import { ReactNode } from 'react'
import { useTranslation } from '@/i18n'
import { formatHolidayName } from '@/utils/dates'
import type { CalendarDayType } from '@/types'

export interface CalendarDayProps {
  date: string
  events?: { type: string; color: string; title?: string }[] | undefined
  isCurrentMonth?: boolean | undefined
  onClick?: (() => void) | undefined
  isToday?: boolean | undefined
  isSelected?: boolean | undefined
  onPointerDown?: ((date: string) => void) | undefined
  onPointerEnter?: ((date: string) => void) | undefined
  onActivate?: (() => void) | undefined
  /** §3.4 — statutory calendar classification for this date, from `GET /api/calendar/days`. */
  dayType?: CalendarDayType | undefined
  /** Exact holiday name (possibly the combined "X; Söndag" form); only meaningful when `dayType === 'red_day'`. */
  holidayName?: string | null | undefined
  /** §3.6 — true iff this date has a workspace day override. */
  isOverride?: boolean | undefined
  /** The override's value when `isOverride` is true (true = marked as a working day). */
  overrideIsWorkingDay?: boolean | null | undefined
}

export function CalendarDay({
  date,
  events = [],
  isCurrentMonth = true,
  onClick,
  isToday = false,
  isSelected = false,
  onPointerDown,
  onPointerEnter,
  onActivate,
  dayType,
  holidayName,
  isOverride = false,
  overrideIsWorkingDay = null,
}: CalendarDayProps): ReactNode {
  const { t } = useTranslation()
  const dateObj = new Date(date + 'T00:00:00Z')
  const dayNum = dateObj.getUTCDate()

  // §3.4 (Swedish almanacka parity) — the backend collapses Saturday and
  // Sunday into a single "weekend" day_type (see calendar_service.py), but
  // the almanacka the user compares against marks Sunday red and Saturday
  // neutral grey. A holiday that happens to land on Sunday already arrives
  // as day_type "red_day" (see get_red_days's exact-match on "Söndag" — a
  // *bare* Sunday is never "red_day"), so a plain Sunday is detected here
  // from the weekday, not from day_type.
  const weekday = dateObj.getUTCDay() // 0 = Sunday, 6 = Saturday
  const isBareSunday = dayType === 'weekend' && weekday === 0
  const isPlainSaturday = dayType === 'weekend' && weekday === 6
  const isRedDay = dayType === 'red_day' || isBareSunday

  const handleKeyDown = (e: React.KeyboardEvent<HTMLDivElement>) => {
    if (e.key === 'Enter' || e.key === ' ') {
      if (onActivate) {
        onActivate()
      } else {
        onClick?.()
      }
    }
  }

  const cleanHolidayName = holidayName ? formatHolidayName(holidayName) : null

  // Non-color signals describing the day's calendar status, appended to the
  // existing aria-label formula so unrelated call sites (no dayType/override
  // props supplied) keep their exact previous aria-label.
  const descriptors: string[] = []
  if (cleanHolidayName) {
    descriptors.push(cleanHolidayName)
  } else if (dayType === 'klamdag') {
    descriptors.push(t('calendarDay.klamdagAria'))
  } else if (isBareSunday) {
    descriptors.push(t('calendarDay.sundayAria'))
  }
  if (isOverride) {
    descriptors.push(
      overrideIsWorkingDay ? t('calendarDay.overrideWorkingAria') : t('calendarDay.overrideFreeAria'),
    )
  }

  const baseLabel = events.length > 0 ? t('calendarDay.ariaWithEvents', { date, count: events.length }) : date
  const ariaLabel = descriptors.length > 0 ? `${baseLabel}, ${descriptors.join(', ')}` : baseLabel
  const title = descriptors.length > 0 ? descriptors.join(' · ') : undefined

  const className = [
    'calendar-day',
    !isCurrentMonth ? 'calendar-day--disabled' : '',
    events.length > 0 ? 'calendar-day--has-events' : '',
    isToday ? 'calendar-day--today' : '',
    isSelected ? 'calendar-day--selected' : '',
    isRedDay ? 'calendar-day--red-day' : '',
    dayType === 'klamdag' ? 'calendar-day--klamdag' : '',
    isPlainSaturday ? 'calendar-day--weekend' : '',
    isOverride ? 'calendar-day--override' : '',
  ]
    .filter(Boolean)
    .join(' ')

  return (
    <div
      data-testid="calendar-day"
      onClick={onClick}
      role="button"
      tabIndex={0}
      aria-label={ariaLabel}
      title={title}
      className={className}
      onKeyDown={handleKeyDown}
      onPointerDown={(e) => {
        // Touch browsers implicitly capture the pointer to the element it
        // went down on, so subsequent `pointermove`s never fire
        // `pointerenter` on the cells the finger drags across — collapsing
        // a multi-day drag into a single-day tap. Releasing capture
        // immediately restores normal hover-style `pointerenter` targeting
        // for the rest of the drag. jsdom (unit tests) doesn't implement
        // the Pointer Capture API at all, hence the guards.
        const target = e.currentTarget
        if (typeof target.hasPointerCapture === 'function' && target.hasPointerCapture(e.pointerId)) {
          target.releasePointerCapture(e.pointerId)
        }
        onPointerDown?.(date)
      }}
      onPointerEnter={() => onPointerEnter?.(date)}
    >
      <div className="calendar-day__number">{dayNum}</div>
      {(isRedDay || dayType === 'klamdag') && (
        <span className="calendar-day__type-badge" data-testid="calendar-day-type-badge" aria-hidden="true">
          {dayType === 'klamdag' ? 'K' : 'R'}
        </span>
      )}
      {cleanHolidayName && (
        <div className="calendar-day__holiday-name" data-testid="calendar-day-holiday-name" title={cleanHolidayName}>
          {cleanHolidayName}
        </div>
      )}
      {isOverride && (
        <span className="calendar-day__override-badge" data-testid="calendar-day-override-badge" aria-hidden="true">
          {overrideIsWorkingDay ? '⚒' : '✓'}
        </span>
      )}
      {events.length > 0 && (
        <div className="calendar-day__events" data-testid="calendar-day-events">
          {events.map((event, idx) => (
            <div
              key={idx}
              className="calendar-day__event"
              style={{ backgroundColor: event.color }}
              title={event.title ?? event.type}
              data-testid={`event-${idx}`}
            />
          ))}
        </div>
      )}
    </div>
  )
}