import { useState, useEffect, useRef, forwardRef } from 'react'
import { useTranslation } from 'react-i18next'
import dayjs from 'dayjs'
import isToday from 'dayjs/plugin/isToday'
import localeData from 'dayjs/plugin/localeData'
import updateLocale from 'dayjs/plugin/updateLocale'

import { Button, ToggleField } from '/src/components'
import { useSettingsStore, useLocaleUpdateStore } from '/src/stores'

import {
  Wrapper,
  StyledLabel,
  StyledSubLabel,
  CalendarHeader,
  CalendarDays,
  CalendarBody,
  Date,
  Day,
} from './CalendarField.styles'

dayjs.extend(isToday)
dayjs.extend(localeData)
dayjs.extend(updateLocale)

const calculateMonth = (month, year, weekStart) => {
  const date = dayjs().month(month).year(year)
  const daysInMonth = date.daysInMonth()
  const daysBefore = date.date(1).day() - weekStart
  const daysAfter = 6 - date.date(daysInMonth).day() + weekStart

  const dates = []
  let curDate = date.date(1).subtract(daysBefore, 'day')
  let y = 0
  let x = 0
  for (let i = 0; i < daysBefore + daysInMonth + daysAfter; i++) {
    if (x === 0) dates[y] = []
    dates[y][x] = curDate.clone()
    curDate = curDate.add(1, 'day')
    x++
    if (x > 6) {
      x = 0
      y++
    }
  }

  return dates
}

const CalendarField = forwardRef(({
  label,
  subLabel,
  id,
  setValue,
  ...props
}, ref) => {
  const weekStart = useSettingsStore(state => state.weekStart)
  const locale = useLocaleUpdateStore(state => state.locale)
  const { t } = useTranslation('home')

  const [type, setType] = useState(0)

  const [dates, setDates] = useState(calculateMonth(dayjs().month(), dayjs().year(), weekStart))
  const [month, setMonth] = useState(dayjs().month())
  const [year, setYear] = useState(dayjs().year())

  const [selectedDates, setSelectedDates] = useState([])
  const [selectingDates, _setSelectingDates] = useState([])
  const staticSelectingDates = useRef([])
  const setSelectingDates = newDates => {
    staticSelectingDates.current = newDates
    _setSelectingDates(newDates)
  }

  const [selectedDays, setSelectedDays] = useState([])
  const [selectingDays, _setSelectingDays] = useState([])
  const staticSelectingDays = useRef([])
  const setSelectingDays = newDays => {
    staticSelectingDays.current = newDays
    _setSelectingDays(newDays)
  }

  const startPos = useRef({})
  const staticMode = useRef(null)
  const [mode, _setMode] = useState(staticMode.current)
  const setMode = newMode => {
    staticMode.current = newMode
    _setMode(newMode)
  }

  useEffect(() => setValue(props.name, type ? JSON.stringify(selectedDays) : JSON.stringify(selectedDates)), [type, selectedDays, selectedDates, setValue, props.name])

  useEffect(() => {
    if (dayjs.Ls?.[locale] && weekStart !== dayjs.Ls[locale].weekStart) {
      dayjs.updateLocale(locale, { weekStart })
    }
    setDates(calculateMonth(month, year, weekStart))
  }, [weekStart, month, year, locale])

  return (
    <Wrapper locale={locale}>
      {label && <StyledLabel htmlFor={id}>{label}</StyledLabel>}
      {subLabel && <StyledSubLabel htmlFor={id}>{subLabel}</StyledSubLabel>}
      <input
        id={id}
        type="hidden"
        ref={ref}
        value={type ? JSON.stringify(selectedDays) : JSON.stringify(selectedDates)}
        {...props}
      />

      <ToggleField
        id="calendarMode"
        name="calendarMode"
        options={{
          'specific': t('form.dates.options.specific'),
          'week': t('form.dates.options.week'),
        }}
        value={type === 0 ? 'specific' : 'week'}
        onChange={value => setType(value === 'specific' ? 0 : 1)}
      />

      {type === 0 ? (
        <>
          <CalendarHeader>
            <Button
              size="30px"
              title={t('form.dates.tooltips.previous')}
              onClick={() => {
                if (month-1 < 0) {
                  setYear(year-1)
                  setMonth(11)
                } else {
                  setMonth(month-1)
                }
              }}
            >&lt;</Button>
            <span>{dayjs.months()[month]} {year}</span>
            <Button
              size="30px"
              title={t('form.dates.tooltips.next')}
              onClick={() => {
                if (month+1 > 11) {
                  setYear(year+1)
                  setMonth(0)
                } else {
                  setMonth(month+1)
                }
              }}
            >&gt;</Button>
          </CalendarHeader>

