#!/usr/bin/env node
/**
 * regtest-doublespend-sweep.mjs — the topology × first-seen × DSProof sweep.
 *
 * PURPOSE (the Karame–Androulaki–Capkun 2012 reproduction, on our terms).
 * The 2012 paper measured a propagation-race double-spend against 0-conf fast
 * payments. The open questions we want answered with our OWN hands, not theirs:
 *
 *   Q1. Does the race need a *malicious modified client*?  → NO if it works with
 *       stock BCHN driven only by standard RPC (createrawtransaction /
 *       sendrawtransaction). This harness uses unmodified bitcoind exclusively.
 *   Q2. Does the race need *attacker-controlled topology*?  → We run it BOTH ways:
 *       Variant A targets the vendor and the miner separately (KAC topology);
 *       Variant B dumps both conflicting txs into the SAME node (no topology
 *       control). The contrast is the answer.
 *   Q3. Is DSProof the thing that actually protects the merchant?  → We record
 *       whether the vendor node receives a Double-Spend Proof for the conflicted
 *       input, i.e. whether a DSProof-aware merchant would have been warned.
 *
 * MECHANISM under test (first-seen, no RBF — BCH / whitepaper Bitcoin):
 *   - TRV pays the vendor (B); TRA double-spends the same coin to the attacker (C).
 *   - "first-seen" is LOCAL: each node keeps the first version IT saw and rejects
 *     the conflicting one. So if the VENDOR sees TRV first while the MINER sees
 *     TRA first, the vendor's mempool holds TRV (merchant thinks he's paid) while
 *     the block confirms TRA (attacker keeps the coin). That divergence is the
 *     whole attack — and it is protocol-VALID at every step. DSProof does not
 *     prevent it; it ALERTS the vendor that the input was double-spent.
 *
 * HONEST EXPECTATION (so we don't fool ourselves):
 *   - Variant A (targeted) should SUCCEED at the ledger level — vendor holds TRV,
 *     block confirms TRA — which would VINDICATE KAC's mechanism, not debunk it.
 *   - Variant B (same node) should FAIL — first-seen rejects the second tx outright.
 *   - DSProof should fire on the vendor in Variant A → a *waiting, DSProof-aware*
 *     merchant declines; a *naive instant-accept* merchant is fooled.
 *   If A fails too, KAC's real-world reach was thinner than claimed. Either result
 *   is a finding. We report what happens; we don't pre-judge it.
 *
 * REQUIREMENTS: Bitcoin Cash Node (BCHN) binaries — bitcoind + bitcoin-cli.
 *   Not installed? See scripts/regtest-doublespend-sweep.README at the bottom of
 *   this file, or run with --help. Point the harness at them via:
 *     BCHN_BIN_DIR=/path/to/bchn/bin  node scripts/regtest-doublespend-sweep.mjs
 *   (auto-detected on PATH if present.)
 *
 * SAFETY: regtest only. Spawns ephemeral nodes in a temp dir, mines local coins
 * with no value, and tears everything down at the end. Touches no real network.
 *
 * Run:  npm run regtest:dsweep        (after BCHN is available)
 */
import { spawn, spawnSync } from 'node:child_process';
import { mkdtempSync, rmSync, writeFileSync, mkdirSync } from 'node:fs';
import { tmpdir, platform } from 'node:os';
import { join } from 'node:path';

const EXE = platform() === 'win32' ? '.exe' : '';
const BIN_DIR = process.env.BCHN_BIN_DIR ?? '';
const bin = (name) => (BIN_DIR ? join(BIN_DIR, name + EXE) : name + EXE);
const BITCOIND = bin('bitcoind');
const CLI = bin('bitcoin-cli');

const FEE_SATS = 1000n;
const sleep = (ms) => new Promise((r) => setTimeout(r, ms));
const line = (c = '=') => console.log(c.repeat(76));

// ── node definitions: V = vendor (the merchant's node), M = miner (the network).
//    Distinct rpc/p2p ports so two regtest daemons coexist on one host.
const NODES = {
  V: { name: 'vendor', rpcport: 18510, port: 18511, dir: '', proc: null },
  M: { name: 'miner', rpcport: 18520, port: 18521, dir: '', proc: null },
};
const RPC_USER = 'ds';
const RPC_PASS = 'ds';

