// Bitcoin (BTC) chain adapter — mainnet + testnet3. BIP84 native SegWit,
// bitcoinjs-lib for the tx/PSBT primitives, Aegis's own ElectrumX transport
// for the network side. Very close in shape to chain-dgb.js; the two could
// share a "bip84-electrum" helper later, but for now a distinct file keeps
// the chain-specific tuning (electrum pool, network object) visible.
//
// Address family: BIP84 only in this rev — bc1q… (mainnet) / tb1q… (testnet).
// BIP44 (1…) and BIP49 (3…) are trivially reachable by editing accountPath
// to m/44'/0'/0' or m/49'/0'/0' respectively; the PSBT layer already
// supports the resulting scripts because bitcoinjs-lib does. An explicit
// address-family picker like DGB's is a follow-up.

const NETWORKS = {
  mainnet: {
    id: "mainnet", label: "Mainnet",
    hrp: "bc", coinType: 0,
    defaultAccountPath: "m/84'/0'/0'",
    explorerTx: "https://mempool.space/tx/",
    explorerAddr: "https://mempool.space/address/",
    defaultServers: [
      "wss://electrum.blockstream.info:50004",
      "wss://bitcoin.lu.ke:50004",
      "wss://fulcrum.grey.pw:50004",
    ],
    faucet: null,
  },
  testnet: {
    id: "testnet", label: "Testnet3",
    hrp: "tb", coinType: 1,
    defaultAccountPath: "m/84'/1'/0'",
    explorerTx: "https://mempool.space/testnet/tx/",
    explorerAddr: "https://mempool.space/testnet/address/",
    defaultServers: [
      "wss://testnet.aranguren.org:51004",
      "wss://blockstream.info:993",
    ],
    faucet: "https://coinfaucet.eu/en/btc-testnet/",
  },
  signet: {
    // Signet (BIP-325) shares testnet's address format and SLIP-44 coin
    // type (1), so bitcoinjs-lib's `networks.testnet` handles address
    // derivation unchanged. The chain itself is a separate, permissioned
    // testnet with its own genesis + signer-signed blocks; from a wallet's
    // point of view, the only differences are the electrum pool serving
    // it and the explorer URL for tx lookups.
    id: "signet", label: "Signet",
    hrp: "tb", coinType: 1,
    defaultAccountPath: "m/84'/1'/0'",
    explorerTx: "https://mempool.space/signet/tx/",
    explorerAddr: "https://mempool.space/signet/address/",
    defaultServers: [
      "wss://signet.aranguren.org:51102",
      "wss://signet-electrumx.wakiyamap.dev:50003",
    ],
    faucet: "https://signetfaucet.com/",
  },
};

module.exports = function makeBtcAdapter({
  bitcoinjs, bip32Factory, ecpairFactory, ecc, sha256, electrum,
}) {
  if (!bitcoinjs || !bip32Factory || !ecpairFactory || !ecc || !electrum) {
    throw new Error("chain-btc: missing dep");
  }
  const { payments, Psbt, networks: bjsNetworks } = bitcoinjs;
  const bip32 = bip32Factory(ecc);
  const ECPair = ecpairFactory(ecc);
  // Taproot (p2tr) address derivation needs bitcoinjs-lib's schnorr backend
  // wired to a curve implementation — @bitcoinerlab/secp256k1 provides both
  // ECDSA and schnorr, so initEccLib once at load makes p2tr resolve.
  try { bitcoinjs.initEccLib && bitcoinjs.initEccLib(ecc); } catch {}

  // Map our network id → bitcoinjs-lib Network object. Signet shares
  // testnet's address prefixes + magic (BIP-325 defines only new consensus
  // rules; the p2p / address layer stays testnet-compatible).
  function bjsNetworkFor(id) {
    if (id === "mainnet") return bjsNetworks.bitcoin;
    if (id === "testnet" || id === "signet") return bjsNetworks.testnet;
    throw new Error("chain-btc: unknown network " + id);
  }

  const toHex = (b) => Buffer.from(b).toString("hex");
  const scripthashOf = (scriptBuf) => Buffer.from(sha256(scriptBuf)).reverse().toString("hex");

  function scopedStorage(storage, keyPrefix) {
    const k = (key) => keyPrefix + key;
    return {
      get: (key, fallback = null) => storage.get(k(key), fallback),
      set: (key, value) => storage.set(k(key), value),
    };
  }

