/* 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/. */

/**
 * This file is in transition. It was originally conceived to fulfill the
 * needs of only Firefox Health Report. It is slowly being morphed into
 * fulfilling the needs of all data reporting facilities in Gecko applications.
 * As a result, some things feel a bit weird.
 *
 * DataReportingPolicy is both a driver for data reporting notification
 * (a true policy) and the driver for FHR data submission. The latter should
 * eventually be split into its own type and module.
 */

"use strict";

//@line 19 "e:\firefox\mozilla-release\services\datareporting\policy.jsm"

this.EXPORTED_SYMBOLS = [
  "DataSubmissionRequest", // For test use only.
  "DataReportingPolicy",
];

const {classes: Cc, interfaces: Ci, utils: Cu} = Components;

//@line 28 "e:\firefox\mozilla-release\services\datareporting\policy.jsm"

Cu.import("resource://gre/modules/Promise.jsm");
Cu.import("resource://gre/modules/Log.jsm");
Cu.import("resource://services-common/utils.js");

const MILLISECONDS_PER_DAY = 24 * 60 * 60 * 1000;

// Used as a sanity lower bound for dates stored in prefs. This module was
// implemented in 2012, so any earlier dates indicate an incorrect clock.
const OLDEST_ALLOWED_YEAR = 2012;

/**
 * Represents a request to display data policy.
 *
 * Instances of this are created when the policy is requesting the user's
 * approval to agree to the data submission policy.
 *
 * Receivers of these instances are expected to call one or more of the on*
 * functions when events occur.
 *
 * When one of these requests is received, the first thing a callee should do
 * is present notification to the user of the data policy. When the notice
 * is displayed to the user, the callee should call `onUserNotifyComplete`.
 * This begins a countdown timer that upon completion will signal implicit
 * acceptance of the policy. If for whatever reason the callee could not
 * display a notice, it should call `onUserNotifyFailed`.
 *
 * Once the user is notified of the policy, the callee has the option of
 * signaling explicit user acceptance or rejection of the policy. They do this
 * by calling `onUserAccept` or `onUserReject`, respectively. These functions
 * are essentially proxies to
 * DataReportingPolicy.{recordUserAcceptance,recordUserRejection}.
 *
 * If the user never explicitly accepts or rejects the policy, it will be
 * implicitly accepted after a specified duration of time. The notice is
 * expected to remain displayed even after implicit acceptance (in case the
 * user is away from the device). So, no event signaling implicit acceptance
 * is exposed.
 *
 * Receivers of instances of this type should treat it as a black box with
 * the exception of the on* functions.
 *
 * @param policy
 *        (DataReportingPolicy) The policy instance this request came from.
 * @param deferred
 *        (deferred) The promise that will be fulfilled when display occurs.
 */
function NotifyPolicyRequest(policy, deferred) {
  this.policy = policy;
  this.deferred = deferred;
}
NotifyPolicyRequest.prototype = {
  /**
   * Called when the user is notified of the policy.
   *
   * This starts a countdown timer that will eventually signify implicit
   * acceptance of the data policy.
   */
  onUserNotifyComplete: function onUserNotified() {
    this.deferred.resolve();
    return this.deferred.promise;
  },

  /**
   * Called when there was an error notifying the user about the policy.
   *
   * @param error
   *        (Error) Explains what went wrong.
   */
  onUserNotifyFailed: function onUserNotifyFailed(error) {
    this.deferred.reject(error);
  },

  /**
   * Called when the user agreed to the data policy.
   *
   * @param reason
   *        (string) How the user agreed to the policy.
   */
  onUserAccept: function onUserAccept(reason) {
    this.policy.recordUserAcceptance(reason);
  },

  /**
   * Called when the user rejected the data policy.
   *
   * @param reason
   *        (string) How the user rejected the policy.
   */
  onUserReject: function onUserReject(reason) {
    this.policy.recordUserRejection(reason);
  },
};

Object.freeze(NotifyPolicyRequest.prototype);

/**
 * Represents a request to submit data.
 *
 * Instances of this are created when the policy requests data upload or
 * deletion.
 *
 * Receivers are expected to call one of the provided on* functions to signal
 * completion of the request.
 *
 * Instances of this type should not be instantiated outside of this file.
 * Receivers of instances of this type should not attempt to do anything with
 * the instance except call one of the on* methods.
 */
this.DataSubmissionRequest = function (promise, expiresDate, isDelete) {
  this.promise = promise;
  this.expiresDate = expiresDate;
  this.isDelete = isDelete;

  this.state = null;
  this.reason = null;
}

this.DataSubmissionRequest.prototype = Object.freeze({
  NO_DATA_AVAILABLE: "no-data-available",
  SUBMISSION_SUCCESS: "success",
  SUBMISSION_FAILURE_SOFT: "failure-soft",
  SUBMISSION_FAILURE_HARD: "failure-hard",

