinned_containers, containers = get_bufferline_containers(layout, bufnrs, refocus)
+  local data = layout.calculate()
+  local pinned, unpinned, current_buffer_index = get_bufferline_containers(data, bufnrs, refocus)
 
   -- Create actual tabline string
   local result = ''
@@ -546,102 +551,89 @@ local function generate_tabline(bufnrs, refocus)
     local content = { { hl = hl, text = state.offset.left.text } }
     local content_max_width = state.offset.left.width - 2
 
-    offset_nodes =
-      Nodes.insert_many(
-        offset_nodes,
-        1,
-        Nodes.slice_right(content, content_max_width))
-
-    result = result .. Nodes.to_string(offset_nodes)
+    offset_nodes = nodes.insert_many(offset_nodes, 1, nodes.slice_right(content, content_max_width))
+    result = result .. nodes.to_string(offset_nodes)
   end
 
   -- Buffer tabs
   do
     --- @type barbar.ui.container
-    local content = { { hl = HL.FILL, text = (' '):rep(layout.buffers.width) } }
+    local content = { { hl = HL.FILL, text = (' '):rep(data.buffers.width) } }
 
     do
-      local current_container = nil
-      for _, container in ipairs(containers) do
-        -- We insert the current buffer after the others so it's always on top
-        if container.activity ~= Buffer.activities.Current then
-          content = Nodes.insert_many(
-            content,
-            container.position - scroll.current,
-            container.nodes)
-        else
-          current_container = container
-        end
+      local current_container
+      if current_buffer_index ~= nil and current_buffer_index.pinned == false then
+        current_container = table_remove(unpinned, current_buffer_index[1])
+      end
+
+      for _, container in ipairs(unpinned) do
+        content = nodes.insert_many(content, container.position - scroll.current, container.nodes)
       end
 
       if current_container ~= nil then
-        local container = current_container
-        content = Nodes.insert_many(
-          content,
-          container.position - scroll.current,
-          container.nodes)
+        content = nodes.insert_many(content, current_container.position - scroll.current, current_container.nodes)
       end
     end
 
     do
       local inactive_separator = config.options.icons.inactive.separator.left
-      if inactive_separator ~= nil and #containers > 0 and
-        layout.buffers.unpinned_width + strwidth(inactive_separator) <= layout.buffers.unpinned_allocated_width
+      if inactive_separator ~= nil and #unpinned > 0 and
+        data.buffers.unpinned_width + strwidth(inactive_separator) <= data.buffers.unpinned_allocated_width
       then
-        content = Nodes.insert(
-          content,
-          layout.buffers.used_width,
-          { text = inactive_separator, hl = HL.SIGN_INACTIVE })
+        content = nodes.insert(content, data.buffers.used_width, { text = inactive_separator, hl = HL.SIGN_INACTIVE })
       end
     end
 
-    if #pinned_containers > 0 then
-      local current_container = nil
-      for _, container in ipairs(pinned_containers) do
-        if container.activity ~= Buffer.activities.Current then
-          content = Nodes.insert_many(content, container.position, container.nodes)
-        else
-          current_container = container
-        end
+    if #pinned > 0 then
+      local current_container
+      if current_buffer_index ~= nil and current_buffer_index.pinned == true then
+        current_container = table_remove(pinned, current_buffer_index[1])
       end
+
+      for _, container in ipairs(pinned) do
+        content = nodes.insert_many(content, container.position - scroll.current, container.nodes)
+      end
+
       if current_container ~= nil then
-        local container = current_container
-        content = Nodes.insert_many(content, container.position, container.nodes)
+        content = nodes.insert_many(content, current_container.position - scroll.current, current_container.nodes)
       end
     end
 
-    local filler = { { hl = HL.FILL, text = (' '):rep(layout.buffers.width) } }
-    content = Nodes.insert_many(filler, 0, content)
-    content = Nodes.slice_right(content, layout.buffers.width)
+    local filler = { { hl = HL.FILL, text = (' '):rep(data.buffers.width) } }
+    content = nodes.insert_many(filler, 0, content)
+    content = nodes.slice_right(content, data.buffers.width)
 
     local has_left_scroll = scroll.current > 0
     if has_left_scroll then
-      content = Nodes.insert(content, layout.buffers.pinned_width,
-        { hl = HL.SCROLL_ARROW, text = config.options.icons.scroll.left })
+      content = nodes.insert(content, data.buffers.pinned_width, {
+        hl = HL.SCROLL_ARROW,
+        text = config.options.icons.scroll.left,
+      })
     end
 
