/*
 * Copyright 2014 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.
 */
/*jslint node: true */

'use strict';

var fs = require('fs');
var crypto = require('crypto');
var http = require('http');
var https = require('https');

function downloadFile(file, url, callback, redirects) {
  var completed = false;
  var protocol = /^https:\/\//.test(url) ? https : http;
  protocol.get(url, function (response) {
    var redirectTo;
    if (response.statusCode === 301 || response.statusCode === 302 ||
        response.statusCode === 307 || response.statusCode === 308) {
      if (redirects > 10) {
        callback('Too many redirects');
      }
      redirectTo = response.headers.location;
      redirectTo = require('url').resolve(url, redirectTo);
      downloadFile(file, redirectTo, callback, (redirects || 0) + 1);
      return;
    }
    if (response.statusCode === 404 && url.indexOf('web.archive.org') < 0) {
      // trying waybackmachine
      redirectTo = 'http://web.archive.org/web/' + url;
      downloadFile(file, redirectTo, callback, (redirects || 0) + 1);
      return;
    }

    if (response.statusCode !== 200) {
      if (!completed) {
        completed = true;
        callback('HTTP ' + response.statusCode);
      }
      return;
    }
    var stream = fs.createWriteStream(file);
    stream.on('error', function (err) {
      if (!completed) {
        completed = true;
        callback(err);
      }
    });
    response.pipe(stream);
    stream.on('finish', function() {
      stream.close();
      if (!completed) {
        completed = true;
        callback();
      }
    });
  }).on('error', function (err) {
    if (!completed) {
      if (typeof err === 'object' && err.errno === 'ENOTFOUND' &&
          url.indexOf('web.archive.org') < 0) {
        // trying waybackmachine
        var redirectTo = 'http://web.archive.org/web/' + url;
        downloadFile(file, redirectTo, callback, (redirects || 0) + 1);
        return;
      }
      completed = true;
      callback(err);
    }
  });
}

function downloadManifestFiles(manifest, callback) {
  function downloadNext() {
    if (i >= links.length) {
      callback();
      return;
    }
    var file = links[i].file;
    var url = links[i].url;
    console.log('Downloading ' + url + ' to ' + file + '...');
    downloadFile(file, url, function (err) {
      if (err) {
        console.error('Error during downloading of ' + url + ': ' + err);
        fs.writeFileSync(file, ''); // making it empty file
        fs.writeFileSync(file + '.error', err);
      }
      i++;
      downloadNext();
    });
  }

  var links = manifest.filter(function (item) {
    return item.link && !fs.existsSync(item.file);
  }).map(function (item) {
    var file = item.file;
    var linkfile = file + '.link';
    var url = fs.readFileSync(linkfile).toString();
    url = url.replace(/\s+$/, '');
    return {file: file, url: url};
  });

  var i = 0;
  downloadNext();
}

function calculateMD5(file, callback) {
  var hash = crypto.createHash('md5');
  var stream = fs.createReadStream(file);
  stream.on('data', function (data) {
    hash.update(data);
  });
  stream.on('error', function (err) {
    callback(err);
  });
  stream.on('end', function() {
    var result = hash.digest('hex');
    callback(null, result);
  });
}

function verifyManifestFiles(manifest, callback) {
  function verifyNext() {
    if (i >= manifest.length) {
      callback(error);
      return;
    }
    var item = manifest[i];
    if (fs.existsSync(item.file + '.error')) {
      console.error('WARNING: File was not downloaded. See "' +
                    item.file + '.error" file.');
      error = true;
      i++;
      verifyNext();
      return;
    }
    calculateMD5(item.file, function (err, md5) {
      if (err) {
        console.log('WARNING: Unable to open file for reading "' + err + '".');
        error = true;
      } else if (!item.md5) {
        console.error('WARNING: Missing md5 for file "' + item.file + '". ' +
                      'Hash for current file is "' + md5 + '"');
        error = true;
      } else if (md5 !== item.md5) {
        console.error('WARNING: MD5 of file "' + item.file +
                      '" does not match file. Expected "' +
                      item.md5 + '" computed "' + md5 + '"');
        error = true;
      }
      i++;
      verifyNext();
    });
  }
  var i = 0;
  var error = false;
  verifyNext();
}

exports.downloadManifestFiles = downloadManifestFiles;
exports.verifyManifestFiles = verifyManifestFiles;