  /**
   * No submission was attempted because no data was available.
   *
   * In the case of upload, this means there is no data to upload (perhaps
   * it isn't available yet). In case of remote deletion, it means that there
   * is no remote data to delete.
   */
  onNoDataAvailable: function onNoDataAvailable() {
    this.state = this.NO_DATA_AVAILABLE;
    this.promise.resolve(this);
    return this.promise.promise;
  },

  /**
   * Data submission has completed successfully.
   *
   * In case of upload, this means the upload completed successfully. In case
   * of deletion, the data was deleted successfully.
   *
   * @param date
   *        (Date) When data submission occurred.
   */
  onSubmissionSuccess: function onSubmissionSuccess(date) {
    this.state = this.SUBMISSION_SUCCESS;
    this.submissionDate = date;
    this.promise.resolve(this);
    return this.promise.promise;
  },

  /**
   * There was a recoverable failure when submitting data.
   *
   * Perhaps the server was down. Perhaps the network wasn't available. The
   * policy may request submission again after a short delay.
   *
   * @param reason
   *        (string) Why the failure occurred. For logging purposes only.
   */
  onSubmissionFailureSoft: function onSubmissionFailureSoft(reason=null) {
    this.state = this.SUBMISSION_FAILURE_SOFT;
    this.reason = reason;
    this.promise.resolve(this);
    return this.promise.promise;
  },

  /**
   * There was an unrecoverable failure when submitting data.
   *
   * Perhaps the client is misconfigured. Perhaps the server rejected the data.
   * Attempts at performing submission again will yield the same result. So,
   * the policy should not try again (until the next day).
   *
   * @param reason
   *        (string) Why the failure occurred. For logging purposes only.
   */
  onSubmissionFailureHard: function onSubmissionFailureHard(reason=null) {
    this.state = this.SUBMISSION_FAILURE_HARD;
    this.reason = reason;
    this.promise.resolve(this);
    return this.promise.promise;
  },
});

/**
 * Manages scheduling of Firefox Health Report data submission.
 *
 * The rules of data submission are as follows:
 *
 *  1. Do not submit data more than once every 24 hours.
 *  2. Try to submit as close to 24 hours apart as possible.
 *  3. Do not submit too soon after application startup so as to not negatively
 *     impact performance at startup.
 *  4. Before first ever data submission, the user should be notified about
 *     data collection practices.
 *  5. User should have opportunity to react to this notification before
 *     data submission.
 *  6. Display of notification without any explicit user action constitutes
 *     implicit consent after a certain duration of time.
 *  7. If data submission fails, try at most 2 additional times before giving
 *     up on that day's submission.
 *
 * The listener passed into the instance must have the following properties
 * (which are callbacks that will be invoked at certain key events):
 *
 *   * onRequestDataUpload(request) - Called when the policy is requesting
 *     data to be submitted. The function is passed a `DataSubmissionRequest`.
 *     The listener should call one of the special resolving functions on that
 *     instance (see the documentation for that type).
 *
 *   * onRequestRemoteDelete(request) - Called when the policy is requesting
 *     deletion of remotely stored data. The function is passed a
 *     `DataSubmissionRequest`. The listener should call one of the special
 *     resolving functions on that instance (just like `onRequestDataUpload`).
 *
 *   * onNotifyDataPolicy(request) - Called when the policy is requesting the
 *     user to be notified that data submission will occur. The function
 *     receives a `NotifyPolicyRequest` instance. The callee should call one or
 *     more of the functions on that instance when specific events occur. See
 *     the documentation for that type for more.
 *
 * Note that the notification method is abstracted. Different applications
 * can have different mechanisms by which they notify the user of data
 * submission practices.
 *
 * @param policyPrefs
 *        (Preferences) Handle on preferences branch on which state will be
 *        queried and stored.
 * @param healthReportPrefs
 *        (Preferences) Handle on preferences branch holding Health Report state.
 * @param listener
 *        (object) Object with callbacks that will be invoked at certain key
 *        events.
 */
this.DataReportingPolicy = function (prefs, healthReportPrefs, listener) {
  this._log = Log.repository.getLogger("Services.DataReporting.Policy");
  this._log.level = Log.Level["Debug"];

  for (let handler of this.REQUIRED_LISTENERS) {
    if (!listener[handler]) {
      throw new Error("Passed listener does not contain required handler: " +
                      handler);
    }
  }

  this._prefs = prefs;
  this._healthReportPrefs = healthReportPrefs;
  this._listener = listener;