-    local has_right_scroll = layout.buffers.used_width - scroll.current > layout.buffers.width
+    local has_right_scroll = data.buffers.used_width - scroll.current > data.buffers.width
     if has_right_scroll then
-      content = Nodes.insert(content, layout.buffers.width - 1,
-        { hl = HL.SCROLL_ARROW, text = config.options.icons.scroll.right })
+      content = nodes.insert(content, data.buffers.width - 1, {
+        hl = HL.SCROLL_ARROW,
+        text = config.options.icons.scroll.right,
+      })
     end
 
     -- Render bufferline string
-    result = result .. Nodes.to_string(content)
+    result = result .. nodes.to_string(content)
 
-    -- Prevent the expansion of the last click node
+    -- Prevent the expansion of the last click group
     if config.options.clickable then
       result = result .. '%0@barbar#events#main_click_handler@'
     end
   end
 
   -- Tabpages
-  do
-    if layout.tabpages.width > 0 then
-      result = result .. Nodes.to_string({
-        { hl = HL.TABPAGES, text = ' ' .. tabpagenr() .. '/' .. tabpagenr('$') .. ' ', },
-      })
-    end
+  if data.tabpages.width > 0 then
+    result = result .. nodes.to_string({{
+      hl = HL.TABPAGES,
+      text = ' ' .. tabpagenr() .. '/' .. tabpagenr('$') .. ' ',
+    }})
   end
 
   -- Right offset
@@ -652,13 +644,9 @@ local function generate_tabline(bufnrs, refocus)
     local content = { { hl = hl, text = state.offset.right.text } }
     local content_max_width = state.offset.right.width - 2
 
-    offset_nodes =
-      Nodes.insert_many(
-        offset_nodes,
-        1,
-        Nodes.slice_right(content, content_max_width))
+    offset_nodes = nodes.insert_many(offset_nodes, 1, nodes.slice_right(content, content_max_width))
 
-    result = result .. Nodes.to_string(offset_nodes)
+    result = result .. nodes.to_string(offset_nodes)
   end
 
   -- NOTE: For development or debugging purposes, the following code can be used:
@@ -683,7 +671,7 @@ function render.update(update_names, refocus)
     return
   end
 
-  local buffers = Buffer.hide(render.get_updated_buffers(update_names))
+  local buffers = buffer.hide(render.get_updated_buffers(update_names))
 
   -- Auto hide/show if applicable
   if config.options.auto_hide then
@@ -717,7 +705,7 @@ function render.update(update_names, refocus)
 
   if not ok then
     command('BarbarDisable')
-    utils.notify(
+    notify(
       "Barbar detected an error while running. Barbar disabled itself :/ " ..
         "Include this in your report: " ..
         tostring(result),
diff --git a/lua/barbar/ui/types.lua b/lua/barbar/ui/types.lua
index bf88e3a3..bdaa51d9 100644
--- a/lua/barbar/ui/types.lua
+++ b/lua/barbar/ui/types.lua
@@ -5,7 +5,6 @@
 --- @field text string the content being rendered
 
 --- @class barbar.ui.container
---- @field activity barbar.buffer.activity
 --- @field nodes barbar.ui.node[]
 --- @field position integer
 --- @field width integer
diff --git a/lua/barbar/utils.lua b/lua/barbar/utils.lua
index fe8cde61..0df00ed5 100644
--- a/lua/barbar/utils.lua
+++ b/lua/barbar/utils.lua
@@ -2,345 +2,45 @@
 -- utils.lua
 --
 
-local table_insert = table.insert
-
-local fnamemodify = vim.fn.fnamemodify --- @type function
-local get_hl = vim.api.nvim_get_hl --- @type function
-local get_hl_by_name = vim.api.nvim_get_hl_by_name --- @type function
-local hlexists = vim.fn.hlexists --- @type function
-local list_slice = vim.list_slice
 local notify = vim.notify
 local notify_once = vim.notify_once
-local set_hl = vim.api.nvim_set_hl --- @type function
-local tbl_isempty = vim.tbl_isempty
-
---- @type {[string]: table}
-local hl_groups_cache = {}
 
---- Remove `tbl[key]` from `tbl` and return it
---- @param tbl table
---- @param key string
---- @return any
-local function tbl_remove_key (tbl, key)
-  local value = rawget(tbl, key)
-  rawset(tbl, key, nil)
-  return value
-end
+--- @class barbar.Utils
+local utils = {}
 