  // Address-family shape from the derivation-path purpose. Every field the
  // PSBT layer might need for signing an input funded by this family is
  // captured here so signAndBroadcast has one code path per family.
  function paymentFor(purpose, node, network) {
    const pubkey = Buffer.from(node.publicKey);
    if (purpose === 44) {
      // Legacy P2PKH. Signing needs the full previous transaction
      // (nonWitnessUtxo) — one extra electrum call per input at send time.
      const p = payments.p2pkh({ pubkey, network });
      return { family: "bip44", address: p.address, output: Buffer.from(p.output), send: "p2pkh", needsPrevTx: true };
    }
    if (purpose === 49) {
      // P2SH-wrapped SegWit. PSBT needs the redeem script (the inner p2wpkh
      // output) alongside the witnessUtxo.
      const redeem = payments.p2wpkh({ pubkey, network });
      const p = payments.p2sh({ redeem, network });
      return { family: "bip49", address: p.address, output: Buffer.from(p.output), redeem: Buffer.from(redeem.output), send: "p2sh-p2wpkh" };
    }
    if (purpose === 86) {
      // BIP86 Taproot key-path. Signing goes through a tap-tweaked ECPair
      // (see signerFor + signAndBroadcast); the internal 32-byte x-only
      // pubkey is captured here so the PSBT input can carry it.
      const internalPubkey = Buffer.from(pubkey.subarray(1, 33));
      const p = payments.p2tr({ internalPubkey, network });
      return { family: "bip86", address: p.address, output: Buffer.from(p.output), internalPubkey, send: "p2tr" };
    }
    // Default: BIP84 native SegWit.
    const p = payments.p2wpkh({ pubkey, network });
    return { family: "bip84", address: p.address, output: Buffer.from(p.output), send: "p2wpkh" };
  }
  function purposeOfPath(accountPath) {
    const m = /^m\/(\d+)'\//.exec(String(accountPath || ""));
    return m ? Number(m[1]) : 84;
  }

  class WalletKeys {
    constructor(root32, accountPath, bjsNetwork) {
      this._accountPath = /^m(\/\d+'?)+$/.test(accountPath) ? accountPath : "m/84'/0'/0'";
      this._purpose = purposeOfPath(this._accountPath);
      this._network = bjsNetwork;
      this._root = bip32.fromSeed(Buffer.from(root32), bjsNetwork);
      this._account = this._root.derivePath(this._accountPath);
      this._branch = [this._account.derive(0), this._account.derive(1)];
      this._cache = new Map();
    }
    get xpub() { return this._account.neutered().toBase58(); }
    get xprv() { return this._account.toBase58(); }
    get accountPath() { return this._accountPath; }
    get purpose() { return this._purpose; }
    entry(branch, index) {
      const k = branch + "/" + index;
      let e = this._cache.get(k);
      if (!e) {
        const node = this._branch[branch].derive(index);
        const pay = paymentFor(this._purpose, node, this._network);
        e = {
          branch, index, path: this._accountPath + "/" + branch + "/" + index,
          publicKey: Buffer.from(node.publicKey),
          family: pay.family, sendKind: pay.send,
          script: pay.output, scriptHex: pay.output.toString("hex"),
          scripthash: scripthashOf(pay.output),
          address: pay.address,
          redeemScript: pay.redeem || null,
          tapInternalKey: pay.internalPubkey || null,
          _node: node,
        };
        this._cache.set(k, e);
      }
      return e;
    }
    signerFor(entry) {
      return ECPair.fromPrivateKey(Buffer.from(entry._node.privateKey), { network: this._network });
    }
    wipe() {
      for (const e of this._cache.values()) e._node = null;
      this._cache.clear();
      this._branch = null;
      this._account = null;
      this._root = null;
    }
  }