  // If we've never run before, record the current time.
  if (!this.firstRunDate.getTime()) {
    this.firstRunDate = this.now();
  }

  // Install an observer so that we can act on changes from external
  // code (such as Android UI).
  // Use a function because this is the only place where the Preferences
  // abstraction is way less usable than nsIPrefBranch.
  //
  // Hang on to the observer here so that tests can reach it.
  this.uploadEnabledObserver = function onUploadEnabledChanged() {
    if (this.pendingDeleteRemoteData || this.healthReportUploadEnabled) {
      // Nothing to do: either we're already deleting because the caller
      // came through the front door (rHRUE), or they set the flag to true.
      return;
    }
    this._log.info("uploadEnabled pref changed. Scheduling deletion.");
    this.deleteRemoteData();
  }.bind(this);

  healthReportPrefs.observe("uploadEnabled", this.uploadEnabledObserver);

  // Ensure we are scheduled to submit.
  if (!this.nextDataSubmissionDate.getTime()) {
    this.nextDataSubmissionDate = this._futureDate(MILLISECONDS_PER_DAY);
  }

  // Date at which we performed user notification of acceptance.
  // This is an instance variable because implicit acceptance should only
  // carry forward through a single application instance.
  this._dataSubmissionPolicyNotifiedDate = null;

  // Record when we last requested for submitted data to be sent. This is
  // to avoid having multiple outstanding requests.
  this._inProgressSubmissionRequest = null;
};

this.DataReportingPolicy.prototype = Object.freeze({
  /**
   * How long after first run we should notify about data submission.
   */
  SUBMISSION_NOTIFY_INTERVAL_MSEC: 12 * 60 * 60 * 1000,

  /**
   * Time that must elapse with no user action for implicit acceptance.
   *
   * THERE ARE POTENTIAL LEGAL IMPLICATIONS OF CHANGING THIS VALUE. Check with
   * Privacy and/or Legal before modifying.
   */
  IMPLICIT_ACCEPTANCE_INTERVAL_MSEC: 8 * 60 * 60 * 1000,

  /**
   *  How often to poll to see if we need to do something.
   *
   * The interval needs to be short enough such that short-lived applications
   * have an opportunity to submit data. But, it also needs to be long enough
   * to not negatively impact performance.
   *
   * The random bit is to ensure that other systems scheduling around the same
   * interval don't all get scheduled together.
   */
  POLL_INTERVAL_MSEC: (60 * 1000) + Math.floor(2.5 * 1000 * Math.random()),

  /**
   * How long individual data submission requests live before expiring.
   *
   * Data submission requests have this long to complete before we give up on
   * them and try again.
   *
   * We want this to be short enough that we retry frequently enough but long
   * enough to give slow networks and systems time to handle it.
   */
  SUBMISSION_REQUEST_EXPIRE_INTERVAL_MSEC: 10 * 60 * 1000,

  /**
   * Our backoff schedule in case of submission failure.
   *
   * This dictates both the number of times we retry a daily submission and
   * when to retry after each failure.
   *
   * Each element represents how long to wait after each recoverable failure.
   * After the first failure, we wait the time in element 0 before trying
   * again. After the second failure, we wait the time in element 1. Once
   * we run out of values in this array, we give up on that day's submission
   * and schedule for a day out.
   */
  FAILURE_BACKOFF_INTERVALS: [
    15 * 60 * 1000,
    60 * 60 * 1000,
  ],

  /**
   * State of user notification of data submission.
   */
  STATE_NOTIFY_UNNOTIFIED: "not-notified",
  STATE_NOTIFY_WAIT: "waiting",
  STATE_NOTIFY_COMPLETE: "ok",

  REQUIRED_LISTENERS: [
    "onRequestDataUpload",
    "onRequestRemoteDelete",
    "onNotifyDataPolicy",
  ],

  /**
   * The first time the health report policy came into existence.
   *
   * This is used for scheduling of the initial submission.
   */
  get firstRunDate() {
    return CommonUtils.getDatePref(this._prefs, "firstRunTime", 0, this._log,
                                   OLDEST_ALLOWED_YEAR);
  },

  set firstRunDate(value) {
    this._log.debug("Setting first-run date: " + value);
    CommonUtils.setDatePref(this._prefs, "firstRunTime", value,
                            OLDEST_ALLOWED_YEAR);
  },