-local get_hl_util = get_hl and
-  --- @param name string
-  --- @return table
-  function(name) return get_hl(0, {link = false, name = name}) end or
+utils.deprecate = vim.deprecate and
+  --- Notify a user that something has been deprecated, and that there is an alternative.
   --- @param name string
-  --- @return table
-  function(name)
-    if hlexists(name) < 1 then
-      return {}
-    end
-
-    local definition = get_hl_by_name(name, true)
-    for original, new in pairs {background = 'bg', foreground = 'fg', special = 'sp'} do
-      local attribute_definition = tbl_remove_key(definition, original)
-      if attribute_definition then
-        definition[new] = attribute_definition
-      end
-    end
-
-    local cterm = get_hl_by_name(name, false)
-    definition.ctermfg = cterm.foreground
-    definition.ctermbg = cterm.background
-
-    return definition
-  end
-
---- @param group string the groups to source the color from.
---- @return table
-local function get_hl_cached(group)
-  local hl_cached = hl_groups_cache[group]
-  if hl_cached then
-    return hl_cached
-  end
-
-  local hl = get_hl_util(group)
-  hl_groups_cache[group] = hl
-  return hl
-end
-
---- Generate a color.
---- @param groups string[] the groups to source the color from.
---- @param attribute 'bg'|'ctermbg'|'ctermfg'|'fg'|'sp' where to look for the color.
---- @param default barbar.utils.hl.color.value a color name (`string`), GUI hex (`string`), or cterm color code (`integer`).
---- @return barbar.utils.hl.color.value color
-local function get_hl_color_or_default(groups, attribute, default)
-  for _, group in ipairs(groups) do
-    local hl_attribute = get_hl_cached(group)[attribute]
-    if hl_attribute then
-      return hl_attribute
-    end
+  --- @param alternative string
+  --- @return nil
+  function(name, alternative)
+    vim.deprecate(name, alternative, '2.0.0', 'barbar.nvim')
+  end or
+  function(name, alternative)
+    utils.notify_once(name .. ' is deprecated. Use ' .. alternative .. 'instead.', vim.log.levels.WARN)
   end
 
-  return default
+--- Return "\``s`\`"
+--- @param s string
+--- @return string inline_code
+function utils.markdown_inline_code(s)
+  return '`' .. s .. '`'
 end
 
---- Return the index of element `n` in `list.
---- @generic T
---- @param list T[]
---- @param t T
---- @return nil|integer index
-local function index_of(list, t)
-  for i, value in ipairs(list) do
-    if value == t then
-      return i
-    end
-  end
-  return nil
+--- Use `vim.notify` with a `msg` and log `level`. Integrates with `nvim-notify`.
+--- @param msg string
+--- @param level 0|1|2|3|4|5
+--- @return nil
+function utils.notify(msg, level)
+  notify(msg, level, {title = 'barbar.nvim'})
 end
 
 --- Use `vim.notify` with a `msg` and log `level`. Integrates with `nvim-notify`.
 --- @param msg string
 --- @param level 0|1|2|3|4|5
 --- @return nil
-local function notify_once_util(msg, level)
+function utils.notify_once(msg, level)
   notify_once(msg, level, {title = 'barbar.nvim'})
 end
 
