<template>
  <div class="data-picker" v-show-date-pannel>
    <input type="text" :value="formatDate" />
    <div class="pannel" v-if="pannelVisible">
      <div class="pannel-header">
        <span @click="preYear">&lt;&lt;</span>
        <span @click="preMonth">&lt;</span>
        <span
          >{{ time.year }}年{{
            (time.month + 1).toString().padStart(2, "0")
          }}月</span
        >
        <span @click="nextMonth">&gt;</span>
        <span @click="nextYear">&gt;&gt;</span>
      </div>
      <div class="pannel-content">
        <div>
          <span>日</span>
          <span>一</span>
          <span>二</span>
          <span>三</span>
          <span>四</span>
          <span>五</span>
          <span>六</span>
        </div>
        <div v-for="i in 6" :key="i">
          <span
            v-for="j in 7"
            :class="{
              notCurrentMonth: !isCurrentMonth(
                currentDateList[(i - 1) * 7 + (j - 1)]
              ),
              isSelected: isSelected(currentDateList[(i - 1) * 7 + (j - 1)]),
              today: isTody(currentDateList[(i - 1) * 7 + (j - 1)]),
            }"
            :key="j"
            @click="setDay(currentDateList[(i - 1) * 7 + (j - 1)])"
            >{{ currentDateList[(i - 1) * 7 + (j - 1)].getDate() }}</span
          >
        </div>
      </div>
    </div>
  </div>
</template>

<script>
const getYearMonthDay = function (val) {
  const year = new Date(val).getFullYear();
  const month = new Date(val).getMonth();
  const day = new Date(val).getDate();
  return {
    year,
    month,
    day,
  };
};
export default {
  props: ["value"],
  data() {
    const { year, month, day } = getYearMonthDay(this.value);
    return {
      pannelVisible: false,
      time: { year, month },
    };
  },
  computed: {
    formatDate() {
      const { year, month, day } = getYearMonthDay(this.value);
      const m = (month+1).toString().padStart(2, "0");
      return `${year}-${m}-${day}`;
    },
    // 需要循环的数据
    currentDateList() {
      const { year, month } = this.time;
      // 求出当月第一天的时间 ---> 格林威治时间
      const firstMonthDay = new Date(year, month, 1);
      // 求出第一天是星期几
      const firstMonthWeek = firstMonthDay.getDay();
      // 求出42天中的第一天
      const currenFirstDay =
        firstMonthDay - firstMonthWeek * 24 * 60 * 60 * 1000;
      // 循环42天加入数组
      const dateArr = [];
      for (let index = 0; index < 42; index++) {
        const day = new Date(currenFirstDay + index * 24 * 60 * 60 * 1000);
        dateArr.push(day);
      }
      return dateArr;
    },
    // 是否是当月
    isCurrentMonth() {
      return function (date) {
        const { year, month } = getYearMonthDay(date);
        // const { year: y, month: m } = getYearMonthDay(new Date());
        const { year: y, month: m } = this.time;
        return year === y && month === m;
      };
    },
    // 是否是选中的那一天
    isSelected() {
      return function (date) {
        const { year, month, day } = getYearMonthDay(date);
        const { year: y, month: m, day: d } = getYearMonthDay(this.value);
        return year === y && month === m && day === d;
      };
    },
    // 是否是当天
    isTody() {
      return function (date) {
        const { year, month, day } = getYearMonthDay(date);
        const { year: y, month: m, day: d } = getYearMonthDay(new Date());
        return year === y && month === m && day === d;
      };
    },
  },
  methods: {
    showPannel() {
      this.pannelVisible = true;
    },
    hidePannel() {
      this.pannelVisible = false;
    },
    // 上一年
    preYear() {
      const date = new Date(this.time.year, this.time.month, 1);
      this.time = getYearMonthDay(date.setFullYear(this.time.year - 1));
    },
    // 上一个月
    preMonth() {
      const date = new Date(this.time.year, this.time.month, 1);
      this.time = getYearMonthDay(date.setMonth(this.time.month - 1));
    },
    // 下一年
    nextYear() {
      const date = new Date(this.time.year, this.time.month, 1);
      this.time = getYearMonthDay(date.setFullYear(this.time.year + 1));
    },
    // 下一个月
    nextMonth() {
      const date = new Date(this.time.year, this.time.month, 1);
      this.time = getYearMonthDay(date.setMonth(this.time.month + 1));
    },
    // 设置值
    setDay(val) {
      const { year, month, day } = getYearMonthDay(val);
      this.$emit("input", val);
      this.pannelVisible = false;
    },
  },
  directives: {
    showDatePannel: {
      bind(el, binding, vnode) {
        function handler(e) {
          if (el.contains(e.target)) {
            !vnode.context.pannelVisible && vnode.context.showPannel();
          } else {
            vnode.context.pannelVisible && vnode.context.hidePannel();
          }
        }
        el.handler = handler;
        document.addEventListener("click", el.handler);
      },
      unbind(el, binding, vnode) {
        document.removeEventListener("click", el.handler);
      },
    },
  },
};
</script>

<style lang="less" scoped>
@import "~@/styles/var.less";
.data-picker {
  width: 210px;
  .pannel .pannel-header {
    display: flex;
    justify-content: space-around;
    span {
      cursor: pointer;
      box-sizing: border-box;
    }
  }
  .pannel .pannel-content div {
    display: flex;
    span {
      flex: 1;
      text-align: center;
      border-radius: 50%;
      cursor: pointer;
      box-sizing: border-box;
    }
    .notCurrentMonth {
      color: @gray;
    }
    .isSelected {
      color: #fff;
      background-color: @primary;
    }
    .today {
      color: @primary;
    }
  }
}
</style>