// Portions of this file are taken from GNOME Shell and adapted.
// Because of that, this gnome extension is distributed under
// the terms of the GNU General Public License, version 2.


const {
  AccountsService, Atk, Clutter, Gio,
  GLib, Graphene, Meta, Shell, St,
} = imports.gi;

const Background = imports.ui.background;
const Layout = imports.ui.layout;
const Main = imports.ui.main;

// half of the time for which a frame is displayed
const HALF_FRAME_TIME_MS = 8;

const BLUR_BRIGHTNESS = 0.55;
const BLUR_SIGMA = 60;

const POINTER_HIDE_TIMEOUT = 10 * GLib.USEC_PER_SEC;

let actor;
let lockDialog;
let labelCountdown;
let labelTitle;
let labelMessage;
let labelUser;

const bgManagers = [];
let backgroundGroup;

let cursorTracker;
let motionId = 0;
let lastMotionTime = 0;
let pointerHidden = false;
let pointerHideId = 0;

let user;

let grab;
let countdownTimeoutId = 0;

let configFile;
let configMonitor;
let config;
let startTime;

let isExtensionEnabled = false;
let isActive = false;
let isShellReady = false;
let isActiveChanging = false;

function extLog (msg) {
  log(`[contest-lock] ${msg}`)
}

function extLogError (msg) {
  printerr(`[contest-lock] Error: ${msg}`);
}

function loadConfig () {
  configFile.load_contents_async(null, (obj, res) => {
    // If there is a poblem with the config file, log an error and keep
    // using the old config.
    let newConfig;
    try {
      const [ok, bytes] = configFile.load_contents_finish(res);
      // TextDecoder is used in upstream gnome-shell, but not yet
      // supported in current Debian.
      const contentStr = imports.byteArray.toString(bytes);
      //const contentStr = new TextDecoder().decode(bytes);
      newConfig = JSON.parse(contentStr);
    } catch (err) {
      logError(err, '[contest-lock] config file');
      return;
    }
    if (!(typeof newConfig === 'object' && newConfig != null)) {
      extLogError('config file: invalid format');
      return;
    }
    if (typeof newConfig.title !== 'string') {
      extLogError('config file: "title" must be a string');
      return;
    }
    if (typeof newConfig.message !== 'string') {
      extLogError('config file: "message" must be a string');
      return;
    }
    if (
      typeof newConfig.startTime !== 'string' ||
      !/^\d{4,}-\d\d-\d\dT\d\d:\d\d:\d\d\+\d\d:\d\d$/.test(newConfig.startTime)
    ) {
      extLogError('config file: "startTime" must be a string with format 0000-00-00T00:00:00+00:00');
      return;
    }

    extLog('Loaded new config.')
    config = newConfig;
    startTime = (new Date(newConfig.startTime)).getTime();

    updateConfig();
    syncActive();
  });
}

function syncActive () {
  if (isActiveChanging) return;
  let beforeStart = false;
  if (startTime != null) {
    const now = new Date();
    const timeToStart = startTime - now.getTime() - HALF_FRAME_TIME_MS;
    beforeStart = timeToStart > 0;
  }
  // ignore disable event when active
  if (beforeStart && isShellReady && (isExtensionEnabled || isActive)) {
    activate();
  } else {
    deactivate();
  }
}

function updateConfig () {
  if (labelTitle != null) {
    labelTitle.text = config.title;
  }
  if (labelMessage != null) {
    labelMessage.text = config.message;
  }
}

function updateUser () {
  if (labelUser != null) {
    const realName = user.get_real_name();
    if (realName != null) labelUser.text = realName;
  }
}

function updateCountdown () {
  countdownTimeoutId = 0;
  const now = new Date();
  const nowTime = now.getTime() + HALF_FRAME_TIME_MS;
  const timeToStart = startTime - nowTime;
  const beforeStart = timeToStart > 0;
  if (!beforeStart) {
    deactivate();
    return GLib.SOURCE_REMOVE;
  }
  const allSecondsToStart = Math.floor(timeToStart / 1000);
  const secondsToStart = allSecondsToStart % 60
  const allMinutesToStart = Math.floor(allSecondsToStart / 60);
  const minutesToStart = allMinutesToStart % 60;
  const hoursToStart = Math.floor(allMinutesToStart / 60);