  // Fee vsize model per family. Values are rounded vsize contributions from
  // standard tx-size tables; the estimator is pessimistic enough to cover a
  // real broadcast without underpaying.
  const OVERHEAD_VB = 10.5;
  const OUTPUT_VB = 31;                     // P2WPKH / P2SH / P2PKH outputs are all ~31 vB give or take
  const INPUT_VB = {
    p2pkh:       148,                       // (32+4)+1+107+4 legacy input
    "p2sh-p2wpkh": 91,                      // 40 base + ~205/4 witness
    p2wpkh:      68,                        // 41 base + 108/4 witness
    p2tr:        58,                        // 41 base + 66/4 witness (key-path)
  };
  const feeVb = (kind, nIn, nOut, feePerVb) => Math.ceil((OVERHEAD_VB + nIn * (INPUT_VB[kind] || 68) + nOut * OUTPUT_VB) * feePerVb);

  class BtcWallet {
    constructor(root32, networkId, {
      walletId, storage, log = () => {}, onChange = () => {}, servers,
      accountPath,
    } = {}) {
      if (!walletId) throw new Error("chain-btc: walletId required");
      const net = NETWORKS[networkId];
      if (!net) throw new Error("chain-btc: unknown network " + networkId);
      this.walletId = walletId;
      this.chain = "btc";
      this.network = net.id;
      this._net = net;
      this._bjsNet = bjsNetworkFor(net.id);
      this.log = log;
      this.onChange = onChange;
      this.storage = scopedStorage(storage, `wallets/${walletId}/`);
      this._servers = Array.isArray(servers) && servers.length ? servers : net.defaultServers.slice();
      const wantPath = accountPath || net.defaultAccountPath;
      this._keys = new WalletKeys(root32, wantPath, this._bjsNet);
      this._root = new Uint8Array(root32);
      this._client = new electrum.Client(this._servers);
      this._client.onServer = () => this._emit();
      this._state = {
        used: new Set(),
        watched: new Map(),
        height: 0,
        balance: { confirmed: 0, unconfirmed: 0 },
        utxos: [],
        history: [],
        receiveIndex: 0,
        scanning: false,
        error: null,
      };
      this._refreshTimer = null;
      this._subscribedHeaders = false;
      this._client.onNotify = (method, params) => {
        if (method === "blockchain.headers.subscribe") {
          const h = params && params[0] && params[0].height;
          if (h) { this._state.height = h; this._scheduleRefresh(1500); }
        } else if (method === "blockchain.scripthash.subscribe") {
          this._scheduleRefresh(800);
        }
      };
    }

