// Copyright 2009 Google Inc.  All Rights Reserved.

/**

 * A multipart form data construction class for XHR.

 * @see http://www.w3.org/Protocols/rfc1341/7_2_Multipart.html

 * @constructor

 */

var MultipartFormData = function() {

  /**

   * @type {Array}

   */

  this.headers = [];

  /**

   * @type {Array}

   */

  this.parts = [];

  /**

   * A random string for the boundary.

   * @type {string}

   */

  this.boundary = MultipartFormData.getRandomBoundary();

};

/**

 * @type {string}

 */

MultipartFormData.CRLF = '\r\n';

/**

 * @type {string}

 * @private

 */

MultipartFormData.TEN_CHARS_ =

/**

 * Generates a random number and some random characters from it.

 */

MultipartFormData.getRandomBoundary = function() {

  var anyTenCharacters = 'DiStRIcT10';

  var randomNumber = Math.floor(Math.random() * 10000000);

  var nums = randomNumber.toString().split('');

  var randomChars = '';

  for (var i = 0, num; num = nums[i]; i++) {

    randomChars += anyTenCharacters[num];

  }

  return randomChars + '-' + randomNumber;

};

/**

 * @param {string} name The name for this header.

 * @param {string} value The value for this header.

 */

MultipartFormData.prototype.addHeader = function(name, value) {

  this.headers.push({

    'name': name,

    'value': value

  });

};

/**

 * @param {?string} name The name for this part.

 * @param {string} value The value for this part.

 * @param {string} opt_contentType Content-type for this part.

 * @param {string} opt_contentDisposition Content disposition for this part.

 * @param {string} opt_filename The filename for this part

 */

MultipartFormData.prototype.addPart = function(name, value, opt_contentType,

    opt_contentDisposition, opt_filename) {

  var contentType = opt_contentType || null;

  var contentDisposition = opt_contentDisposition || null;

  var filename = opt_filename || null;

  this.parts.push({

    'name': name,

    'value': value,

    'contentType': contentType,

    'contentDisposition': contentDisposition,

    'filename': filename

  });

};

/**

 * @return {string} The string to set as a payload.

 */

MultipartFormData.prototype.toString = function() {

  var lines = [];

  for (var i = 0, header; header = this.headers[i]; i++) {

    lines.push(header['name'] + ': ' + header['value']);

  }

  if (this.headers.length > 0) {

    lines.push('');

  }

  for (var i = 0, part; part = this.parts[i]; i++) {

    lines.push('--' + this.boundary);

    if (part['contentDisposition']) {

      var contentDisposition = 'Content-Disposition: form-data; ';

      contentDisposition += 'name="' + part['name'] + '"';

      if (part['filename']) {

        contentDisposition += '; filename="' + part['filename'] + '"';

      }

      lines.push(contentDisposition);

    }

    if (part['contentType']) {

      lines.push('Content-Type: ' + part['contentType']);

    }

    lines.push('');

    lines.push(part['value']);

  }

  lines.push('--' + this.boundary + '--');

  return lines.join(MultipartFormData.CRLF) + MultipartFormData.CRLF;

};