Add demo of cross contract calls

templates/06-cross-contract-calls/README.md

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+# Using Token in AssemblyScript
+
+## Description
+
+This project contains example of contract using token similar to [ERC20](https://theethereum.wiki/w/index.php/ERC20_Token_Standard).
+
+The contract allows multiple participants to lock up same amount of funds in a "deal". They cannot unlock finances until they all confirm that "deal" conditions have been upheld.
+
+This is a back-end contract only so there is no front-end included.
+
+
+## To Run
+
+*In NEAR Studio (https://studio.nearprotocol.com)*
+
+1. Click the "Run" button on the top of the Studio window
+
+2. You will be redirected to the output for the JavaScript tests described in `src/main.js` to show that the contract is performing properly. This is a fully back-end contract so there is no front end.
+
+
+## To Explore
+
+See `assembly/main.ts` for the contract code and `src/main.js` for the JavaScript tests which define its usage.
+
+## Usage Example (from JS)
+
+Create a deal to lock 5 tokens between <code>test1.near</code> and <code>vasya.near</code>:
+
+```
+await contract.makeDeal({ dealId: DEAL_ID, amount: "5", participants: ["test1.near", "vasya.near"] });
+```
+
+Lock funds into the deal:
+```
+await tokenContract.approve({ spender: "studio-853u597r1", tokens: "5" });
+await contract.fundDeal({ dealId: DEAL_ID });
+```
+
+To see current state of the deal:
+```
+await contract.getDeal({ dealId: DEAL_ID });
+```
+
+Funds are returned back when all participants confirm deal completion:
+```
+await contract.confirmDeal({ dealId: DEAL_ID })
+```
+<code>DEAL_ID</code> can be any unique string used to identify given deal.

templates/06-cross-contract-calls/assembly/main.ts

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+import "allocator/arena";
+export { memory };
+
+import { contractContext, globalStorage, near, ContractPromise } from "./near";
+import { Deal, TransferCompleteArgs } from "./model.near";
+import { Token } from "./token";
+
+// --- contract code goes below 
+
+// TODO: Replace contract address with actual DAI bridge or any other token
+let token = new Token("studio-31fz6jnjv");
+
+// TODO: Replace with name of current contract
+let CONTRACT_NAME = "studio-853u597r1";
+
+export function getDeal(dealId: string): Deal {
+  let dealKey = "deal:" + dealId;
+  return Deal.decode(globalStorage.getBytes(dealKey));
+}
+
+export function makeDeal(dealId: string, amount: string, participants: string[]): void {
+  near.log("makeDeal: " + dealId + " amount: " + amount + " participants: " + participants.toString());
+
+  let dealKey = "deal:" + dealId;
+  let existingDeal = globalStorage.getBytes(dealKey);
+  assert(!existingDeal, "Deal " + dealId + " already exists");
+
+  let everythingFalse: bool[] = new Array(participants.length);
+  let deal: Deal = { amount, participants, approved: everythingFalse, deposited: everythingFalse, confirmed: everythingFalse };
+  globalStorage.setBytes(dealKey, deal.encode()); 
+}
+
+export function fundDeal(dealId: string): void {
+  near.log("fundDeal: " + dealId);
+
+  let dealKey = "deal:" + dealId;
+  let deal = Deal.decode(globalStorage.getBytes(dealKey));
+  let senderIndex = deal.participants.indexOf(contractContext.sender);
+
+  assert(senderIndex != -1, contractContext.sender + " is not part of the deal");
+  assert(!deal.approved[senderIndex], contractContext.sender + " already funding the deal");
+
+  deal.approved[senderIndex] = true;
+  globalStorage.setBytes(dealKey, deal.encode()); 
+
+  let args: TransferCompleteArgs = { dealId, sender: contractContext.sender };
+  token.transferFrom(contractContext.sender, CONTRACT_NAME, deal.amount).then("transferComplete", args.encode(), 1).returnAsResult();
+}
+
+export function transferComplete(dealId: string, sender: string): void {
+  near.log("transferComplete: " + dealId + " sender: " + sender);
+
+  let transferResults = ContractPromise.getResults();
+  assert(transferResults.length == 1, "Expect only one result from transfer call");
+
+  let dealKey = "deal:" + dealId;
+  let deal = Deal.decode(globalStorage.getBytes(dealKey));
+  let senderIndex = deal.participants.indexOf(sender);
+  assert(senderIndex != -1, sender + " is not part of the deal");
+
+  if (transferResults[0].success) {
+    deal.deposited[senderIndex] = true;
+  } else {
+    deal.approved[senderIndex] = false;
+  }
+
+  globalStorage.setBytes(dealKey, deal.encode());
+}
+
+export function cancelDeal(dealId: string): void {
+  // TODO: Allow to get out of deal if not everybody funded yet
+}
+
+export function confirmDeal(dealId: string): void {
+  let dealKey = "deal:" + dealId;
+  let deal = Deal.decode(globalStorage.getBytes(dealKey));
+  let senderIndex = deal.participants.indexOf(contractContext.sender);
+  assert(senderIndex != -1, contractContext.sender + " is not part of the deal");
+  assert(deal.confirmed[senderIndex] == false, contractContext.sender + " already confirmed the deal")
+
+  deal.confirmed[senderIndex] = true;
+  globalStorage.setBytes(dealKey, deal.encode());
+
+  let allConfirmed = deal.confirmed.every((confirmed: bool, index: i32, arr: Array<bool>): bool => confirmed);
+  if (allConfirmed) {
+    // TODO: Robust implementation should also track who actually got paid out
+    for (let i = 0; i < deal.participants.length; i++) {
+      let participant = deal.participants[i];
+      token.transfer(participant, deal.amount);
+    }
+  }
+}

