<!--
Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-->

<!--
`paper-slider` allows user to select a value from a range of values by
moving the slider thumb.  The interactive nature of the slider makes it a 
great choice for settings that reflect intensity levels, such as volume, 
brightness, or color saturation.

Example:

    <paper-slider></paper-slider>

Use `min` and `max` to specify the slider range.  Default is 0 to 100.

Example:

    <paper-slider min="10" max="200" value="110"></paper-slider>

Styling slider:

To change the slider progress bar color:

    paper-slider::shadow #sliderBar::shadow #activeProgress {
      background-color: #0f9d58;
    }

To change the slider knob color:

    paper-slider::shadow #sliderKnobInner {
      background-color: #0f9d58;
    }

To change the slider pin color:

    paper-slider::shadow #sliderKnobInner::before {
      background-color: #0f9d58;
    }

To change the slider pin's value:

    paper-slider::shadow #sliderKnobInner::after {
      color: #0f9d58
    }

To change the slider secondary progress bar color:

    paper-slider::shadow #sliderBar::shadow #secondaryProgress {
      background-color: #0f9d58;
    }

@group Paper Elements
@element paper-slider
@extends core-range
@homepage github.io
-->

<link rel="import" href="../core-a11y-keys/core-a11y-keys.html">
<link rel="import" href="../paper-progress/paper-progress.html">
<link rel="import" href="../paper-input/paper-input.html">

<polymer-element name="paper-slider" extends="core-range" attributes="snaps pin disabled secondaryProgress editable immediateValue" role="slider" tabindex="0" aria-valuemin="0" aria-valuemax="100">
<template>

  <link rel="stylesheet" href="paper-slider.css">

  <template if="{{!disabled}}">
    <core-a11y-keys target="{{}}" keys="left down pagedown home" on-keys-pressed="{{decrementKey}}"></core-a11y-keys>
    <core-a11y-keys target="{{}}" keys="right up pageup end" on-keys-pressed="{{incrementKey}}"></core-a11y-keys>
  </template>

  <div id="sliderContainer" class="{{ {disabled: disabled, pin: pin, snaps: snaps, ring: immediateValue <= min, expand: expand, dragging: dragging, transiting: transiting, editable: editable} | tokenList }}">

    <div class="bar-container">
      <paper-progress id="sliderBar" aria-hidden="true" min="{{min}}" max="{{max}}" value="{{immediateValue}}" secondaryProgress="{{secondaryProgress}}"
          on-down="{{bardown}}" on-up="{{resetKnob}}" 
          on-trackstart="{{trackStart}}" on-trackx="{{trackx}}" on-trackend="{{trackEnd}}"></paper-progress>
    </div>

    <template if="{{snaps && !disabled}}">
      <div class="slider-markers" horizontal layout>
        <template repeat="{{markers}}">
          <div flex class="slider-marker"></div>
        </template>
      </div>
    </template>

    <div id="sliderKnob" on-down="{{expandKnob}}" on-up="{{resetKnob}}"
        on-trackstart="{{trackStart}}" on-trackx="{{trackx}}" on-trackend="{{trackEnd}}"
        on-transitionend="{{knobTransitionEnd}}"
        center-justified center horizontal layout>

      <div id="sliderKnobInner" value="{{immediateValue}}"></div>

    </div>

  </div>

  <template if="{{editable}}">
    <paper-input id="input" class="slider-input" value="{{immediateValue}}" disabled?="{{disabled}}" on-change="{{inputChange}}"></paper-input>
  </template>

</template>
<script>

  Polymer('paper-slider', {

    /**
     * Fired when the slider's value changes.
     *
     * @event core-change
     */

    /**
     * Fired when the slider's value changes due to user interaction.
     *
     * Changes to the slider's value due to changes in an underlying
     * bound variable will not trigger this event.
     *
     * @event change
     */

    /**
     * If true, the slider thumb snaps to tick marks evenly spaced based
     * on the `step` property value.
     *
     * @attribute snaps
     * @type boolean
     * @default false
     */
    snaps: false,

    /**
     * If true, a pin with numeric value label is shown when the slider thumb 
     * is pressed.  Use for settings for which users need to know the exact 
     * value of the setting.
     *
     * @attribute pin
     * @type boolean
     * @default false
     */
    pin: false,

    /**
     * If true, this slider is disabled.  A disabled slider cannot be tapped
     * or dragged to change the slider value.
     *
     * @attribute disabled
     * @type boolean
     * @default false
     */
    disabled: false,