    _emit() { try { this.onChange(); } catch {} }

    async _historyOf(entry) {
      const h = await this._client.call("blockchain.scripthash.get_history", [entry.scripthash]);
      return Array.isArray(h) ? h : [];
    }
    async _scan() {
      const cursor = Number(this.storage.get("receiveCursor", 0)) || 0;
      const GAP = 20;
      for (const branch of [0, 1]) {
        let gap = 0, i = 0;
        const minIndex = branch === 0 ? cursor + 1 : 0;
        while (gap < GAP || i < minIndex + GAP) {
          const batch = [];
          for (let k = 0; k < 10; k++) batch.push(this._keys.entry(branch, i + k));
          const results = await Promise.all(batch.map((e) => this._historyOf(e)));
          for (let k = 0; k < batch.length; k++) {
            const e = batch[k];
            this._state.watched.set(e.scripthash, e);
            if (results[k].length) { this._state.used.add(branch + "/" + e.index); gap = 0; } else gap++;
            i++;
            if (gap >= GAP && i >= minIndex + GAP) break;
          }
        }
      }
      let r = cursor;
      while (this._state.used.has("0/" + r)) r++;
      this._state.receiveIndex = r;
      this._state.watched.set(this._keys.entry(0, r).scripthash, this._keys.entry(0, r));
    }
    async _subscribeAll() {
      if (!this._subscribedHeaders) {
        this._subscribedHeaders = true;
        const tip = await this._client.subscribe("blockchain.headers.subscribe", []);
        if (tip && tip.height) this._state.height = tip.height;
      }
      await Promise.all([...this._state.watched.values()].map((e) =>
        this._client.subscribe("blockchain.scripthash.subscribe", [e.scripthash]).catch(() => {})));
    }
    async _loadUtxos() {
      const lists = await Promise.all([...this._state.watched.values()].map(async (e) => {
        const u = await this._client.call("blockchain.scripthash.listunspent", [e.scripthash]);
        return (Array.isArray(u) ? u : []).map((x) => ({ txid: x.tx_hash, vout: x.tx_pos, value: x.value, height: x.height, entry: e }));
      }));
      this._state.utxos = lists.flat();
      let confirmed = 0, unconfirmed = 0;
      for (const u of this._state.utxos) { if (u.height > 0) confirmed += u.value; else unconfirmed += u.value; }
      this._state.balance = { confirmed, unconfirmed };
    }
    async _loadHistory() {
      const entries = [...this._state.watched.values()].filter((e) => this._state.used.has(e.branch + "/" + e.index));
      const merged = new Map();
      const lists = await Promise.all(entries.map((e) => this._historyOf(e)));
      for (const list of lists) for (const h of list) {
        const prev = merged.get(h.tx_hash);
        if (!prev || (h.height > 0 && prev.height <= 0)) merged.set(h.tx_hash, { txid: h.tx_hash, height: h.height });
      }
      const ordered = [...merged.values()].sort((a, b) => {
        const ha = a.height > 0 ? a.height : Infinity, hb = b.height > 0 ? b.height : Infinity;
        return hb - ha;
      }).slice(0, 25);
      const ours = new Set([...this._state.watched.values()].map((e) => e.scriptHex));
      const out = [];
      for (const h of ordered) {
        let received = 0, spent = 0;
        try {
          const t = await this._client.call("blockchain.transaction.get", [h.txid, true]);
          for (const o of t.vout || []) {
            const hex = o.scriptPubKey && o.scriptPubKey.hex;
            if (hex && ours.has(hex)) received += Math.round(Number(o.value || 0) * 1e8);
          }
          for (const i of t.vin || []) {
            if (!i.txid) continue;
            try {
              const p = await this._client.call("blockchain.transaction.get", [i.txid, true]);
              const po = p.vout && p.vout[i.vout];
              const hex = po && po.scriptPubKey && po.scriptPubKey.hex;
              if (hex && ours.has(hex)) spent += Math.round(Number(po.value || 0) * 1e8);
            } catch {}
          }
          out.push({
            txid: h.txid, height: h.height, confirmations: t.confirmations || 0,
            time: t.blocktime || t.time || 0,
            delta: received - spent, fee: null, to: null,
            status: (t.confirmations || 0) > 0 ? "confirmed" : "pending",
            kind: "transfer",
          });
        } catch {
          out.push({ txid: h.txid, height: h.height, confirmations: 0, time: 0, delta: 0, fee: null, to: null, status: "pending", kind: "transfer" });
        }
      }
      this._state.history = out;
    }
    async refresh(full = false) {
      if (this._state.scanning) return;
      this._state.scanning = true; this._state.error = null; this._emit();
      try {
        if (full || !this._state.watched.size) await this._scan();
        else {
          let r = Number(this.storage.get("receiveCursor", 0)) || 0;
          while (this._state.used.has("0/" + r)) r++;
          this._state.receiveIndex = r;
          this._state.watched.set(this._keys.entry(0, r).scripthash, this._keys.entry(0, r));
        }
        await this._loadUtxos();
        await this._loadHistory();
        await this._subscribeAll();
        for (const u of this._state.utxos) this._state.used.add(u.entry.branch + "/" + u.entry.index);
        let r = Number(this.storage.get("receiveCursor", 0)) || 0;
        while (this._state.used.has("0/" + r)) r++;
        this._state.receiveIndex = r;
      } catch (e) {
        this._state.error = e?.message || String(e);
        this.log("refresh failed:", this._state.error);
      } finally {
        this._state.scanning = false;
        this._emit();
      }
    }
    _scheduleRefresh(ms = 800) {
      clearTimeout(this._refreshTimer);
      this._refreshTimer = setTimeout(() => this.refresh(false), ms);
    }

