import {
  html, useState, useEffect, useMemo, useCallback, useRef,
} from './vendor/htm-preact.js';
import { t } from './i18n.js';
import { Icon } from './icon.js';
import {
  formatSize, CHUNK_SIZE, pipelinedDownload, downloadDirectory,
} from './file-utils.js';
import { transfers } from './transfers.js';
import { MediaThumb, LazyTile } from './video-app.js';
import { SourceTag } from './group-name.js';

// ── Photos ───────────────────────────────────────────────────────────────────
//
// docs/MESHBAY_DESIGN.md §9.9. Unlike Videos/Music: several root folders per group
// (photoRoots is a list, §2.1), one album-grid view with no mode toggle and
// no third-party matching step (§2.3), and per-photo info read from the
// file's own EXIF at index time rather than fetched live. Every directory
// containing at least one image under a configured root is one album card;
// opening one shows its photos in a grid with a lightbox (next/previous,
// keyboard arrows, EXIF info when present) and a "zip this album" button
// that reuses Files' own zip mechanism unchanged (file-utils.js's
// downloadDirectory, lifted out of files-app.js for exactly this reuse).

function underAnyPhotoRoot(entry, photoRoots) {
  const p = entry.path || '';
  return (photoRoots || []).some((r) => p === r || p.startsWith(r + '/'));
}

function groupPhotoAlbums(entries, photoRoots) {
  const byDir = new Map();
  for (const e of entries) {
    if (e.type !== 'image' || !underAnyPhotoRoot(e, photoRoots)) continue;
    // e.path is already the file's containing directory, not the full
    // path+filename (files-app.js's own convention, also relied on by
    // zipstream.js's entriesUnder) — it must not be stripped a second time,
    // or every album collapses one level up into its parent (found live:
    // a "backup" root with several subfolders showed as a single "backup"
    // album holding everything, because this line was extracting the
    // dirname of a value that was already a dirname).
    const dir = e.path || '';
    if (!byDir.has(dir)) byDir.set(dir, []);
    byDir.get(dir).push(e);
  }
  return [...byDir.entries()]
    .map(([dir, photos]) => ({
      dir, photos: photos.sort((a, b) => a.name.localeCompare(b.name)),
    }))
    .sort((a, b) => a.dir.localeCompare(b.dir));
}

// Underscores replaced with spaces for display only — this never touches
// the folder on disk or anything sent to the node, purely how the name
// reads in the grid/heading (a raw "mariage_joce" reads worse than
// "mariage joce" for something meant to look like an album, not a filename).
function albumTitle(dir) {
  return dir ? dir.split('/').pop().replace(/_/g, ' ') : t('photo.root_album');
}

function formatTakenAt(ts) {
  if (!ts) return '';
  return new Date(ts * 1000).toLocaleString(undefined, {
    year: 'numeric', month: 'short', day: 'numeric', hour: '2-digit', minute: '2-digit',
  });
}

// A single year when every dated photo in the album agrees, a range when
// they don't (an album spanning New Year's Eve, or just a loosely-sorted
// folder) — never guessed for photos with no EXIF date at all, which just
// don't count toward it.
function albumYearLabel(photos) {
  const years = [...new Set(
    photos.filter((p) => p.taken_at).map((p) => new Date(p.taken_at * 1000).getFullYear()),
  )].sort((a, b) => a - b);
  if (years.length === 0) return '';
  if (years.length === 1) return String(years[0]);
  return `${years[0]}–${years[years.length - 1]}`;
}

// ── landing grid: one card per album (directory containing images) ─────────

function AlbumCard({ album, transportRef, gekRef, onOpen }) {
  const cover = album.photos.find((p) => p.thumb_hash) || album.photos[0];
  const tRef = cover._tRef || transportRef;
  const gRef = cover._gRef || gekRef;
  const year = albumYearLabel(album.photos);
  return html`
    <div class="photo-album-card" onClick=${onOpen}>
      <${MediaThumb} thumbHash=${cover.thumb_hash} alt=${albumTitle(album.dir)}
        cls="photo-album-cover" transportRef=${tRef} gekRef=${gRef}
        emptyIcon="image" />
      <div class="photo-album-info">
        <div class="photo-album-title">${albumTitle(album.dir)}</div>
        <div class="photo-album-sub">
          ${year}${year ? ' · ' : ''}${t('photo.n_photos', { n: album.photos.length })}
        </div>
        <${SourceTag} entries=${album.photos} cls="photo-card-group" />
      </div>
    </div>
  `;
}

function AlbumLanding({ albums, transportRef, gekRef, onOpen }) {
  return html`
    <div class="photo-album-grid">
      ${albums.map((a) => html`
        <${LazyTile} key=${a.dir} cls="photo-album-tile-slot">
          <${AlbumCard} album=${a} transportRef=${transportRef} gekRef=${gekRef}
            onOpen=${() => onOpen(a.dir)} />
        </${LazyTile}>
      `)}
    </div>
  `;
}