---- @param path string
---- @return string relative_path
-local function relative(path)
-  return fnamemodify(path, ':~:.')
-end
-
---- @class barbar.utils
-local utils = {
-  --- @param path string
-  --- @param hide_extension? boolean if `true`, exclude the extension of the file in the basename
-  --- @return string basename
-  basename = function(path, hide_extension)
-    local modifier = ':t'
-
-    if hide_extension then
-      modifier = modifier .. ':r'
-    end
-
-    return fnamemodify(path, modifier)
-  end,
-
-  deprecate = vim.deprecate and
-    --- Notify a user that something has been deprecated, and that there is an alternative.
-    --- @param name string
-    --- @param alternative string
-    --- @return nil
-    function(name, alternative)
-      vim.deprecate(name, alternative, '2.0.0', 'barbar.nvim')
-    end or
-    function(name, alternative)
-      notify_once_util(name .. ' is deprecated. Use ' .. alternative .. 'instead.', vim.log.levels.WARN)
-    end,
-
-  --- utilities for working with highlight groups.
-  --- @class barbar.utils.hl
-  hl = {
-    --- @class barbar.utils.hl.attributes see |:h attr-list|
-    --- @field blend? integer 0–100
-    --- @field bold? boolean
-    --- @field default? boolean
-    --- @field italic? boolean
-    --- @field nocombine? boolean
-    --- @field reverse? boolean
-    --- @field standout? boolean
-    --- @field strikethrough? boolean
-    --- @field undercurl? boolean
-    --- @field underdashed? boolean
-    --- @field underdotted? boolean
-    --- @field underdouble? boolean
-    --- @field underline? boolean
-
-    --- @alias barbar.utils.hl.color.value integer|string
-
-    --- @class barbar.utils.hl.color
-    --- @field cterm barbar.utils.hl.color.value
-    --- @field gui barbar.utils.hl.color.value
-
-    --- Generate a color.
-    --- @param groups string[] the groups to source the color from.
-    --- @return nil|barbar.utils.hl.attributes
-    attributes = function(groups)
-      for _, group in ipairs(groups) do
-        local hl = get_hl_cached(group)
-        if not tbl_isempty(hl) then
-          return hl
-        end
-      end
-    end,
-
-    --- Generate a background color.
-    --- @param groups string[] the groups to source the background color from.
-    --- @param default barbar.utils.hl.color.value the background color to use if no `groups` have a valid background color.
-    --- @param default_cterm? barbar.utils.hl.color.value the color to use if no `groups` have a valid color and `termguicolors == false`.
-    --- @return barbar.utils.hl.color color
-    bg_or_default = function(groups, default, default_cterm)
-      return {
-        cterm = get_hl_color_or_default(groups, 'ctermbg', default_cterm or default),
-        gui = get_hl_color_or_default(groups, 'bg', default),
-      }
-    end,
-
-    --- Generate a foreground color.
-    --- @param groups string[] the groups to source the foreground color from.
-    --- @param default barbar.utils.hl.color.value the foreground color to use if no `groups` have a valid foreground color.
-    --- @param default_cterm? barbar.utils.hl.color.value the color to use if no `groups` have a valid color and `termguicolors == false`.
-    --- @return barbar.utils.hl.color color
-    fg_or_default = function(groups, default, default_cterm)
-      return {
-        cterm = get_hl_color_or_default(groups, 'ctermfg', default_cterm or default),
-        gui = get_hl_color_or_default(groups, 'fg', default),
-      }
-    end,
-
-    --- Reset the `nvim_get_hl` cache
-    reset_cache = function() hl_groups_cache = {} end,
-
-    --- Set some highlight `group`'s default definition with respect to `&termguicolors`
-    --- @param group string the name of the highlight group to set
-    --- @param bg barbar.utils.hl.color
-    --- @param fg barbar.utils.hl.color
-    --- @param sp? barbar.utils.hl.color.value
-    --- @param attributes? barbar.utils.hl.attributes whether the highlight group should be bolded
-    --- @return nil
-    set = function(group, bg, fg, sp, attributes)
-      if not attributes then
-        attributes = {}
-      end
-
-      attributes.bg = bg.gui
-      attributes.ctermbg = bg.cterm
-      attributes.ctermfg = fg.cterm
-      attributes.fg = fg.gui
-      attributes.sp = sp
-      attributes[vim.type_idx] = nil
-
-      set_hl(0, group, attributes)
-    end,
-
-    --- Set the default highlight `group_name` as a link to `link_name`
-    --- @param group_name string the name of the group to by-default be linked to `link_name`
-    --- @param link_name string the name of the group to by-default link `group_name` to
-    --- @return nil
-    set_default_link = function(group_name, link_name)
-      set_hl(0, group_name, {default = true, link = link_name})
