import React, { PropTypes } from 'react'

export const insertScriptHelper = (projectId) => {
  const el = document.querySelector('[data-optimizely-snippet]')
  if (!isReadyHelper() && !el) {
    const protocol = `${document.location.protocol}//`
    const scriptTag = document.createElement('script')
    scriptTag.type = 'text/javascript'
    scriptTag.async = true
    scriptTag.src = `${protocol}cdn.optimizely.com/js/${projectId}.js`
    scriptTag.setAttribute('data-optimizely-snippet', true)
    document.getElementsByTagName('head')[0].appendChild(scriptTag)
  }
}

export const triggerEventHelper = (eventName) => {
  try {
    typeof window.optimizely === 'object' &&
    window.optimizely.push({
      type: 'event',
      eventName: eventName,
    })
  } catch (e) {
    throw Error('OptimizelyExperiment triggerEventHelper unexpected error!')
  }
}

export const isReadyHelper = () => {
  return typeof window.optimizely === 'object' &&
          typeof window.optimizely.data === 'object' &&
          typeof window.optimizely.allExperiments === 'object'
}

class OptimizelyExperiment extends React.Component {
  constructor (props) {
    super(props)
    window.optimizely = window.optimizely || []
    window.optimizely.push({
      type: 'log',
      level: 'info',
    })
    this.onReadyRecallMs = 10
    this.defaultState = {
      variantName: null,
      result: null,
      goalCompleted: false,
    }
    this.eventListeners = []
    this.state = Object.assign({}, this.defaultState)
    this.mapVariantToState = this.mapVariantToState.bind(this)
    this.eventHandler = this.eventHandler.bind(this)
  }

  componentWillMount () {
    if (!isReadyHelper()) {
      this.insertScript()
    }
  }

  componentDidMount () {
    this.observeReady(this.mapVariantToState)
  }

  componentDidUpdate (prevProps, prevState) {
    if (isReadyHelper() && prevState.variantName !== this.state.variantName) {
      this.setResult()
    }
    if (prevState.goalCompleted !== this.state.goalCompleted) {
      this.removeAllEventListeners()
    }
  }

  componentWillUnmount () {
    this.removeAllEventListeners()
  }

  observeReady (cb) {
    const { allExperiments } = window.optimizely
    if (allExperiments && typeof allExperiments[this.props.experimentId] !== 'undefined') {
      this.triggerPageActivation()
      this.props.customEvents.forEach(({selector, eventType, eventName}) =>
        this.attachEventHandler(selector, eventType, eventName))
      if (typeof cb === 'function') cb()
    } else {
      const t = setTimeout(() => {
        clearTimeout(t)
        this.observeReady(cb)
      }, this.onReadyRecallMs)
    }
  }

  mapVariantToState () {
    const { experimentId } = this.props
    const { variationIdsMap, allVariations } = window.optimizely
    let variantName = 'Original'

    if (this.isExperimentActive(experimentId)) {
      const variationId = variationIdsMap[experimentId][0] // simple AB test, not multiple
      variantName = allVariations[variationId].name
    }

    this.setState(() => {
      // keep a reference for debugging
      this.setMiddlemanRefHelper({
        variantName,
      })

      return {
        variantName,
      }
    })
  }

  isExperimentActive (experimentId) {
    const { activeExperiments } = window.optimizely
    return activeExperiments.find(v => v === experimentId)
  }

  insertScript () {
    const { projectId } = this.props
    insertScriptHelper(projectId)
  }

  runExperiment () {
    const { variantName } = this.state
    const { experimentsMap } = this.props
    let result = experimentsMap[variantName] || false
    if (typeof result === 'function') {
      result = result()
    }
    return result
  }

  setResult () {
    this.setState({
      result: this.runExperiment(),
    })
  }

  triggerPageActivation () {
    window.optimizely.push({
      type: 'page',
      pageName: this.props.pageName,
    })
  }

  attachEventHandler (selector, eventType, eventName) {
    if (Array.isArray(selector)) {
      return selector.forEach(v => this.attachEventHandler(v, eventType, eventName))
    }

    const target = document.querySelector(selector)
    const eventHandler = this.eventHandler.bind(undefined, target, eventType, eventName)

    if (target) {
      target.addEventListener(eventType, eventHandler, true)

      this.eventListeners.push({
        target,
        eventHandler,
        eventType,
      })
    }
  }

  eventHandler (target, eventType, eventName) {
    this.setState(() => {
      triggerEventHelper(eventName)

      return {
        goalCompleted: true,
      }
    })
  }

  removeAllEventListeners () {
    this.eventListeners.forEach(({target, eventType, eventHandler}) =>
      this.removeEventListener(target, eventType, eventHandler))
  }

  removeEventListener (target, eventType, eventHandler) {
    target.removeEventListener(eventType, eventHandler, true)
  }

  setMiddlemanRefHelper (data) {
    const propName = '__AB_TEST_STATE_REF__'
    window[propName] = Object.assign({}, window[propName], data)
  }

  render () {
    return this.state.result
  }
}

OptimizelyExperiment.propTypes = {
  projectId: PropTypes.string.isRequired,
  experimentId: PropTypes.string.isRequired,
  name: PropTypes.string.isRequired,
  experimentsMap: PropTypes.object.isRequired,
  pageName: PropTypes.string,
  customEvents: PropTypes.array,
}

export default OptimizelyExperiment