<!--
// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
-->
<import src="animation/controller.sky" as="AnimationController" />
<import src="animation/curves.sky" as="Curves" />
<import src="sky-element/sky-element.sky" as="SkyElement" />
<import src="sky-scrollable.sky" />

<sky-element
  name="sky-drawer"
  on-pointerdown="handlePointerDown"
  on-pointermove="handlePointerMove"
  on-pointerup="handlePointerUp"
  on-pointercancel="handlePointerCancel">
<template>
  <style>
    #mask {
      background-color: black;
      will-change: opacity;
      position: absolute;
      top: 0;
      left: 0;
      bottom: 0;
      right: 0;
    }
    #content {
      background-color: yellow;
      will-change: transform;
      position: absolute;
      width: 256px;
      top: 0;
      left: 0;
      bottom: 0;
    }
  </style>
  <div id="mask" on-click="handleMaskClick" />
  <div id="content" on-gestureflingstart="handleFlingStart">
    <content/>
  </div>
</template>
<script>
const kWidth = 256;
const kMinFlingVelocity = 0.4;
const kMinAnimationDurationMS = 246;
const kMaxAnimationDurationMS = 600;
const kAnimationCurve = Curves.easeInOut;

module.exports = class extends SkyElement {
  created() {
    this.position_ = 0;
    this.mask_ = null;
    this.content_ = null;
    this.animation_ = new AnimationController(this);
  }

  shadowRootReady() {
    this.mask_ = this.shadowRoot.getElementById('mask');
    this.content_ = this.shadowRoot.getElementById('content');
    this.position = -kWidth;
  }

  toggle() {
    if (this.isMostlyClosed)
      this.open();
    else
      this.close();
  }

  open() {
    this.animateToPosition_(0);
  }

  close() {
    this.animateToPosition_(-kWidth);
  }

  get isClosed() {
    return this.position_ <= -kWidth;
  }

  get isMostlyClosed() {
    return this.position_ <= -kWidth / 2;
  }

  get position() {
    return this.position_;
  }

  set position(value) {
    var newPosition = Math.min(0, Math.max(value, -kWidth));
    this.position_ = newPosition;
    this.content_.style.transform = 'translateX(' + newPosition + 'px)';
    this.mask_.style.opacity = (newPosition / kWidth + 1) * 0.25;
    this.style.display = this.isClosed ? 'none' : '';
  }

  settle_() {
    if (this.isMostlyClosed)
      this.close();
    else
      this.open();
  }

  animateToPosition_(targetPosition) {
    var currentPosition = this.position_;
    var distance = Math.abs(targetPosition - currentPosition);
    var duration = kMaxAnimationDurationMS * distance / kWidth;
    this.animation_.start({
      begin: currentPosition,
      end: targetPosition,
      duration: Math.max(kMinAnimationDurationMS, duration),
      curve: kAnimationCurve,
    });
  }

  updateAnimation(position) {
    this.position = position;
  }

  handleMaskClick() {
    this.close();
  }

  handlePointerDown(event) {
    this.animation_.stop();
  }

  handlePointerMove(event) {
    this.position += event.dx;
  }

  handlePointerUp(event) {
    if (!this.animation_.isAnimating)
      this.settle_();
  }

  handlePointerCancel(event) {
    if (!this.animation_.isAnimating)
      this.settle_();
  }

  handleFlingStart(event) {
    var direction = Math.sign(event.velocityX);
    var velocityX = Math.abs(event.velocityX) / 1000;
    if (velocityX < kMinFlingVelocity)
      return;
    var targetPosition = direction < 0 ? -kWidth : 0;
    var currentPosition = this.position_;
    var distance = Math.abs(targetPosition - currentPosition);
    var duration = distance / velocityX;
    this.animation_.start({
      begin: currentPosition,
      end: targetPosition,
      duration: duration,
      curve: Curves.linear,
    });
  }
}.register();
</script>
</sky-element>