AlgoliaSearchCore.js

module.exports = AlgoliaSearchCore;

var errors = require('./errors');
var exitPromise = require('./exitPromise.js');
var IndexCore = require('./IndexCore.js');
var store = require('./store.js');

// We will always put the API KEY in the JSON body in case of too long API KEY,
// to avoid query string being too long and failing in various conditions (our server limit, browser limit,
// proxies limit)
var MAX_API_KEY_LENGTH = 500;
var RESET_APP_DATA_TIMER =
  process.env.RESET_APP_DATA_TIMER && parseInt(process.env.RESET_APP_DATA_TIMER, 10) ||
  60 * 2 * 1000; // after 2 minutes reset to first host

/*
 * Algolia Search library initialization
 * https://www.algolia.com/
 *
 * @param {string} applicationID - Your applicationID, found in your dashboard
 * @param {string} apiKey - Your API key, found in your dashboard
 * @param {Object} [opts]
 * @param {number} [opts.timeout=2000] - The request timeout set in milliseconds,
 * another request will be issued after this timeout
 * @param {string} [opts.protocol='https:'] - The protocol used to query Algolia Search API.
 *                                        Set to 'http:' to force using http.
 * @param {Object|Array} [opts.hosts={
 *           read: [this.applicationID + '-dsn.algolia.net'].concat([
 *             this.applicationID + '-1.algolianet.com',
 *             this.applicationID + '-2.algolianet.com',
 *             this.applicationID + '-3.algolianet.com']
 *           ]),
 *           write: [this.applicationID + '.algolia.net'].concat([
 *             this.applicationID + '-1.algolianet.com',
 *             this.applicationID + '-2.algolianet.com',
 *             this.applicationID + '-3.algolianet.com']
 *           ]) - The hosts to use for Algolia Search API.
 *           If you provide them, you will less benefit from our HA implementation
 */
function AlgoliaSearchCore(applicationID, apiKey, opts) {
  var debug = require('debug')('algoliasearch');

  var clone = require('./clone.js');
  var isArray = require('isarray');
  var map = require('./map.js');

  var usage = 'Usage: algoliasearch(applicationID, apiKey, opts)';

  if (opts._allowEmptyCredentials !== true && !applicationID) {
    throw new errors.AlgoliaSearchError('Please provide an application ID. ' + usage);
  }

  if (opts._allowEmptyCredentials !== true && !apiKey) {
    throw new errors.AlgoliaSearchError('Please provide an API key. ' + usage);
  }

  this.applicationID = applicationID;
  this.apiKey = apiKey;

  this.hosts = {
    read: [],
    write: []
  };

  opts = opts || {};

  this._timeouts = opts.timeouts || {
    connect: 1 * 1000, // 500ms connect is GPRS latency
    read: 2 * 1000,
    write: 30 * 1000
  };

  // backward compat, if opts.timeout is passed, we use it to configure all timeouts like before
  if (opts.timeout) {
    this._timeouts.connect = this._timeouts.read = this._timeouts.write = opts.timeout;
  }

  var protocol = opts.protocol || 'https:';
  // while we advocate for colon-at-the-end values: 'http:' for `opts.protocol`
  // we also accept `http` and `https`. It's a common error.
  if (!/:$/.test(protocol)) {
    protocol = protocol + ':';
  }

  if (protocol !== 'http:' && protocol !== 'https:') {
    throw new errors.AlgoliaSearchError('protocol must be `http:` or `https:` (was `' + opts.protocol + '`)');
  }

  this._checkAppIdData();

  if (!opts.hosts) {
    var defaultHosts = map(this._shuffleResult, function(hostNumber) {
      return applicationID + '-' + hostNumber + '.algolianet.com';
    });

    // no hosts given, compute defaults
    var mainSuffix = (opts.dsn === false ? '' : '-dsn') + '.algolia.net';
    this.hosts.read = [this.applicationID + mainSuffix].concat(defaultHosts);
    this.hosts.write = [this.applicationID + '.algolia.net'].concat(defaultHosts);
  } else if (isArray(opts.hosts)) {
    // when passing custom hosts, we need to have a different host index if the number
    // of write/read hosts are different.
    this.hosts.read = clone(opts.hosts);
    this.hosts.write = clone(opts.hosts);
  } else {
    this.hosts.read = clone(opts.hosts.read);
    this.hosts.write = clone(opts.hosts.write);
  }

