'use strict';

/*
  Task 1. Gets IPs for proxies of antizapret/anticenz with dns-lg.com.
          These IPs are used in block-informer to inform user when proxy is ON.
  Task 2. Downloads PAC proxy script from antizapret/anticenz/my Google Drive and sets it in Chromium settings.
  Task 3. Schedules tasks 1 & 2 for every 4 hours.
*/

/*
  In background scripts use window.antiCensorRu public variables.
  In pages window.antiCensorRu are not accessible,
    use chrome.runtime.getBackgroundPage(..),
    avoid old extension.getBackgroundPage.
*/

window.antiCensorRu = {

  // PUBLIC
  
  version: chrome.runtime.getManifest().version,

  pacProviders: {
    Антизапрет: {
      pacUrl: 'http://antizapret.prostovpn.org/proxy.pac',
      proxyHosts: ['proxy.antizapret.prostovpn.org'],
      proxyIps: {
        '195.154.110.37': 'proxy.antizapret.prostovpn.org'
      }
    },
    Антиценз: {
      pacUrl: 'https://config.anticenz.org/proxy.pac',
      proxyHosts: ['gw2.anticenz.org'],
      proxyIps: {
        '5.196.220.114': 'gw2.anticenz.org'
      }
    },
    Оба_и_на_свитчах: {
      pacUrl: 'https://drive.google.com/uc?export=download&id=0B-ZCVSvuNWf0akpCOURNS2VCTmc',
      proxyHosts: ['gw2.anticenz.org', 'proxy.antizapret.prostovpn.org'],
      proxyIps: {
        '5.196.220.114': 'gw2.anticenz.org',
        '195.154.110.37': 'proxy.antizapret.prostovpn.org'
      }
    }
  },

  _currentPacProviderKey: 'Оба_и_на_свитчах',

  get currentPacProviderKey() { return this._currentPacProviderKey },
  set currentPacProviderKey(newKey) {
    if (newKey && !this.pacProviders[newKey])
      throw new IllegalArgumentException('No provider for key:'+newKey);
    this._currentPacProviderKey = newKey;
  },

  get pacProvider() { return this.pacProviders[this.currentPacProviderKey] },

  /*
    Is it the first time extension installed? Do something, e.g. initiate PAC sync.
  */
  ifFirstInstall: false,
  lastPacUpdateStamp: 0,

  // PROTECTED
  _periodicUpdateAlarmReason: 'Периодичное обновление PAC-скрипта Антизапрет',

  pushToStorage(cb) {

    // Copy only settable properties.
    var onlySettable = {};
      for(var key of Object.keys(this))
        if (Object.getOwnPropertyDescriptor(this, key).writable && typeof(this[key]) !== 'function')
          onlySettable[key] = this[key]

    return chrome.storage.local.clear(
      () => chrome.storage.local.set(
        onlySettable,
        () => cb && cb(chrome.runtime.lastError, onlySettable)
      )
    );
    
  },

  pullFromStorage(cb) {
    chrome.storage.local.get(null, storage => {
      console.log('In storage:', storage);
      for(var key of Object.keys(storage))
        this[key] = storage[key];

      console.log('Synced with storage, any callback?', !!cb);
      if (cb)
        cb(chrome.runtime.lastError, storage);
    });
  },

  syncWithPacProvider(cb) {
    var cb = cb || (() => {});
    if (!this.pacProvider)
      return cb({clarification: 'Сперва выберите PAC-провайдера.'});

    var pacSetPromise = new Promise(
      (resolve, reject) => setPacScriptFromProvider(
        this.pacProvider,
        (err, res) => {
          if (err)
            return reject(err);
          this.lastPacUpdateStamp = Date.now();
          this.ifFirstInstall = false;
          return resolve(res);
        }
      )
    );

    return updatePacProxyIps(
      this.pacProvider,
      ipsError => {
        if (ipsError && ipsError.clarification)
          ipsError.clarification.ifNotCritical = true;
        pacSetPromise.then(
          res => this.pushToStorage(
            pushError => pushError ? cb(pushError) : cb(ipsError, res)
          ),
          err => cb(err)
        )
      }
    );
  },
  
  setAlarms() {
    chrome.alarms.create(
      this._periodicUpdateAlarmReason,
      { periodInMinutes: 4*60 }
    );
  },

  installPac(key, cb) {

    if(typeof(key) === 'function') {
      cb = key;
      key = undefined;
    }

    if(key)
      this.currentPacProviderKey = key;

    var cb = asyncLogGroup('Installing PAC...', cb);
    
    this.setAlarms();

    return this.syncWithPacProvider(cb);

  },

  clearPac(cb) {
    var cb = asyncLogGroup('Cearing alarms and PAC...', cb);
    chrome.alarms.clearAll(
      () => chrome.proxy.settings.clear(
        {},
        () => {
          this.currentPacProviderKey = undefined;
          return this.pushToStorage(cb);
        }
      )
    );
  }

};

// ON EACH LAUNCH, STARTUP, RELOAD, UPDATE, ENABLE    
chrome.storage.local.get(null, oldStorage => {

  console.log('Init on storage:', oldStorage);
  
  antiCensorRu.ifFirstInstall = Object.keys(oldStorage).length === 0;