-    end,
-
-    --- Generate a foreground color.
-    --- @param groups string[] the groups to source the foreground color from.
-    --- @param default string the foreground color to use if no `groups` have a valid foreground color.
-    --- @return barbar.utils.hl.color.value color
-    sp_or_default = function(groups, default)
-      return get_hl_color_or_default(groups, 'sp', default)
-    end,
-  },
-
-  index_of = index_of,
-
-  --- @param path string
-  --- @return boolean is_relative `true` if `path` is relative to the CWD
-  is_relative_path = function(path)
-    return relative(path) == path
-  end,
-
-  --- Reverse the order of elements in some `list`.
-  --- @generic T
-  --- @param list T[]
-  --- @return T[] reversed
-  list_reverse = function(list)
-    local reversed = {}
-    for i = #list, 1, -1 do
-      table_insert(reversed, list[i])
-    end
-    return reversed
-  end,
-
-  --- Run `vim.list_slice` on some `list`, `index`ed from the end of the list.
-  --- @generic T
-  --- @param list T[]
-  --- @param index_from_end number
-  --- @return T[] sliced
-  list_slice_from_end = function(list, index_from_end)
-    return list_slice(list, #list - index_from_end + 1)
-  end,
-
-  --- Return "\``s`\`"
-  --- @param s string
-  --- @return string inline_code
-  markdown_inline_code = function(s)
-    return '`' .. s .. '`'
-  end,
-
-  --- Use `vim.notify` with a `msg` and log `level`. Integrates with `nvim-notify`.
-  --- @param msg string
-  --- @param level 0|1|2|3|4|5
-  --- @return nil
-  notify = function(msg, level)
-    notify(msg, level, {title = 'barbar.nvim'})
-  end,
-
-  notify_once = notify_once_util,
-
-  relative = relative,
-
-  --- Set `fallback` as a secondary source of keys when indexing `tbl`. Example:
-  ---
-  --- ```lua
-  --- local fallback = {bar = true}
-  --- local tbl = {}
-  ---
-  --- print(tbl.bar) -- `nil`
-  --- setfallbacktable(tbl, fallback)
-  --- print(tbl.bar) -- `true`
-  ---
-  --- tbl.bar = false
-  --- print(tbl.bar, fallback.bar) -- `false`, `true`
-  --- ```
-  ---
-  --- WARN: this mutates `tbl`!
-  --- @param tbl? table
-  --- @param fallback table
-  --- @return table tbl corresponding to the `tbl` parameter
-  setfallbacktable = function(tbl, fallback)
-    return setmetatable(tbl or {}, {__index = fallback})
-  end,
-
-  tbl_remove_key = tbl_remove_key,
-
-  --- Set a `value` in a `tbl` multiple `keys` deep.
-  --
-  --- ```lua
-  --- assert(vim.deep_equal(
-  ---  {a = {b = {c = 'd'}}},
-  ---  tbl_set({}, {'a', 'b', 'c'}, 'd')
-  --- ))
-  --- ```
-  ---
-  --- WARN: this mutates `tbl`!
-  ---
-  --- @generic T
-  --- @param tbl table
-  --- @param keys table<number|string|table>
-  --- @param value T
-  --- @return nil
-  tbl_set = function(tbl, keys, value)
-    local current = tbl
-    for i = 1, #keys - 1 do
-      local key = keys[i]
-
-      if current[key] == nil then
-        current[key] = {}
-      end
-
-      current = current[key]
-    end
-
-    current[keys[#keys]] = value
-  end,
-}
-
 return utils
diff --git a/lua/barbar/utils/highlight.lua b/lua/barbar/utils/highlight.lua
new file mode 100644
index 00000000..b60795ae
--- /dev/null
+++ b/lua/barbar/utils/highlight.lua
@@ -0,0 +1,169 @@
+local get_hl = vim.api.nvim_get_hl --- @type function
+local get_hl_by_name = vim.api.nvim_get_hl_by_name --- @type function
+local hlexists = vim.fn.hlexists --- @type function
+local set_hl = vim.api.nvim_set_hl --- @type function
+local tbl_isempty = vim.tbl_isempty
+
+local tbl = require('barbar.utils.table')
+
+--- @type {[string]: nil|table}
+local hl_groups_cache = {}
+
+local get_hl_util = get_hl and
+  --- @param name string
+  --- @return table
+  function(name) return get_hl(0, {link = false, name = name}) end or
+  function(name)
+    if hlexists(name) < 1 then
+      return {}
+    end
+
+    local definition = get_hl_by_name(name, true)
+    for original, new in pairs {background = 'bg', foreground = 'fg', special = 'sp'} do
+      local attribute_definition = tbl.remove_key(definition, original)
+      if attribute_definition then
+        definition[new] = attribute_definition
+      end
+    end
+
+    local cterm = get_hl_by_name(name, false)
+    definition.ctermfg = cterm.foreground
+    definition.ctermbg = cterm.background
+
+    return definition
+  end
+
+--- @param group string the groups to source the color from.
+--- @return table
+local function get_hl_cached(group)
+  do
+    local hl_cached = hl_groups_cache[group]
+    if hl_cached then
+      return hl_cached
+    end
+  end
+
+  local hl = get_hl_util(group)
+  hl_groups_cache[group] = hl
+  return hl
+end
+
+--- Generate a color.
+--- @param groups string[] the groups to source the color from.