  /**
   * Short circuit policy checking and always assume acceptance.
   *
   * This shuld never be set by the user. Instead, it is a per-application or
   * per-deployment default pref.
   */
  get dataSubmissionPolicyBypassAcceptance() {
    return this._prefs.get("dataSubmissionPolicyBypassAcceptance", false);
  },

  /**
   * When the user was notified that data submission could occur.
   *
   * This is used for logging purposes. this._dataSubmissionPolicyNotifiedDate
   * is what's used internally.
   */
  get dataSubmissionPolicyNotifiedDate() {
    return CommonUtils.getDatePref(this._prefs,
                                   "dataSubmissionPolicyNotifiedTime", 0,
                                   this._log, OLDEST_ALLOWED_YEAR);
  },

  set dataSubmissionPolicyNotifiedDate(value) {
    this._log.debug("Setting user notified date: " + value);
    CommonUtils.setDatePref(this._prefs, "dataSubmissionPolicyNotifiedTime",
                            value, OLDEST_ALLOWED_YEAR);
  },

  /**
   * When the user accepted or rejected the data submission policy.
   *
   * If there was implicit acceptance, this will be set to the time of that.
   */
  get dataSubmissionPolicyResponseDate() {
    return CommonUtils.getDatePref(this._prefs,
                                   "dataSubmissionPolicyResponseTime",
                                   0, this._log, OLDEST_ALLOWED_YEAR);
  },

  set dataSubmissionPolicyResponseDate(value) {
    this._log.debug("Setting user notified reaction date: " + value);
    CommonUtils.setDatePref(this._prefs,
                            "dataSubmissionPolicyResponseTime",
                            value, OLDEST_ALLOWED_YEAR);
  },

  /**
   * Records the result of user notification of data submission policy.
   *
   * This is used for logging and diagnostics purposes. It can answer the
   * question "how was data submission agreed to on this profile?"
   *
   * Not all values are defined by this type and can come from other systems.
   *
   * The value must be a string and should be something machine readable. e.g.
   * "accept-user-clicked-ok-button-in-info-bar"
   */
  get dataSubmissionPolicyResponseType() {
    return this._prefs.get("dataSubmissionPolicyResponseType",
                           "none-recorded");
  },

  set dataSubmissionPolicyResponseType(value) {
    if (typeof(value) != "string") {
      throw new Error("Value must be a string. Got " + typeof(value));
    }

    this._prefs.set("dataSubmissionPolicyResponseType", value);
  },

  /**
   * Whether submission of data is allowed.
   *
   * This is the master switch for remote server communication. If it is
   * false, we never request upload or deletion.
   */
  get dataSubmissionEnabled() {
    // Default is true because we are opt-out.
    return this._prefs.get("dataSubmissionEnabled", true);
  },

  set dataSubmissionEnabled(value) {
    this._prefs.set("dataSubmissionEnabled", !!value);
  },

  /**
   * Whether the user has accepted that data submission can occur.
   *
   * This overrides dataSubmissionEnabled.
   */
  get dataSubmissionPolicyAccepted() {
    // Be conservative and default to false.
    return this._prefs.get("dataSubmissionPolicyAccepted", false);
  },

  set dataSubmissionPolicyAccepted(value) {
    this._prefs.set("dataSubmissionPolicyAccepted", !!value);
  },

  set dataSubmissionPolicyAcceptedVersion(value) {
    this._prefs.set("dataSubmissionPolicyAcceptedVersion", value);
  },

  /**
   * The state of user notification of the data policy.
   *
   * This must be DataReportingPolicy.STATE_NOTIFY_COMPLETE before data
   * submission can occur.
   *
   * @return DataReportingPolicy.STATE_NOTIFY_* constant.
   */
  get notifyState() {
    if (this.dataSubmissionPolicyResponseDate.getTime()) {
      return this.STATE_NOTIFY_COMPLETE;
    }

    // We get the local state - not the state from prefs - because we don't want
    // a value from a previous application run to interfere. This prevents
    // a scenario where notification occurs just before application shutdown and
    // notification is displayed for shorter than the policy requires.
    if (!this._dataSubmissionPolicyNotifiedDate) {
      return this.STATE_NOTIFY_UNNOTIFIED;
    }

    return this.STATE_NOTIFY_WAIT;
  },

  /**
   * When this policy last requested data submission.
   *
   * This is used mainly for forensics purposes and should have no bearing
   * on scheduling or run-time behavior.
   */
  get lastDataSubmissionRequestedDate() {
    return CommonUtils.getDatePref(this._healthReportPrefs,
                                   "lastDataSubmissionRequestedTime", 0,
                                   this._log, OLDEST_ALLOWED_YEAR);
  },

  set lastDataSubmissionRequestedDate(value) {
    CommonUtils.setDatePref(this._healthReportPrefs,
                            "lastDataSubmissionRequestedTime",
                            value, OLDEST_ALLOWED_YEAR);
  },

