SearchSuggestionController.jsm

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

"use strict";

var EXPORTED_SYMBOLS = ["SearchSuggestionController"];

const { XPCOMUtils } = ChromeUtils.import(
  "resource://gre/modules/XPCOMUtils.jsm"
);
const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
const { PromiseUtils } = ChromeUtils.import(
  "resource://gre/modules/PromiseUtils.jsm"
);

XPCOMUtils.defineLazyGlobalGetters(this, ["XMLHttpRequest"]);

const SEARCH_RESPONSE_SUGGESTION_JSON = "application/x-suggestions+json";
const DEFAULT_FORM_HISTORY_PARAM = "searchbar-history";
const HTTP_OK = 200;
const BROWSER_SUGGEST_PREF = "browser.search.suggest.enabled";
const REMOTE_TIMEOUT_PREF = "browser.search.suggest.timeout";
const REMOTE_TIMEOUT_DEFAULT = 500; // maximum time (ms) to wait before giving up on a remote suggestions

XPCOMUtils.defineLazyServiceGetter(
  this,
  "UUIDGenerator",
  "@mozilla.org/uuid-generator;1",
  "nsIUUIDGenerator"
);

/**
 * Remote search suggestions will be shown if gRemoteSuggestionsEnabled
 * is true. Global because only one pref observer is needed for all instances.
 */
var gRemoteSuggestionsEnabled = Services.prefs.getBoolPref(
  BROWSER_SUGGEST_PREF
);
Services.prefs.addObserver(BROWSER_SUGGEST_PREF, function(
  aSubject,
  aTopic,
  aData
) {
  gRemoteSuggestionsEnabled = Services.prefs.getBoolPref(BROWSER_SUGGEST_PREF);
});

/**
 * Generates an UUID.
 *
 * @returns {string}
 *   An UUID string, without leading or trailing braces.
 */
function uuid() {
  let uuid = UUIDGenerator.generateUUID().toString();
  return uuid.slice(1, uuid.length - 1);
}

// Maps each engine name to a unique firstPartyDomain, so that requests to
// different engines are isolated from each other and from normal browsing.
// This is the same for all the controllers.
var gFirstPartyDomains = new Map();

/**
 * SearchSuggestionController.jsm exists as a helper module to allow multiple consumers to request and display
 * search suggestions from a given engine, regardless of the base implementation. Much of this
 * code was originally in nsSearchSuggestions.js until it was refactored to separate it from the
 * nsIAutoCompleteSearch dependency.
 * One instance of SearchSuggestionController should be used per field since form history results are cached.
 */

/**
 * @param {function} [callback] - Callback for search suggestion results. You can use the promise
 *                                returned by the search method instead if you prefer.
 * @constructor
 */
function SearchSuggestionController(callback = null) {
  this._callback = callback;
}

this.SearchSuggestionController.prototype = {
  /**
   * The maximum number of local form history results to return. This limit is
   * only enforced if remote results are also returned.
   */
  maxLocalResults: 5,

  /**
   * The maximum number of remote search engine results to return.
   * We'll actually only display at most
   * maxRemoteResults - <displayed local results count> remote results.
   */
  maxRemoteResults: 10,

  /**
   * The additional parameter used when searching form history.
   */
  formHistoryParam: DEFAULT_FORM_HISTORY_PARAM,

  // Private properties
  /**
   * The last form history result used to improve the performance of subsequent searches.
   * This shouldn't be used for any other purpose as it is never cleared and therefore could be stale.
   */
  _formHistoryResult: null,

  /**
   * The remote server timeout timer, if applicable. The timer starts when form history
   * search is completed.
   */
  _remoteResultTimer: null,

  /**
   * The deferred for the remote results before its promise is resolved.
   */
  _deferredRemoteResult: null,

  /**
   * The optional result callback registered from the constructor.
   */
  _callback: null,

  /**
   * The XMLHttpRequest object for remote results.
   */
  _request: null,

  // Public methods

  /**
   * Gets the firstPartyDomains Map, useful for tests.
   * @returns {Map} firstPartyDomains mapped by engine names.
   */
  get firstPartyDomains() {
    return gFirstPartyDomains;
  },

