一击必杀版.js

(function () {
  if (location.host !== 'shop.48.cn') {
    console.error('kidding me?');
    return ;
  }

  if (typeof jQuery !== 'function') {
    console.error('缺少基础库');
    return ;
  }

  if (typeof Promise !== 'function') {
    console.error('请升级浏览器');
    return ;
  }

  var seat = {
    'vip坐票': '2',
    '普通坐票': '3',
    '普通站票': '4'
  };

  function buy(ticketId, ticketsCount, seatType) {
    ticketId = ticketId || /\/(\d+)$/.exec(location.href)[1];
    ticketsCount = ticketsCount || 1;
    seatType = seatType || '普通坐票';

    return new Promise(function (resolve, reject) {
      $.ajax({
        url: '/TOrder/add',
        type: 'post',
        dataType: 'json',
        data: {
          id: ticketId,
          num: ticketsCount,
          seattype: seat[seatType] || '3',
          brand_id: '1',
          r: Math.random()
        },
        error: reject,
        success: function (result) {
          if (result.HasError) {
            reject(result.Message);
          }
          else {
            resolve(result.ReturnObject);
          }
        }
      });
    });
  }

  function delay(tick) {
    return new Promise(function (resolve, reject) {
      setTimeout(resolve, tick);
    });
  }

  /////////// 延迟计算
  function getServerTime() {
    return new Promise(function (resolve, reject) {
      $.ajax({
        type: 'GET',
        url: '/TOrder/gettimestamp',
        dataType: 'json',
        data: {r: Math.random()},
        success: function (timestamp) {
          // "/Date(1462878288234)/"
          var date = /\/Date\((\d+)\)/.exec(timestamp)[1];
          date = +date;
          resolve(date);
        }
      })
    });
  }

  function calcNetDelay() {
    var tStart = Date.now();
    return getServerTime().then(function (servTime) {
      var tEnd = Date.now();

      var midPoint = (tStart + tEnd) >> 1;
      var delay = servTime - midPoint;

      return delay;
    });
  }

  var tasks = (new Array(11)).join(',').split(',').map(function () {
    return calcNetDelay();
  });

  Promise.all(tasks).then(function (delays) {
    // 对延迟结果进行排序
    delays.sort(function (a, b) {
      return a - b;
    });
    // 分别去掉2个最高和最低延迟
    delays.shift();
    delays.shift();
    delays.pop();
    delays.pop();

    // 取出其中最大的值作为延迟
    var maxDelay = Math.max.apply(Math, delays);
    console.info('计算出本地与服务器之间的延迟是', maxDelay);

    // 返回取服务器时间的函数
    return function () {
      var now = Date.getTime();
      return now + maxDelay;
    };
  }).then(function (getTime) {

    function check(targetTime) {

      function taskFn() {
        return buy('106', 1, '普通坐票')
          .then(function (orderId) {
            if (orderId) window.location.href = orderId;  // 跳到下单页面
          }, function (failedReason) {
            console.info(failedReason);
          });
      }

      var now = getTime();
      var delay;
      if (targetTime - now > 15 * 1000) {
        // 如果距离目标时间大于15s，则15s后刷一次票
        delay = 15 * 1000;
      } else {
        // 否则，准点刷新
        delay = targetTime - now;
      }

      console.log(delay, '秒钟后尝试一次！');
      setTimeout(function () {
        taskFn.then(check.bind(null, targetTime));
      }, delay);
    }

    
    var checkTime = new Date('2016-05-10 20:00:00').getTime();
    check(checkTime);
  });
})();