// ── open album: grid of its own photos ──────────────────────────────────────

function PhotoTile({ entry, transportRef, gekRef, onOpen }) {
  const tRef = entry._tRef || transportRef;
  const gRef = entry._gRef || gekRef;
  return html`
    <div class="photo-tile" onClick=${onOpen}>
      <${MediaThumb} thumbHash=${entry.thumb_hash} alt=${entry.name}
        cls="photo-tile-thumb" transportRef=${tRef} gekRef=${gRef}
        emptyIcon="image" />
    </div>
  `;
}

// ── lightbox: full image, next/previous, per-photo info, zoom ──────────────
//
// Cached per session by file id, same shape as video-app.js's
// _thumbBlobCache — clicking back and forth between two photos decrypts
// each once, not once per visit.
const _fullBlobCache = new Map();

// Zoom is only ever meaningful for the lightbox's own full-resolution
// image — nowhere else in the app shows one, so there is nothing to gate
// this behind beyond the component itself only ever being mounted for a
// photo.
const ZOOM_STEP = 25;
const ZOOM_MIN = 25;
const ZOOM_MAX = 400;

function Lightbox({ photos, index, transportRef, gekRef, onClose, onNav }) {
  const entry = photos[index];
  const tRef = entry._tRef || transportRef;
  const gRef = entry._gRef || gekRef;
  const [blobUrl, setBlobUrl] = useState(() => _fullBlobCache.get(entry.id) || null);
  const [loading, setLoading] = useState(!_fullBlobCache.has(entry.id));
  // null = "fit to window" (the default, object-fit: contain); a number is
  // an explicit percentage of the image's own natural size, read off the
  // loaded <img> itself rather than trusted from EXIF — accurate whether or
  // not enrichment ever ran, and already EXIF-orientation-corrected the
  // same way the browser renders the <img> itself.
  const [zoomPercent, setZoomPercent] = useState(null);
  const [naturalSize, setNaturalSize] = useState(null);
  const slotRef = useRef(null);

  useEffect(() => {
    const cached = _fullBlobCache.get(entry.id);
    if (cached) { setBlobUrl(cached); setLoading(false); return; }
    setBlobUrl(null);
    setLoading(true);
    let cancelled = false;
    (async () => {
      const transport = tRef.current;
      if (!transport || !transport.connected) { setLoading(false); return; }
      try {
        const totalChunks = Math.ceil(entry.size / CHUNK_SIZE);
        const chunks = await pipelinedDownload(
          transport, gRef.current, entry.id, totalChunks);
        if (cancelled) return;
        const url = URL.createObjectURL(new Blob(chunks));
        _fullBlobCache.set(entry.id, url);
        setBlobUrl(url);
      } catch {
        /* leave the placeholder — a transient fetch failure isn't fatal, next/close still work */
      } finally {
        if (!cancelled) setLoading(false);
      }
    })();
    return () => { cancelled = true; };
  }, [entry.id]);

  // Every photo opens fit-to-window, same as any other viewer — a zoom
  // level chosen for one picture saying nothing about the next.
  useEffect(() => { setZoomPercent(null); setNaturalSize(null); }, [entry.id]);

  useEffect(() => {
    const onKey = (e) => {
      if (e.key === 'Escape') onClose();
      else if (e.key === 'ArrowLeft' && index > 0) onNav(-1);
      else if (e.key === 'ArrowRight' && index < photos.length - 1) onNav(1);
    };
    window.addEventListener('keydown', onKey);
    return () => window.removeEventListener('keydown', onKey);
  }, [onClose, onNav, index, photos.length]);

  const handleImgLoad = (e) => {
    setNaturalSize({ w: e.target.naturalWidth, h: e.target.naturalHeight });
  };

