<template>
  <table
    @click="handleMonthTableClick"
    @mousemove="handleMouseMove"
    class="el-month-table"
  >
    <tbody>
      <tr v-for="(row, key) in rows" :key="key">
        <td :class="getCellStyle(cell)" v-for="(cell, key) in row" :key="key">
          <div>
            <a class="cell">{{
              t('el.datepicker.months.' + months[cell.text])
            }}</a>
          </div>
        </td>
      </tr>
    </tbody>
  </table>
</template>

<script type="text/babel">
import Locale from '../../../../src/mixins/locale'
import {
  isDate,
  range,
  getDayCountOfMonth,
  nextDate
} from '../../../../src/utils/date-util'
import { hasClass } from '../../../../src/utils/dom'
import {
  arrayFindIndex,
  coerceTruthyValueToArray,
  arrayFind
} from '../../../../src/utils/util'

const datesInMonth = (year, month) => {
  const numOfDays = getDayCountOfMonth(year, month)
  const firstDay = new Date(year, month, 1)
  return range(numOfDays).map((n) => nextDate(firstDay, n))
}

const clearDate = (date) => {
  return new Date(date.getFullYear(), date.getMonth())
}

const getMonthTimestamp = function (time) {
  if (typeof time === 'number' || typeof time === 'string') {
    return clearDate(new Date(time)).getTime()
  } else if (time instanceof Date) {
    return clearDate(time).getTime()
  } else {
    return NaN
  }
}
export default {
  emits: ['pick'],
  props: {
    disabledDate: {},
    value: {},
    selectionMode: {
      default: 'month'
    },
    minDate: {},

    maxDate: {},
    defaultValue: {
      validator(val) {
        // null or valid Date Object
        return (
          val === null ||
          isDate(val) ||
          (Array.isArray(val) && val.every(isDate))
        )
      }
    },
    date: {},
    rangeState: {
      default() {
        return {
          endDate: null,
          selecting: false
        }
      }
    }
  },

  mixins: [Locale],

  watch: {
    'rangeState.endDate'(newVal) {
      this.markRange(this.minDate, newVal)
    },

    minDate(newVal, oldVal) {
      if (getMonthTimestamp(newVal) !== getMonthTimestamp(oldVal)) {
        this.markRange(this.minDate, this.maxDate)
      }
    },

    maxDate(newVal, oldVal) {
      if (getMonthTimestamp(newVal) !== getMonthTimestamp(oldVal)) {
        this.markRange(this.minDate, this.maxDate)
      }
    }
  },

  data() {
    return {
      months: [
        'jan',
        'feb',
        'mar',
        'apr',
        'may',
        'jun',
        'jul',
        'aug',
        'sep',
        'oct',
        'nov',
        'dec'
      ],
      tableRows: [[], [], []],
      lastRow: null,
      lastColumn: null
    }
  },

  methods: {
    cellMatchesDate(cell, date) {
      const value = new Date(date)
      return (
        this.date.getFullYear() === value.getFullYear() &&
        Number(cell.text) === value.getMonth()
      )
    },
    getCellStyle(cell) {
      const style = {}
      const year = this.date.getFullYear()
      const today = new Date()
      const month = cell.text
      const defaultValue = this.defaultValue
        ? Array.isArray(this.defaultValue)
          ? this.defaultValue
          : [this.defaultValue]
        : []
      style.disabled =
        typeof this.disabledDate === 'function'
          ? datesInMonth(year, month).every(this.disabledDate)
          : false
      style.current =
        arrayFindIndex(
          coerceTruthyValueToArray(this.value),
          (date) => date.getFullYear() === year && date.getMonth() === month
        ) >= 0
      style.today = today.getFullYear() === year && today.getMonth() === month
      style.default = defaultValue.some((date) =>
        this.cellMatchesDate(cell, date)
      )

