NodeJS File object

file.js

var File = {
  open: function (path, mode) {
    var fd, queue, enc;

    enc = 'utf8';
    queue = [];
    
    // This is called after each step in the queue finishes, when the queue is empty, then we close the file descriptor.
    function run_next() {
      if (queue.length > 0) {
        node.debug("pulling from queue");
        (queue.shift())();
      } else {
        node.debug("done, closing");
        node.fs.close(fd);
      }
    }
    
    // generator is a function that returns an array of [fn, arg1, arg2, ...]
    function enqueue(generator) {
      var promise, args, fn;
      promise = new node.Promise();
      queue.push(function () {
        args = generator();
        fn = args.shift();
        node.debug(fn + JSON.stringify(args));
        fn.apply(this, args).addCallback(function () {
          node.debug("action returned " + Array.prototype.slice.call(arguments));
          promise.emitSuccess.apply(promise, arguments);
          run_next();
        });
      });
      return promise;
    }
    
    // Kick off the process
    node.fs.open(path, mode, 0644).addCallback(function (file_descriptor) {
      fd = file_descriptor;
      node.debug("File opened, starting queue: " + fd);
      run_next();
    });
    
    // Return an object with public facing methods
    return {
      write: function (message) {
        node.debug("enqueue write command");
        return enqueue(function () {
          node.debug("write generated: " + fd)
          return [node.fs.write, fd, message, 0, enc];
        });
      }
    };
  }
}

// This should open the file, then write to the file, then close the file, all as chained events
// and automatically.
var f = File.open("test.txt", "w");
f.write("Hello World\n");
f.write("Hello World2\n");