  let hoursString = '';
  if (hoursToStart !== 0) hoursString = `${hoursToStart}∶`;
  labelCountdown.text = hoursString +
    minutesToStart.toString().padStart(2, '0') + '∶' +
    secondsToStart.toString().padStart(2, '0');

  const nextUpdateTime = 1000 - nowTime % 1000
  countdownTimeoutId = GLib.timeout_add(
    GLib.PRIORITY_HIGH,
    nextUpdateTime,
    updateCountdown
  );
  GLib.Source.set_name_by_id(countdownTimeoutId, '[contest-lock] updateCountdown');

  return GLib.SOURCE_REMOVE;
}

function updateBackgrounds () {
  if (!isActive) return;
  while (bgManagers.length) bgManagers.pop().destroy();
  backgroundGroup.destroy_all_children();

  for (let monitorIndex = 0; monitorIndex < Main.layoutManager.monitors.length; monitorIndex++) {
    const monitor = Main.layoutManager.monitors[monitorIndex];
    const widget = new St.Widget({
      style_class: 'screen-shield-background',
      x: monitor.x,
      y: monitor.y,
      width: monitor.width,
      height: monitor.height,
      effect: new Shell.BlurEffect({
        name: 'blur',
        brightness: BLUR_BRIGHTNESS,
        sigma: BLUR_SIGMA,
      }),
    });

    const bgManager = new Background.BackgroundManager({
      container: widget,
      monitorIndex,
      controlPosition: false,
    });

    bgManagers.push(bgManager);

    backgroundGroup.add_child(widget);
  }
}

function pointerHideTimer () {
  if (pointerHideId !== 0) {
    GLib.source_remove(pointerHideId);
    pointerHideId = 0;
  }
  if (!isActive) return GLib.SOURCE_REMOVE;

  const timeToHide = lastMotionTime + POINTER_HIDE_TIMEOUT - GLib.get_monotonic_time();
  if (timeToHide <= 0) {
    cursorTracker.set_pointer_visible(false);
    pointerHidden = true;
    return GLib.SOURCE_REMOVE;
  }

  pointerHideId = GLib.timeout_add(
    GLib.PRIORITY_HIGH,
    timeToHide / 1000 + 20,
    pointerHideTimer
  );
  GLib.Source.set_name_by_id(pointerHideId, '[contest-lock] pointerHide');

  return GLib.SOURCE_REMOVE;
}

function activate () {
  if (isActive) return;
  isActiveChanging = true;
  isActive = true;

  grab = Main.pushModal(Main.uiGroup, { actionMode: Shell.ActionMode.LOCK_SCREEN });
  if (typeof grab === 'boolean') { // gnome 38
    if (!grab) {
      grab = Main.pushModal(Main.uiGroup, {
        options: Meta.ModalOptions.POINTER_ALREADY_GRABBED,
        actionMode: Shell.ActionMode.LOCK_SCREEN
      });
    }
    if (!grab) {
      extLogError('Failed to activate: Could not obtain keyboard grab.');
      return;
    }
    grab = Main.uiGroup;
  } else if ((grab.get_seat_state() & Clutter.GrabState.KEYBOARD) === 0) {
    Main.popModal(grab);
    grab = null;
    extLogError('Failed to activate: Could not obtain keyboard grab.');
    return;
  }

  actor.show();

  Main.sessionMode.pushMode('unlock-dialog');

  backgroundGroup = new Clutter.Actor();

  motionId = global.stage.connect('captured-event', (stage, event) => {
    if (event.type() === Clutter.EventType.MOTION) {
      lastMotionTime = GLib.get_monotonic_time();
      if (pointerHidden) {
        cursorTracker.set_pointer_visible(true);
        pointerHidden = false;
        pointerHideTimer();
      }
    }

    return Clutter.EVENT_PROPAGATE;
  });
  cursorTracker.set_pointer_visible(false);
  pointerHidden = true;

  labelCountdown = new St.Label({
      style_class: 'contest-lock-countdown',
      x_align: Clutter.ActorAlign.CENTER,
  });
  labelTitle = new St.Label({
      style_class: 'contest-lock-title',
      x_align: Clutter.ActorAlign.CENTER,
  });
  labelMessage = new St.Label({
      style_class: 'contest-lock-message',
      x_align: Clutter.ActorAlign.CENTER,
  });
  labelUser = new St.Label({
    style_class: 'contest-lock-user',
    x_align: Clutter.ActorAlign.CENTER,
  });