      if (cell.inRange) {
        style['in-range'] = true

        if (cell.start) {
          style['start-date'] = true
        }

        if (cell.end) {
          style['end-date'] = true
        }
      }
      return style
    },
    getMonthOfCell(month) {
      const year = this.date.getFullYear()
      return new Date(year, month, 1)
    },
    markRange(minDate, maxDate) {
      minDate = getMonthTimestamp(minDate)
      maxDate = getMonthTimestamp(maxDate) || minDate
      ;[minDate, maxDate] = [
        Math.min(minDate, maxDate),
        Math.max(minDate, maxDate)
      ]
      const rows = this.rows
      for (let i = 0, k = rows.length; i < k; i++) {
        const row = rows[i]
        for (let j = 0, l = row.length; j < l; j++) {
          const cell = row[j]
          const index = i * 4 + j
          const time = new Date(this.date.getFullYear(), index).getTime()

          cell.inRange = minDate && time >= minDate && time <= maxDate
          cell.start = minDate && time === minDate
          cell.end = maxDate && time === maxDate
        }
      }
    },
    handleMouseMove(event) {
      if (!this.rangeState.selecting) return

      let target = event.target
      if (target.tagName === 'A') {
        target = target.parentNode.parentNode
      }
      if (target.tagName === 'DIV') {
        target = target.parentNode
      }
      if (target.tagName !== 'TD') return

      const row = target.parentNode.rowIndex
      const column = target.cellIndex
      // can not select disabled date
      if (this.rows[row][column].disabled) return

      // only update rangeState when mouse moves to a new cell
      // this avoids frequent Date object creation and improves performance
      if (row !== this.lastRow || column !== this.lastColumn) {
        this.lastRow = row
        this.lastColumn = column
        this.$emit('changerange', {
          minDate: this.minDate,
          maxDate: this.maxDate,
          rangeState: {
            selecting: true,
            endDate: this.getMonthOfCell(row * 4 + column)
          }
        })
      }
    },
    handleMonthTableClick(event) {
      let target = event.target
      if (target.tagName === 'A') {
        target = target.parentNode.parentNode
      }
      if (target.tagName === 'DIV') {
        target = target.parentNode
      }
      if (target.tagName !== 'TD') return
      if (hasClass(target, 'disabled')) return
      const column = target.cellIndex
      const row = target.parentNode.rowIndex
      const month = row * 4 + column
      const newDate = this.getMonthOfCell(month)
      if (this.selectionMode === 'range') {
        if (!this.rangeState.selecting) {
          this.$emit('pick', { minDate: newDate, maxDate: null })
          // eslint-disable-next-line vue/no-mutating-props
          this.rangeState.selecting = true
        } else {
          if (newDate >= this.minDate) {
            this.$emit('pick', { minDate: this.minDate, maxDate: newDate })
          } else {
            this.$emit('pick', { minDate: newDate, maxDate: this.minDate })
          }
          // eslint-disable-next-line vue/no-mutating-props
          this.rangeState.selecting = false
        }
      } else {
        this.$emit('pick', month)
      }
    }
  },

  computed: {
    rows() {
      // TODO: refactory rows / getCellClasses
      const rows = this.tableRows
      const disabledDate = this.disabledDate
      const selectedDate = []
      const now = getMonthTimestamp(new Date())

      for (let i = 0; i < 3; i++) {
        const row = rows[i]
        for (let j = 0; j < 4; j++) {
          let cell = row[j]
          if (!cell) {
            cell = {
              row: i,
              column: j,
              type: 'normal',
              inRange: false,
              start: false,
              end: false
            }
          }

          cell.type = 'normal'

          const index = i * 4 + j
          const time = new Date(this.date.getFullYear(), index).getTime()
          cell.inRange =
            time >= getMonthTimestamp(this.minDate) &&
            time <= getMonthTimestamp(this.maxDate)
          cell.start = this.minDate && time === getMonthTimestamp(this.minDate)
          cell.end = this.maxDate && time === getMonthTimestamp(this.maxDate)
          const isToday = time === now

          if (isToday) {
            cell.type = 'today'
          }
          cell.text = index
          const cellDate = new Date(time)
          cell.disabled =
            typeof disabledDate === 'function' && disabledDate(cellDate)
          cell.selected = arrayFind(
            selectedDate,
            (date) => date.getTime() === cellDate.getTime()
          )
          row[j] = cell
        }
      }
      return rows
    }
  }
}
</script>
