1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5// Routines used to normalize arguments to messaging functions.
6
7function alignSendMessageArguments(args, hasOptionsArgument) {
8  // Align missing (optional) function arguments with the arguments that
9  // schema validation is expecting, e.g.
10  //   extension.sendRequest(req)     -> extension.sendRequest(null, req)
11  //   extension.sendRequest(req, cb) -> extension.sendRequest(null, req, cb)
12  if (!args || !args.length)
13    return null;
14  var lastArg = args.length - 1;
15
16  // responseCallback (last argument) is optional.
17  var responseCallback = null;
18  if (typeof args[lastArg] == 'function')
19    responseCallback = args[lastArg--];
20
21  var options = null;
22  if (hasOptionsArgument && lastArg >= 1) {
23    // options (third argument) is optional. It can also be ambiguous which
24    // argument it should match. If there are more than two arguments remaining,
25    // options is definitely present:
26    if (lastArg > 1) {
27      options = args[lastArg--];
28    } else {
29      // Exactly two arguments remaining. If the first argument is a string,
30      // it should bind to targetId, and the second argument should bind to
31      // request, which is required. In other words, when two arguments remain,
32      // only bind options when the first argument cannot bind to targetId.
33      if (!(args[0] === null || typeof args[0] == 'string'))
34        options = args[lastArg--];
35    }
36  }
37
38  // request (second argument) is required.
39  var request = args[lastArg--];
40
41  // targetId (first argument, extensionId in the manifest) is optional.
42  var targetId = null;
43  if (lastArg >= 0)
44    targetId = args[lastArg--];
45
46  if (lastArg != -1)
47    return null;
48  if (hasOptionsArgument)
49    return [targetId, request, options, responseCallback];
50  return [targetId, request, responseCallback];
51}
52
53exports.alignSendMessageArguments = alignSendMessageArguments;
54