const formatTime = date => {
  const year = date.getFullYear()
  const month = date.getMonth() + 1
  const day = date.getDate()
  const hour = date.getHours()
  const minute = date.getMinutes()
  const second = date.getSeconds()
  return `${[year, month, day].map(formatNumber).join('/')} ${[hour, minute, second].map(formatNumber).join(':')}`
}

const formatNumber = n => {
  n = n.toString()
  return n[1] ? n : `0${n}`
}

const promisify =  (api) => {
  return (options, ...params) => {
      return new Promise((resolve, reject) => {
          api(Object.assign({}, options, { success: resolve, fail: reject }), ...params);
      });
  }
}

const BeaconUtils = {
  
// 计算距离
calculateAccuracy:function(txPower, rssi, n) {
  // return (0.89976) * Math.pow(rssi / txPower, 7.7095) + 0.111

  return Math.pow(10, Math.abs(rssi - txPower) / (10 * n))
},

//求数组平均值
arrayAverage:function (arr) {
   let tmp = arr.reduce((acc, val) => acc + val, 0) / arr.length
   return tmp
},

//数组分类
classification:function (list,key) {
  let data = {}
  for(var i = 0; i < list.length; i++) {
      if(!data[list[i][key]]) {
          var arr = [];
          arr.push(list[i]);
          data[list[i][key]] = arr;
      }else {
          data[list[i][key]].push(list[i])
      }
  }

  return data
},

//求一维队列某点的高斯模糊权重 @param(队列长度，目标位置, 平均差)
getOneGuassionArray: function(size, kerR, sigma) {
    if (size % 2 > 0) {
      size -= 1
    }
    if (!size) {
      return []
    }
    if (kerR > size-1){
      return []
    }
    let sum = 0;
    let arr = new Array(size);

    for (let i = 0; i < size; i++) {
      arr[i] = Math.exp(-((i - kerR) * (i - kerR)) / (2 * sigma * sigma));
      sum += arr[i];
    }

    return arr.map(e => e / sum);
  }
}

module.exports = {
  formatTime,
  promisify,
  BeaconUtils
}