  // add protocol and lowercase hosts
  this.hosts.read = map(this.hosts.read, prepareHost(protocol));
  this.hosts.write = map(this.hosts.write, prepareHost(protocol));

  this.extraHeaders = {};

  // In some situations you might want to warm the cache
  this.cache = opts._cache || {};

  this._ua = opts._ua;
  this._useCache = opts._useCache === undefined || opts._cache ? true : opts._useCache;
  this._useRequestCache = this._useCache && opts._useRequestCache;
  this._useFallback = opts.useFallback === undefined ? true : opts.useFallback;

  this._setTimeout = opts._setTimeout;

  debug('init done, %j', this);
}

/*
 * Get the index object initialized
 *
 * @param indexName the name of index
 * @param callback the result callback with one argument (the Index instance)
 */
AlgoliaSearchCore.prototype.initIndex = function(indexName) {
  return new IndexCore(this, indexName);
};

/**
* Add an extra field to the HTTP request
*
* @param name the header field name
* @param value the header field value
*/
AlgoliaSearchCore.prototype.setExtraHeader = function(name, value) {
  this.extraHeaders[name.toLowerCase()] = value;
};

/**
* Get the value of an extra HTTP header
*
* @param name the header field name
*/
AlgoliaSearchCore.prototype.getExtraHeader = function(name) {
  return this.extraHeaders[name.toLowerCase()];
};

/**
* Remove an extra field from the HTTP request
*
* @param name the header field name
*/
AlgoliaSearchCore.prototype.unsetExtraHeader = function(name) {
  delete this.extraHeaders[name.toLowerCase()];
};

/**
* Augment sent x-algolia-agent with more data, each agent part
* is automatically separated from the others by a semicolon;
*
* @param algoliaAgent the agent to add
*/
AlgoliaSearchCore.prototype.addAlgoliaAgent = function(algoliaAgent) {
  var algoliaAgentWithDelimiter = '; ' + algoliaAgent;

  if (this._ua.indexOf(algoliaAgentWithDelimiter) === -1) {
    this._ua += algoliaAgentWithDelimiter;
  }
};

/*
 * Wrapper that try all hosts to maximize the quality of service
 */
AlgoliaSearchCore.prototype._jsonRequest = function(initialOpts) {
  this._checkAppIdData();

  var requestDebug = require('debug')('algoliasearch:' + initialOpts.url);


  var body;
  var cacheID;
  var additionalUA = initialOpts.additionalUA || '';
  var cache = initialOpts.cache;
  var client = this;
  var tries = 0;
  var usingFallback = false;
  var hasFallback = client._useFallback && client._request.fallback && initialOpts.fallback;
  var headers;

  if (
    this.apiKey.length > MAX_API_KEY_LENGTH &&
    initialOpts.body !== undefined &&
    (initialOpts.body.params !== undefined || // index.search()
    initialOpts.body.requests !== undefined) // client.search()
  ) {
    initialOpts.body.apiKey = this.apiKey;
    headers = this._computeRequestHeaders({
      additionalUA: additionalUA,
      withApiKey: false,
      headers: initialOpts.headers
    });
  } else {
    headers = this._computeRequestHeaders({
      additionalUA: additionalUA,
      headers: initialOpts.headers
    });
  }

  if (initialOpts.body !== undefined) {
    body = safeJSONStringify(initialOpts.body);
  }

  requestDebug('request start');
  var debugData = [];


  function doRequest(requester, reqOpts) {
    client._checkAppIdData();

    var startTime = new Date();

    if (client._useCache && !client._useRequestCache) {
      cacheID = initialOpts.url;
    }

    // as we sometime use POST requests to pass parameters (like query='aa'),
    // the cacheID must also include the body to be different between calls
    if (client._useCache && !client._useRequestCache && body) {
      cacheID += '_body_' + reqOpts.body;
    }

    // handle cache existence
    if (isCacheValidWithCurrentID(!client._useRequestCache, cache, cacheID)) {
      requestDebug('serving response from cache');

      var responseText = cache[cacheID];

      // Cache response must match the type of the original one
      return client._promise.resolve({
        body: JSON.parse(responseText),
        responseText: responseText
      });
    }

