import React from 'react'
import ReactDOM from 'react-dom'
import deepEqual from 'deep-equal'

const excludePropNames = ['defer', 'iScroll', 'onRefresh', 'options']

// Events available on iScroll instance
// {`react component event name`: `iScroll event name`}
const availableEventNames = {}
const iScrollEventNames = ['beforeScrollStart', 'scrollCancel', 'scrollStart', 'scroll', 'scrollEnd', 'flick', 'zoomStart', 'zoomEnd']

for (let i = 0, len = iScrollEventNames.length; i < len; i++) {
  const iScrollEventName = iScrollEventNames[i]
  const reactEventName = `on${iScrollEventName[0].toUpperCase()}${iScrollEventName.slice(1)}`
  availableEventNames[reactEventName] = iScrollEventName
  excludePropNames.push(reactEventName)
}

export default class ReactIScroll extends React.Component {
  static displayName = 'ReactIScroll'

  static defaultProps = {
    defer: true,
    options: {},
    style: {
      position: 'relative',
      height: '100%',
      width: '100%',
      overflow: 'hidden'
    }
  }

  constructor(props) {
    super(props)

    this._isMounted = false
    this._initializeTimeout = null
    this._queuedCallbacks = []
    this._iScrollBindedEvents = {}
  }

  componentDidMount() {
    this._isMounted = true
    this._initializeIScroll()
  }

  componentWillUnmount() {
    this._isMounted = false
    this._teardownIScroll()
  }

  // There is no state, we can compare only props.
  shouldComponentUpdate(nextProps, nextContext) {
    return !deepEqual(this.props, nextProps) || !deepEqual(this.context, nextContext)
  }

  // Check if iScroll options has changed and recreate instance with new one
  componentDidUpdate(prevProps) {
    // If options are same, iScroll behaviour will not change. Just refresh events and trigger refresh
    if (deepEqual(prevProps.options, this.props.options)) {
      this._updateIScrollEvents(prevProps, this.props)
      this.refresh()

      // If options changed, we will destroy iScroll instance and create new one with same scroll position
      // TODO test if this will work with indicators
    } else {
      this.withIScroll(true, iScrollInstance => {
        // Save current state
        const { x, y, scale } = iScrollInstance

        // Destroy current and Create new instance of iScroll
        this._teardownIScroll()
        this._initializeIScroll()

        this.withIScroll(true, newIScrollInstance => {
          // Restore previous state
          if (scale && newIScrollInstance.zoom) {
            newIScrollInstance.zoom(scale, 0, 0, 0)
          }

          newIScrollInstance.scrollTo(x, y)
        })
      })
    }
  }

  getIScroll() {
    return this._iScrollInstance
  }

  getIScrollInstance() {
    console.warn("Function 'getIScrollInstance' is deprecated. Instead use 'getIScroll'")
    return this._iScrollInstance
  }

  withIScroll(waitForInit, callback) {
    if (!callback && typeof waitForInit == 'function') {
      callback = waitForInit
    }

    if (this.getIScroll()) {
      callback(this.getIScroll())
    } else if (waitForInit === true) {
      this._queuedCallbacks.push(callback)
    }
  }

  refresh() {
    this.withIScroll(iScrollInstance => iScrollInstance.refresh())
  }

  _runInitializeIScroll() {
    const { iScroll, options } = this.props

    // Create iScroll instance with given options
    const iScrollInstance = new iScroll(ReactDOM.findDOMNode(this), options)
    this._iScrollInstance = iScrollInstance

    // TODO there should be new event 'onInitialize'
    this._triggerRefreshEvent()

    // Patch iScroll instance .refresh() function to trigger our onRefresh event
    iScrollInstance.originalRefresh = iScrollInstance.refresh

    iScrollInstance.refresh = () => {
      iScrollInstance.originalRefresh.apply(iScrollInstance)
      this._triggerRefreshEvent()
    }

    // Bind iScroll events
    this._bindIScrollEvents()

    this._callQueuedCallbacks()
  }

  _initializeIScroll() {
    if (this._isMounted === false) {
      return
    }

    const { defer } = this.props

    if (defer === false) {
      this._runInitializeIScroll()
    } else {
      const timeout = defer === true ? 0 : defer
      this._initializeTimeout = setTimeout(() => this._runInitializeIScroll(), timeout)
    }
  }

  _callQueuedCallbacks() {
    const callbacks = this._queuedCallbacks, len = callbacks.length

    this._queuedCallbacks = []

    for (let i = 0; i < len; i++) {
      callbacks[i](this.getIScroll())
    }
  }

  _teardownIScroll() {
    this._clearInitializeTimeout()

    if (this._iScrollInstance) {
      this._iScrollInstance.destroy()
      this._iScrollInstance = undefined
    }

    this._iScrollBindedEvents = {}
    this._queuedCallbacks = []
  }

  _clearInitializeTimeout() {
    if (this._initializeTimeout !== null) {
      clearTimeout(this._initializeTimeout)
      this._initializeTimeout = null
    }
  }

  _bindIScrollEvents() {
    // Bind events on iScroll instance
    this._iScrollBindedEvents = {}
    this._updateIScrollEvents({}, this.props)
  }

  // Iterate through available events and update one by one
  _updateIScrollEvents(prevProps, nextProps) {
    for (const reactEventName in availableEventNames) {
      this._updateIScrollEvent(availableEventNames[reactEventName], prevProps[reactEventName], nextProps[reactEventName])
    }
  }

  // Unbind and/or Bind event if it was changed during update
  _updateIScrollEvent(iScrollEventName, prevPropEvent, currentPropEvent) {
    if (prevPropEvent !== currentPropEvent) {
      const currentEvents = this._iScrollBindedEvents

      this.withIScroll(true, function(iScrollInstance) {
        if (typeof prevPropEvent === 'function') {
          iScrollInstance.off(iScrollEventName, currentEvents[iScrollEventName])
          currentEvents[iScrollEventName] = undefined
        }

        if (typeof currentPropEvent === 'function') {
          const wrappedCallback = function(...args) {
            currentPropEvent(iScrollInstance, ...args)
          }

          iScrollInstance.on(iScrollEventName, wrappedCallback)
          currentEvents[iScrollEventName] = wrappedCallback
        }
      })
    }
  }

  _triggerRefreshEvent() {
    const { onRefresh } = this.props

    if (typeof onRefresh === 'function') {
      this.withIScroll(iScrollInstance => onRefresh(iScrollInstance))
    }
  }

  render() {
    // Keep only non ReactIScroll properties
    const props = {}

    for (const prop in this.props) {
      if (!~excludePropNames.indexOf(prop)) {
        props[prop] = this.props[prop]
      }
    }

    return <div {...props} />
  }
}

if (process.env.NODE_ENV !== 'production') {
  const propTypesMaker = require('./prop_types').default
  ReactIScroll.propTypes = propTypesMaker(availableEventNames)
}