import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
import { useHotkeys } from 'react-hotkeys-hook'
import { X, Info } from 'lucide-react'
import { usePhotoStore } from '../../store/photoStore'
import { usePhotosQuery } from '../../hooks/usePhotosQuery'
import type { Photo } from '../../types/photo'
import { PreviewImage } from './PreviewImage'
import { PreviewFilmstrip } from './PreviewFilmstrip'
import { getPreviewImageSrc, isVideo } from './previewSrc'
import { PhotoInfoPanel } from '../sidebar/PhotoInfoPanel'

export function PreviewView() {
  const activePhotoId = usePhotoStore((s) => s.activePhotoId)
  const setActivePhoto = usePhotoStore((s) => s.setActivePhoto)
  const closePreview = usePhotoStore((s) => s.closePreview)
  const visiblePhotoIds = usePhotoStore((s) => s.visiblePhotoIds)

  const containerRef = useRef<HTMLDivElement>(null)
  const previouslyFocusedRef = useRef<HTMLElement | null>(null)
  const [infoPanelOpen, setInfoPanelOpen] = useState(false)

  // Same hook Timeline uses, so we share one cache entry rather than looking
  // it up by key (which broke when the key gained the filter params).
  const { data: rawPhotos = [] } = usePhotosQuery()

  // Walk the timeline's visible-order sequence (published by Timeline
  // into the photo store), which respects tag-grouping and any other
  // grid-layout rearrangement. Falls back to the raw photos list when
  // the sequence isn't populated yet — relevant on a fresh page load
  // where the user opened preview before the timeline mounted.
  const photos: Photo[] = useMemo(() => {
    if (visiblePhotoIds.length === 0) return rawPhotos
    const byId = new Map(rawPhotos.map((p) => [p.id, p]))
    const out: Photo[] = []
    for (const id of visiblePhotoIds) {
      const p = byId.get(id)
      if (p) out.push(p)
    }
    return out
  }, [visiblePhotoIds, rawPhotos])

  const currentIndex = activePhotoId
    ? photos.findIndex((p) => p.id === activePhotoId)
    : 0
  const safeIndex = currentIndex < 0 ? 0 : currentIndex
  const currentPhoto: Photo | undefined = photos[safeIndex]

  // Keep the latest photos array + active id in a ref so the keyboard
  // handlers ALWAYS read the freshest state. Without this, react-hotkeys-
  // hook can fire a closure that captured an older photos array (e.g.
  // the empty initial render before visiblePhotoIds was applied) and
  // arrow nav lands on the wrong photo or no-ops.
  const navRef = useRef({ photos, activePhotoId })
  navRef.current = { photos, activePhotoId }

  const goPrev = useCallback(() => {
    const { photos: ps, activePhotoId: aid } = navRef.current
    if (ps.length === 0) return
    const idx = aid ? ps.findIndex((p) => p.id === aid) : 0
    const safe = idx < 0 ? 0 : idx
    const next = Math.max(0, safe - 1)
    setActivePhoto(ps[next].id)
  }, [setActivePhoto])

  const goNext = useCallback(() => {
    const { photos: ps, activePhotoId: aid } = navRef.current
    if (ps.length === 0) return
    const idx = aid ? ps.findIndex((p) => p.id === aid) : 0
    const safe = idx < 0 ? 0 : idx
    const next = Math.min(ps.length - 1, safe + 1)
    setActivePhoto(ps[next].id)
  }, [setActivePhoto])

  // Preview-scoped hotkeys: only mounted while PreviewView is rendered.
  // The handlers themselves are stable (refs internally) so the deps
  // array stays empty — useHotkeys won't have to re-bind on every render.
  useHotkeys('escape', closePreview, { preventDefault: true })
  useHotkeys('left', goPrev, { preventDefault: true })
  useHotkeys('right', goNext, { preventDefault: true })
  useHotkeys('i', () => setInfoPanelOpen((v) => !v), { preventDefault: true })

