import * as cornerstone from 'cornerstone-core'
var taskPool = [] // 请求池
let numRequest = 0 // 正在执行数量
const maxRequest = 6 // 可配置
let taskTimer // 轮询的定时器
var cachedTask = {} // 存放的任务数据

// 执行下载
async function executeTask() {
  if (taskPool.length > 0) {
    sortTaskPool()
    var taskPromises = []
      for (let i = 0; i < maxRequest; i++) {
        const task = taskPool.shift()
        if (!task) return
        taskPromises.push((task.execute))
      }
    await Promise.all(taskPromises.map(task=>task()));
    executeTask()
    // await new Promise(resolve => setTimeout(resolve, delay));

    // const taskPromises = [];
    // const delay = 50
    // for(let i = 0;i< taskPool.length; i++ ){
    //   taskPromises.push(()=>cornerstone.loadAndCacheImage(taskPool[i].key))
    // }
    // for (let i = 0; i < taskPromises.length; i += maxRequest) {
    //   const tasks = taskPromises.slice(i, i + maxRequest);
    //   await Promise.all(tasks.map(task=>task()));
    //   await new Promise(resolve => setTimeout(resolve, delay));
    // }


    // while (taskPool.length > 0) {
      
    //   var requestNum = taskPool.length > maxRequest ? maxRequest : taskPool.length
    //   for (let i = 0; i < requestNum; i++) {
    //     sortTaskPool()
    //     const task = taskPool.shift()
    //     if (!task) return
    //     batchPromises.push(cornerstone.loadAndCacheImage(task.key))
    //   }
    //   await Promise.all(batchPromises);
    // }
  }else{
    startTaskTimer()
  }
}
function sortTaskPool() {
  if (taskPool.length > 0) {
    taskPool.sort((a, b) =>  b.priority-a.priority )
    
  }
}

// 轮询检查请求池中是否有请求需要执行
function startTaskTimer() {
  // if(taskTimer){
  //   clearInterval(taskTimer)
  //   taskTimer = null
  // }
  // taskTimer = setInterval(() => {
  //   if (taskPool.length > 0) {
  //     stopTaskTimer()
  //     executeTask()
  //   }else{
  //     return
  //   }
  // }, 50)
  taskTimer = setInterval(() => {
    if (taskPool.length > 0) {
      stopTaskTimer()
      executeTask()
    }
  }, 50)
}

// 停止轮询
function stopTaskTimer() {
  clearInterval(taskTimer)
  taskTimer = null
}
function loadAndCacheImagePlus(imageId,seriesId, priority) {
  return new Promise((resolve, reject) => {
    const imageLoadObject = cornerstone.imageCache.getImageLoadObject(imageId)
    if (imageLoadObject) {
      imageLoadObject.promise.then((image) => {
        resolve(image)
      }, (err) => {
        reject(err)
      })
    } else {
      const imageTask = buildImageRequestTask(imageId,seriesId, { priority })
      // addTaskIntoPool(imageTask).then((res) => {
      //   resolve(res)
      // }).catch(e => {
      //   reject(e)
      // })
      taskPool.push(imageTask)
    }
  })
}
// 预加载池的添加
function addTaskIntoPool(task) {
  taskPool.push(task)
}
function removeTask(seriesId){
  stopTaskTimer()
  if (taskPool.length > 0) {
    for(var i =taskPool.length-1; i>=0;i--){
      if(taskPool[i] && taskPool[i].seriesId === seriesId){
        delete cachedTask[taskPool[i].key]
        taskPool.splice(i,1)
       
      }
    }
    
  }
  startTaskTimer()
}
function resetRequestPool(){
  taskPool = []
  pendingList =[]
  cachedTask = {}
}
function resetCachedTask(){
  taskPool = []
  pendingList =[]
  cachedTask = {}
}
function buildImageRequestTask(imageId,seriesId, config = {}) {
  return {
      key: imageId,
      seriesId:seriesId,
      ...config,
      execute: () => {
          return cornerstone.loadAndCacheImage(imageId)
      }
  };
}

export default {
  addTaskIntoPool,
  executeTask,
  startTaskTimer,
  stopTaskTimer,
  loadAndCacheImagePlus,
  removeTask,
  resetRequestPool,
  resetCachedTask
}