    // if we reached max tries
    if (tries >= client.hosts[initialOpts.hostType].length) {
      if (!hasFallback || usingFallback) {
        requestDebug('could not get any response');
        // then stop
        return client._promise.reject(new errors.AlgoliaSearchError(
          'Cannot connect to the AlgoliaSearch API.' +
          ' Send an email to support@algolia.com to report and resolve the issue.' +
          ' Application id was: ' + client.applicationID, {debugData: debugData}
        ));
      }

      requestDebug('switching to fallback');

      // let's try the fallback starting from here
      tries = 0;

      // method, url and body are fallback dependent
      reqOpts.method = initialOpts.fallback.method;
      reqOpts.url = initialOpts.fallback.url;
      reqOpts.jsonBody = initialOpts.fallback.body;
      if (reqOpts.jsonBody) {
        reqOpts.body = safeJSONStringify(reqOpts.jsonBody);
      }
      // re-compute headers, they could be omitting the API KEY
      headers = client._computeRequestHeaders({
        additionalUA: additionalUA,
        headers: initialOpts.headers
      });

      reqOpts.timeouts = client._getTimeoutsForRequest(initialOpts.hostType);
      client._setHostIndexByType(0, initialOpts.hostType);
      usingFallback = true; // the current request is now using fallback
      return doRequest(client._request.fallback, reqOpts);
    }

    var currentHost = client._getHostByType(initialOpts.hostType);

    var url = currentHost + reqOpts.url;
    var options = {
      body: reqOpts.body,
      jsonBody: reqOpts.jsonBody,
      method: reqOpts.method,
      headers: headers,
      timeouts: reqOpts.timeouts,
      debug: requestDebug,
      forceAuthHeaders: reqOpts.forceAuthHeaders
    };

    requestDebug('method: %s, url: %s, headers: %j, timeouts: %d',
      options.method, url, options.headers, options.timeouts);

    if (requester === client._request.fallback) {
      requestDebug('using fallback');
    }

    // `requester` is any of this._request or this._request.fallback
    // thus it needs to be called using the client as context
    return requester.call(client, url, options).then(success, tryFallback);

    function success(httpResponse) {
      // compute the status of the response,
      //
      // When in browser mode, using XDR or JSONP, we have no statusCode available
      // So we rely on our API response `status` property.
      // But `waitTask` can set a `status` property which is not the statusCode (it's the task status)
      // So we check if there's a `message` along `status` and it means it's an error
      //
      // That's the only case where we have a response.status that's not the http statusCode
      var status = httpResponse && httpResponse.body && httpResponse.body.message && httpResponse.body.status ||

        // this is important to check the request statusCode AFTER the body eventual
        // statusCode because some implementations (jQuery XDomainRequest transport) may
        // send statusCode 200 while we had an error
        httpResponse.statusCode ||

        // When in browser mode, using XDR or JSONP
        // we default to success when no error (no response.status && response.message)
        // If there was a JSON.parse() error then body is null and it fails
        httpResponse && httpResponse.body && 200;

      requestDebug('received response: statusCode: %s, computed statusCode: %d, headers: %j',
        httpResponse.statusCode, status, httpResponse.headers);

      var httpResponseOk = Math.floor(status / 100) === 2;

      var endTime = new Date();
      debugData.push({
        currentHost: currentHost,
        headers: removeCredentials(headers),
        content: body || null,
        contentLength: body !== undefined ? body.length : null,
        method: reqOpts.method,
        timeouts: reqOpts.timeouts,
        url: reqOpts.url,
        startTime: startTime,
        endTime: endTime,
        duration: endTime - startTime,
        statusCode: status
      });

      if (httpResponseOk) {
        if (client._useCache && !client._useRequestCache && cache) {
          cache[cacheID] = httpResponse.responseText;
        }

        return {
          responseText: httpResponse.responseText,
          body: httpResponse.body
        };
      }

      var shouldRetry = Math.floor(status / 100) !== 4;

      if (shouldRetry) {
        tries += 1;
        return retryRequest();
      }

      requestDebug('unrecoverable error');