  /**
   * When the last data submission actually occurred.
   *
   * This is used mainly for forensics purposes and should have no bearing on
   * actual scheduling.
   */
  get lastDataSubmissionSuccessfulDate() {
    return CommonUtils.getDatePref(this._healthReportPrefs,
                                   "lastDataSubmissionSuccessfulTime", 0,
                                   this._log, OLDEST_ALLOWED_YEAR);
  },

  set lastDataSubmissionSuccessfulDate(value) {
    CommonUtils.setDatePref(this._healthReportPrefs,
                            "lastDataSubmissionSuccessfulTime",
                            value, OLDEST_ALLOWED_YEAR);
  },

  /**
   * When we last encountered a submission failure.
   *
   * This is used for forensics purposes and should have no bearing on
   * scheduling.
   */
  get lastDataSubmissionFailureDate() {
    return CommonUtils.getDatePref(this._healthReportPrefs,
                                   "lastDataSubmissionFailureTime",
                                   0, this._log, OLDEST_ALLOWED_YEAR);
  },

  set lastDataSubmissionFailureDate(value) {
    CommonUtils.setDatePref(this._healthReportPrefs,
                            "lastDataSubmissionFailureTime",
                            value, OLDEST_ALLOWED_YEAR);
  },

  /**
   * When the next data submission is scheduled to occur.
   *
   * This is maintained internally by this type. External users should not
   * mutate this value.
   */
  get nextDataSubmissionDate() {
    return CommonUtils.getDatePref(this._healthReportPrefs,
                                   "nextDataSubmissionTime", 0,
                                   this._log, OLDEST_ALLOWED_YEAR);
  },

  set nextDataSubmissionDate(value) {
    CommonUtils.setDatePref(this._healthReportPrefs,
                            "nextDataSubmissionTime", value,
                            OLDEST_ALLOWED_YEAR);
  },

  /**
   * The number of submission failures for this day's upload.
   *
   * This is used to drive backoff and scheduling.
   */
  get currentDaySubmissionFailureCount() {
    let v = this._healthReportPrefs.get("currentDaySubmissionFailureCount", 0);

    if (!Number.isInteger(v)) {
      v = 0;
    }

    return v;
  },

  set currentDaySubmissionFailureCount(value) {
    if (!Number.isInteger(value)) {
      throw new Error("Value must be integer: " + value);
    }

    this._healthReportPrefs.set("currentDaySubmissionFailureCount", value);
  },

  /**
   * Whether a request to delete remote data is awaiting completion.
   *
   * If this is true, the policy will request that remote data be deleted.
   * Furthermore, no new data will be uploaded (if it's even allowed) until
   * the remote deletion is fulfilled.
   */
  get pendingDeleteRemoteData() {
    return !!this._healthReportPrefs.get("pendingDeleteRemoteData", false);
  },

  set pendingDeleteRemoteData(value) {
    this._healthReportPrefs.set("pendingDeleteRemoteData", !!value);
  },

  /**
   * Whether upload of Firefox Health Report data is enabled.
   */
  get healthReportUploadEnabled() {
    return !!this._healthReportPrefs.get("uploadEnabled", true);
  },

  // External callers should update this via `recordHealthReportUploadEnabled`
  // to ensure appropriate side-effects are performed.
  set healthReportUploadEnabled(value) {
    this._healthReportPrefs.set("uploadEnabled", !!value);
  },

  /**
   * Whether the FHR upload enabled setting is locked and can't be changed.
   */
  get healthReportUploadLocked() {
    return this._healthReportPrefs.locked("uploadEnabled");
  },

  /**
   * Record user acceptance of data submission policy.
   *
   * Data submission will not be allowed to occur until this is called.
   *
   * This is typically called through the `onUserAccept` property attached to
   * the promise passed to `onUserNotify` in the policy listener. But, it can
   * be called through other interfaces at any time and the call will have
   * an impact on future data submissions.
   *
   * @param reason
   *        (string) How the user accepted the data submission policy.
   */
  recordUserAcceptance: function recordUserAcceptance(reason="no-reason") {
    this._log.info("User accepted data submission policy: " + reason);
    this.dataSubmissionPolicyResponseDate = this.now();
    this.dataSubmissionPolicyResponseType = "accepted-" + reason;
    this.dataSubmissionPolicyAccepted = true;
    this.dataSubmissionPolicyAcceptedVersion = 1;
  },