+--- @param attribute 'bg'|'ctermbg'|'ctermfg'|'fg'|'sp' where to look for the color.
+--- @param default barbar.utils.hl.color.value a color name (`string`), GUI hex (`string`), or cterm color code (`integer`).
+--- @return barbar.utils.hl.color.value color
+local function get_hl_color_or_default(groups, attribute, default)
+  for _, group in ipairs(groups) do
+    local hl_attribute = get_hl_cached(group)[attribute]
+    if hl_attribute then
+      return hl_attribute
+    end
+  end
+
+  return default
+end
+
+--- @class barbar.utils.hl.attributes see |:h attr-list|
+--- @field blend? integer 0–100
+--- @field bold? boolean
+--- @field default? boolean
+--- @field italic? boolean
+--- @field nocombine? boolean
+--- @field reverse? boolean
+--- @field standout? boolean
+--- @field strikethrough? boolean
+--- @field undercurl? boolean
+--- @field underdashed? boolean
+--- @field underdotted? boolean
+--- @field underdouble? boolean
+--- @field underline? boolean
+
+--- @alias barbar.utils.hl.color.value integer|string
+
+--- @class barbar.utils.hl.color
+--- @field cterm barbar.utils.hl.color.value
+--- @field gui barbar.utils.hl.color.value
+
+--- utilities for working with highlight groups.
+--- @class barbar.utils.Hl
+local hl = {}
+
+--- Generate a color.
+--- @param groups string[] the groups to source the color from.
+--- @return nil|barbar.utils.hl.attributes
+function hl.attributes(groups)
+  for _, group in ipairs(groups) do
+    local cached = get_hl_cached(group)
+    if not tbl_isempty(cached) then
+      return cached
+    end
+  end
+end
+
+--- Generate a background color.
+--- @param groups string[] the groups to source the background color from.
+--- @param default barbar.utils.hl.color.value the background color to use if no `groups` have a valid background color.
+--- @param default_cterm? barbar.utils.hl.color.value the color to use if no `groups` have a valid color and `termguicolors == false`.
+--- @return barbar.utils.hl.color color
+function hl.bg_or_default(groups, default, default_cterm)
+  return {
+    cterm = get_hl_color_or_default(groups, 'ctermbg', default_cterm or default),
+    gui = get_hl_color_or_default(groups, 'bg', default),
+  }
+end
+
+--- Generate a foreground color.
+--- @param groups string[] the groups to source the foreground color from.
+--- @param default barbar.utils.hl.color.value the foreground color to use if no `groups` have a valid foreground color.
+--- @param default_cterm? barbar.utils.hl.color.value the color to use if no `groups` have a valid color and `termguicolors == false`.
+--- @return barbar.utils.hl.color color
+function hl.fg_or_default(groups, default, default_cterm)
+  return {
+    cterm = get_hl_color_or_default(groups, 'ctermfg', default_cterm or default),
+    gui = get_hl_color_or_default(groups, 'fg', default),
+  }
+end
+
+--- Reset the `nvim_get_hl` cache
+function hl.reset_cache() hl_groups_cache = {} end
+
+--- Set some highlight `group`'s default definition with respect to `&termguicolors`
+--- @param group string the name of the highlight group to set
+--- @param bg barbar.utils.hl.color
+--- @param fg barbar.utils.hl.color
+--- @param sp? barbar.utils.hl.color.value
+--- @param attributes? barbar.utils.hl.attributes whether the highlight group should be bolded
+--- @return nil
+function hl.set(group, bg, fg, sp, attributes)
+  if not attributes then
+    attributes = {}
+  end
+
+  attributes.bg = bg.gui
+  attributes.ctermbg = bg.cterm
+  attributes.ctermfg = fg.cterm
+  attributes.fg = fg.gui
+  attributes.sp = sp
+  attributes[vim.type_idx] = nil
+
+  set_hl(0, group, attributes)
+end
+
+--- Set the default highlight `group_name` as a link to `link_name`
+--- @param group_name string the name of the group to by-default be linked to `link_name`
+--- @param link_name string the name of the group to by-default link `group_name` to
+--- @return nil
+function hl.set_default_link(group_name, link_name)
+  set_hl(0, group_name, {default = true, link = link_name})
+end
+
+--- Generate a foreground color.
+--- @param groups string[] the groups to source the foreground color from.
+--- @param default string the foreground color to use if no `groups` have a valid foreground color.
+--- @return barbar.utils.hl.color.value color
+function hl.sp_or_default(groups, default)
+  return get_hl_color_or_default(groups, 'sp', default)
+end
+
+return hl
diff --git a/lua/barbar/utils/list.lua b/lua/barbar/utils/list.lua
new file mode 100644
index 00000000..19128267
--- /dev/null
+++ b/lua/barbar/utils/list.lua
@@ -0,0 +1,43 @@
+local table_insert = table.insert
+
+local list_slice = vim.list_slice
+
+--- @class barbar.utils.List
+local list = {}
+
+--- Return the index of element `n` in `list.
+--- @generic T
+--- @param tbl T[]
