Edit text in system editor

editTextInSystemEditor.mts

type PathString = string & { __brand: "path" }
function call<R>(fn: () => R) { return fn(); }

/** TODO: Return null if the user cancels/doesn't save the file (like in git) */
export async function editTextInSystemEditor(originalText: string): Promise<string | null> {
  // Create a unique temp directory using Bun's file APIs
  const tmpDir = `/tmp/context-edit-${Date.now()}-${Math.random().toString(36).slice(2)}`;
  await Bun.$`mkdir -p ${tmpDir}`;
  const tmpFile = `${tmpDir}/prompt-edit.txt` as PathString;

  try {
    await Bun.write(tmpFile, originalText);

    const args =
      (await guessEditorDarwin(tmpFile)) ||
      call(() => {
        const editor = process.env.EDITOR || "code";
        const vsCodeBased = /^(code|cursor|windsurf|codeium)$|^code\-|/.test(editor);
        return vsCodeBased ? [editor, "--wait", tmpFile] : [editor, tmpFile];
      });
    const child = Bun.spawn(args, {
      stdio: ["inherit", "inherit", "inherit"],
    });

    await child.exited;

    let editedText = originalText;
    if (child.exitCode === 0) {
      editedText = await Bun.file(tmpFile).text();
    }

    return editedText.trim().length > 0 ? editedText : null;
  } finally {
    // Clean up temp directory and its contents
    await Bun.$`rm -rf ${tmpDir}`;
  }
}
async function guessEditorDarwin(filePath: PathString): Promise<null | string[]> {
  // guess the editor based on current app (terminal inside one of these products)
  const bundleId = process.env.__CFBundleIdentifier;

  switch (bundleId) {
    case "com.todesktop.230313mzl4w4u92":
      return ["cursor", "--wait", filePath];
    case "com.microsoft.VSCode":
      return ["code", "--wait", filePath];
    case "com.microsoft.VSCodeInsiders":
      return ["code-insiders", "--wait", filePath];
    case "com.exafunction.windsurf":
      return ["windsurf", "--wait", filePath];
    default:
      return null;
  }
}