Add Reddit strategy for posting to specific subreddits

README.md

@@ -31,6 +31,7 @@ The API is split into two parts:
     - `TelegramStrategy`
     - `DevtoStrategy`
     - `NostrStrategy` (requires Node.js v22+)
+    - `RedditStrategy`
 
 Each strategy requires its own parameters that are specific to the service. If you only want to post to a particular service, you can just directly use the strategy for that service.
 
@@ -46,6 +47,7 @@ import {
 	TelegramStrategy,
 	DevtoStrategy,
 	NostrStrategy,
+	RedditStrategy,
 } from "@humanwhocodes/crosspost";
 
 // Note: Use an app password, not your login password!
@@ -102,6 +104,12 @@ const nostr = new NostrStrategy({
 	relays: ["wss://relay.example.com", "wss://relay2.example.com"],
 });
 
+// Note: OAuth token and subreddit required
+const reddit = new RedditStrategy({
+	accessToken: "your-access-token",
+	subreddit: "javascript",
+});
+
 // create a client that will post to all services
 const client = new Client({
 	strategies: [
@@ -114,6 +122,7 @@ const client = new Client({
 		telegram,
 		devto,
 		nostr,
+		reddit,
 	],
 });
 
@@ -185,6 +194,7 @@ Usage: crosspost [options] ["Message to post."]
 --telegram      Post to Telegram.
 --slack, -s     Post to Slack.
 --nostr, -n     Post to Nostr.
+--reddit, -r    Post to Reddit.
 --mcp           Start MCP server.
 --file          The file to read the message from.
 --image         The image file to upload with the message.
@@ -247,6 +257,9 @@ Each strategy requires a set of environment variables in order to execute:
 - Nostr
     - `NOSTR_PRIVATE_KEY`
     - `NOSTR_RELAYS`
+- Reddit
+    - `REDDIT_ACCESS_TOKEN`
+    - `REDDIT_SUBREDDIT`
 
 Tip: You can load environment variables from a `.env` file by setting the environment variable `CROSSPOST_DOTENV`. Set it to `1` to use `.env` in the current working directory, or set it to a specific filepath to use a different location.
 
@@ -507,6 +520,30 @@ Nostr posts are "short text notes" (kind 1 events) with a 280 character limit. I
 
 **Security:** Keep your private key secure and never share it. Consider using a dedicated key for crossposting rather than your main Nostr identity key.
 
+### Reddit
+
+To enable posting to Reddit:
+
+1. Go to [Reddit Apps](https://www.reddit.com/prefs/apps) and click "create another app...".
+2. Enter a name for your app and choose **script** as the app type.
+3. Set `http://localhost:8080` as the redirect URI and click "create app".
+4. Note the app's client ID and secret from the app details.
+5. Generate an OAuth access token for your script app (see the [Reddit OAuth API docs](https://www.reddit.com/dev/api/oauth)). Example:
+
+   ```shell
+   curl -u "<CLIENT_ID>:<CLIENT_SECRET>" \
+     -d "grant_type=password&username=<REDDIT_USERNAME>&password=<REDDIT_PASSWORD>" \
+     -A "Crosspost by u/<REDDIT_USERNAME>" \
+     https://www.reddit.com/api/v1/access_token
+   ```
+
+   Copy the `access_token` value from the JSON response and set it as `REDDIT_ACCESS_TOKEN`.
+6. Set `REDDIT_SUBREDDIT` to the target community name (without `r/`).
+
+Reddit submissions created by this strategy are self/text posts. The first line before the first newline character (`\n`) is used as the post title and remaining lines are used as the post body.
+
+For example, `"Post title\n\nPost body"` sends `Post title` as the title and `Post body` as the body. If there is only one line, then only the title is sent and the body is empty.
+
 ## License
 