      // no success and no retry => fail
      var unrecoverableError = new errors.AlgoliaSearchError(
        httpResponse.body && httpResponse.body.message, {debugData: debugData, statusCode: status}
      );

      return client._promise.reject(unrecoverableError);
    }

    function tryFallback(err) {
      // error cases:
      //  While not in fallback mode:
      //    - CORS not supported
      //    - network error
      //  While in fallback mode:
      //    - timeout
      //    - network error
      //    - badly formatted JSONP (script loaded, did not call our callback)
      //  In both cases:
      //    - uncaught exception occurs (TypeError)
      requestDebug('error: %s, stack: %s', err.message, err.stack);

      var endTime = new Date();
      debugData.push({
        currentHost: currentHost,
        headers: removeCredentials(headers),
        content: body || null,
        contentLength: body !== undefined ? body.length : null,
        method: reqOpts.method,
        timeouts: reqOpts.timeouts,
        url: reqOpts.url,
        startTime: startTime,
        endTime: endTime,
        duration: endTime - startTime
      });

      if (!(err instanceof errors.AlgoliaSearchError)) {
        err = new errors.Unknown(err && err.message, err);
      }

      tries += 1;

      // stop the request implementation when:
      if (
        // we did not generate this error,
        // it comes from a throw in some other piece of code
        err instanceof errors.Unknown ||

        // server sent unparsable JSON
        err instanceof errors.UnparsableJSON ||

        // max tries and already using fallback or no fallback
        tries >= client.hosts[initialOpts.hostType].length &&
        (usingFallback || !hasFallback)) {
        // stop request implementation for this command
        err.debugData = debugData;
        return client._promise.reject(err);
      }

      // When a timeout occurred, retry by raising timeout
      if (err instanceof errors.RequestTimeout) {
        return retryRequestWithHigherTimeout();
      }

      return retryRequest();
    }

    function retryRequest() {
      requestDebug('retrying request');
      client._incrementHostIndex(initialOpts.hostType);
      return doRequest(requester, reqOpts);
    }

    function retryRequestWithHigherTimeout() {
      requestDebug('retrying request with higher timeout');
      client._incrementHostIndex(initialOpts.hostType);
      client._incrementTimeoutMultipler();
      reqOpts.timeouts = client._getTimeoutsForRequest(initialOpts.hostType);
      return doRequest(requester, reqOpts);
    }
  }

  function isCacheValidWithCurrentID(
    useRequestCache,
    currentCache,
    currentCacheID
  ) {
    return (
      client._useCache &&
      useRequestCache &&
      currentCache &&
      currentCache[currentCacheID] !== undefined
    );
  }


  function interopCallbackReturn(request, callback) {
    if (isCacheValidWithCurrentID(client._useRequestCache, cache, cacheID)) {
      request.catch(function() {
        // Release the cache on error
        delete cache[cacheID];
      });
    }

    if (typeof initialOpts.callback === 'function') {
      // either we have a callback
      request.then(function okCb(content) {
        exitPromise(function() {
          initialOpts.callback(null, callback(content));
        }, client._setTimeout || setTimeout);
      }, function nookCb(err) {
        exitPromise(function() {
          initialOpts.callback(err);
        }, client._setTimeout || setTimeout);
      });
    } else {
      // either we are using promises
      return request.then(callback);
    }
  }

  if (client._useCache && client._useRequestCache) {
    cacheID = initialOpts.url;
  }

  // as we sometime use POST requests to pass parameters (like query='aa'),
  // the cacheID must also include the body to be different between calls
  if (client._useCache && client._useRequestCache && body) {
    cacheID += '_body_' + body;
  }

  if (isCacheValidWithCurrentID(client._useRequestCache, cache, cacheID)) {
    requestDebug('serving request from cache');

    var maybePromiseForCache = cache[cacheID];

    // In case the cache is warmup with value that is not a promise
    var promiseForCache = typeof maybePromiseForCache.then !== 'function'
      ? client._promise.resolve({responseText: maybePromiseForCache})
      : maybePromiseForCache;

    return interopCallbackReturn(promiseForCache, function(content) {
      // In case of the cache request, return the original value
      return JSON.parse(content.responseText);
    });
  }

  var request = doRequest(
    client._request, {
      url: initialOpts.url,
      method: initialOpts.method,
      body: body,
      jsonBody: initialOpts.body,
      timeouts: client._getTimeoutsForRequest(initialOpts.hostType),
      forceAuthHeaders: initialOpts.forceAuthHeaders
    }
  );

  if (client._useCache && client._useRequestCache && cache) {
    cache[cacheID] = request;
  }

  return interopCallbackReturn(request, function(content) {
    // In case of the first request, return the JSON value
    return content.body;
  });
};