  /**
   * Fetch search suggestions from all of the providers. Fetches in progress will be stopped and
   * results from them will not be provided.
   *
   * @param {string} searchTerm - the term to provide suggestions for
   * @param {boolean} privateMode - whether the request is being made in the context of private browsing
   * @param {nsISearchEngine} engine - search engine for the suggestions.
   * @param {int} userContextId - the userContextId of the selected tab.
   *
   * @returns {Promise} resolving to an object containing results or null.
   */
  fetch(searchTerm, privateMode, engine, userContextId = 0) {
    // There is no smart filtering from previous results here (as there is when looking through
    // history/form data) because the result set returned by the server is different for every typed
    // value - e.g. "ocean breathes" does not return a subset of the results returned for "ocean".

    this.stop();

    if (!Services.search.isInitialized) {
      throw new Error("Search not initialized yet (how did you get here?)");
    }
    if (typeof privateMode === "undefined") {
      throw new Error(
        "The privateMode argument is required to avoid unintentional privacy leaks"
      );
    }
    if (!engine.getSubmission) {
      throw new Error("Invalid search engine");
    }
    if (!this.maxLocalResults && !this.maxRemoteResults) {
      throw new Error("Zero results expected, what are you trying to do?");
    }
    if (this.maxLocalResults < 0 || this.maxRemoteResults < 0) {
      throw new Error("Number of requested results must be positive");
    }

    // Array of promises to resolve before returning results.
    let promises = [];
    this._searchString = searchTerm;

    // Remote results
    if (
      searchTerm &&
      gRemoteSuggestionsEnabled &&
      this.maxRemoteResults &&
      engine.supportsResponseType(SEARCH_RESPONSE_SUGGESTION_JSON)
    ) {
      this._deferredRemoteResult = this._fetchRemote(
        searchTerm,
        engine,
        privateMode,
        userContextId
      );
      promises.push(this._deferredRemoteResult.promise);
    }

    // Local results from form history
    if (this.maxLocalResults) {
      promises.push(this._fetchFormHistory(searchTerm));
    }

    function handleRejection(reason) {
      if (reason == "HTTP request aborted") {
        // Do nothing since this is normal.
        return null;
      }
      Cu.reportError("SearchSuggestionController rejection: " + reason);
      return null;
    }
    return Promise.all(promises).then(
      this._dedupeAndReturnResults.bind(this),
      handleRejection
    );
  },

  /**
   * Stop pending fetches so no results are returned from them.
   *
   * Note: If there was no remote results fetched, the fetching cannot be stopped and local results
   * will still be returned because stopping relies on aborting the XMLHTTPRequest to reject the
   * promise for Promise.all.
   */
  stop() {
    if (this._request) {
      this._request.abort();
    } else if (!this.maxRemoteResults) {
      Cu.reportError(
        "SearchSuggestionController: Cannot stop fetching if remote results were not " +
          "requested"
      );
    }
    this._reset();
  },

  // Private methods

  _fetchFormHistory(searchTerm) {
    return new Promise(resolve => {
      let acSearchObserver = {
        // Implements nsIAutoCompleteSearch
        onSearchResult: (search, result) => {
          this._formHistoryResult = result;

          if (this._request) {
            this._remoteResultTimer = Cc["@mozilla.org/timer;1"].createInstance(
              Ci.nsITimer
            );
            this._remoteResultTimer.initWithCallback(
              this._onRemoteTimeout.bind(this),
              this.remoteTimeout,
              Ci.nsITimer.TYPE_ONE_SHOT
            );
          }