  /**
   * Record user rejection of submission policy.
   *
   * Data submission will not be allowed to occur if this is called.
   *
   * This is typically called through the `onUserReject` property attached to
   * the promise passed to `onUserNotify` in the policy listener. But, it can
   * be called through other interfaces at any time and the call will have an
   * impact on future data submissions.
   */
  recordUserRejection: function recordUserRejection(reason="no-reason") {
    this._log.info("User rejected data submission policy: " + reason);
    this.dataSubmissionPolicyResponseDate = this.now();
    this.dataSubmissionPolicyResponseType = "rejected-" + reason;
    this.dataSubmissionPolicyAccepted = false;
  },

  /**
   * Record the user's intent for whether FHR should upload data.
   *
   * This is the preferred way for XUL applications to record a user's
   * preference on whether Firefox Health Report should upload data to
   * a server.
   *
   * If upload is disabled through this API, a request for remote data
   * deletion is initiated automatically.
   *
   * If upload is being disabled and this operation is scheduled to
   * occur immediately, a promise will be returned. This promise will be
   * fulfilled when the deletion attempt finishes. If upload is being
   * disabled and a promise is not returned, callers must poll
   * `haveRemoteData` on the HealthReporter instance to see if remote
   * data has been deleted.
   *
   * @param flag
   *        (bool) Whether data submission is enabled or disabled.
   * @param reason
   *        (string) Why this value is being adjusted. For logging
   *        purposes only.
   */
  recordHealthReportUploadEnabled: function (flag, reason="no-reason") {
    let result = null;
    if (!flag) {
      result = this.deleteRemoteData(reason);
    }

    this.healthReportUploadEnabled = flag;
    return result;
  },

  /**
   * Request that remote data be deleted.
   *
   * This will record an intent that previously uploaded data is to be deleted.
   * The policy will eventually issue a request to the listener for data
   * deletion. It will keep asking for deletion until the listener acknowledges
   * that data has been deleted.
   */
  deleteRemoteData: function deleteRemoteData(reason="no-reason") {
    this._log.info("Remote data deletion requested: " + reason);

    this.pendingDeleteRemoteData = true;

    // We want delete deletion to occur as soon as possible. Move up any
    // pending scheduled data submission and try to trigger.
    this.nextDataSubmissionDate = this.now();
    return this.checkStateAndTrigger();
  },

  /**
   * Start background polling for activity.
   *
   * This will set up a recurring timer that will periodically check if
   * activity is warranted.
   *
   * You typically call this function for each constructed instance.
   */
  startPolling: function startPolling() {
    this.stopPolling();

    this._timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
    this._timer.initWithCallback({
      notify: function notify() {
        this.checkStateAndTrigger();
      }.bind(this)
    }, this.POLL_INTERVAL_MSEC, this._timer.TYPE_REPEATING_SLACK);
  },

  /**
   * Stop background polling for activity.
   *
   * This should be called when the instance is no longer needed.
   */
  stopPolling: function stopPolling() {
    if (this._timer) {
      this._timer.cancel();
      this._timer = null;
    }
  },

  /**
   * Abstraction for obtaining current time.
   *
   * The purpose of this is to facilitate testing. Testing code can monkeypatch
   * this on instances instead of modifying the singleton Date object.
   */
  now: function now() {
    return new Date();
  },

  /**
   * Check state and trigger actions, if necessary.
   *
   * This is what enforces the submission and notification policy detailed
   * above. You can think of this as the driver for health report data
   * submission.
   *
   * Typically this function is called automatically by the background polling.
   * But, it can safely be called manually as needed.
   */
  checkStateAndTrigger: function checkStateAndTrigger() {
    // If the master data submission kill switch is toggled, we have nothing
    // to do. We don't notify about data policies because this would have
    // no effect.
    if (!this.dataSubmissionEnabled) {
      this._log.debug("Data submission is disabled. Doing nothing.");
      return;
    }

    let now = this.now();
    let nowT = now.getTime();
    let nextSubmissionDate = this.nextDataSubmissionDate;

    // If the system clock were ever set to a time in the distant future,
    // it's possible our next schedule date is far out as well. We know
    // we shouldn't schedule for more than a day out, so we reset the next
    // scheduled date appropriately. 3 days was chosen arbitrarily.
    if (nextSubmissionDate.getTime() >= nowT + 3 * MILLISECONDS_PER_DAY) {
      this._log.warn("Next data submission time is far away. Was the system " +
                     "clock recently readjusted? " + nextSubmissionDate);