  // Finish each init with this callback setting alarm listeners.
  function cb(err) {
    chrome.alarms.onAlarm.addListener(
      alarm => {
        if (alarm.name === antiCensorRu._periodicUpdateAlarmReason) {
          console.log('Periodic update triggered:', new Date());
          antiCensorRu.syncWithPacProvider();
        }
      }
    );
    console.log('Alarm listener installed. We won\'t miss any PAC update.');

    chrome.alarms.get(
      antiCensorRu._periodicUpdateAlarmReason,
      alarm => {
        if (alarm)
          console.log(
            'Next update is scheduled on', new Date(alarm.scheduledTime).toLocaleString('ru-RU')
          );
        else if (!antiCensorRu.ifFirstInstall && antiCensorRu.pacProvider) {
          antiCensorRu.setAlarms();
          console.error('KNOWN BUG: Alarms were lost. See issues on GitHub. Don\'t worry, next update was rescheduled.');
        }
      }
    );
  }

  // INSTALL  
  if (antiCensorRu.ifFirstInstall) {
    console.log('Installing...');
    return chrome.runtime.openOptionsPage(cb);
  }

  /* 
    1. There is no way to check that chrome.runtime.onInstalled wasn't fired except timeout.
       Otherwise we could put storage migration code only there.
    2. We have to check storage for migration before using it.
       Better on each launch then on each pull.
  */

  // LAUNCH, RELOAD, UPDATE
  
  antiCensorRu._currentPacProviderKey = oldStorage._currentPacProviderKey;
  antiCensorRu.lastPacUpdateStamp = oldStorage.lastPacUpdateStamp || antiCensorRu.lastPacUpdateStamp;

  if (antiCensorRu.version === oldStorage.version) {
    // LAUNCH, RELOAD
    console.log('Launch or reload. Do nothing.');
    return cb();
  }

  // UPDATE & MIGRATION
  console.log('Updating...');
  return antiCensorRu.pacProvider &&
    updatePacProxyIps(
      antiCensorRu.pacProvider,
      ipsError => {
        if (ipsError) ipsError.ifNotCritical = true;
        antiCensorRu.pushToStorage( pushError => cb( pushError || ipsError ) );
      }
    );

  /*

    History of Changes to Storage (Migration Guide)
    -----------------------------------------------

    Version 0.0.0.10

      * Added this.version
      * PacProvider.proxyIps changed from {ip -> Boolean} to {ip -> hostname}

    Version 0.0.0.8-9

      * Changed storage.ifNotInstalled to storage.ifFirstInstall
      * Added storage.lastPacUpdateStamp

  **/
});

// PRIVATE

function asyncLogGroup() {
  var args = [].slice.apply(arguments);
  var cb = args.pop();
  console.group.apply(console, args);
  return function() {
    console.log('Finished');
    console.groupEnd();
    var _cb = cb || (() => {});
    return _cb.apply(this, arguments);
  }
}

function ifSuccessfulCode(status) {
  return status >= 200 && status < 300 || status === 304;
}

function httpGet(url, cb) {
  var cb = cb || (() => {});
  var req = new XMLHttpRequest();
  var ifAsync = true;
  req.open('GET', url, ifAsync);
  req.onload = event => {
    if ( !ifSuccessfulCode(req.status) ) {
      req.clarification = {message: 'Получен ответ с неудачным HTTP-кодом '+req.status+ '.'};
      return cb(req);
    }
    console.log('GETed with success.');
    return cb(null, req.responseText)
  };
  req.onerror = event => { event.clarification = {message: 'Что-то не так с сетью, проверьте соединение.'}; return cb(event); };
  req.send();
}

function updatePacProxyIps(provider, cb) {
  var cb = asyncLogGroup('Getting IP for '+ provider.proxyHosts.join(', ') +'...', cb);
  var failure = {
    clarification: {message:'Не удалось получить один или несколько IP адресов для прокси-серверов. Иконка для уведомления об обходе блокировок может не отображаться.'},
    errors: {}
  };
  var i = 0;
  for (var proxyHost of provider.proxyHosts) {
    httpGet(
      'http://www.dns-lg.com/google1/'+ proxyHost +'/A',
      (err, res) => {
        if (!err) {
          provider.proxyIps = provider.proxyIps || {};
          provider.proxyIps[ JSON.parse(res).answer[0].rdata ] = proxyHost;
        } else
          failure.errors[proxyHost] = err;

        if ( ++i == provider.proxyHosts.length ) {
          failure = Object.keys(failure.errors).length ? failure : null;
          return cb(failure, provider.proxyIps);
        }
      }
    );
  }
}

function setPacScriptFromProvider(provider, cb) {
  var cb = asyncLogGroup('Getting pac script from provider...', provider.pacUrl, cb);

  httpGet(
    provider.pacUrl,
    (err, res) => {
      if (err) {
        err.clarification = {
          message: 'Не удалось скачать PAC-скрипт с адреса: ' +provider.pacUrl+ '.',
          prev: err.clarification
        };
        return cb(err);
      }
      console.log('Clearing chrome proxy settings...');
      return chrome.proxy.settings.clear({}, () => {
        var config = {
          mode: 'pac_script',
          pacScript: {
            mandatory: false,
            data: res
          }
        };
        console.log('Setting chrome proxy settings...');
        chrome.proxy.settings.set( {value: config}, cb );
      });
    }
  );
}