import { ReactNode, useLayoutEffect, useRef, useState } from 'react'
import type { PlannedLeaveDay } from '@/types'
import { useTranslation } from '@/i18n'
import { getLabelForType } from '@/utils/leaveTypes'
import { datesInRange, formatWeekdayAndDate } from '@/utils/dates'
import './band-day-hover-card.css'

/** Vertical gap between the card and the slot it describes, and the margin
 * kept from the viewport edge when clamping horizontally — both in px. */
const ANCHOR_GAP_PX = 6
const VIEWPORT_MARGIN_PX = 8
/** Fallback size used before the card has painted once (`offsetWidth`/
 * `offsetHeight` are 0 pre-layout) — matches `band-day-hover-card.css`'s
 * `max-width`, so the very first frame's guess is already close. */
const FALLBACK_WIDTH_PX = 220
const FALLBACK_HEIGHT_PX = 60

export interface BandDayHoverCardProps {
  /** DOM id this card is described by (`aria-describedby` on the hovered
   * slot points at it) — see `CalendarWeek`'s `useId()`-generated id. */
  id: string
  parentName: string
  date: string
  /** `null` for a bridged gap day (weekend/red day the band passes through
   * without a funded row) — see `BandDayInfo.isGap` in CalendarWeek. */
  dayType: PlannedLeaveDay['dayType'] | null
  isGap: boolean
  isDubbeldag: boolean
  isPinned: boolean
  /** The whole period's date range (not just this row's slice of it), so
   * the card always reports the period's true length. */
  periodStart: string
  periodEnd: string
  /** The hovered/focused `.calendar-band__day` slot the card describes and
   * positions itself against. `CalendarWeek` portals this component to
   * `document.body` (see its render) specifically so the card can escape
   * `.calendar-week`'s `overflow: hidden` — that clip is deliberate there
   * (it stops a band bleeding into the next row) but would otherwise also
   * clip this card, which needs to poke out above the row. Positioning is
   * computed from `anchorEl`'s real screen position instead of the band's
   * own grid/percentage math, so it works the same regardless of which
   * ancestor would otherwise have clipped it, and flips below when hovering
   * the calendar's very first row leaves no room above the viewport.
   */
  anchorEl: HTMLElement
}

export function BandDayHoverCard({
  id,
  parentName,
  date,
  dayType,
  isGap,
  isDubbeldag,
  isPinned,
  periodStart,
  periodEnd,
  anchorEl,
}: BandDayHoverCardProps): ReactNode {
  const { t, locale } = useTranslation()
  const cardRef = useRef<HTMLDivElement>(null)
  const [position, setPosition] = useState<{ top: number; left: number } | null>(null)

  useLayoutEffect(() => {
    const updatePosition = (): void => {
      const anchorRect = anchorEl.getBoundingClientRect()
      const cardWidth = cardRef.current?.offsetWidth || FALLBACK_WIDTH_PX
      const cardHeight = cardRef.current?.offsetHeight || FALLBACK_HEIGHT_PX

      // Prefer above the slot; flip below when there isn't room (the
      // calendar's top week row has nothing above it to clip into anyway).
      let top = anchorRect.top - cardHeight - ANCHOR_GAP_PX
      if (top < VIEWPORT_MARGIN_PX) {
        top = anchorRect.bottom + ANCHOR_GAP_PX
      }

      // Center on the slot, then clamp so a day near either edge (the
      // Sunday column, or the leading Monday when week numbers are off)
      // never pushes the card off-screen.
      let left = anchorRect.left + anchorRect.width / 2 - cardWidth / 2
      const maxLeft = window.innerWidth - VIEWPORT_MARGIN_PX - cardWidth
      left = Math.min(Math.max(left, VIEWPORT_MARGIN_PX), Math.max(maxLeft, VIEWPORT_MARGIN_PX))

      setPosition({ top, left })
    }

    updatePosition()
    // A drag-scroll or a window resize while the card is showing would
    // otherwise leave it pointing at empty space instead of the slot.
    window.addEventListener('scroll', updatePosition, true)
    window.addEventListener('resize', updatePosition)
    return () => {
      window.removeEventListener('scroll', updatePosition, true)
      window.removeEventListener('resize', updatePosition)
    }
  }, [anchorEl])

  const typeLabel = isGap ? t('calendarBand.hover.gapDay') : getLabelForType(dayType ?? 'vacation', t)
  const dayCount = datesInRange(periodStart, periodEnd).length
  const periodLabel = t('calendarBand.hover.period', { start: periodStart, end: periodEnd, count: dayCount })

  return (
    <div
      ref={cardRef}
      id={id}
      role="tooltip"
      className="band-day-hover-card"
      style={{
        top: `${position?.top ?? -9999}px`,
        left: `${position?.left ?? -9999}px`,
      }}
    >
      <div className="band-day-hover-card__header">
        <span className="band-day-hover-card__parent">{parentName}</span>
        <span className="band-day-hover-card__date">{formatWeekdayAndDate(date, locale)}</span>
      </div>
      <div className="band-day-hover-card__type">{typeLabel}</div>
      {isDubbeldag && <div className="band-day-hover-card__flag">{t('calendarBand.hover.dubbeldag')}</div>}
      {isPinned && <div className="band-day-hover-card__flag">{t('calendarDay.pinnedAria')}</div>}
      <div className="band-day-hover-card__period">{periodLabel}</div>
    </div>
  )
}