  // The percentage "fit to window" actually renders at, so the first zoom
  // step moves from *there* rather than silently snapping to 100% first —
  // object-fit: contain never upscales past the image's own natural size
  // (nothing here sets width/height:100% to force it to), so fit is never
  // above 100% either.
  const fitPercent = () => {
    if (!naturalSize || !slotRef.current) return 100;
    const rect = slotRef.current.getBoundingClientRect();
    return Math.min(1, rect.width / naturalSize.w, rect.height / naturalSize.h) * 100;
  };
  const zoomIn = () => setZoomPercent(
    (z) => Math.min(ZOOM_MAX, Math.round(z ?? fitPercent()) + ZOOM_STEP));
  const zoomOut = () => setZoomPercent(
    (z) => Math.max(ZOOM_MIN, Math.round(z ?? fitPercent()) - ZOOM_STEP));
  const zoomFit = () => setZoomPercent(null);
  const zoomActual = () => setZoomPercent(100);

  const zoomed = zoomPercent != null;
  const imgStyle = zoomed && naturalSize
    ? `width:${Math.round(naturalSize.w * zoomPercent / 100)}px; `
    + `height:${Math.round(naturalSize.h * zoomPercent / 100)}px;`
    : '';

  return html`
    <div class="video-overlay photo-lightbox" onClick=${(e) => {
      if (e.target.classList.contains('photo-lightbox')) onClose();
    }}>
      <div class="video-top-bar">
        <span class="video-title">${entry.name}</span>
        <div class="photo-zoom-controls">
          <button class="photo-icon-btn" disabled=${!blobUrl || zoomPercent === ZOOM_MIN}
            onClick=${zoomOut} title=${t('photo.zoom_out')}>
            <${Icon} name="zoom-out" cls="photo-icon-btn-icon" /></button>
          <span class="photo-zoom-percent">
            ${zoomed ? `${zoomPercent}%` : t('photo.zoom_fit_label')}</span>
          <button class="photo-icon-btn" disabled=${!blobUrl || zoomPercent === ZOOM_MAX}
            onClick=${zoomIn} title=${t('photo.zoom_in')}>
            <${Icon} name="zoom-in" cls="photo-icon-btn-icon" /></button>
          <button class="photo-icon-btn ${!zoomed ? 'active' : ''}" disabled=${!blobUrl}
            onClick=${zoomFit} title=${t('photo.zoom_fit_title')}>
            <${Icon} name="frame" cls="photo-icon-btn-icon" /></button>
          <button class="photo-icon-btn photo-icon-btn-text ${zoomPercent === 100 ? 'active' : ''}"
            disabled=${!blobUrl} onClick=${zoomActual} title=${t('photo.zoom_100')}>100%</button>
        </div>
        <button class="video-close" onClick=${onClose} title=${t('video.close')}>
          <${Icon} name="close" /></button>
      </div>
      <div class="photo-lightbox-body">
        <button class="photo-nav photo-nav-prev" disabled=${index === 0}
          onClick=${() => onNav(-1)} title=${t('photo.prev')}>
          <${Icon} name="chevron" cls="photo-nav-icon photo-nav-prev-icon" /></button>
        <div ref=${slotRef} class="photo-lightbox-image-slot ${zoomed ? 'zoomed' : ''}">
          ${loading && html`<span class="spinner"></span>`}
          ${blobUrl && html`<img class="photo-lightbox-image ${zoomed ? 'zoomed' : ''}"
            style=${imgStyle} src=${blobUrl} alt=${entry.name} onLoad=${handleImgLoad} />`}
        </div>
        <button class="photo-nav photo-nav-next" disabled=${index === photos.length - 1}
          onClick=${() => onNav(1)} title=${t('photo.next')}>
          <${Icon} name="chevron" cls="photo-nav-icon photo-nav-next-icon" /></button>
      </div>
      <div class="photo-lightbox-info">
        ${entry.width && entry.height && html`<span>${entry.width}×${entry.height}</span>`}
        <span>${formatSize(entry.size)}</span>
        ${entry.taken_at && html`<span>${formatTakenAt(entry.taken_at)}</span>`}
        ${entry.camera && html`<span>${entry.camera}</span>`}
        <span class="photo-lightbox-count">${index + 1} / ${photos.length}</span>
      </div>
    </div>
  `;
}

function AlbumView({ album, entries, transportRef, gekRef, setError, onBack, readOnly }) {
  const [lightboxIndex, setLightboxIndex] = useState(null);

  const zip = useCallback(async () => {
    const transport = transportRef.current;
    await downloadDirectory(
      transfers, transport, gekRef.current, entries, album.dir, { setError });
  }, [entries, album.dir]);

  const navigate = useCallback((delta) => {
    setLightboxIndex((i) => {
      const next = i + delta;
      return next >= 0 && next < album.photos.length ? next : i;
    });
  }, [album.photos.length]);