/*
* Transform search param object in query string
* @param {object} args arguments to add to the current query string
* @param {string} params current query string
* @return {string} the final query string
*/
AlgoliaSearchCore.prototype._getSearchParams = function(args, params) {
  if (args === undefined || args === null) {
    return params;
  }
  for (var key in args) {
    if (key !== null && args[key] !== undefined && args.hasOwnProperty(key)) {
      params += params === '' ? '' : '&';
      params += key + '=' + encodeURIComponent(Object.prototype.toString.call(args[key]) === '[object Array]' ? safeJSONStringify(args[key]) : args[key]);
    }
  }
  return params;
};

/**
 * Compute the headers for a request
 *
 * @param [string] options.additionalUA semi-colon separated string with other user agents to add
 * @param [boolean=true] options.withApiKey Send the api key as a header
 * @param [Object] options.headers Extra headers to send
 */
AlgoliaSearchCore.prototype._computeRequestHeaders = function(options) {
  var forEach = require('foreach');

  var ua = options.additionalUA ?
    this._ua + '; ' + options.additionalUA :
    this._ua;

  var requestHeaders = {
    'x-algolia-agent': ua,
    'x-algolia-application-id': this.applicationID
  };

  // browser will inline headers in the url, node.js will use http headers
  // but in some situations, the API KEY will be too long (big secured API keys)
  // so if the request is a POST and the KEY is very long, we will be asked to not put
  // it into headers but in the JSON body
  if (options.withApiKey !== false) {
    requestHeaders['x-algolia-api-key'] = this.apiKey;
  }

  if (this.userToken) {
    requestHeaders['x-algolia-usertoken'] = this.userToken;
  }

  if (this.securityTags) {
    requestHeaders['x-algolia-tagfilters'] = this.securityTags;
  }

  forEach(this.extraHeaders, function addToRequestHeaders(value, key) {
    requestHeaders[key] = value;
  });

  if (options.headers) {
    forEach(options.headers, function addToRequestHeaders(value, key) {
      requestHeaders[key] = value;
    });
  }

  return requestHeaders;
};

/**
 * Search through multiple indices at the same time
 * @param  {Object[]}   queries  An array of queries you want to run.
 * @param {string} queries[].indexName The index name you want to target
 * @param {string} [queries[].query] The query to issue on this index. Can also be passed into `params`
 * @param {Object} queries[].params Any search param like hitsPerPage, ..
 * @param  {Function} callback Callback to be called
 * @return {Promise|undefined} Returns a promise if no callback given
 */
AlgoliaSearchCore.prototype.search = function(queries, opts, callback) {
  var isArray = require('isarray');
  var map = require('./map.js');

  var usage = 'Usage: client.search(arrayOfQueries[, callback])';

  if (!isArray(queries)) {
    throw new Error(usage);
  }

  if (typeof opts === 'function') {
    callback = opts;
    opts = {};
  } else if (opts === undefined) {
    opts = {};
  }

  var client = this;

  var postObj = {
    requests: map(queries, function prepareRequest(query) {
      var params = '';

      // allow query.query
      // so we are mimicing the index.search(query, params) method
      // {indexName:, query:, params:}
      if (query.query !== undefined) {
        params += 'query=' + encodeURIComponent(query.query);
      }

      return {
        indexName: query.indexName,
        params: client._getSearchParams(query.params, params)
      };
    })
  };

  var JSONPParams = map(postObj.requests, function prepareJSONPParams(request, requestId) {
    return requestId + '=' +
      encodeURIComponent(
        '/1/indexes/' + encodeURIComponent(request.indexName) + '?' +
        request.params
      );
  }).join('&');

  var url = '/1/indexes/*/queries';

  if (opts.strategy !== undefined) {
    postObj.strategy = opts.strategy;
  }

  return this._jsonRequest({
    cache: this.cache,
    method: 'POST',
    url: url,
    body: postObj,
    hostType: 'read',
    fallback: {
      method: 'GET',
      url: '/1/indexes/*',
      body: {
        params: JSONPParams
      }
    },
    callback: callback
  });
};

