import {
  html, useState, useCallback, useEffect,
} from './vendor/htm-preact.js';
import { t } from './i18n.js';
import { ask } from './ask.js';
import { Icon } from './icon.js';
import { Menu, useMenu } from './menu.js';
import * as P from './playlists.js';

/**
 * The playlist verbs, behind one button in Music's toolbar.
 *
 * `docs/playlists.md` §10.3. One button and one icon, no label: the toolbar
 * already wraps to three rows at a phone width and has no room for a word, and
 * it sits in the sticky band so it is reachable at any scroll position.
 *
 * Mounted by `music-app.js`, which the group page and the Search page both
 * render — so a playlist built inside a group is managed from the consolidated
 * view with no second surface and no application-registry entry.
 *
 * **Every list here is drawn from the manifest**, which is a few kilobytes and
 * always in IndexedDB. The menu opens instantly with every node offline, and no
 * playlist body is read until one is actually wanted. The one exception is the
 * tracklist under "remove a track", which is fetched when that submenu is
 * expanded and not before.
 */

// ── modals ───────────────────────────────────────────────────────────────────
//
// A field, never `window.prompt`: Electron does not implement prompt, and it
// does not return null — it throws, which is how the Files toolbar's New folder
// button came to do nothing at all (`test_no_prompt_in_the_spa.py`).

function NameModal({ title, initial, onSubmit, onClose }) {
  const [name, setName] = useState(initial || '');
  const [error, setError] = useState('');
  const [busy, setBusy] = useState(false);

  const submit = async (e) => {
    e.preventDefault();
    if (!name.trim() || busy) return;
    setBusy(true);
    try {
      await onSubmit(name.trim());
      onClose();
    } catch (err) {
      setError(err.message === 'duplicate name'
        ? t('playlists.err_duplicate') : (err.message || String(err)));
      setBusy(false);
    }
  };

  return html`
    <div class="video-overlay" onClick=${(e) => {
      if (e.target.classList.contains('video-overlay')) onClose();
    }}>
      <form class="music-detail playlist-modal" onSubmit=${submit}>
        <div class="video-top-bar">
          <span class="video-title">${title}</span>
          <button type="button" class="video-close" onClick=${onClose}
            title=${t('video.close')}><${Icon} name="close" /></button>
        </div>
        <div class="playlist-modal-body">
          <input type="text" autofocus value=${name} maxlength="120"
            placeholder=${t('playlists.name_placeholder')}
            onInput=${(e) => { setName(e.target.value); setError(''); }} />
          ${error && html`<div class="playlist-modal-error">${error}</div>`}
          <div class="playlist-modal-actions">
            <button type="button" class="tb-btn" onClick=${onClose}>
              ${t('playlists.cancel')}</button>
            <button type="submit" class="admin-btn" disabled=${!name.trim() || busy}>
              ${t('playlists.save')}</button>
          </div>
        </div>
      </form>
    </div>
  `;
}

// ── the button ───────────────────────────────────────────────────────────────

/**
 * The account's playlists, from the manifest, and a way to re-read them.
 *
 * Held once by whoever mounts both surfaces — the toolbar button and the
 * per-item "add to playlist" submenu are two views of one list, and two copies
 * of it would drift the moment either one wrote.
 */
function usePlaylists(userId) {
  const [lists, setLists] = useState([]);

  const reload = useCallback(async () => {
    if (!userId) { setLists([]); return; }
    try { setLists(await P.listPlaylists(userId)); } catch { setLists([]); }
  }, [userId]);

  useEffect(() => { reload(); }, [reload]);

  return { lists, reload };
}

function PlaylistMenuButton({ userId, lists, reload, onPlayQueue, onSync, cachedIndexes }) {
  const { menu, openAt, close } = useMenu();
  const [modal, setModal] = useState(null);
  const [note, setNote] = useState('');

