Retrieve completion suggestions from GitHub Copilot programmatically in a Node.js program

getCompletionsCycling.mjs

import path from "node:path";
import fs from "node:fs";
import { spawn } from "node:child_process";

/**
* $ node getCompletionsCycling.mjs ./sample.ts
*/

const server = spawn("node", ["./copilot.vim/dist/agent.js"]); // https://github.com/github/copilot.vim

const sendMessage = (data) => {
  const dataString = JSON.stringify({ ...data, jsonrpc: "2.0" });
  const contentLength = Buffer.byteLength(dataString, "utf8");
  const rpcString = `Content-Length: ${contentLength}\r\n\r\n${dataString}`;
  server.stdin.write(rpcString);
};

let requestId = 0;
const resolveMap = new Map();
const rejectMap = new Map();

const sendRequest = (method, params) => {
  sendMessage({ id: ++requestId, method, params });
  return new Promise((resolve, reject) => {
    resolveMap.set(requestId, resolve);
    rejectMap.set(requestId, reject);
  });
};

const sendNotification = (method, params) => {
  sendMessage({ method, params });
};

const handleReceivedPayload = (payload) => {
  // console.log("Received payload:", payload);
  if ("id" in payload) {
    if ("result" in payload) {
      const resolve = resolveMap.get(payload.id);
      if (resolve) {
        resolve(payload.result);
        resolveMap.delete(payload.id);
      }
    } else if ("error" in payload) {
      const reject = rejectMap.get(payload.id);
      if (reject) {
        reject(payload.error);
        rejectMap.delete(payload.id);
      }
    }
  }
};

server.stdout.on("data", (data) => {
  const rawString = data.toString("utf-8");
  const payloadStrings = rawString
    .split(/Content-Length: \d+\r\n\r\n/)
    .filter((s) => s);

  for (const payloadString of payloadStrings) {
    let payload;
    payload = JSON.parse(payloadString);
    handleReceivedPayload(payload);
  }
});

const main = async () => {
  const filePath = process.argv[2];
  const languageId = "plaintext"; // e.g. typescript
  const text = fs.readFileSync(filePath, "utf-8");
  
  await sendRequest("initialize", {
    capabilities: { workspace: { workspaceFolders: true } },
  });

  sendNotification("textDocument/didOpen", {
    textDocument: {
      uri: `file://${path.resolve(filePath)}`,
      languageId,
      version: 0,
      text,
    },
  });

  const completions = await sendRequest("getCompletionsCycling", {
    doc: {
      version: 0,
      position: { line: 2, character: 1 },
      uri: `file://${path.resolve(filePath)}`,
    },
  });

  console.log("Completions:", completions);

  process.exit(0);
};

void main();