import * as maptalks from 'maptalks'
import FnTask from './Task.js'
import Event from './Event'


// 从远程中获取数据
function getRemoteData (url) {
  return new Promise((resolve, reject) => {
    maptalks.Ajax.getJSON(url, (err, data) => {
      if (err || !data || !data.features.length) {
        reject()
      } else {
        resolve(data.features)
      }
    })
  })
}




const LOADDING = 1;
const SUCCESS = 2;

class Reveal extends Event {
  constructor() {
    super()
    this.urlStatue = {}
    this.cache = {}
    this.loaddingGeos = {}
    this.remoteTask = new FnTask({maxParallel: 3})
    this.loadTask = new FnTask({maxParallel: 5})
  }

  // 获取数据先从内存，再从远程获取
  preloadingFeatures(url) {
    this.urlStatue[url] = LOADDING
    this.remoteTask.push(
      async () => {
        try {
          return await getRemoteData(url)
        } catch (e) {
          delete this.urlStatue[url]
          return null
        }
      },
      data => {
        this.emit(url, data)
      }
    )
  }

  checkFeatureState (id) {
    for (let key in this.loaddingGeos) {
      if (~this.loaddingGeos[key].indexOf(id)) return true
    }
  }

  // 分批加载
  async inBatches(url, features, addArchitecture) {
    if (this.urlStatue[url] === LOADDING) {
      for (let i = 0, len = features.length; i < len; i++) {
        if (this.checkFeatureState(features[i].id)) {
          features.splice(i, 1)
          i--
          len--
        } else {
          
        }
      }

      this.loaddingGeos[url] = features.map(f => f.id)
      this.cache[url] = await addArchitecture(features)
      this.urlStatue[url] = SUCCESS
    }
  }

  // 加载模型
  async loaddingFeatures(url, cb) {
    this.loadTask.push(async () => {
      this.preloadingFeatures(url)
      this.off(url)
      this.once(url, features => {
        if (features) {
          if (document.hidden) {
            this.once('visibilityshow', () => this.inBatches(url, features, cb))
          } else {
            this.inBatches(url, features, cb)
          }
        }
      })
    })
  }

  async loadRegion(urls, loadCb) {
    for (let key of urls) {
      if (this.urlStatue[key]) continue
      this.loaddingFeatures(key, loadCb)
    }
  }

  eliminate (urls) {
    if (!Array.isArray(urls)) {
      urls = [urls]
    }

    urls.forEach(url => {
      delete this.urlStatue[url]
      delete this.cache[url]
      delete this.loaddingGeos[url]
    })
  }
}

const reveal = new Reveal()

document.addEventListener('visibilitychange', function () {
  if (!document.hidden) {
    reveal.emit('visibilityshow')
  }
});

export default reveal