    /**
     * The number that represents the current secondary progress.
     *
     * @attribute secondaryProgress
     * @type number
     * @default 0
     */
    secondaryProgress: 0,

    /**
     * If true, an input is shown and user can use it to set the slider value.
     *
     * @attribute editable
     * @type boolean
     * @default false
     */
    editable: false,

    /**
     * The immediate value of the slider.  This value is updated while the user
     * is dragging the slider.
     *
     * @attribute immediateValue
     * @type number
     * @default 0
     */

    observe: {
      'step snaps': 'update'
    },

    ready: function() {
      this.update();
    },

    update: function() {
      this.positionKnob(this.calcRatio(this.value));
      this.updateMarkers();
    },

    minChanged: function() {
      this.update();
      this.setAttribute('aria-valuemin', this.min);
    },

    maxChanged: function() {
      this.update();
      this.setAttribute('aria-valuemax', this.max);
    },

    valueChanged: function() {
      this.update();
      this.setAttribute('aria-valuenow', this.value);
      this.fire('core-change');
    },

    disabledChanged: function() {
      if (this.disabled) {
        this.removeAttribute('tabindex');
      } else {
        this.tabIndex = 0;
      }
    },

    immediateValueChanged: function() {
      if (!this.dragging) {
        this.value = this.immediateValue;
      }
    },

    expandKnob: function() {
      this.expand = true;
    },

    resetKnob: function() {
      this.expandJob && this.expandJob.stop();
      this.expand = false;
    },

    positionKnob: function(ratio) {
      this.immediateValue = this.calcStep(this.calcKnobPosition(ratio)) || 0;
      this._ratio = this.snaps ? this.calcRatio(this.immediateValue) : ratio;
      this.$.sliderKnob.style.left = this._ratio * 100 + '%';
    },

    inputChange: function() {
      this.value = this.$.input.value;
      this.fire('change');
    },

    calcKnobPosition: function(ratio) {
      return (this.max - this.min) * ratio + this.min;
    },

    trackStart: function(e) {
      this._w = this.$.sliderBar.offsetWidth;
      this._x = this._ratio * this._w;
      this._startx = this._x || 0;
      this._minx = - this._startx;
      this._maxx = this._w - this._startx;
      this.$.sliderKnob.classList.add('dragging');
      this.dragging = true;
      e.preventTap();
    },

    trackx: function(e) {
      var x = Math.min(this._maxx, Math.max(this._minx, e.dx));
      this._x = this._startx + x;
      this.immediateValue = this.calcStep(
          this.calcKnobPosition(this._x / this._w)) || 0;
      var s =  this.$.sliderKnob.style;
      s.transform = s.webkitTransform = 'translate3d(' + (this.snaps ? 
          (this.calcRatio(this.immediateValue) * this._w) - this._startx : x) + 'px, 0, 0)';
    },

    trackEnd: function() {
      var s =  this.$.sliderKnob.style;
      s.transform = s.webkitTransform = '';
      this.$.sliderKnob.classList.remove('dragging');
      this.dragging = false;
      this.resetKnob();
      this.value = this.immediateValue;
      this.fire('change');
    },

    bardown: function(e) {
      this.transiting = true;
      this._w = this.$.sliderBar.offsetWidth;
      var rect = this.$.sliderBar.getBoundingClientRect();
      var ratio = (e.x - rect.left) / this._w;
      this.positionKnob(ratio);
      this.expandJob = this.job(this.expandJob, this.expandKnob, 60);
      this.fire('change');
    },

    knobTransitionEnd: function(e) {
      if (e.target === this.$.sliderKnob) {
        this.transiting = false;
      }
    },

    updateMarkers: function() {
      this.markers = [], l = (this.max - this.min) / this.step;
      for (var i = 0; i < l; i++) {
        this.markers.push('');
      }
    },

    increment: function() {
      this.value = this.clampValue(this.value + this.step);
    },

    decrement: function() {
      this.value = this.clampValue(this.value - this.step);
    },

    incrementKey: function(ev, keys) {
      if (keys.key === "end") {
        this.value = this.max;
      } else {
        this.increment();
      }
      this.fire('change');
    },

    decrementKey: function(ev, keys) {
      if (keys.key === "home") {
        this.value = this.min;
      } else {
        this.decrement();
      }
      this.fire('change');
    }

  });

</script>
</polymer-element>
