/* Copyright 2012 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import {
  assert, MissingPDFException, UnexpectedResponseException
} from '../shared/util';
import { getFilenameFromUrl } from './dom_utils';

function validateRangeRequestCapabilities({ getResponseHeader, isHttp,
                                            rangeChunkSize, disableRange, }) {
  assert(rangeChunkSize > 0, 'Range chunk size must be larger than zero');
  let returnValues = {
    allowRangeRequests: false,
    suggestedLength: undefined,
  };
  if (disableRange || !isHttp) {
    return returnValues;
  }
  if (getResponseHeader('Accept-Ranges') !== 'bytes') {
    return returnValues;
  }

  let contentEncoding = getResponseHeader('Content-Encoding') || 'identity';
  if (contentEncoding !== 'identity') {
    return returnValues;
  }

  let length = parseInt(getResponseHeader('Content-Length'), 10);
  if (!Number.isInteger(length)) {
    return returnValues;
  }

  returnValues.suggestedLength = length;
  if (length <= 2 * rangeChunkSize) {
    // The file size is smaller than the size of two chunks, so it does not
    // make any sense to abort the request and retry with a range request.
    return returnValues;
  }

  returnValues.allowRangeRequests = true;
  return returnValues;
}

function createResponseStatusError(status, url) {
  if (status === 404 || status === 0 && /^file:/.test(url)) {
    return new MissingPDFException('Missing PDF "' + url + '".');
  }
  return new UnexpectedResponseException(
    'Unexpected server response (' + status +
    ') while retrieving PDF "' + url + '".', status);
}

function validateResponseStatus(status) {
  return status === 200 || status === 206;
}

function extractFilenameFromHeader(getResponseHeader) {
  const contentDisposition = getResponseHeader('Content-Disposition');

  if (contentDisposition) {
    let parts =
      /.+;\s*filename=(?:"|')(.+\.pdf)(?:"|')/gi.exec(contentDisposition);
    if (parts !== null && parts.length > 1) {
      return getFilenameFromUrl(parts[1]);
    }
  }

  return null;
}

export {
  createResponseStatusError,
  validateRangeRequestCapabilities,
  validateResponseStatus,
  extractFilenameFromHeader,
};