  const stack = new St.BoxLayout({
    style_class: 'contest-lock-stack',
    vertical: true,
    x_expand: true,
    y_expand: true,
    x_align: Clutter.ActorAlign.CENTER,
    y_align: Clutter.ActorAlign.CENTER,
  })
  stack.add_child(labelUser);
  stack.add_child(labelCountdown);
  stack.add_child(labelTitle);
  stack.add_child(labelMessage);

  const mainBox = new St.BoxLayout();
  mainBox.add_constraint(new Layout.MonitorConstraint({ primary: true }));
  mainBox.add_child(stack);

  lockDialog = new St.Widget({
    name: 'contestLockDialog',
    accessible_role: Atk.Role.WINDOW,
    visible: false,
    reactive: true,
    can_focus: true,
    x_expand: true,
    y_expand: true,
    pivot_point: new Graphene.Point({ x: 0.5, y: 0.5 }),
  });
  lockDialog.add_child(backgroundGroup);
  lockDialog.add_child(mainBox);

  updateConfig();
  updateUser();
  updateCountdown();
  updateBackgrounds();

  // countdown may have just expired before we called updateCountdown
  if (!isActive) return;

  actor.add_child(lockDialog);
  lockDialog.show();

  extLog('Activated.')
  isActiveChanging = false;
}

function deactivate () {
  if (!isActive) return;
  isActiveChanging = true;
  isActive = false;

  if (Main.sessionMode.currentMode === 'unlock-dialog') {
    Main.sessionMode.popMode('unlock-dialog');
  }

  Main.popModal(grab);
  grab = null;

  if (countdownTimeoutId !== 0) {
    GLib.source_remove(countdownTimeoutId);
    countdownTimeoutId = 0;
  }

  actor.hide();
  labelCountdown = null;
  labelTitle = null;
  labelMessage = null;
  labelUser = null;
  while (bgManagers.length) bgManagers.pop().destroy();
  lockDialog.destroy();
  lockDialog = null;

  if (motionId) {
    global.stage.disconnect(motionId);
    motionId = 0;
  }
  cursorTracker.set_pointer_visible(true);

  extLog('Deactivated.');
  isActiveChanging = false;
}

function init (extension) {
  actor = Main.layoutManager.screenShieldGroup;

  const userName = GLib.get_user_name();
  user = AccountsService.UserManager.get_default().get_user(userName);
  if (!user) return;

  user.connect('notify::is-loaded', updateUser);
  user.connect('changed', updateUser);
  updateUser();

  Main.layoutManager.connect('monitors-changed', updateBackgrounds);

  cursorTracker = Meta.CursorTracker.get_for_display(global.display);

  if (!Main.layoutManager._startingUp) {
    isShellReady = true;
  } else {
    Main.layoutManager.connect('startup-complete', () => {
      isShellReady = true;
      syncActive();
    });
  }

  // TODO: When we drop compatibility with gnome <42, remove this code,
  // rename the stylesheet back to stylesheet.css (so that it is loaded
  // by the extension system) and add a session-modes property which
  // includes unlock-dialog to metadata.json.
  const theme = St.ThemeContext.get_for_stage(global.stage).get_theme();
  const stylesheetFile = extension.dir.get_child('stylesheet-always.css');
  theme.load_stylesheet(stylesheetFile);

  // TODO: When we drop compatibility with gnome <42, remove this code.
  // gnome 38 has a bug that causes extensions to break when running
  // `dconf update` while the screen is locked.
  Main.extensionManager.reloadExtension = function () {};

  configFile = Gio.File.new_for_path('/etc/contest-lock.json');
  configMonitor = configFile.monitor_file(Gio.FileMonitorFlags.NONE, null);
  configMonitor.set_rate_limit(1000);
  configMonitor.connect('changed', loadConfig);
  loadConfig();
}

function enable () {
  isExtensionEnabled = true;
  syncActive();
}

function disable () {
  isExtensionEnabled = false;
  syncActive();
}