  const year = albumYearLabel(album.photos);

  return html`
    <div class="photo-album-bar">
      <div class="photo-album-heading">
        <button class="photo-icon-btn" onClick=${onBack} title=${t('photo.back')}>
          <${Icon} name="chevron" cls="photo-icon-btn-icon photo-back-icon" /></button>
        <div class="photo-album-heading-text">
          <span class="photo-album-heading-title">${albumTitle(album.dir)}</span>
          ${year && html`<span class="photo-album-heading-year">${year}</span>`}
        </div>
      </div>
      ${!readOnly && html`<button class="photo-icon-btn" onClick=${zip} title=${t('photo.zip_album')}>
        <${Icon} name="archive" cls="photo-icon-btn-icon" /></button>`}
    </div>
    <div class="photo-grid">
      ${album.photos.map((e, i) => html`
        <${LazyTile} key=${e.id} cls="photo-tile-slot">
          <${PhotoTile} entry=${e} transportRef=${transportRef} gekRef=${gekRef}
            onOpen=${() => setLightboxIndex(i)} />
        </${LazyTile}>
      `)}
    </div>
    ${lightboxIndex !== null && html`
      <${Lightbox} photos=${album.photos} index=${lightboxIndex}
        transportRef=${transportRef} gekRef=${gekRef}
        onClose=${() => setLightboxIndex(null)} onNav=${navigate} />
    `}
  `;
}

// ── shell ────────────────────────────────────────────────────────────────────

function PhotosApp({
  groupId, transportRef, gekRef, status, entries, availableEntries,
  photoDirectories, setError,
  hideFilter, readOnly,
}) {
  const [openDir, setOpenDir] = useState(null);
  const [filter, setFilter] = useState('');

  useEffect(() => { setOpenDir(null); setFilter(''); }, [groupId]);

  const photoEntries = availableEntries || entries;
  const albums = useMemo(
    () => groupPhotoAlbums(photoEntries, photoDirectories),
    [photoEntries, photoDirectories]);

  const needle = filter.trim().toLowerCase();
  const filteredAlbums = useMemo(() => (!needle ? albums : albums.filter(
    (a) => albumTitle(a.dir).toLowerCase().includes(needle))), [albums, needle]);

  const openAlbum = openDir != null ? albums.find((a) => a.dir === openDir) : null;

  return html`
    ${(status === 'discovering' || status === 'connecting' || status === 'fetching') && html`
      <p class="page-message"><span class="spinner"></span>${' '}${t('status.connecting_short')}</p>
    `}
    ${status === 'offline' && html`
      <p class="page-message">${t('group.offline_title')} ${t('group.offline_hint')}</p>
    `}
    ${status === 'connected' && (photoDirectories || []).length === 0 && html`
      <p class="page-message">${t('photo.no_roots_configured')}</p>
    `}
    ${status === 'connected' && (photoDirectories || []).length > 0 && !openAlbum && html`
      ${/* The filter is the only thing in it, so under `hideFilter` there is
            no toolbar rather than an empty one — an empty band still pins,
            and would hold a strip of the page open under the search field
            for nothing. */
        !hideFilter && html`
        <div class="photo-toolbar">
          <div class="tb-search">
            <${Icon} name="search" />
            <input type="text" placeholder="${t('group.filter')}"
              value=${filter} onInput=${(e) => setFilter(e.target.value)} />
          </div>
        </div>
      `}
      ${filteredAlbums.length === 0 && html`
        <p class="page-message">${needle ? t('group.empty_filter') : t('photo.empty')}</p>
      `}
      <${AlbumLanding} albums=${filteredAlbums}
        transportRef=${transportRef} gekRef=${gekRef}
        onOpen=${(dir) => setOpenDir(dir)} />
    `}
    ${status === 'connected' && openAlbum && html`
      <${AlbumView} album=${openAlbum} entries=${entries}
        transportRef=${transportRef} gekRef=${gekRef} setError=${setError}
        onBack=${() => setOpenDir(null)} readOnly=${readOnly} />
    `}
  `;
}

// groupPhotoAlbums is exported for the Search page, which needs the album a
// photo belongs to in order to merge duplicate sources per album rather than
// per file (docs/MESHBAY_DESIGN.md §9.11). It calls this one, never a copy:
// a second implementation of the album key would keep agreeing with this one
// right up until one of them changed.
export { PhotosApp, groupPhotoAlbums };