// Public kind-1 thread context, available before wallet unlock as well as
// inside a wallet. Keep complete event text/tags; truncating a cached event
// would make the content change when a relay answered after the first paint.
const KEY = 'btc-wallet-note-threads';
const MAX_THREADS = 12;
const MAX_EVENTS = 160;
const MAX_BYTES = 1_000_000; // JSON code units; at most about 2 MB in storage
const validNote = (e) => e?.kind === 1 && typeof e.id === 'string'
  && /^[0-9a-f]{64}$/.test(e.id) && typeof e.pubkey === 'string'
  && /^[0-9a-f]{64}$/.test(e.pubkey) && typeof e.content === 'string'
  && Number.isFinite(e.created_at) && Array.isArray(e.tags)
  && e.tags.every((t) => Array.isArray(t) && t.every((v) => typeof v === 'string'));
const savedNote = ({ id, pubkey, kind, created_at, content, tags }) => ({ id, pubkey, kind, created_at, content, tags });
const savedProfile = (p) => {
  if (!p || typeof p !== 'object') return null;
  const name = typeof p.name === 'string' ? p.name.slice(0, 120) : null;
  const picture = typeof p.picture === 'string' ? p.picture.slice(0, 1000) : null;
  if (!name && !picture) return null;
  const out = { name, picture, eventAt: Number.isFinite(p.eventAt) ? p.eventAt : 0, t: Number.isFinite(p.t) ? p.t : 0 };
  if (picture && p.thumbFor === picture && typeof p.thumb === 'string'
    && p.thumb.length <= 16000 && /^data:image\/(?:webp|jpeg|png);base64,/.test(p.thumb)) {
    out.thumb = p.thumb; out.thumbFor = picture; out.thumbPx = p.thumbPx || 0;
  }
  return out;
};
const savedCounts = (c) => {
  if (!c || typeof c !== 'object') return null;
  const count = (n) => Number.isSafeInteger(n) && n >= 0 && n <= 1_000_000_000 ? n : 0;
  return { likes: count(c.likes), boosts: count(c.boosts), sats: count(c.sats) };
};

export function createThreadStore(storage) {
  if (storage === undefined) { try { storage = globalThis.localStorage; } catch {} }
  const read = () => {
    try {
      const raw = storage?.getItem(KEY);
      if (!raw || raw.length > MAX_BYTES) return [];
      const data = JSON.parse(raw);
      if (!Array.isArray(data)) return [];
      return data.filter((c) => validNote(c?.root) && c.rootId === c.root.id
        && Array.isArray(c.replies) && c.replies.length < MAX_EVENTS
        && c.replies.every(validNote)).slice(0, MAX_THREADS);
    } catch { return []; }
  };
  return {
    find(id) {
      return read().find((c) => c.rootId === id || c.replies.some((e) => e.id === id)) || null;
    },
    save(thread, focusId, profiles = {}, counts = {}) {
      if (!validNote(thread.root)) return;
      const events = new Map([thread.root, ...thread.replies.filter(validNote)].map((e) => [e.id, e]));
      const keep = new Map([[thread.root.id, thread.root]]);
      // The selected reply and every locally known ancestor get priority
      // over sibling replies when a large conversation needs trimming.
      const visit = (id) => {
        if (keep.has(id) || keep.size >= MAX_EVENTS) return;
        const e = events.get(id);
        if (!e) return;
        keep.set(id, e);
        for (const t of e.tags) if (t[0] === 'e' && t[3] !== 'mention') visit(t[1]);
      };
      visit(focusId);
      for (const e of events.values()) {
        if (keep.size >= MAX_EVENTS) break;
        visit(e.id);
      }
      const previous = read().find((c) => c.rootId === thread.root.id);
      const authors = [...new Set([...keep.values()].map((e) => e.pubkey))].slice(0, 24);
      const faces = {};
      for (const pk of authors) {
        const fresh = savedProfile(profiles[pk]);
        const old = savedProfile(previous?.profiles?.[pk]);
        const face = !fresh || (old && old.eventAt > fresh.eventAt) ? old : fresh;
        if (face === fresh && old?.thumb && !fresh.thumb && old.picture === fresh.picture) {
          face.thumb = old.thumb; face.thumbFor = old.thumbFor; face.thumbPx = old.thumbPx;
        }
        if (face) faces[pk] = face;
      }
      const tallies = {};
      for (const id of keep.keys()) {
        const tally = savedCounts(counts[id] || previous?.counts?.[id]);
        if (tally) tallies[id] = tally;
      }
      const entry = { rootId: thread.root.id, root: savedNote(thread.root),
        profiles: faces, counts: tallies,
        replies: [...keep.values()].filter((e) => e.id !== thread.root.id).map(savedNote) };
      const entries = [entry, ...read().filter((c) => c.rootId !== entry.rootId)].slice(0, MAX_THREADS);
      let json = JSON.stringify(entries);
      while (json.length > MAX_BYTES && entries.length > 1) { entries.pop(); json = JSON.stringify(entries); }
      if (json.length > MAX_BYTES) return; // keep the previous cache if this thread alone is too large
      try { storage?.setItem(KEY, json); } catch {} // full/disabled storage must not break reading
    },
  };
}