// BCMR (Bitcoin Cash Metadata Registry) fetcher + cache. Resolves a
// CashTokens category hex to human-readable metadata: name, description,
// symbol, decimals, icon URL, and per-NFT metadata when the registry
// carries it.
//
// Registries are plain JSON documents (Bitauth "Bitcoin Cash Metadata
// Registries v2" schema). We support two ways to reach a registry today:
//
//   1. HTTPS URL configured per-user in Settings ("registry endpoints").
//      The registry publishes a compact JSON with keyed identities;
//      lookup by category is O(1).
//   2. A local name the user sets themselves, stored under
//      "bcmr/local/<categoryHex>" and taking precedence over any registry.
//      Self-minted tokens — anything on chipnet, anything from a project
//      that keeps its own names client-side — publish no metadata at all:
//      no registry entry, and often not even an OP_RETURN in the genesis
//      transaction, so there is nowhere for a wallet to look. A local label
//      is the only thing that can name those.
//
// (An earlier comment here promised a bundled static fallback for well-known
// tokens. There is no such directory and never was; it is not a load path.)
//
// Cache is on-disk via api.storage under "bcmr/<categoryHex>" =
// { snapshot, fetchedAt, source }. A metadata refresh runs at most once
// per REFRESH_MIN_MS per category to keep the panel snappy on repaint.
// No signature verification yet (BCMR v2 spec allows authchain-anchored
// signing; adding that is a follow-up once we support arbitrary chain
// script parsing).

const REFRESH_MIN_MS = 6 * 60 * 60 * 1000;  // 6 hours

// Well-known registries seeded on first run so a fresh wallet doesn't need
// any configuration to see names for the top BCH tokens. Users can add /
// remove entries in Settings.
// Both of the previous defaults were dead — checked 2026-09-29:
//   raw.githubusercontent.com/cashonize/registry/main/bcmr.json -> 404
//   bcmr.salemkode.com/registry.json                            -> DNS fail
// So NO token ever resolved a name, on any chain, and the panel's
// .catch(() => {}) meant the failure was completely silent. Anything added
// here should be re-checked rather than trusted; a registry that 404s is
// indistinguishable from a token nobody has registered.
const DEFAULT_REGISTRIES = [
  { id: "otr", label: "OpenTokenRegistry", url: "https://otr.cash/.well-known/bitcoin-cash-metadata-registry.json" },
];

module.exports = function makeBcmr({ storage, log = () => {} }) {

  function registryList() {
    // Filtered on read as well: a list saved before setRegistries enforced
    // https still carries its http entries.
    const custom = storage.get("bcmr/registries", null);
    const clean = Array.isArray(custom) ? custom.filter((r) => r && typeof r.url === "string" && /^https:\/\//i.test(r.url)) : [];
    if (clean.length) return clean;
    return DEFAULT_REGISTRIES.slice();
  }
  function setRegistries(list) {
    // https only: a registry decides what a token is called on the approval
    // path, and plain http lets anyone on the network rewrite that.
    const clean = Array.isArray(list) ? list.filter((r) => r && typeof r.url === "string" && /^https:\/\//i.test(r.url)) : [];
    storage.set("bcmr/registries", clean);
  }

  // Registry lookup: index-into-registry by category. BCMR v2 stores
  // identities keyed by category id (hex). Each identity has a history
  // array; the newest history[0] entry is the current snapshot.
  function pickIdentity(regJson, categoryHex) {
    const identities = regJson?.identities || {};
    const identity = identities[categoryHex];
    if (!identity) return null;
    // History is a { <timestamp>: snapshot } map. Newest wins by ISO
    // string sort — the schema recommends ISO 8601 timestamps and both
    // registries above emit them, so lexicographic sort matches temporal
    // sort for anything after 1000 AD.
    const entries = Object.entries(identity);
    if (!entries.length) return null;
    entries.sort((a, b) => (b[0] > a[0] ? 1 : -1));
    const [, snap] = entries[0];
    return snap;
  }

  async function fetchRegistry(url) {
    const r = await fetch(url, { cache: "no-store" });
    if (!r.ok) throw new Error(`bcmr: HTTP ${r.status} from ${url}`);
    return r.json();
  }

  // Attempt every configured registry in parallel; first identity found
  // wins. When two registries carry a category, we prefer the one earlier
  // in the list (user-configured order = priority).
  async function lookup(categoryHex) {
    const registries = registryList();
    if (!registries.length) return null;
    // Try cache first.
    const cached = storage.get(`bcmr/${categoryHex}`, null);
    if (cached && Date.now() - (cached.fetchedAt || 0) < REFRESH_MIN_MS) return cached;

    const attempts = await Promise.all(registries.map(async (reg) => {
      try {
        const json = await fetchRegistry(reg.url);
        const identity = pickIdentity(json, categoryHex);
        return identity ? { identity, source: reg.label || reg.id, url: reg.url } : null;
      } catch (e) {
        log(`bcmr: registry "${reg.label || reg.url}" failed:`, e?.message || e);
        return null;
      }
    }));

    const hit = attempts.find((a) => a);
    if (!hit) {
      // Negative cache with a short TTL so a missing category doesn't
      // hammer every registry on every wallet refresh.
      const miss = { snapshot: null, fetchedAt: Date.now(), source: null, url: null };
      storage.set(`bcmr/${categoryHex}`, miss);
      return miss;
    }
    const entry = {
      snapshot: hit.identity,
      fetchedAt: Date.now(),
      source: hit.source,
      url: hit.url,
    };
    storage.set(`bcmr/${categoryHex}`, entry);
    return entry;
  }