+--- @param t T
+--- @return nil|integer index
+function list.index_of(tbl, t)
+  for i, value in ipairs(tbl) do
+    if value == t then
+      return i
+    end
+  end
+  return nil
+end
+
+--- reverse the order of elements in some `list`.
+--- perf: don't do `ipairs(list_reverse(list))`, just do `for i = #list, 1, -1` instead.
+--- @generic t
+--- @param tbl t[]
+function list.reverse(tbl)
+  local reversed = {}
+  for i = #tbl, 1, -1 do
+    table_insert(reversed, tbl[i])
+  end
+  return reversed
+end
+
+--- Run `vim.list_slice` on some `list`, `index`ed from the end of the list.
+--- @generic T
+--- @param tbl T[]
+--- @param index_from_end number
+--- @return T[] sliced
+function list.slice_from_end(tbl, index_from_end)
+  return list_slice(tbl, #tbl - index_from_end + 1)
+end
+
+return list
diff --git a/lua/barbar/utils/table.lua b/lua/barbar/utils/table.lua
new file mode 100644
index 00000000..a5daab62
--- /dev/null
+++ b/lua/barbar/utils/table.lua
@@ -0,0 +1,45 @@
+--- @class barbar.utils.Table
+local table = {}
+
+--- Remove `tbl[key]` from `tbl` and return it
+--- @param tbl table
+--- @param key string
+--- @return any
+function table.remove_key(tbl, key)
+  local value = rawget(tbl, key)
+  rawset(tbl, key, nil)
+  return value
+end
+
+--- Set a `value` in a `tbl` multiple `keys` deep.
+--
+--- ```lua
+--- assert(vim.deep_equal(
+---  {a = {b = {c = 'd'}}},
+---  tbl_set({}, {'a', 'b', 'c'}, 'd')
+--- ))
+--- ```
+---
+--- WARN: this mutates `tbl`!
+---
+--- @generic T
+--- @param tbl table
+--- @param keys table<number|string|table>
+--- @param value T
+--- @return nil
+function table.set(tbl, keys, value)
+  local current = tbl
+  for i = 1, #keys - 1 do
+    local key = keys[i]
+
+    if current[key] == nil then
+      current[key] = {}
+    end
+
+    current = current[key]
+  end
+
+  current[keys[#keys]] = value
+end
+
+return table
diff --git a/lua/bufferline.lua b/lua/bufferline.lua
index e3b5e09a..f48d72ae 100644
--- a/lua/bufferline.lua
+++ b/lua/bufferline.lua
@@ -1 +1 @@
-return require'barbar'
+return require('barbar')
diff --git a/lua/bufferline/animate.lua b/lua/bufferline/animate.lua
index 2efb7fca..65236720 100644
--- a/lua/bufferline/animate.lua
+++ b/lua/bufferline/animate.lua
@@ -1 +1 @@
-return require'barbar.animate'
+return require('barbar.animate')
diff --git a/lua/bufferline/api.lua b/lua/bufferline/api.lua
index 18a336d0..46b7eed0 100644
--- a/lua/bufferline/api.lua
+++ b/lua/bufferline/api.lua
@@ -1 +1 @@
-return require'barbar.api'
+return require('barbar.api')
diff --git a/lua/bufferline/bbye.lua b/lua/bufferline/bbye.lua
index 3951c0c3..85b77475 100644
--- a/lua/bufferline/bbye.lua
+++ b/lua/bufferline/bbye.lua
@@ -1 +1 @@
-return require'barbar.bbye'
+return require('barbar.bbye')
diff --git a/lua/bufferline/buffer.lua b/lua/bufferline/buffer.lua
index 1f647b12..ce4521cd 100644
--- a/lua/bufferline/buffer.lua
+++ b/lua/bufferline/buffer.lua
@@ -1 +1 @@
-return require'barbar.buffer'
+return require('barbar.buffer')
diff --git a/lua/bufferline/config.lua b/lua/bufferline/config.lua
index 396d0bac..8e4b3deb 100644
--- a/lua/bufferline/config.lua
+++ b/lua/bufferline/config.lua
@@ -1 +1 @@
-return require'barbar.config'
+return require('barbar.config')
diff --git a/lua/bufferline/events.lua b/lua/bufferline/events.lua
index 9672a499..015486ba 100644
--- a/lua/bufferline/events.lua
+++ b/lua/bufferline/events.lua
@@ -1 +1 @@
-return require'barbar.events'
+return require('barbar.events')
diff --git a/lua/bufferline/highlight.lua b/lua/bufferline/highlight.lua
index 74077ec3..ac763e9a 100644
--- a/lua/bufferline/highlight.lua
+++ b/lua/bufferline/highlight.lua
@@ -1 +1 @@
-return require'barbar.highlight'
+return require('barbar.highlight')
diff --git a/lua/bufferline/icons.lua b/lua/bufferline/icons.lua
index 7deca167..570b8dae 100644
--- a/lua/bufferline/icons.lua
+++ b/lua/bufferline/icons.lua
@@ -1 +1 @@
-return require'barbar.icons'
+return require('barbar.icons')
diff --git a/lua/bufferline/jump_mode.lua b/lua/bufferline/jump_mode.lua
index 5910663e..f0916772 100644
--- a/lua/bufferline/jump_mode.lua
+++ b/lua/bufferline/jump_mode.lua
@@ -1 +1 @@
-return require'barbar.jump_mode'
+return require('barbar.jump_mode')
diff --git a/lua/bufferline/layout.lua b/lua/bufferline/layout.lua
index 5926ef18..27aa5844 100644
--- a/lua/bufferline/layout.lua
+++ b/lua/bufferline/layout.lua
@@ -1 +1 @@
-return require'barbar.ui.layout'
+return require('barbar.ui.layout')
diff --git a/lua/bufferline/render.lua b/lua/bufferline/render.lua
index dcdb3a69..58e7629b 100644
--- a/lua/bufferline/render.lua
+++ b/lua/bufferline/render.lua
@@ -1,4 +1,4 @@
-local render = require('barbar.ui.render')
+local render = vim.deepcopy(require('barbar.ui.render'))
 