  // A one-line result, self-clearing: "42 tracks added", "2 nodes unreachable".
  // Enough to know it happened, never a dialog to dismiss.
  const say = useCallback((text) => {
    setNote(text);
    setTimeout(() => setNote(''), 4000);
  }, []);

  const loadPlaylist = useCallback(async (id) => {
    const tracks = await P.getPlaylistTracks(userId, id, cachedIndexes);
    if (!tracks.length) { say(t('playlists.empty_playlist')); return; }
    onPlayQueue(tracks, 0);
  }, [userId, onPlayQueue, cachedIndexes, say]);

  const removeTrack = useCallback(async (id, at) => {
    await P.removeTrackAt(userId, id, at);
    await reload();
    say(t('playlists.track_removed'));
  }, [userId, reload, say]);

  const deletePlaylist = useCallback(async (p) => {
    // Asked first: a deletion is a tombstone rather than something that can be
    // undone from the interface.
    if (!await ask(t('playlists.confirm_delete', { name: p.name }))) return;
    await P.deletePlaylist(userId, p.id);
    await reload();
    say(t('playlists.deleted', { name: p.name }));
  }, [userId, reload, say]);

  const openMenu = useCallback((e) => {
    openAt(e, [
      {
        label: t('playlists.load'), icon: 'play',
        items: lists.map((p) => ({
          key: p.id, label: p.name,
          hint: t('music.n_tracks', { n: p.count || 0 }),
          onSelect: () => loadPlaylist(p.id),
        })),
        empty: t('playlists.none_yet'),
      },
      {
        label: t('playlists.create'), icon: 'plus',
        onSelect: () => setModal({ kind: 'create' }),
      },
      {
        label: t('playlists.delete'), icon: 'trash',
        // Favourites is never offered: it is refused by the store anyway, and
        // offering an action that always fails is worse than not offering it.
        items: lists.filter((p) => p.id !== P.FAVORITES_ID).map((p) => ({
          key: p.id, label: p.name, danger: true,
          onSelect: () => deletePlaylist(p),
        })),
        empty: t('playlists.none_yet'),
      },
      {
        label: t('playlists.remove_track'), icon: 'close',
        // Two levels, as asked. The second is fetched when it is expanded and
        // not before — building it eagerly would read every playlist's tracks
        // to draw a menu nobody may open.
        items: lists.map((p) => ({
          key: p.id, label: p.name,
          empty: t('playlists.empty_playlist'),
          loadItems: async () => {
            const tracks = await P.getPlaylistTracks(userId, p.id);
            return tracks.map((tr, i) => ({
              key: `${p.id}:${i}`, danger: true,
              label: tr.display_title || tr.name,
              hint: tr.artist || '',
              onSelect: () => removeTrack(p.id, i),
            }));
          },
        })),
        empty: t('playlists.none_yet'),
      },
      { divider: true },
      {
        label: t('playlists.sync_now'), icon: 'refresh',
        onSelect: async () => {
          const r = await onSync();
          await reload();
          // The reason, not just "it failed": a sync that quietly does nothing
          // is the one failure mode nobody can act on, and the reason is what
          // separates an offline node from a wedged one.
          // On success, say how much moved; on failure, say why. Either way
          // the reader learns something they can act on — the one thing this
          // never did.
          const last = P.lastSync();
          const why = (r && r.reason) || last.reason || '?';
          // `no_key` is not a fault the reader can do anything about unless it
          // is spelled out. This browser signed in with its remembered device
          // key, so the only bundle key it has is one persisted before the
          // playlist subkey existed — and an AES handle is non-extractable, so
          // there is nothing to derive it from. One sign-in with the passphrase
          // fixes it for good; a code on screen does not say that.
          // A playlist too large to send is reported ahead of the totals. The
          // sync itself worked — everything else moved — so `ok` is true, and
          // saying "synced" while one playlist silently stayed behind would be
          // the lie this whole report exists to stop.
          const big = (r && r.tooLarge) || [];
          say(big.length
            ? t('playlists.err_too_large', { name: big[0], n: 500 })
            : (r && r.ok
              ? `${t('playlists.synced')} (${r.pushed || 0}↑ ${r.pulled || 0}↓)`
              : (why === 'no_key'
                ? t('playlists.err_no_key')
                : `${t('playlists.sync_failed')}: ${why}`)));
        },
      },
    ]);
  }, [openAt, lists, userId, loadPlaylist, deletePlaylist, removeTrack, onSync, reload, say]);

  return html`
    <button class="tb-btn" title=${t('playlists.menu')} onClick=${openMenu}>
      <${Icon} name="playlist" />
    </button>
    ${menu && html`<${Menu} ...${menu} onClose=${close} />`}
    ${note && html`<div class="playlist-note">${note}</div>`}
    ${modal && modal.kind === 'create' && html`
      <${NameModal} title=${t('playlists.create')}
        onSubmit=${async (name) => { await P.createPlaylist(userId, name); await reload(); }}
        onClose=${() => setModal(null)} />
    `}
  `;
}

export { PlaylistMenuButton, NameModal, usePlaylists };