// Cross-device sync feature — encrypted wallet state on Nostr relays
// (NIP-44 to self, replaceable kind 30078) plus the wallet's nostr identity
// (used e.g. to DM locked-gift claim codes). Installed onto the core wallet;
// a build without sync ships none of it and never talks to a relay.

import {
  NostrSync, getSyncConfig, setSyncConfig, npubOf, syncDtag, deviceDtag,
  domainDtag, isOurDtag, isCoreDtag, isOwnDeviceDtag,
  fetchNostrProfile, PROFILE_RELAYS,
} from '../nostr.js';
import { t } from '../i18n.js';

// Keep a published snapshot under the relay's event-size cap. relay.coinos.io
// rejects events over 64KB and nip44 expands the plaintext ~1.5x, so the JSON
// must stay under ~40KB. The on-chain tx history is the main unbounded growth;
// drop the oldest (this.txs is newest-first) — another device backfills the
// rest with a rescan. Only trims oversized snapshots, so typical wallets are
// untouched.
const RELAY_JSON_BUDGET = 40000;
function trimForRelay(snap) {
  if (JSON.stringify(snap).length <= RELAY_JSON_BUDGET) return snap;
  const s = { ...snap };
  let txs = (s.txs || []).slice();
  while (txs.length > 25 && JSON.stringify(s).length > RELAY_JSON_BUDGET) {
    txs = txs.slice(0, Math.max(25, txs.length - 25));
    s.txs = txs;
  }
  return s;
}

// Split a snapshot into per-domain pieces, each published as its own
// replaceable event: an extension registered with a `domain` claims its keys,
// everything left is the core wallet. Every piece carries netName + savedAt so
// readers can apply the same guards as for full snapshots. Small events scale
// on vanilla relays (no special size rules) and only changed domains
// republish, so a payment burst no longer re-uploads the whole wallet.
export function splitSnapshotDomains(snap, extensions = []) {
  const core = { ...snap };
  const out = {};
  for (const e of extensions) {
    if (!e.domain || !e.save) continue;
    let obj;
    try { obj = e.save(); } catch { continue; }
    const keys = Object.keys(obj || {});
    if (!keys.length) continue;
    out[e.domain] = { netName: snap.netName, savedAt: snap.savedAt, ...obj };
    for (const k of keys) delete core[k];
  }
  out.core = core;
  return out;
}

export function installSyncWallet(wallet) {
  if (wallet.syncFromNostr) return; // already installed
  wallet.nostr = new NostrSync();
  wallet._nostrPubTimer = null;

  Object.assign(wallet, {
    // Our nostr identity (used to DM a locked gift's claim code to the recipient).
    nostrPubkey() { return (this.nostr && this.nostr.pk) || null; },

    nostrNpub() { const pk = this.nostrPubkey(); return pk ? npubOf(pk) : null; },

    // Send a nostr DM (e.g. a locked gift's claim code) to a recipient pubkey.
    async sendNostrDM(recipientPkHex, text) {
      return this.nostr && this.nostr.sk ? this.nostr.sendDM(recipientPkHex, text) : false;
    },

    // Generic event publish/fetch on the configured sync relays — the seam
    // other features (ark zaps) use to speak their own kinds. No-ops when
    // sync is disabled or the wallet is offline.
    async nostrPublish(partial) {
      const sync = getSyncConfig();
      if (this.offline || !sync.enabled || !this.nostr.sk) return null;
      this.nostr.setRelays(sync.relays);
      return this.nostr.publishEvent(partial);
    },
    // Publish an event signed by another key (the NWC wallet service keys).
    async nostrPublishSigned(evt) {
      const sync = getSyncConfig();
      if (this.offline || !sync.enabled) return null;
      this.nostr.setRelays(sync.relays);
      return this.nostr.publishSigned(evt);
    },
    async nostrFetch(filter, maxWait) {
      const sync = getSyncConfig();
      if (this.offline || !sync.enabled) return [];
      this.nostr.setRelays(sync.relays);
      return this.nostr.fetchEvents(filter, maxWait);
    },
    nostrSubscribe(filter, onEvent) {
      const sync = getSyncConfig();
      if (this.offline || !sync.enabled) return () => {};
      this.nostr.setRelays(sync.relays);
      return this.nostr.subscribeEvents(filter, onEvent);
    },