 Copyright 2024-2025 Nicholas C. Zakas

src/bin.js

@@ -23,6 +23,7 @@ import {
 	TelegramStrategy,
 	SlackStrategy,
 	NostrStrategy,
+	RedditStrategy,
 } from "./index.js";
 import { CrosspostMcpServer } from "./mcp-server.js";
 import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
@@ -66,6 +67,7 @@ const options = {
 	telegram: { type: booleanType },
 	slack: { type: booleanType, short: "s" },
 	nostr: { type: booleanType, short: "n" },
+	reddit: { type: booleanType, short: "r" },
 	mcp: { type: booleanType },
 	file: { type: stringType },
 	image: { type: stringType },
@@ -104,6 +106,7 @@ if (
 		!flags.telegram &&
 		!flags.slack &&
 		!flags.nostr &&
+		!flags.reddit &&
 		!flags.mcp)
 ) {
 	console.log('Usage: crosspost [options] ["Message to post."]');
@@ -117,6 +120,7 @@ if (
 	console.log("--telegram	Post to Telegram.");
 	console.log("--slack, -s	Post to Slack.");
 	console.log("--nostr, -n	Post to Nostr.");
+	console.log("--reddit, -r	Post to Reddit.");
 	console.log("--mcp		Start MCP server.");
 	console.log("--file		The file to read the message from.");
 	console.log("--image		The image file to upload with the message.");
@@ -258,6 +262,15 @@ if (flags.nostr) {
 	);
 }
 
+if (flags.reddit) {
+	strategies.push(
+		new RedditStrategy({
+			accessToken: env.require("REDDIT_ACCESS_TOKEN"),
+			subreddit: env.require("REDDIT_SUBREDDIT"),
+		}),
+	);
+}
+
 //-----------------------------------------------------------------------------
 // Main
 //-----------------------------------------------------------------------------

src/index.ts

@@ -65,4 +65,10 @@ export {
 	NostrEvent,
 	NostrEventResponse,
 } from "./strategies/nostr.js";
+export {
+	RedditStrategy,
+	RedditOptions,
+	RedditErrorEntry,
+	RedditSubmitResponse,
+} from "./strategies/reddit.js";
 export { Client, ClientOptions, Strategy } from "./client.js";

