/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
/* 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/. */

/**
 * Read the data saved by nsTerminator during shutdown and feed it to the
 * relevant telemetry histograms.
 */

const lazy = {};

ChromeUtils.defineESModuleGetters(lazy, {
  PromiseUtils: "resource://gre/modules/PromiseUtils.sys.mjs",
  setTimeout: "resource://gre/modules/Timer.sys.mjs",
});

export function nsTerminatorTelemetry() {
  this._wasNotified = false;
  this._deferred = lazy.PromiseUtils.defer();

  IOUtils.sendTelemetry.addBlocker(
    "TerminatoryTelemetry: Waiting to submit telemetry",
    this._deferred.promise,
    () => ({
      wasNotified: this._wasNotified,
    })
  );
}

var HISTOGRAMS = {
  "quit-application": "SHUTDOWN_PHASE_DURATION_TICKS_QUIT_APPLICATION",
  "profile-change-net-teardown":
    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_CHANGE_NET_TEARDOWN",
  "profile-change-teardown":
    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_CHANGE_TEARDOWN",
  "profile-before-change":
    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_BEFORE_CHANGE",
  "profile-before-change-qm":
    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_BEFORE_CHANGE_QM",
  "xpcom-will-shutdown": "SHUTDOWN_PHASE_DURATION_TICKS_XPCOM_WILL_SHUTDOWN",
  "xpcom-shutdown": "SHUTDOWN_PHASE_DURATION_TICKS_XPCOM_SHUTDOWN",

  // The following keys appear in the JSON, but do not have associated
  // histograms.
  "xpcom-shutdown-threads": null,
  XPCOMShutdownFinal: null,
  CCPostLastCycleCollection: null,
};

nsTerminatorTelemetry.prototype = {
  classID: Components.ID("{3f78ada1-cba2-442a-82dd-d5fb300ddea7}"),

  // nsISupports

  QueryInterface: ChromeUtils.generateQI(["nsIObserver"]),

  // nsIObserver

  observe: function DS_observe(aSubject, aTopic, aData) {
    this._wasNotified = true;

    (async () => {
      try {
        //
        // This data is hardly critical, reading it can wait for a few seconds.
        //
        await new Promise(resolve => lazy.setTimeout(resolve, 3000));

        let PATH = PathUtils.join(
          Services.dirsvc.get("ProfLD", Ci.nsIFile).path,
          "ShutdownDuration.json"
        );
        let data;
        try {
          data = await IOUtils.readJSON(PATH);
        } catch (ex) {
          if (DOMException.isInstance(ex) && ex.name == "NotFoundError") {
            return;
          }
          // Let other errors be reported by Promise's error-reporting.
          throw ex;
        }

        // Clean up
        await IOUtils.remove(PATH);
        await IOUtils.remove(PATH + ".tmp");

        for (let k of Object.keys(data)) {
          let id = HISTOGRAMS[k];
          if (id === null) {
            // No histogram associated with this entry.
            continue;
          }

          try {
            let histogram = Services.telemetry.getHistogramById(id);
            histogram.add(Number.parseInt(data[k]));
          } catch (ex) {
            // Make sure that the error is reported and causes test failures,
            // but otherwise, ignore it.
            Promise.reject(ex);
            continue;
          }
        }

        // Inform observers that we are done.
        Services.obs.notifyObservers(
          null,
          "shutdown-terminator-telemetry-updated"
        );
      } finally {
        this._deferred.resolve();
      }
    })();
  },
};

// Module