          <CalendarDays>
            {(weekStart ? [...dayjs.weekdaysShort().filter((_,i) => i !== 0), dayjs.weekdaysShort()[0]] : dayjs.weekdaysShort()).map(name =>
              <Day key={name}>{name}</Day>
            )}
          </CalendarDays>
          <CalendarBody>
            {dates.length > 0 && dates.map((dateRow, y) =>
              dateRow.map((date, x) =>
                <Date
                  key={y+x}
                  $otherMonth={date.month() !== month}
                  $isToday={date.isToday()}
                  title={`${date.date()} ${dayjs.months()[date.month()]}${date.isToday() ? ` (${t('form.dates.tooltips.today')})` : ''}`}
                  $selected={selectedDates.includes(date.format('DDMMYYYY'))}
                  $selecting={selectingDates.includes(date)}
                  $mode={mode}
                  type="button"
                  onKeyPress={e => {
                    if (e.key === ' ' || e.key === 'Enter') {
                      if (selectedDates.includes(date.format('DDMMYYYY'))) {
                        setSelectedDates(selectedDates.filter(d => d !== date.format('DDMMYYYY')))
                      } else {
                        setSelectedDates([...selectedDates, date.format('DDMMYYYY')])
                      }
                    }
                  }}
                  onPointerDown={e => {
                    startPos.current = {x, y}
                    setMode(selectedDates.includes(date.format('DDMMYYYY')) ? 'remove' : 'add')
                    setSelectingDates([date])
                    e.currentTarget.releasePointerCapture(e.pointerId)

                    document.addEventListener('pointerup', () => {
                      if (staticMode.current === 'add') {
                        setSelectedDates([...selectedDates, ...staticSelectingDates.current.map(d => d.format('DDMMYYYY'))])
                      } else if (staticMode.current === 'remove') {
                        const toRemove = staticSelectingDates.current.map(d => d.format('DDMMYYYY'))
                        setSelectedDates(selectedDates.filter(d => !toRemove.includes(d)))
                      }
                      setMode(null)
                    }, { once: true })
                  }}
                  onPointerEnter={() => {
                    if (staticMode.current) {
                      const found = []
                      for (let cy = Math.min(startPos.current.y, y); cy < Math.max(startPos.current.y, y)+1; cy++) {
                        for (let cx = Math.min(startPos.current.x, x); cx < Math.max(startPos.current.x, x)+1; cx++) {
                          found.push({y: cy, x: cx})
                        }
                      }
                      setSelectingDates(found.map(d => dates[d.y][d.x]))
                    }
                  }}
                >{date.date()}</Date>
              )
            )}
          </CalendarBody>
        </>
      ) : (
        <CalendarBody>
          {(weekStart ? [...dayjs.weekdaysShort().filter((_,i) => i !== 0), dayjs.weekdaysShort()[0]] : dayjs.weekdaysShort()).map((name, i) =>
            <Date
              key={name}
              $isToday={(weekStart ? [...dayjs.weekdaysShort().filter((_,i) => i !== 0), dayjs.weekdaysShort()[0]] : dayjs.weekdaysShort())[dayjs().day()-weekStart === -1 ? 6 : dayjs().day()-weekStart] === name}
              title={(weekStart ? [...dayjs.weekdaysShort().filter((_,i) => i !== 0), dayjs.weekdaysShort()[0]] : dayjs.weekdaysShort())[dayjs().day()-weekStart === -1 ? 6 : dayjs().day()-weekStart] === name ? t('form.dates.tooltips.today') : ''}
              $selected={selectedDays.includes(((i + weekStart) % 7 + 7) % 7)}
              $selecting={selectingDays.includes(((i + weekStart) % 7 + 7) % 7)}
              $mode={mode}
              type="button"
              onKeyPress={e => {
                if (e.key === ' ' || e.key === 'Enter') {
                  if (selectedDays.includes(((i + weekStart) % 7 + 7) % 7)) {
                    setSelectedDays(selectedDays.filter(d => d !== ((i + weekStart) % 7 + 7) % 7))
                  } else {
                    setSelectedDays([...selectedDays, ((i + weekStart) % 7 + 7) % 7])
                  }
                }
              }}
              onPointerDown={e => {
                startPos.current = i
                setMode(selectedDays.includes(((i + weekStart) % 7 + 7) % 7) ? 'remove' : 'add')
                setSelectingDays([((i + weekStart) % 7 + 7) % 7])
                e.currentTarget.releasePointerCapture(e.pointerId)

                document.addEventListener('pointerup', () => {
                  if (staticMode.current === 'add') {
                    setSelectedDays([...selectedDays, ...staticSelectingDays.current])
                  } else if (staticMode.current === 'remove') {
                    const toRemove = staticSelectingDays.current
                    setSelectedDays(selectedDays.filter(d => !toRemove.includes(d)))
                  }
                  setMode(null)
                }, { once: true })
              }}
              onPointerEnter={() => {
                if (staticMode.current) {
                  const found = []
                  for (let ci = Math.min(startPos.current, i); ci < Math.max(startPos.current, i)+1; ci++) {
                    found.push(((ci + weekStart) % 7 + 7) % 7)
                  }
                  setSelectingDays(found)
                }
              }}
            >{name}</Date>
          )}
        </CalendarBody>
      )}
    </Wrapper>
  )
})

export default CalendarField