          switch (result.searchResult) {
            case Ci.nsIAutoCompleteResult.RESULT_SUCCESS:
            case Ci.nsIAutoCompleteResult.RESULT_NOMATCH:
              if (result.searchString !== this._searchString) {
                resolve(
                  "Unexpected response, this._searchString does not match form history response"
                );
                return;
              }
              let fhEntries = [];
              for (let i = 0; i < result.matchCount; ++i) {
                fhEntries.push(result.getValueAt(i));
              }
              resolve({
                result: fhEntries,
                formHistoryResult: result,
              });
              break;
            case Ci.nsIAutoCompleteResult.RESULT_FAILURE:
            case Ci.nsIAutoCompleteResult.RESULT_IGNORED:
              resolve("Form History returned RESULT_FAILURE or RESULT_IGNORED");
              break;
          }
        },
      };

      let formHistory = Cc[
        "@mozilla.org/autocomplete/search;1?name=form-history"
      ].createInstance(Ci.nsIAutoCompleteSearch);
      formHistory.startSearch(
        searchTerm,
        this.formHistoryParam || DEFAULT_FORM_HISTORY_PARAM,
        this._formHistoryResult,
        acSearchObserver
      );
    });
  },

  /**
   * Fetch suggestions from the search engine over the network.
   *
   * @param {string} searchTerm
   *   The term being searched for.
   * @param {SearchEngine} engine
   *   The engine to request suggestions from.
   * @param {boolean} privateMode
   *   Set to true if this is coming from a private browsing mode request.
   * @param {number} userContextId
   *   The id of the user container this request was made from.
   * @returns {Promise}
   *   Returns a promise that is resolved when the response is received, or
   *   rejected if there is an error.
   */
  _fetchRemote(searchTerm, engine, privateMode, userContextId) {
    let deferredResponse = PromiseUtils.defer();
    this._request = new XMLHttpRequest();
    let submission = engine.getSubmission(
      searchTerm,
      SEARCH_RESPONSE_SUGGESTION_JSON
    );
    let method = submission.postData ? "POST" : "GET";
    this._request.open(method, submission.uri.spec, true);
    // Don't set or store cookies or on-disk cache.
    this._request.channel.loadFlags =
      Ci.nsIChannel.LOAD_ANONYMOUS | Ci.nsIChannel.INHIBIT_PERSISTENT_CACHING;
    // Use a unique first-party domain for each engine, to isolate the
    // suggestions requests.
    if (!gFirstPartyDomains.has(engine.name)) {
      // Use the engine identifier, or an uuid when not available, because the
      // domain cannot contain invalid chars and the engine name may not be
      // suitable. When using an uuid the firstPartyDomain of the same engine
      // will differ across restarts, but that's acceptable for now.
      // TODO (Bug 1511339): use a persistent unique identifier per engine.
      gFirstPartyDomains.set(
        engine.name,
        `${engine.identifier || uuid()}.search.suggestions.mozilla`
      );
    }
    let firstPartyDomain = gFirstPartyDomains.get(engine.name);

    this._request.setOriginAttributes({
      userContextId,
      privateBrowsingId: privateMode ? 1 : 0,
      firstPartyDomain,
    });

    this._request.mozBackgroundRequest = true; // suppress dialogs and fail silently

    this._request.addEventListener(
      "load",
      this._onRemoteLoaded.bind(this, deferredResponse)
    );
    this._request.addEventListener("error", evt =>
      deferredResponse.resolve("HTTP error")
    );
    // Reject for an abort assuming it's always from .stop() in which case we shouldn't return local
    // or remote results for existing searches.
    this._request.addEventListener("abort", evt =>
      deferredResponse.reject("HTTP request aborted")
    );

    if (submission.postData) {
      this._request.sendInputStream(submission.postData);
    } else {
      this._request.send();
    }

    return deferredResponse;
  },

  /**
   * Called when the request completed successfully (thought the HTTP status could be anything)
   * so we can handle the response data.
   *
   * @param {Promise} deferredResponse
   *   The promise to resolve when a response is received.
   * @private
   */
  _onRemoteLoaded(deferredResponse) {
    if (!this._request) {
      deferredResponse.resolve(
        "Got HTTP response after the request was cancelled"
      );
      return;
    }

    let status, serverResults;
    try {
      status = this._request.status;
    } catch (e) {
      // The XMLHttpRequest can throw NS_ERROR_NOT_AVAILABLE.
      deferredResponse.resolve("Unknown HTTP status: " + e);
      return;
    }