  // Batch lookup — returns { <categoryHex>: cacheEntry }. Reuses individual
  // lookup() which handles per-category caching + negative caching.
  async function lookupMany(categoryHexes) {
    const out = {};
    await Promise.all(categoryHexes.map(async (cat) => {
      try { out[cat] = await lookup(cat); }
      catch (e) { out[cat] = { snapshot: null, error: e?.message || String(e) }; }
    }));
    return out;
  }

  // Read-only cached lookup — never hits network. Used for the panel's
  // synchronous render path so tokens draw immediately with whatever's
  // in the cache; the async lookup() runs in the background afterwards.
  function cached(categoryHex) {
    return storage.get(`bcmr/${categoryHex}`, null);
  }

  // ---- local names ---------------------------------------------------------
  // A name the user typed for a category no registry knows about. Kept
  // separate from the BCMR cache so a later registry fetch cannot clobber it,
  // and so clearing it falls back to whatever the registry says.
  function localName(categoryHex) {
    const v = storage.get(`bcmr/local/${categoryHex}`, null);
    return v && (v.name || v.symbol) ? v : null;
  }
  function setLocalName(categoryHex, { name, symbol, decimals } = {}) {
    const key = `bcmr/local/${categoryHex}`;
    const n = String(name || "").trim().slice(0, 40);
    const s = String(symbol || "").trim().slice(0, 12);
    const d = Number(decimals);
    if (!n && !s) { storage.set(key, null); return null; }
    const rec = { name: n || null, symbol: s || null };
    if (Number.isFinite(d) && d >= 0 && d <= 18) rec.decimals = Math.floor(d);
    storage.set(key, rec);
    return rec;
  }

  // Compact metadata slice the panel wants: { name, symbol, description,
  // decimals, iconUri }. Handles both the top-level identity fields and
  // the token subobject (BCMR v2 puts token-specific data there).
  //
  // A local name wins over the registry: the user typed it for this exact
  // category, which is better evidence than a third-party document.
  // Control, bidi-override, zero-width and BOM characters, plus the soft
  // hyphen, the Arabic letter mark, the Mongolian vowel separator, the
  // line/paragraph separators and the Unicode tag block. Built from code
  // points so no invisible character has to live in this source file.
  const rng = (a, b) => String.fromCodePoint(a) + "-" + String.fromCodePoint(b);
  const INVISIBLE = new RegExp("[" + rng(0x00, 0x1f) + rng(0x7f, 0x9f) + rng(0xad, 0xad) + rng(0x61c, 0x61c) + rng(0x180e, 0x180e)
    + rng(0x200b, 0x200f) + rng(0x2028, 0x202e) + rng(0x2060, 0x2069) + rng(0xfeff, 0xfeff) + rng(0xe0000, 0xe007f) + "]", "gu");
  function cleanText(v, max) {
    if (typeof v !== "string") return null;
    const s = v.replace(INVISIBLE, "").trim().slice(0, max);
    return s || null;
  }
  function cleanIcon(v) {
    if (typeof v !== "string" || v.length > 512) return null;
    return /^(https:\/\/|ipfs:\/\/)[^\s"'<>]+$/i.test(v) ? v : null;
  }
  function metadataOf(entry, categoryHex) {
    const local = categoryHex ? localName(categoryHex) : null;
    if (!entry || !entry.snapshot) {
      return local
        ? { name: local.name, symbol: local.symbol, description: null,
            decimals: Number.isFinite(local.decimals) ? local.decimals : 0,
            iconUri: null, source: "local", local: true }
        : null;
    }
    const s = entry.snapshot;
    const t = s.token || {};
    // Registry content is third-party and unauthenticated (no authchain
    // check), so everything is bounded before it reaches the panel: text is
    // stripped of control / bidi / zero-width characters and capped, decimals
    // must be a whole number BCMR allows, and an icon is only ever an https
    // or ipfs URL — never data:, javascript: or a plain-http tracker.
    const regDecimals = Number(t.decimals);
    return {
      name: local?.name || cleanText(s.name || t.name, 40),
      symbol: local?.symbol || cleanText(s.token?.symbol || s.symbol, 12),
      description: cleanText(s.description, 280),
      decimals: Number.isFinite(local?.decimals) ? local.decimals
        : (Number.isInteger(regDecimals) && regDecimals >= 0 && regDecimals <= 18 ? regDecimals : 0),
      // Icon URIs live under s.uris.icon per schema; older files use s.icon.
      iconUri: cleanIcon(s.uris?.icon || s.icon),
      source: local ? "local" : (entry.source || null),
      local: !!local,
    };
  }

  return { lookup, lookupMany, cached, metadataOf, localName, setLocalName,
           registryList, setRegistries, DEFAULT_REGISTRIES };
};