 --- @deprecated use `state.restore_buffers` instead
 render.restore_buffers = require('barbar.state').restore_buffers
diff --git a/lua/bufferline/state.lua b/lua/bufferline/state.lua
index 2ccace91..1e5461e3 100644
--- a/lua/bufferline/state.lua
+++ b/lua/bufferline/state.lua
@@ -1 +1 @@
-return require'barbar.state'
+return require('barbar.state')
diff --git a/lua/bufferline/utils.lua b/lua/bufferline/utils.lua
index 958187b3..c1e6ccd0 100644
--- a/lua/bufferline/utils.lua
+++ b/lua/bufferline/utils.lua
@@ -1 +1,25 @@
-return require'barbar.utils'
+local utils = vim.deepcopy(require('barbar.utils'))
+
+do
+  local fs = require('barbar.fs')
+  utils.basename = fs.basename
+  utils.is_relative_path = fs.is_relative_path
+  utils.relative = fs.relative
+end
+
+utils.hl = require('barbar.utils.hl')
+
+do
+  local list = require('barbar.utils.list')
+  utils.index_of = list.index_of
+  utils.list_reverse = list.reverse
+  utils.list_slice_from_end = list.slice_from_end
+end
+
+do
+  local tbl = require('barbar.utils.table')
+  utils.tbl_remove_key = tbl.remove_key
+  utils.tbl_set = tbl.set
+end
+
+return utils
diff --git a/plugin/barbar.lua b/plugin/barbar.lua
index bb74c874..d99b339a 100644
--- a/plugin/barbar.lua
+++ b/plugin/barbar.lua
@@ -8,12 +8,12 @@ if vim.g.barbar_auto_setup ~= false then
   local options = vim.g.bufferline
 
   if options then
-    require'barbar.utils'.notify_once(
-      "`g:bufferline` is deprecated, use `require'barbar'.setup` instead. " ..
+    require('barbar.utils').notify_once(
+      "`g:bufferline` is deprecated, use `require('barbar').setup` instead. " ..
         'See `:h barbar-setup` for more information.',
       vim.log.levels.WARN
     )
   end
 
-  require'barbar'.setup(options)
+  require('barbar').setup(options)
 end