      // It shouldn't really matter what we set this to. 1 day in the future
      // should be pretty safe.
      this._moveScheduleForward24h();

      // Fall through since we may have other actions.
    }

    // Tend to any in progress work.
    if (this._processInProgressSubmission()) {
      return;
    }

    // Requests to delete remote data take priority above everything else.
    if (this.pendingDeleteRemoteData) {
      if (nowT < nextSubmissionDate.getTime()) {
        this._log.debug("Deletion request is scheduled for the future: " +
                        nextSubmissionDate);
        return;
      }

      return this._dispatchSubmissionRequest("onRequestRemoteDelete", true);
    }

    if (!this.healthReportUploadEnabled) {
      this._log.debug("Data upload is disabled. Doing nothing.");
      return;
    }

    // If the user hasn't responded to the data policy, don't do anything.
    if (!this.ensureNotifyResponse(now)) {
      return;
    }

    // User has opted out of data submission.
    if (!this.dataSubmissionPolicyAccepted && !this.dataSubmissionPolicyBypassAcceptance) {
      this._log.debug("Data submission has been disabled per user request.");
      return;
    }

    // User has responded to data policy and data submission is enabled. Now
    // comes the scheduling part.

    if (nowT < nextSubmissionDate.getTime()) {
      this._log.debug("Next data submission is scheduled in the future: " +
                     nextSubmissionDate);
      return;
    }

    return this._dispatchSubmissionRequest("onRequestDataUpload", false);
  },

  /**
   * Ensure user has responded to data submission policy.
   *
   * This must be called before data submission. If the policy has not been
   * responded to, data submission must not occur.
   *
   * @return bool Whether user has responded to data policy.
   */
  ensureNotifyResponse: function ensureNotifyResponse(now) {
    if (this.dataSubmissionPolicyBypassAcceptance) {
      return true;
    }

    let notifyState = this.notifyState;

    if (notifyState == this.STATE_NOTIFY_UNNOTIFIED) {
      let notifyAt = new Date(this.firstRunDate.getTime() +
                              this.SUBMISSION_NOTIFY_INTERVAL_MSEC);

      if (now.getTime() < notifyAt.getTime()) {
        this._log.debug("Don't have to notify about data submission yet.");
        return false;
      }

      let onComplete = function onComplete() {
        this._log.info("Data submission notification presented.");
        let now = this.now();

        this._dataSubmissionPolicyNotifiedDate = now;
        this.dataSubmissionPolicyNotifiedDate = now;
      }.bind(this);

      let deferred = Promise.defer();

      deferred.promise.then(onComplete, function onError(error) {
        this._log.warn("Data policy notification presentation failed: " +
                       CommonUtils.exceptionStr(error));
      });

      this._log.info("Requesting display of data policy.");
      let request = new NotifyPolicyRequest(this, deferred);

      try {
        this._listener.onNotifyDataPolicy(request);
      } catch (ex) {
        this._log.warn("Exception when calling onNotifyDataPolicy: " +
                       CommonUtils.exceptionStr(ex));
      }
      return false;
    }

    // We're waiting for user action or implicit acceptance after display.
    if (notifyState == this.STATE_NOTIFY_WAIT) {
      // Check for implicit acceptance.
      let implicitAcceptance =
        this._dataSubmissionPolicyNotifiedDate.getTime() +
        this.IMPLICIT_ACCEPTANCE_INTERVAL_MSEC;

      this._log.debug("Now: " + now.getTime());
      this._log.debug("Will accept: " + implicitAcceptance);
      if (now.getTime() < implicitAcceptance) {
        this._log.debug("Still waiting for reaction or implicit acceptance. " +
                        "Now: " + now.getTime() + " < " +
                        "Accept: " + implicitAcceptance);
        return false;
      }

      this.recordUserAcceptance("implicit-time-elapsed");
      return true;
    }

    // If this happens, we have a coding error in this file.
    if (notifyState != this.STATE_NOTIFY_COMPLETE) {
      throw new Error("Unknown notification state: " + notifyState);
    }

    return true;
  },

  _processInProgressSubmission: function _processInProgressSubmission() {
    if (!this._inProgressSubmissionRequest) {
      return false;
    }

    let now = this.now().getTime();
    if (this._inProgressSubmissionRequest.expiresDate.getTime() > now) {
      this._log.info("Waiting on in-progress submission request to finish.");
      return true;
    }

    this._log.warn("Old submission request has expired from no activity.");
    this._inProgressSubmissionRequest.promise.reject(new Error("Request has expired."));
    this._inProgressSubmissionRequest = null;
    this._handleSubmissionFailure();

    return false;
  },

  _dispatchSubmissionRequest: function _dispatchSubmissionRequest(handler, isDelete) {
    let now = this.now();