    // Sign an event with our nostr key without publishing (NIP-57 zap request).
    nostrSign(partial) { return this.nostr ? this.nostr.signEvent(partial) : null; },

    // Fetch a pubkey's profile (name/picture + lud16/lud06 for zaps) from the
    // broad profile relays — independent of whether cross-device sync is on.
    async nostrProfile(pkHex) {
      if (this.offline) return null;
      return fetchNostrProfile(pkHex);
    },

    // Relays to advertise in a zap request so we can later find the receipt:
    // our sync relays plus the broad profile relays.
    nostrRelays() {
      const sync = getSyncConfig();
      const base = sync.enabled ? sync.relays : [];
      return [...new Set([...base, ...PROFILE_RELAYS])].slice(0, 8);
    },

    // Pull the latest state from Nostr; apply it if it's newer than what we have.
    // Returns true if state was applied (so the caller can skip a full scan).
    async syncFromNostr() {
      const sync = getSyncConfig();
      if (this.offline || !sync.enabled) return false;
      this.nostr.setRelays(sync.relays);
      let all;
      try {
        all = await this.nostr.fetchAllStates();
      } catch {
        return false;
      }
      // Each device publishes to its OWN slot now, so there can be several
      // snapshots for this network. Keep only ours-for-this-network: the
      // netName inside is the real guard against cross-network bleed (legacy
      // shared-tag events are ambiguous), the d-tag check filters the rest.
      const mine = all.filter((s) => s.state.netName === this.netName && isOurDtag(s.dtag, this.netName));
      if (!mine.length) return false;
      // Merge every device's merge-safe extension state (ark vtxos union) — a
      // device sees ALL devices' coins, not only the newest snapshot's. Domain
      // fragments route themselves: an extension's load() only reads its keys.
      for (const s of mine) this._mergeSnapshotExtensions(s.state);
      // Apply the newest CORE-carrying snapshot for the rescannable on-chain
      // state. Domain fragments (ark/nwc slices) must never be applied as a
      // full snapshot — they'd blank the core fields they don't carry.
      const fulls = mine.filter((s) => isCoreDtag(s.dtag, this.netName));
      const newest = fulls[0] && fulls[0].state; // fetchAllStates returns newest-first
      if (newest && (newest.savedAt || 0) > (this._savedAt || 0)) {
        this._applySnapshot(newest); // re-runs extension loads (idempotent merge)
        this.emit();
      }
      this.saveCache(); // persist the merged result + republish our own slot
      return true;
    },
  });

  // identity follows the open wallet
  wallet.registerLoadHook(() => {
    if (wallet.mnemonic) wallet.nostr.load(wallet.mnemonic, wallet.passphrase);
    else wallet.nostr.unload();
    wallet._syncPubSeen = {}; // a new identity has published nothing yet
  });
  // Live cross-device state: subscribe to ALL our devices' slots so a save on
  // another device merges here within seconds. Merge-safe extension state (ark
  // vtxos union) applies live; full snapshots stay a load-time affair. With
  // per-device slots no device overwrites another's, so this only ever adds.
  let stateUnsub = null;
  wallet.registerRealtimeHook({
    start: () => {
      const sync = getSyncConfig();
      if (!sync.enabled || !wallet.nostr.pk) return;
      wallet.nostr.setRelays(sync.relays);
      if (stateUnsub) { try { stateUnsub(); } catch {} }
      stateUnsub = wallet.nostr.subscribeStates((v, dtag) => {
        if (!v.netName || v.netName !== wallet.netName) return;
        if (!isOurDtag(dtag, wallet.netName)) return;
        if (isOwnDeviceDtag(dtag, wallet.netName) && (v.savedAt || 0) === (wallet._savedAt || 0)) return; // our own echo
        wallet._mergeSnapshotExtensions(v);
      });
    },
    stop: () => { if (stateUnsub) { try { stateUnsub(); } catch {} stateUnsub = null; } },
  });