/**
* Search for facet values
* https://www.algolia.com/doc/rest-api/search#search-for-facet-values
* This is the top-level API for SFFV.
*
* @param {object[]} queries An array of queries to run.
* @param {string} queries[].indexName Index name, name of the index to search.
* @param {object} queries[].params Query parameters.
* @param {string} queries[].params.facetName Facet name, name of the attribute to search for values in.
* Must be declared as a facet
* @param {string} queries[].params.facetQuery Query for the facet search
* @param {string} [queries[].params.*] Any search parameter of Algolia,
* see https://www.algolia.com/doc/api-client/javascript/search#search-parameters
* Pagination is not supported. The page and hitsPerPage parameters will be ignored.
*/
AlgoliaSearchCore.prototype.searchForFacetValues = function(queries) {
  var isArray = require('isarray');
  var map = require('./map.js');

  var usage = 'Usage: client.searchForFacetValues([{indexName, params: {facetName, facetQuery, ...params}}, ...queries])'; // eslint-disable-line max-len

  if (!isArray(queries)) {
    throw new Error(usage);
  }

  var client = this;

  return client._promise.all(map(queries, function performQuery(query) {
    if (
      !query ||
      query.indexName === undefined ||
      query.params.facetName === undefined ||
      query.params.facetQuery === undefined
    ) {
      throw new Error(usage);
    }

    var clone = require('./clone.js');
    var omit = require('./omit.js');

    var indexName = query.indexName;
    var params = query.params;

    var facetName = params.facetName;
    var filteredParams = omit(clone(params), function(keyName) {
      return keyName === 'facetName';
    });
    var searchParameters = client._getSearchParams(filteredParams, '');

    return client._jsonRequest({
      cache: client.cache,
      method: 'POST',
      url:
        '/1/indexes/' +
        encodeURIComponent(indexName) +
        '/facets/' +
        encodeURIComponent(facetName) +
        '/query',
      hostType: 'read',
      body: {params: searchParameters}
    });
  }));
};

/**
 * Set the extra security tagFilters header
 * @param {string|array} tags The list of tags defining the current security filters
 */
AlgoliaSearchCore.prototype.setSecurityTags = function(tags) {
  if (Object.prototype.toString.call(tags) === '[object Array]') {
    var strTags = [];
    for (var i = 0; i < tags.length; ++i) {
      if (Object.prototype.toString.call(tags[i]) === '[object Array]') {
        var oredTags = [];
        for (var j = 0; j < tags[i].length; ++j) {
          oredTags.push(tags[i][j]);
        }
        strTags.push('(' + oredTags.join(',') + ')');
      } else {
        strTags.push(tags[i]);
      }
    }
    tags = strTags.join(',');
  }

  this.securityTags = tags;
};

/**
 * Set the extra user token header
 * @param {string} userToken The token identifying a uniq user (used to apply rate limits)
 */
AlgoliaSearchCore.prototype.setUserToken = function(userToken) {
  this.userToken = userToken;
};

/**
 * Clear all queries in client's cache
 * @return undefined
 */
AlgoliaSearchCore.prototype.clearCache = function() {
  this.cache = {};
};

/**
* Set the number of milliseconds a request can take before automatically being terminated.
* @deprecated
* @param {Number} milliseconds
*/
AlgoliaSearchCore.prototype.setRequestTimeout = function(milliseconds) {
  if (milliseconds) {
    this._timeouts.connect = this._timeouts.read = this._timeouts.write = milliseconds;
  }
};

/**
* Set the three different (connect, read, write) timeouts to be used when requesting
* @param {Object} timeouts
*/
AlgoliaSearchCore.prototype.setTimeouts = function(timeouts) {
  this._timeouts = timeouts;
};

/**
* Get the three different (connect, read, write) timeouts to be used when requesting
* @param {Object} timeouts
*/
AlgoliaSearchCore.prototype.getTimeouts = function() {
  return this._timeouts;
};

AlgoliaSearchCore.prototype._getAppIdData = function() {
  var data = store.get(this.applicationID);
  if (data !== null) this._cacheAppIdData(data);
  return data;
};

AlgoliaSearchCore.prototype._setAppIdData = function(data) {
  data.lastChange = (new Date()).getTime();
  this._cacheAppIdData(data);
  return store.set(this.applicationID, data);
};

AlgoliaSearchCore.prototype._checkAppIdData = function() {
  var data = this._getAppIdData();
  var now = (new Date()).getTime();
  if (data === null || now - data.lastChange > RESET_APP_DATA_TIMER) {
    return this._resetInitialAppIdData(data);
  }

  return data;
};