templates/06-cross-contract-calls/assembly/model.ts

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+export class Deal {
+  amount: string;
+  participants: string[];
+  approved: bool[];
+  deposited: bool[];
+  confirmed: bool[];
+}
+
+export class TransferCompleteArgs {
+  sender: string;
+  dealId: string;
+}
+
+export class BalanceOfArgs {
+  tokenOwner: string;
+}
+
+export class TransferArgs {
+  to: string;
+  tokens: string;
+}
+
+export class AllowanceArgs {
+  tokenOwner: string;
+  spender: string;
+}
+
+export class ApproveArgs {
+  spender: string;
+  tokens: string;
+}
+
+export class TransferFromArgs {
+  from: string;
+  to: string;
+  tokens: string;
+}
+
+export class EmptyArgs {
+}

templates/06-cross-contract-calls/assembly/token.ts

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+import "allocator/arena";
+import { contractContext, globalStorage, near, ContractPromise } from "./near";
+import { BalanceOfArgs, TransferArgs, AllowanceArgs, ApproveArgs, TransferFromArgs, EmptyArgs } from "./model.near";
+
+export class Token {
+  contract: string;
+
+  constructor(contract: string) {
+    this.contract = contract;
+  }
+
+  totalSupply(): ContractPromise {
+    let args: EmptyArgs = {};
+    return ContractPromise.create(this.contract, "totalSupply", args.encode(), 1);
+  }
+
+  balanceOf(tokenOwner: string): ContractPromise {
+    let args: BalanceOfArgs = { tokenOwner };
+    return ContractPromise.create(this.contract, "balanceOf", args.encode(), 1);
+  }
+
+  allowance(tokenOwner: string, spender: string): ContractPromise {
+    let args: AllowanceArgs = { tokenOwner, spender };
+    return ContractPromise.create(this.contract, "allowance", args.encode(), 1);
+  }
+
+  transfer(to: string, tokens: string): ContractPromise {
+    let args: TransferArgs = { to, tokens };
+    return ContractPromise.create(this.contract, "transfer", args.encode(), 1);
+  }
+
+  approve(spender: string, tokens: string): boolean {
+    let args: ApproveArgs = { spender, tokens };
+    return ContractPromise.create(this.contract, "approve", args.encode(), 1);
+  }
+
+  transferFrom(from: string, to: string, tokens: string): ContractPromise {
+    let args: TransferFromArgs = { from, to, tokens };
+    return ContractPromise.create(this.contract, "transferFrom", args.encode(), 1);
+  }
+}

templates/06-cross-contract-calls/assembly/tsconfig.json

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+{
+  "extends": "../node_modules/assemblyscript/std/assembly.json",
+  "include": [
+    "./**/*.ts"
+  ]
+}

templates/06-cross-contract-calls/gulpfile.js

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+const gulp = require("gulp");
+
+function generateBindings(inputFile, outputFile, callback) {
+  const asc = require("assemblyscript/bin/asc");
+  asc.main([
+    inputFile,
+    "--baseDir", "assembly",
+    "--nearFile", outputFile, 
+    "--measure"
+  ], callback);
+}
+
+function compile(inputFile, outputFile, callback) {
+  const asc = require("assemblyscript/bin/asc");
+  asc.main([
+    inputFile,
+    "--baseDir", "assembly",
+    "--binaryFile", outputFile,
+    "--sourceMap",
+    "--measure"
+  ], callback);
+}
+
+gulp.task("build:model", callback => {
+  generateBindings("model.ts", "../out/model.near.ts", callback);
+});
+
+gulp.task("build:bindings", ["build:model"], callback => {
+  generateBindings("main.ts", "../out/main.near.ts", callback);
+});
+
+gulp.task("build", ["build:bindings"], callback => {
+  compile("../out/main.near.ts", "../out/main.wasm", callback);
+});
+
+gulp.task("default", ["build"]);
+
+// This task is not required when running the project locally. Its purpose is to set up the
+// AssemblyScript compiler when a new project has been loaded in WebAssembly Studio.
+gulp.task("project:load", () => {
+  const utils = require("@wasm/studio-utils");
+  utils.eval(utils.project.getFile("setup.js").getData(), {
+    logLn,
+    project,
+    monaco,
+    fileTypeForExtension,
+  });
+});