    // We're past our scheduled next data submission date, so let's do it!
    this.lastDataSubmissionRequestedDate = now;
    let deferred = Promise.defer();
    let requestExpiresDate =
      this._futureDate(this.SUBMISSION_REQUEST_EXPIRE_INTERVAL_MSEC);
    this._inProgressSubmissionRequest = new DataSubmissionRequest(deferred,
                                                                  requestExpiresDate,
                                                                  isDelete);

    let onSuccess = function onSuccess(result) {
      this._inProgressSubmissionRequest = null;
      this._handleSubmissionResult(result);
    }.bind(this);

    let onError = function onError(error) {
      this._log.error("Error when handling data submission result: " +
                      CommonUtils.exceptionStr(result));
      this._inProgressSubmissionRequest = null;
      this._handleSubmissionFailure();
    }.bind(this);

    let chained = deferred.promise.then(onSuccess, onError);

    this._log.info("Requesting data submission. Will expire at " +
                   requestExpiresDate);
    try {
      this._listener[handler](this._inProgressSubmissionRequest);
    } catch (ex) {
      this._log.warn("Exception when calling " + handler + ": " +
                     CommonUtils.exceptionStr(ex));
      this._inProgressSubmissionRequest = null;
      this._handleSubmissionFailure();
      return;
    }

    return chained;
  },

  _handleSubmissionResult: function _handleSubmissionResult(request) {
    let state = request.state;
    let reason = request.reason || "no reason";
    this._log.info("Got submission request result: " + state);

    if (state == request.SUBMISSION_SUCCESS) {
      if (request.isDelete) {
        this.pendingDeleteRemoteData = false;
        this._log.info("Successful data delete reported.");
      } else {
        this._log.info("Successful data upload reported.");
      }

      this.lastDataSubmissionSuccessfulDate = request.submissionDate;

      let nextSubmissionDate =
        new Date(request.submissionDate.getTime() + MILLISECONDS_PER_DAY);

      // Schedule pending deletes immediately. This has potential to overload
      // the server. However, the frequency of delete requests across all
      // clients should be low, so this shouldn't pose a problem.
      if (this.pendingDeleteRemoteData) {
        nextSubmissionDate = this.now();
      }

      this.nextDataSubmissionDate = nextSubmissionDate;
      this.currentDaySubmissionFailureCount = 0;
      return;
    }

    if (state == request.NO_DATA_AVAILABLE) {
      if (request.isDelete) {
        this._log.info("Remote data delete requested but no remote data was stored.");
        this.pendingDeleteRemoteData = false;
        return;
      }

      this._log.info("No data was available to submit. May try later.");
      this._handleSubmissionFailure();
      return;
    }

    // We don't special case request.isDelete for these failures because it
    // likely means there was a server error.

    if (state == request.SUBMISSION_FAILURE_SOFT) {
      this._log.warn("Soft error submitting data: " + reason);
      this.lastDataSubmissionFailureDate = this.now();
      this._handleSubmissionFailure();
      return;
    }

    if (state == request.SUBMISSION_FAILURE_HARD) {
      this._log.warn("Hard error submitting data: " + reason);
      this.lastDataSubmissionFailureDate = this.now();
      this._moveScheduleForward24h();
      return;
    }

    throw new Error("Unknown state on DataSubmissionRequest: " + request.state);
  },

  _handleSubmissionFailure: function _handleSubmissionFailure() {
    if (this.currentDaySubmissionFailureCount >= this.FAILURE_BACKOFF_INTERVALS.length) {
      this._log.warn("Reached the limit of daily submission attempts. " +
                     "Rescheduling for tomorrow.");
      this._moveScheduleForward24h();
      return false;
    }

    let offset = this.FAILURE_BACKOFF_INTERVALS[this.currentDaySubmissionFailureCount];
    this.nextDataSubmissionDate = this._futureDate(offset);
    this.currentDaySubmissionFailureCount++;
    return true;
  },

  _moveScheduleForward24h: function _moveScheduleForward24h() {
    let d = this._futureDate(MILLISECONDS_PER_DAY);
    this._log.info("Setting next scheduled data submission for " + d);

    this.nextDataSubmissionDate = d;
    this.currentDaySubmissionFailureCount = 0;
  },

  _futureDate: function _futureDate(offset) {
    return new Date(this.now().getTime() + offset);
  },
});