src/strategies/reddit.js

@@ -0,0 +1,199 @@
+/**
+ * @fileoverview Reddit strategy for posting messages.
+ * @author Nicholas C. Zakas
+ */
+
+/* global fetch, URLSearchParams */
+
+//-----------------------------------------------------------------------------
+// Imports
+//-----------------------------------------------------------------------------
+
+import { validatePostOptions } from "../util/options.js";
+
+//-----------------------------------------------------------------------------
+// Type Definitions
+//-----------------------------------------------------------------------------
+
+/** @typedef {import("../types.js").PostOptions} PostOptions */
+
+/**
+ * @typedef {Object} RedditOptions
+ * @property {string} accessToken The OAuth access token for the Reddit API.
+ * @property {string} subreddit The subreddit to post to (without the `r/` prefix).
+ */
+
+/** @typedef {[string, string, string]} RedditErrorEntry */
+
+/**
+ * @typedef {Object} RedditSubmitResponse
+ * @property {Object} json The response body from Reddit.
+ * @property {Array<RedditErrorEntry>} json.errors Any API validation errors.
+ * @property {Object} [json.data] Information about the submitted post.
+ * @property {string} [json.data.url] The canonical URL of the submitted post.
+ * @property {string} [json.data.permalink] The permalink path for the submitted post.
+ */
+
+//-----------------------------------------------------------------------------
+// Constants
+//-----------------------------------------------------------------------------
+
+const API_BASE = "https://oauth.reddit.com";
+
+//-----------------------------------------------------------------------------
+// Helpers
+//-----------------------------------------------------------------------------
+
+/**
+ * Formats Reddit API errors into a single string.
+ * @param {Array<RedditErrorEntry>} errors The Reddit API errors.
+ * @returns {string} The formatted error message.
+ */
+function formatErrors(errors) {
+	return errors.map(error => error.filter(Boolean).join(": ")).join("\n");
+}
+
+//-----------------------------------------------------------------------------
+// Exports
+//-----------------------------------------------------------------------------
+
+/**
+ * A strategy for posting messages to Reddit.
+ */
+export class RedditStrategy {
+	/**
+	 * The ID of the strategy.
+	 * @type {string}
+	 * @readonly
+	 */
+	id = "reddit";
+
+	/**
+	 * The display name of the strategy.
+	 * @type {string}
+	 * @readonly
+	 */
+	name = "Reddit";
+
+	/**
+	 * Maximum length of a Reddit self-post message in characters.
+	 * @type {number}
+	 * @const
+	 */
+	MAX_MESSAGE_LENGTH = 40300;
+
+	/**
+	 * Options for this instance.
+	 * @type {RedditOptions}
+	 */
+	#options;
+
+	/**
+	 * Creates a new instance.
+	 * @param {RedditOptions} options Options for the instance.
+	 * @throws {Error} When options are missing.
+	 */
+	constructor(options) {
+		const { accessToken, subreddit } = options;
+
+		if (!accessToken) {
+			throw new TypeError("Missing access token.");
+		}
+
+		if (!subreddit) {
+			throw new TypeError("Missing subreddit.");
+		}
+
+		this.#options = options;
+	}
+
+	/**
+	 * Posts a message to Reddit as a self post.
+	 * The first line of the message is used as the title.
+	 * Remaining lines are used as the post body.
+	 * @param {string} message The message to post.
+	 * @param {PostOptions} [postOptions] Additional options for the post.
+	 * @returns {Promise<RedditSubmitResponse>} A promise that resolves with the Reddit API response.
+	 */
+	async post(message, postOptions) {
+		if (!message) {
+			throw new TypeError("Missing message to post.");
+		}
+
+		validatePostOptions(postOptions);
+
+		if (postOptions?.images?.length) {
+			throw new Error("Images are not supported in Reddit text posts.");
+		}
+
+		const [firstLine, ...remainingLines] = message.split(/\r?\n/g);
+		const title = firstLine.trim();
+		const text = remainingLines.join("\n").trim();
+		const body = new URLSearchParams({
+			api_type: "json",
+			kind: "self",
+			sr: this.#options.subreddit,
+			title,
+			text,
+			resubmit: "true",
+		});
+
+		const response = await fetch(`${API_BASE}/api/submit`, {
+			method: "POST",
+			headers: {
+				Authorization: `Bearer ${this.#options.accessToken}`,
+				"Content-Type": "application/x-www-form-urlencoded",
+				"User-Agent":
+					"Crosspost (https://github.com/humanwhocodes/crosspost, v1.0.4)", // x-release-please-version
+			},
+			body,
+			signal: postOptions?.signal,
+		});
+
+		const result = /** @type {RedditSubmitResponse} */ (await response.json());
+		const errors = result.json?.errors ?? [];
+
+		if (!response.ok) {
+			const errorMessage = errors.length
+				? formatErrors(errors)
+				: "Unknown Reddit API error.";
+			throw new Error(
+				`${response.status} Failed to submit post: ${response.statusText}\n${errorMessage}`,
+			);
+		}
+
+		if (errors.length) {
+			throw new Error(`Failed to submit post:\n${formatErrors(errors)}`);
+		}
+
+		return result;
+	}
+
+	/**
+	 * Extracts a URL from a Reddit API response.
+	 * @param {RedditSubmitResponse} response The response from the Reddit API.
+	 * @returns {string} The URL of the Reddit post.
+	 */
+	getUrlFromResponse(response) {
+		const { url, permalink } = response?.json?.data ?? {};
+		const postUrl = url ?? permalink;
+
+		if (!postUrl) {
+			throw new Error("Post URL not found in response");
+		}
+
+		return postUrl.startsWith("http")
+			? postUrl
+			: `https://reddit.com${postUrl}`;
+	}
+
+	/**
+	 * Calculates the length of a message according to Reddit's algorithm.
+	 * All Unicode characters are counted as is.
+	 * @param {string} message The message to calculate the length of.
+	 * @returns {number} The calculated length of the message.
+	 */
+	calculateMessageLength(message) {
+		return [...message].length;
+	}
+}