"use script" // 开发环境建议开启严格模式

const url = "https://api.waqi.info/mapq/bounds/?bounds={RECTANGLE}&inc=placeholders&k={KEY}&_={DATA}"
const table = [
  {
    level: "一级（优）",
    influence: "空气质量令人满意，基本无空气污染",
    suggestion: "各类人群可正常活动"
  },
  {
    level: "二级（良）",
    influence: "空气质量可接受，但某些污染物可能对极少数异常敏感人群健康有较弱影响",
    suggestion: "心脏病和肺病患者症状显著加剧，运动耐受力降低，健康人群普遍出现症状"
  },
  {
    level: "三级（轻度污染）",
    influence: "易感人群症状有轻度加剧，健康人群出现刺激症状",
    suggestion: "儿童、老年人及心脏病、呼吸系统疾病患者应减少长时间、高强度的户外锻炼"
  },
  {
    level: "四级（中度污染）",
    influence: "易感人群症状有轻度加剧，健康人群出现刺激症状",
    suggestion: "儿童、老年人及心脏病、呼吸系统疾病患者避免长时间、高强度的户外锻炼，一般人群适量减少户外运动"
  },
  {
    level: "五级（重度污染）",
    influence: "心脏病和肺病患者症状显著加剧，运动耐受力降低，健康人群普遍出现症状",
    suggestion: "儿童、老年人及心脏病、肺病患者应停留在室内，停止户外运动，一般人群减少户外运动"
  },
  {
    level: "六级（严重污染）",
    influence: "心脏病和肺病患者症状显著加剧，运动耐受力降低，健康人群普遍出现症状",
    suggestion: "儿童、老年人和病人应停留在室内，避免体力消耗，一般人群避免户外活动"
  }
]

let xmlHttpRequest
const nWidth = 500
let currTime

onmessage = function (e) {
  const bounds = e.data.bounds
  currTime = new Date().getTime()

  const strKey = jskey()
  const nowUrl = url.replace("{RECTANGLE}", bounds).replace("{KEY}", strKey).replace("{DATA}", currTime)

  xmlHttpRequest = new XMLHttpRequest()

  // 2.设置回调函数
  xmlHttpRequest.onreadystatechange = callback

  // 3.初始化XMLHttpRequest组建
  xmlHttpRequest.open("POST", nowUrl, true)

  // 4.发送请求
  xmlHttpRequest.send()
}

function callback() {
  if (xmlHttpRequest.readyState === 4 && xmlHttpRequest.status === 200) {
    const entityTable = []
    /// /////////////////////////////////////////////////
    const currentData = JSON.parse(xmlHttpRequest.responseText)
    for (let i = currentData.length - 1; i >= 0; i--) {
      const item = currentData[i]
      let aqi = parseInt(item.aqi)
      if (!isNumber(aqi)) {
        continue
      }

      let level = 0
      if (aqi > nWidth) {
        level = 5
        aqi = nWidth - 1
      } else {
        if (aqi > 300) {
          level = 5
        } else if (aqi > 200) {
          level = 4
        } else if (aqi > 150) {
          level = 3
        } else if (aqi > 100) {
          level = 2
        } else if (aqi > 50) {
          level = 1
        }
      }

      const newItem = {
        ...item,
        aqi: aqi,
        level: table[level].level,
        influence: table[level].influence,
        suggestion: table[level].suggestion
      }
      entityTable.push(newItem)
    }
    /// ///////////////////////////////////////////////////
    // self代表子线程自身
    self.postMessage({ currTime: currTime, entityTable: entityTable })
    self.close()
  } else if (xmlHttpRequest.readyState === 4 && xmlHttpRequest.status === 0) {
    self.postMessage({ currTime: currTime, entityTable: [] })
    self.close()
  }
}

function isNumber(obj) {
  return typeof obj === "number" && !isNaN(obj)
}

function jskey() {
  return (function () {
    let u = ""
    decodeURIComponent("%603Z3F%7BWS%3A3BSBdIRlJTySXYnmecFR%2CF%7BeSGHhkMh%3E%3E")
      .split("")
      .forEach(function (c) {
        u += String.fromCharCode(c.charCodeAt(0) - 1)
      })
    return u
  })()
}