/**
 * Mixin to handle stack
 */

import React, {PropTypes as types} from 'react'
'use strict'

const INSETS_STATE_KEY = '_apStackInsets'

/** @lends ApStackMixin */
const ApStackMixin = {

  // --------------------
  // Custom
  // --------------------
  $apStackMixed: true,

  /**
   * Get insets of the stack.
   * @returns {object}
   */
  getStackInsets () {
    const s = this
    return s.state[ INSETS_STATE_KEY ] || {}
  },
  /**
   * Set insets of the stack.
   * @param {object} nextInsets - Insets to set.
   */
  setStackInsets (nextInsets) {
    const s = this
    let insets = s.getStackInsets()
    s.setState({
      [INSETS_STATE_KEY]: Object.assign(insets, nextInsets)
    })
  },

  /**
   * Bind stacker events.
   * @param {Stacker} stacker - A stacker instance.
   */
  bindStacker (stacker) {
    const s = this
    s._addStackerListener(stacker, 'push', s.stackedViewDidPush)
    s._addStackerListener(stacker, 'pop', s.stackedViewDidPop)
  },

  /**
   * Unbind stacker events.
   * @param {Stacker} stacker - A stacker instance.
   */
  unbindStacker (stacker) {
    const s = this
    s._removeStackerListener(stacker, 'push', s.stackedViewDidPush)
    s._removeStackerListener(stacker, 'pop', s.stackedViewDidPop)
  },

  /**
   * Get width of scrollable content in the top view.
   * @returns {number|null}
   */
  getStackedScrollWidth () {
    const s = this
    let { stacker } = s.props
    let topView = stacker && stacker.topView()
    if (!topView) {
      return null
    }
    let wrapElm = document && document.getElementById(`view-wrap-${topView.id}`)
    if (!wrapElm) {
      return null
    }
    let bodyElm = wrapElm.querySelector('.ap-view-body')
    if (!bodyElm) {
      return null
    }
    return bodyElm.scrollWidth || null
  },

  // --------------------
  // Specs
  // --------------------

  statics: {},

  propTypes: {
    stacker: types.object.isRequired,
    stackInsets: types.object
  },

  getInitialState () {
    return {
      [INSETS_STATE_KEY]: {}
    }
  },

  // --------------------
  // Lifecycle
  // --------------------

  componentWillMount () {
    const s = this
    let { props } = s

    s.bindStacker(props.stacker)
  },

  componentDidMount () {
    const s = this
    let { props } = s
    if (props.stackInsets) {
      s.setStackInsets(props.stackInsets)
    }
  },

  componentWillReceiveProps (nextProps) {
    const s = this
    let { props } = s

    if (nextProps.stackInsets) {
      s.setStackInsets(nextProps.stackInsets)
    }
    if (nextProps.stacker) {
      s.unbindStacker(props.stacker)
      s.bindStacker(nextProps.stacker)
    }
  },

  componentWillUnmount () {
    const s = this
    let { props } = s
    s.unbindStacker(props.stacker)
  },

  // ------------------
  // Private
  // ------------------

  _addStackerListener (stacker, event, listner) {
    const s = this
    if (listner && stacker) {
      stacker.addListener(event, listner)
    }
  },

  _removeStackerListener (stacker, event, listner) {
    const s = this
    if (listner && stacker) {
      stacker.removeListener(event, listner)
    }
  }

}

export default Object.freeze(ApStackMixin)