    current() { return this._keys.entry(0, this._state.receiveIndex); }
    nextAddress() {
      let r = this._state.receiveIndex + 1;
      while (this._state.used.has("0/" + r)) r++;
      this.storage.set("receiveCursor", r);
      this._state.receiveIndex = r;
      const e = this._keys.entry(0, r);
      this._state.watched.set(e.scripthash, e);
      this._client.subscribe("blockchain.scripthash.subscribe", [e.scripthash]).catch(() => {});
      this._emit();
      return this.current();
    }
    _changeEntry() {
      let i = 0;
      while (this._state.used.has("1/" + i)) i++;
      return this._keys.entry(1, i);
    }

    setServers(list) {
      this._servers = Array.isArray(list) && list.length ? list : this._net.defaultServers.slice();
      this._client.setServers(this._servers);
    }

    plan({ to, amount, feeRate = 5, sendMax = false }) {
      const rate = Math.min(500, Math.max(1, Number(feeRate) || 5));
      const dest = String(to || "");
      try { bitcoinjs.address.toOutputScript(dest, this._bjsNet); }
      catch (e) { throw new Error(`bad Bitcoin address: ${e?.message || dest}`); }
      const cur = this.current();
      if (!cur.sendKind) throw new Error(`no sender for ${cur.family} — registry bug`);
      const spendable = this._state.utxos.slice().sort((a, b) => (b.height > 0) - (a.height > 0));
      const change = this._changeEntry();
      const kind = cur.sendKind;
      if (sendMax) {
        const chosen = spendable;
        const sum = chosen.reduce((a, u) => a + u.value, 0);
        const fee = feeVb(kind, chosen.length, 1, rate);
        if (sum <= fee) throw new Error("balance does not cover the fee");
        return {
          _chosen: chosen, _rate: rate, _to: dest, _sendMax: true, _change: change, _kind: kind,
          recipients: [{ to: dest, value: sum - fee }],
          fee, feeRate: rate, change: 0,
          total: sum,
        };
      }
      const value = Math.round(Number(amount) || 0);
      if (!(value > 0)) throw new Error("amount must be > 0");
      let sum = 0; const chosen = [];
      for (const u of spendable) {
        chosen.push(u); sum += u.value;
        const withChange = feeVb(kind, chosen.length, 2, rate);
        if (sum >= value + withChange) {
          const changeVal = sum - value - withChange;
          const fee = changeVal > 546 ? withChange : sum - value;
          return {
            _chosen: chosen, _rate: rate, _to: dest, _value: value,
            _change: change, _changeVal: changeVal > 546 ? changeVal : 0, _kind: kind,
            recipients: [{ to: dest, value }],
            fee, feeRate: rate,
            change: changeVal > 546 ? changeVal : 0,
            total: value + fee,
          };
        }
      }
      throw new Error("insufficient funds");
    }