  // Preload the immediate neighbors so arrow nav feels instant. Skip videos
  // (browsers can't preload them via Image()) and skip when at the edges.
  useEffect(() => {
    const neighbors: Photo[] = []
    if (safeIndex > 0) neighbors.push(photos[safeIndex - 1])
    if (safeIndex < photos.length - 1) neighbors.push(photos[safeIndex + 1])
    for (const p of neighbors) {
      if (isVideo(p)) continue
      const img = new Image()
      img.src = getPreviewImageSrc(p)
    }
  }, [safeIndex, photos])

  // Focus trap: focus the preview container on mount, restore focus on
  // unmount. The container is keyboard-focusable (tabIndex=-1) so screen
  // readers and tab navigation stay scoped here.
  useEffect(() => {
    previouslyFocusedRef.current = document.activeElement as HTMLElement | null
    containerRef.current?.focus()
    return () => {
      previouslyFocusedRef.current?.focus?.()
    }
  }, [])

  // Trap Tab inside the dialog so users can't accidentally tab into the
  // hidden grid behind. Simple cycle implementation.
  const handleKeyDown = (e: React.KeyboardEvent) => {
    if (e.key !== 'Tab') return
    const root = containerRef.current
    if (!root) return
    const focusable = root.querySelectorAll<HTMLElement>(
      'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
    )
    if (focusable.length === 0) {
      e.preventDefault()
      root.focus()
      return
    }
    const first = focusable[0]
    const last = focusable[focusable.length - 1]
    const active = document.activeElement as HTMLElement | null
    if (e.shiftKey && active === first) {
      e.preventDefault()
      last.focus()
    } else if (!e.shiftKey && active === last) {
      e.preventDefault()
      first.focus()
    }
  }

  if (!currentPhoto) {
    return (
      <div
        ref={containerRef}
        role="dialog"
        aria-modal="true"
        aria-label="Photo preview"
        tabIndex={-1}
        className="fixed inset-0 z-40 flex flex-col items-center justify-center bg-black text-text-muted outline-none"
      >
        <div>No photo to display</div>
        <button
          onClick={closePreview}
          className="mt-4 rounded border border-border px-3 py-1 text-sm hover:bg-surface"
        >
          Close
        </button>
      </div>
    )
  }

  return (
    <div
      ref={containerRef}
      role="dialog"
      aria-modal="true"
      aria-label={`Photo preview: ${currentPhoto.filename}`}
      tabIndex={-1}
      onKeyDown={handleKeyDown}
      className="fixed inset-0 z-40 flex bg-black outline-none"
    >
      {/* Main column — image + filmstrip */}
      <div className="relative flex min-w-0 flex-1 flex-col">
        {/* Filename + counter */}
        <div className="absolute left-3 top-3 z-10 rounded bg-black/60 px-3 py-1.5 text-xs text-white">
          <div className="font-mono">{currentPhoto.filename}</div>
          <div className="text-text-muted">
            {safeIndex + 1} / {photos.length}
          </div>
        </div>

        {/* Top-right action buttons */}
        <div className="absolute right-3 top-3 z-10 flex items-center gap-2">
          <button
            onClick={() => setInfoPanelOpen((v) => !v)}
            className={
              'flex h-9 w-9 items-center justify-center rounded-full bg-black/60 text-white transition hover:bg-black/80 ' +
              (infoPanelOpen ? 'ring-2 ring-primary' : '')
            }
            title="Toggle info panel (I)"
            aria-label="Toggle info panel"
            aria-pressed={infoPanelOpen}
          >
            <Info className="h-5 w-5" />
          </button>
          <button
            onClick={closePreview}
            className="flex h-9 w-9 items-center justify-center rounded-full bg-black/60 text-white transition hover:bg-black/80"
            title="Close (Esc)"
            aria-label="Close preview"
          >
            <X className="h-5 w-5" />
          </button>
        </div>

        <PreviewImage photo={currentPhoto} />

        <PreviewFilmstrip
          photos={photos}
          currentIndex={safeIndex}
          onSelect={setActivePhoto}
        />
      </div>

      {/* Right info panel — slides in/out, mirrors the grid right sidebar
       *  but lives inside the preview overlay so it isn't covered by it. */}
      {infoPanelOpen && (
        <aside className="w-80 shrink-0 overflow-hidden border-l border-border bg-surface">
          <PhotoInfoPanel photoId={currentPhoto.id} />
        </aside>
      )}
    </div>
  )
}