  // push every saved snapshot to the relays (debounced) unless sync is off —
  // split into per-domain slots on THIS DEVICE's tags, publishing only the
  // domains whose content actually changed since the last publish.
  wallet._syncPubSeen = {}; // domain -> last published JSON (per identity)
  wallet.registerCacheSavedHook((snap) => {
    const sync = getSyncConfig();
    if (wallet.offline || !sync.enabled) return;
    wallet.nostr.setRelays(sync.relays);
    // bind the network now: the debounced publish must keep this snapshot's
    // network even if the wallet switches networks before the timer fires
    const net = wallet.netName;
    clearTimeout(wallet._nostrPubTimer);
    wallet._nostrPubTimer = setTimeout(async () => {
      const domains = splitSnapshotDomains(snap, wallet._cacheExtensions || []);
      domains.core = trimForRelay(domains.core);
      for (const [name, obj] of Object.entries(domains)) {
        const json = JSON.stringify(obj);
        const slot = `${net}:${name}`;
        if (wallet._syncPubSeen[slot] === json) continue; // unchanged
        const ok = await wallet.nostr.publish(obj, domainDtag(net, name));
        if (ok) wallet._syncPubSeen[slot] = json; // a refused publish retries next save
      }
    }, 2500);
  });
  wallet.registerRealtimeHook({ stop: () => clearTimeout(wallet._nostrPubTimer) });
}

export function syncFeature(ctx) {
  const { h, ui, render, wallet } = ctx;
  installSyncWallet(wallet);

  // Cross-device sync settings: toggle + editable relay list (default coinos).
  function syncCard() {
    const cfg = getSyncConfig();
    const setEnabled = (enabled) => {
      if (enabled === cfg.enabled) return;
      setSyncConfig({ enabled, relays: cfg.relays });
      render();
      // On enable, pull anything newer from the relays, then push our copy up.
      if (enabled && !wallet.offline) {
        wallet.syncFromNostr().catch(() => {}).finally(() => wallet.saveCache());
      }
    };
    return h(
      'div',
      { class: 'card col' },
      h('h3', {}, t('deviceSync')),
      h('p', { class: 'small muted', style: 'margin:0' }, t('deviceSyncDesc')),
      h('div', { class: 'row between' },
        h('span', { class: 'lab', style: 'margin:0' }, t('syncAcross')),
        h('div', { class: 'seg' },
          h('button', { type: 'button', class: cfg.enabled ? 'active' : '', onClick: () => setEnabled(true) }, t('syncOn')),
          h('button', { type: 'button', class: !cfg.enabled ? 'active' : '', onClick: () => setEnabled(false) }, t('syncOff'))
        )
      ),
      cfg.enabled
        ? h('label', { class: 'field' },
            h('span', { class: 'lab' }, t('relaysLabel')),
            h('textarea', {
              placeholder: 'wss://relay.example.com',
              autocapitalize: 'none', autocomplete: 'off', spellcheck: 'false',
              style: 'min-height:64px',
              value: cfg.relays.join('\n'),
              onInput: (e) => {
                const relays = e.target.value.split('\n').map((s) => s.trim()).filter(Boolean);
                setSyncConfig({ enabled: true, relays });
              },
            }),
            h('div', { class: 'small faint' }, t('relaysHint'))
          )
        : null
    );
  }

  return {
    id: 'sync',
    settingsCards() {
      return wallet.watchOnly || !wallet.mnemonic ? [] : [syncCard()];
    },
  };
}