    if (status != HTTP_OK || this._request.responseText == "") {
      deferredResponse.resolve(
        "Non-200 status or empty HTTP response: " + status
      );
      return;
    }

    try {
      serverResults = JSON.parse(this._request.responseText);
    } catch (ex) {
      deferredResponse.resolve("Failed to parse suggestion JSON: " + ex);
      return;
    }

    if (
      !serverResults[0] ||
      this._searchString.localeCompare(serverResults[0], undefined, {
        sensitivity: "base",
      })
    ) {
      // something is wrong here so drop remote results
      deferredResponse.resolve(
        "Unexpected response, this._searchString does not match remote response"
      );
      return;
    }
    let results = serverResults[1] || [];
    deferredResponse.resolve({ result: results });
  },

  /**
   * Called when this._remoteResultTimer fires indicating the remote request took too long.
   */
  _onRemoteTimeout() {
    this._request = null;

    // FIXME: bug 387341
    // Need to break the cycle between us and the timer.
    this._remoteResultTimer = null;

    // The XMLHTTPRequest for suggest results is taking too long
    // so send out the form history results and cancel the request.
    if (this._deferredRemoteResult) {
      this._deferredRemoteResult.resolve("HTTP Timeout");
      this._deferredRemoteResult = null;
    }
  },

  /**
   * @param {Array} suggestResults - an array of result objects from different sources (local or remote)
   * @returns {object}
   */
  _dedupeAndReturnResults(suggestResults) {
    if (this._searchString === null) {
      // _searchString can be null if stop() was called and remote suggestions
      // were disabled (stopping if we are fetching remote suggestions will
      // cause a promise rejection before we reach _dedupeAndReturnResults).
      return null;
    }

    let results = {
      term: this._searchString,
      remote: [],
      local: [],
      formHistoryResult: null,
    };

    for (let result of suggestResults) {
      if (typeof result === "string") {
        // Failure message
        Cu.reportError("SearchSuggestionController: " + result);
      } else if (result.formHistoryResult) {
        // Local results have a formHistoryResult property.
        results.formHistoryResult = result.formHistoryResult;
        results.local = result.result || [];
      } else {
        // Remote result
        results.remote = result.result || [];
      }
    }

    // If we have remote results, cap the number of local results
    if (results.remote.length) {
      results.local = results.local.slice(0, this.maxLocalResults);
    }

    // We don't want things to appear in both history and suggestions so remove entries from
    // remote results that are already in local.
    if (results.remote.length && results.local.length) {
      for (let i = 0; i < results.local.length; ++i) {
        let term = results.local[i];
        let dupIndex = results.remote.indexOf(term);
        if (dupIndex != -1) {
          results.remote.splice(dupIndex, 1);
        }
      }
    }

    // Trim the number of results to the maximum requested (now that we've pruned dupes).
    results.remote = results.remote.slice(
      0,
      this.maxRemoteResults - results.local.length
    );

    if (this._callback) {
      this._callback(results);
    }
    this._reset();

    return results;
  },

  _reset() {
    this._request = null;
    if (this._remoteResultTimer) {
      this._remoteResultTimer.cancel();
      this._remoteResultTimer = null;
    }
    this._deferredRemoteResult = null;
    this._searchString = null;
  },
};

/**
 * Determines whether the given engine offers search suggestions.
 *
 * @param {nsISearchEngine} engine - The search engine
 * @returns {boolean} True if the engine offers suggestions and false otherwise.
 */
this.SearchSuggestionController.engineOffersSuggestions = function(engine) {
  return engine.supportsResponseType(SEARCH_RESPONSE_SUGGESTION_JSON);
};

/**
 * The maximum time (ms) to wait before giving up on a remote suggestions.
 */
XPCOMUtils.defineLazyPreferenceGetter(
  this.SearchSuggestionController.prototype,
  "remoteTimeout",
  REMOTE_TIMEOUT_PREF,
  REMOTE_TIMEOUT_DEFAULT
);