templates/06-cross-contract-calls/package.json

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+{
+  "name": "@wasm/token_contract_ts",
+  "description": "",
+  "version": "1.0.0",
+  "scripts": {
+    "build": "gulp"
+  },
+  "devDependencies": {
+    "assemblyscript": "AssemblyScript/assemblyscript",
+    "gulp": "^3"
+  },
+  "wasmStudio": {
+    "name": "Token Smart Contract",
+    "description": "# Token Smart Contract\n\nThis project contains implementation of token contract similar to ERC20. The contract allows you to launch a new token on top of the NEAR blockchain which users can interact with as if it were any other token -- checking balances, transferring, etc.\n\n[AssemblyScript](https://github.com/AssemblyScript/assemblyscript) compiles strictly typed TypeScript to WebAssembly using Binaryen. See the [AssemblyScript wiki](https://github.com/AssemblyScript/assemblyscript/wiki) for further instructions and documentation.",
+    "icon": "typescript-lang-file-icon"
+  }
+}

templates/06-cross-contract-calls/setup.js

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+// This file is not required when running the project locally. Its purpose is to set up the
+// AssemblyScript compiler when a new project has been loaded in WebAssembly Studio.
+
+// Path manipulation lifted from https://gist.github.com/creationix/7435851
+
+// Joins path segments.  Preserves initial "/" and resolves ".." and "."
+// Does not support using ".." to go above/outside the root.
+// This means that join("foo", "../../bar") will not resolve to "../bar"
+function join(/* path segments */) {
+  // Split the inputs into a list of path commands.
+  var parts = [];
+  for (var i = 0, l = arguments.length; i < l; i++) {
+    parts = parts.concat(arguments[i].split("/"));
+  }
+  // Interpret the path commands to get the new resolved path.
+  var newParts = [];
+  for (i = 0, l = parts.length; i < l; i++) {
+    var part = parts[i];
+    // Remove leading and trailing slashes
+    // Also remove "." segments
+    if (!part || part === ".") continue;
+    // Interpret ".." to pop the last segment
+    if (part === "..") newParts.pop();
+    // Push new path segments.
+    else newParts.push(part);
+  }
+  // Preserve the initial slash if there was one.
+  if (parts[0] === "") newParts.unshift("");
+  // Turn back into a single string path.
+  return newParts.join("/") || (newParts.length ? "/" : ".");
+}
+
+// A simple function to get the dirname of a path
+// Trailing slashes are ignored. Leading slash is preserved.
+function dirname(path) {
+  return join(path, "..");
+}
+
+require.config({
+  paths: {
+    "binaryen": "https://cdn.jsdelivr.net/npm/binaryen@64.0.0/index",
+    "assemblyscript": "https://cdn.jsdelivr.net/gh/nearprotocol/assemblyscript@2337262883226a5431b80610ade7b4d379e82a30/dist/assemblyscript",
+    "assemblyscript/bin/asc": "https://cdn.jsdelivr.net/gh/nearprotocol/assemblyscript@2337262883226a5431b80610ade7b4d379e82a30/dist/asc",
+  }
+});
+logLn("Loading AssemblyScript compiler ...");
+require(["assemblyscript/bin/asc"], asc => {
+  monaco.languages.typescript.typescriptDefaults.addExtraLib(asc.definitionFiles.assembly);
+  asc.main = (main => (args, options, fn) => {
+    if (typeof options === "function") {
+      fn = options;
+      options = undefined;
+    }
+
+    return main(args, options || {
+      stdout: asc.createMemoryStream(),
+      stderr: asc.createMemoryStream(logLn),
+      readFile: (filename, baseDir) => {
+        let path = join(baseDir, filename);
+        console.log("readFile", path);
+        if (path.startsWith("out/") && path.indexOf(".near.ts") == -1) {
+          path = path.replace(/^out/, baseDir );
+          console.log("path", path);
+        } else if (path.startsWith(baseDir) && path.indexOf(".near.ts") != -1) {
+          path = path.replace(new RegExp("^" + baseDir), "out");
+          console.log("path", path);
+        }
+        const file = project.getFile(path);
+        return file ? file.data : null;
+      },
+      writeFile: (filename, contents) => {
+        const name = filename.startsWith("../") ? filename.substring(3) : filename;
+        const type = fileTypeForExtension(name.substring(name.lastIndexOf(".") + 1));
+        project.newFile(name, type, true).setData(contents);
+      },
+      listFiles: () => []
+    }, fn);
+  })(asc.main);
+  logLn("AssemblyScript compiler is ready!");
+});

templates/06-cross-contract-calls/src/loader.html

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+<head>
+    <script>
+        window.paceOptions = {
+            elements: {
+                selectors: ['.never-appears']
+            }
+        };
+    </script>
+    <script src="https://cdn.jsdelivr.net/gh/HubSpot/pace@v0.5.3/pace.min.js"></script>
+    <link href="https://cdn.jsdelivr.net/gh/HubSpot/pace@v0.5.3/themes/black/pace-theme-center-radar.css" rel="stylesheet" />
+</head>