AlgoliaSearchCore.prototype._resetInitialAppIdData = function(data) {
  var newData = data || {};
  newData.hostIndexes = {read: 0, write: 0};
  newData.timeoutMultiplier = 1;
  newData.shuffleResult = newData.shuffleResult || shuffle([1, 2, 3]);
  return this._setAppIdData(newData);
};

AlgoliaSearchCore.prototype._cacheAppIdData = function(data) {
  this._hostIndexes = data.hostIndexes;
  this._timeoutMultiplier = data.timeoutMultiplier;
  this._shuffleResult = data.shuffleResult;
};

AlgoliaSearchCore.prototype._partialAppIdDataUpdate = function(newData) {
  var foreach = require('foreach');
  var currentData = this._getAppIdData();
  foreach(newData, function(value, key) {
    currentData[key] = value;
  });

  return this._setAppIdData(currentData);
};

AlgoliaSearchCore.prototype._getHostByType = function(hostType) {
  return this.hosts[hostType][this._getHostIndexByType(hostType)];
};

AlgoliaSearchCore.prototype._getTimeoutMultiplier = function() {
  return this._timeoutMultiplier;
};

AlgoliaSearchCore.prototype._getHostIndexByType = function(hostType) {
  return this._hostIndexes[hostType];
};

AlgoliaSearchCore.prototype._setHostIndexByType = function(hostIndex, hostType) {
  var clone = require('./clone');
  var newHostIndexes = clone(this._hostIndexes);
  newHostIndexes[hostType] = hostIndex;
  this._partialAppIdDataUpdate({hostIndexes: newHostIndexes});
  return hostIndex;
};

AlgoliaSearchCore.prototype._incrementHostIndex = function(hostType) {
  return this._setHostIndexByType(
    (this._getHostIndexByType(hostType) + 1) % this.hosts[hostType].length, hostType
  );
};

AlgoliaSearchCore.prototype._incrementTimeoutMultipler = function() {
  var timeoutMultiplier = Math.max(this._timeoutMultiplier + 1, 4);
  return this._partialAppIdDataUpdate({timeoutMultiplier: timeoutMultiplier});
};

AlgoliaSearchCore.prototype._getTimeoutsForRequest = function(hostType) {
  return {
    connect: this._timeouts.connect * this._timeoutMultiplier,
    complete: this._timeouts[hostType] * this._timeoutMultiplier
  };
};

function prepareHost(protocol) {
  return function prepare(host) {
    return protocol + '//' + host.toLowerCase();
  };
}

// Prototype.js < 1.7, a widely used library, defines a weird
// Array.prototype.toJSON function that will fail to stringify our content
// appropriately
// refs:
//   - https://groups.google.com/forum/#!topic/prototype-core/E-SAVvV_V9Q
//   - https://github.com/sstephenson/prototype/commit/038a2985a70593c1a86c230fadbdfe2e4898a48c
//   - http://stackoverflow.com/a/3148441/147079
function safeJSONStringify(obj) {
  /* eslint no-extend-native:0 */

  if (Array.prototype.toJSON === undefined) {
    return JSON.stringify(obj);
  }

  var toJSON = Array.prototype.toJSON;
  delete Array.prototype.toJSON;
  var out = JSON.stringify(obj);
  Array.prototype.toJSON = toJSON;

  return out;
}

function shuffle(array) {
  var currentIndex = array.length;
  var temporaryValue;
  var randomIndex;

  // While there remain elements to shuffle...
  while (currentIndex !== 0) {
    // Pick a remaining element...
    randomIndex = Math.floor(Math.random() * currentIndex);
    currentIndex -= 1;

    // And swap it with the current element.
    temporaryValue = array[currentIndex];
    array[currentIndex] = array[randomIndex];
    array[randomIndex] = temporaryValue;
  }

  return array;
}

function removeCredentials(headers) {
  var newHeaders = {};

  for (var headerName in headers) {
    if (Object.prototype.hasOwnProperty.call(headers, headerName)) {
      var value;

      if (headerName === 'x-algolia-api-key' || headerName === 'x-algolia-application-id') {
        value = '**hidden for security purposes**';
      } else {
        value = headers[headerName];
      }

      newHeaders[headerName] = value;
    }
  }

  return newHeaders;
}