/* global StackManager, Service, SettingsListener */
'use strict';

(function(exports) {
  var SheetsTransition = {
    transitioning: false,
    _current: null,
    _new: null,

    start: function() {
      SettingsListener.observe('edgesgesture.enabled', false,
                               this._settingUpdate.bind(this));
    },

    begin: function st_begin(direction) {
      this.transitioning = true;
      this._cleanupPreviousTransitions();
      // Ask Homescreen App to fade out when sheets begin moving.
      // Homescreen App would fade in next time it's opened automatically.
      var home = Service.query('getHomescreen');
      home && home.fadeOut();
      var currentApp = StackManager.getCurrent();
      var newApp = (direction === document.documentElement.dir) ?
        StackManager.getPrev() : StackManager.getNext();

      newApp && newApp.broadcast('sheetdisplayed');

      this._current = currentApp ? currentApp.element : null;
      this._new = newApp ? newApp.element : null;

      if (this._current) {
        this._setDuration(this._current, 0);
        this._current.classList.add('inside-edges');
        // XXX: We should setActive(false) here but
        // it will cause image flicking, see
        // https://bugzilla.mozilla.org/show_bug.cgi?id=1125792
        currentApp && currentApp.setNFCFocus(false);
      }

      if (this._new) {
        this._setDuration(this._new, 0);

        this._new.classList.toggle('outside-edges-left', (direction == 'ltr'));
        this._new.classList.toggle('outside-edges-right', (direction == 'rtl'));
      }

      // Note that we send sheets-gesture-end from the StackManager!!!
      window.dispatchEvent(new CustomEvent('sheets-gesture-begin'));
    },

    _lastProgress: null,

    moveInDirection: function st_moveInDirection(direction, progress) {
      var overflowing = !this._new;
      if (overflowing && (progress > 0.20)) {
        progress = 0.20 + (progress - 0.20) / (2 + progress);
      }

      this._lastProgress = progress;

      var factor = (direction == 'ltr') ? 1 : -1;
      var offset = (direction == 'ltr') ? '- 2rem' : '+ 2rem';

      this._setTranslate(this._current, progress * factor * 100);
      this._setTranslate(this._new, (progress - 1) * factor * 100, offset);
    },

    end: function st_end() {
      var commited = false;
      this.transitioning = false;

      var sheets = [this._current, this._new];
      sheets.forEach(function(sheet) {
        if (!sheet) {
          return;
        }

        function finish() {
          sheet.classList.remove('inside-edges');
          sheet.classList.remove('outside-edges-left');
          sheet.classList.remove('outside-edges-right');
          sheet.style.transition = '';

          if (!commited) {
            commited = true;
            StackManager.commit();
          }
        }

        if (!sheet.style.transform) {
          // We won't have a transitionend
          finish();
          return;
        }

        sheet.style.transform = '';

        sheet.addEventListener('transitionend', function trWait(evt) {
          if (evt.propertyName != 'transform') {
            return;
          }
          sheet.removeEventListener('transitionend', trWait);
          finish();
        });
      });

      this._current = null;
      this._new = null;
    },

    snapInPlace: function st_snapInPlace() {
      var TIMEOUT = 200;
      var duration = TIMEOUT - (TIMEOUT * (1 - this._lastProgress));
      duration = Math.max(duration, 90);

      this._setDuration(this._current, duration);
      this._setDuration(this._new, duration);
      this.end();
    },

    snapLeft: function st_snapLeft(speed) {
      this._snapAway(speed, 'outside-edges-right');
    },

    snapRight: function st_snapRight(speed) {
      this._snapAway(speed, 'outside-edges-left');
    },

    _snapAway: function st_snapAway(speed, outClass) {
      if (!this._new) {
        this.snapInPlace();
        return;
      }

      var durationLeft = (1 - this._lastProgress) / speed;
      durationLeft /= 1.2; // boost

      var duration = Math.min(durationLeft, ((1 - this._lastProgress) * 200));

      this._setDuration(this._current, duration);
      this._setDuration(this._new, duration);

      if (this._current) {
        this._current.classList.remove('inside-edges');
        this._current.classList.add(outClass);
      }

      if (this._new) {
        this._new.classList.remove('outside-edges-right');
        this._new.classList.remove('outside-edges-left');
        this._new.classList.add('inside-edges');
      }

      this.end();
    },

    _setTranslate: function st_setTranslate(sheet, percentage, offset) {
      if (!sheet) {
        return;
      }

      var transform;
      if (offset) {
        transform = 'translateX(calc(' + percentage + '% ' + offset + '))';
      } else {
        transform = 'translateX(' + percentage + '%)';
      }
      sheet.style.transform = transform;
    },

    _setDuration: function st_setDuration(sheet, ms) {
      if (!sheet) {
        return;
      }

      sheet.style.transition = 'transform ' + ms + 'ms linear';
    },

    _cleanupPreviousTransitions: function st_cleanUpPreviousTransitions() {
      var sheets = [this._current, this._new];
      sheets.forEach(function(sheet) {
        if (sheet) {
          sheet.style.transform = '';
          sheet.classList.remove('inside-edges');
          sheet.classList.remove('outside-edges-left');
          sheet.classList.remove('outside-edges-right');
          sheet.style.transition = '';
        }
      });
    },

    _edgesEnabled: false,
    _settingUpdate: function st_settingUpdate(enabled) {
      this._edgesEnabled = enabled;
    }
  };
  exports.SheetsTransition = SheetsTransition;
}(window));