    async signAndBroadcast(plan) {
      // BIP44 inputs need the whole previous transaction (nonWitnessUtxo)
      // so PSBT can compute a legacy sighash; fetch each one in parallel
      // before assembling the PSBT.
      const needsPrev = plan._chosen.filter((u) => u.entry.family === "bip44");
      const prevHex = new Map();
      if (needsPrev.length) {
        const results = await Promise.all(needsPrev.map((u) =>
          this._client.call("blockchain.transaction.get", [u.txid, false])
        ));
        needsPrev.forEach((u, i) => prevHex.set(u.txid, String(results[i])));
      }
      const psbt = new Psbt({ network: this._bjsNet });
      for (const u of plan._chosen) {
        const inp = { hash: u.txid, index: u.vout };
        const fam = u.entry.family;
        if (fam === "bip44") {
          inp.nonWitnessUtxo = Buffer.from(prevHex.get(u.txid), "hex");
        } else {
          inp.witnessUtxo = { script: u.entry.script, value: u.value };
          if (fam === "bip49" && u.entry.redeemScript) inp.redeemScript = u.entry.redeemScript;
          if (fam === "bip86" && u.entry.tapInternalKey) inp.tapInternalKey = u.entry.tapInternalKey;
        }
        psbt.addInput(inp);
      }
      const outputs = [{ address: plan._to, value: plan._sendMax ? plan.recipients[0].value : plan._value }];
      if (!plan._sendMax && plan._changeVal > 0) {
        outputs.push({ address: plan._change.address, value: plan._changeVal });
      }
      for (const o of outputs) psbt.addOutput(o);
      for (let i = 0; i < plan._chosen.length; i++) {
        const entry = plan._chosen[i].entry;
        // Taproot key-path: bitcoinjs-lib matches the signer's publicKey
        // against the tweaked output key, so the signer has to be the
        // internal ECPair tweaked with sha256("TapTweak" || internalPubkey).
        // ECPair.tweak() from the ecpair package does exactly that (its
        // internal state becomes the tap-tweaked keypair) and its
        // signSchnorr is what PSBT calls for a key-path spend.
        if (entry.family === "bip86") {
          const raw = ECPair.fromPrivateKey(Buffer.from(entry._node.privateKey), { network: this._bjsNet });
          const tweak = bitcoinjs.crypto.taggedHash("TapTweak", entry.tapInternalKey);
          const tweaked = raw.tweak(tweak);
          psbt.signInput(i, tweaked);
        } else {
          psbt.signInput(i, this._keys.signerFor(entry));
        }
      }
      psbt.finalizeAllInputs();
      const tx = psbt.extractTransaction();
      const hex = tx.toHex();
      const txid = await this._client.call("blockchain.transaction.broadcast", [hex]);
      if (typeof txid !== "string" || txid.length !== 64) throw new Error("broadcast rejected: " + JSON.stringify(txid));
      this.log("broadcast", txid);
      this._scheduleRefresh(1200);
      return { txid, hex, fee: plan.fee };
    }

    // BIP-137 recoverable over sha256d("Bitcoin Signed Message:\n" || msg).
    signMessage(message) {
      const enc = new TextEncoder();
      const varstr = (s) => { const b = enc.encode(s); if (b.length >= 0xfd) throw new Error("too long"); return Uint8Array.from([b.length, ...b]); };
      const MAGIC = "Bitcoin Signed Message:\n";
      const payload = Uint8Array.from([...varstr(MAGIC), ...varstr(String(message))]);
      const digest = sha256(sha256(payload));
      const entry = this.current();
      const signer = this._keys.signerFor(entry);
      const sig = ecc.signRecoverable(Buffer.from(digest), signer.privateKey);
      const out = Buffer.alloc(65);
      out[0] = 27 + sig.recoveryId + 4;    // +4 = compressed
      Buffer.from(sig.signature).copy(out, 1);
      return { address: entry.address, signature: out.toString("base64") };
    }

    recovery() {
      return { accountPath: this._keys.accountPath, xpub: this._keys.xpub, xprv: this._keys.xprv };
    }

    snapshot() {
      const cur = this.current();
      return {
        chain: "btc", network: this._net.id, ticker: "BTC", decimals: 8,
        address: cur.address, addressIndex: this._state.receiveIndex,
        addressPath: cur.path,
        balance: this._state.balance,
        height: this._state.height,
        history: this._state.history,
        scanning: this._state.scanning,
        error: this._state.error,
        server: this._client.url || null,
        servers: this._servers,
        accountPath: this._keys.accountPath,
        xpub: this._keys.xpub,
        explorerTx: this._net.explorerTx,
        explorerAddr: this._net.explorerAddr,
        faucet: this._net.faucet,
      };
    }

    dispose() {
      clearTimeout(this._refreshTimer);
      try { this._keys.wipe(); } catch {}
      try { this._client.disconnect(); } catch {}
      if (this._root) this._root.fill(0);
    }
  }

  return { BtcWallet, NETWORKS };
};