/**
 * Copyright (c) 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule getTextContentFromFiles
 * 
 */

'use strict';

var TEXT_CLIPPING_REGEX = /\.textClipping$/;

var TEXT_TYPES = {
  'text/plain': true,
  'text/html': true,
  'text/rtf': true
};

// Somewhat arbitrary upper bound on text size. Let's not lock up the browser.
var TEXT_SIZE_UPPER_BOUND = 5000;

/**
 * Extract the text content from a file list.
 */
function getTextContentFromFiles(files, callback) {
  var readCount = 0;
  var results = [];
  files.forEach(function ( /*blob*/file) {
    readFile(file, function ( /*string*/text) {
      readCount++;
      text && results.push(text.slice(0, TEXT_SIZE_UPPER_BOUND));
      if (readCount == files.length) {
        callback(results.join('\r'));
      }
    });
  });
}

/**
 * todo isaac: Do work to turn html/rtf into a content fragment.
 */
function readFile(file, callback) {
  if (!global.FileReader || file.type && !(file.type in TEXT_TYPES)) {
    callback('');
    return;
  }

  if (file.type === '') {
    var contents = '';
    // Special-case text clippings, which have an empty type but include
    // `.textClipping` in the file name. `readAsText` results in an empty
    // string for text clippings, so we force the file name to serve
    // as the text value for the file.
    if (TEXT_CLIPPING_REGEX.test(file.name)) {
      contents = file.name.replace(TEXT_CLIPPING_REGEX, '');
    }
    callback(contents);
    return;
  }

  var reader = new FileReader();
  reader.onload = function () {
    callback(reader.result);
  };
  reader.onerror = function () {
    callback('');
  };
  reader.readAsText(file);
}

module.exports = getTextContentFromFiles;