function preflight() {
  const r = spawnSync(BITCOIND, ['-version'], { encoding: 'utf8' });
  if (r.error || r.status !== 0) {
    console.error(`\n✗ Cannot run "${BITCOIND}".`);
    console.error('  This sweep needs Bitcoin Cash Node (BCHN) — bitcoind + bitcoin-cli.');
    console.error('  Install options (pick one):');
    console.error('   • Native Windows: download the BCHN release zip from');
    console.error('     https://bitcoincashnode.org/ , extract, then set');
    console.error('     BCHN_BIN_DIR=C:\\path\\to\\bitcoin-cash-node\\bin');
    console.error('   • WSL/Linux: install BCHN in WSL and run this script from there');
    console.error('     (the bitcoind/bitcoin-cli interface is identical).');
    console.error('   • Then: BCHN_BIN_DIR=<bin> npm run regtest:dsweep\n');
    process.exit(2);
  }
  const v = (r.stdout || '').split('\n')[0];
  console.log(`Using: ${v}`);
}

function writeConf(node) {
  node.dir = mkdtempSync(join(tmpdir(), `dsweep-${node.name}-`));
  const conf = [
    'regtest=1',
    'server=1',
    'listen=1',
    'dnsseed=0',
    'fixedseeds=0',
    `rpcuser=${RPC_USER}`,
    `rpcpassword=${RPC_PASS}`,
    `fallbackfee=0.00001`,
    '[regtest]',
    `rpcport=${node.rpcport}`,
    `port=${node.port}`,
    `bind=127.0.0.1:${node.port}`,
  ].join('\n');
  // BCHN reads bitcoin.conf from the datadir.
  writeFileSync(join(node.dir, 'bitcoin.conf'), conf + '\n');
}

function launch(node) {
  writeConf(node);
  node.proc = spawn(BITCOIND, [`-datadir=${node.dir}`], { stdio: 'ignore' });
  node.proc.on('error', (e) => console.error(`${node.name} spawn error:`, e.message));
}

/** bitcoin-cli call against a node; returns trimmed stdout or throws with stderr. */
function cli(node, ...args) {
  const r = spawnSync(
    CLI,
    [`-datadir=${node.dir}`, `-rpcport=${node.rpcport}`, `-rpcuser=${RPC_USER}`, `-rpcpassword=${RPC_PASS}`, ...args],
    { encoding: 'utf8' },
  );
  if (r.status !== 0) throw new Error((r.stderr || r.stdout || 'cli failed').trim());
  return (r.stdout || '').trim();
}
/** Like cli() but returns {ok,value|error} instead of throwing — for the broadcasts. */
function cliTry(node, ...args) {
  try {
    return { ok: true, value: cli(node, ...args) };
  } catch (e) {
    return { ok: false, error: e.message };
  }
}
const cliJSON = (node, ...args) => JSON.parse(cli(node, ...args));

async function waitReady(node, timeoutMs = 30000) {
  const t = Date.now() + timeoutMs;
  while (Date.now() < t) {
    const r = cliTry(node, 'getblockchaininfo');
    if (r.ok) return;
    await sleep(500);
  }
  throw new Error(`${node.name} RPC not ready within ${timeoutMs}ms`);
}

/** Connect V and M as a single regtest network (one P2P link). */
function peer() {
  cli(NODES.V, 'addnode', `127.0.0.1:${NODES.M.port}`, 'onetry');
}
async function waitConnected() {
  const t = Date.now() + 15000;
  while (Date.now() < t) {
    const n = Number(cli(NODES.V, 'getconnectioncount'));
    if (n >= 1) return;
    await sleep(400);
  }
  throw new Error('V never connected to M');
}

/** Make a mature spendable coin on M's wallet; return {txid, vout, amount(BTC str)}. */
function freshCoin() {
  cliTry(NODES.M, 'createwallet', 'w'); // ignore "already exists"
  const addr = cli(NODES.M, 'getnewaddress');
  cli(NODES.M, 'generatetoaddress', '101', addr); // 100-block coinbase maturity + 1
  const utxos = cliJSON(NODES.M, 'listunspent', '1');
  const u = utxos.find((x) => x.spendable && Number(x.amount) > 1);
  if (!u) throw new Error('no mature coin on M');
  return { txid: u.txid, vout: u.vout, amount: Number(u.amount) };
}

/** Build two conflicting signed txs spending `coin` → B (vendor) and → C (attacker).
 *  Uses ONLY standard RPC on stock bitcoind: this is the "no modified client" proof. */
function buildConflict(coin, addrB, addrC) {
  const out = (coin.amount - Number(FEE_SATS) / 1e8).toFixed(8);
  const mk = (to) => {
    const raw = cli(NODES.M, 'createrawtransaction',
      JSON.stringify([{ txid: coin.txid, vout: coin.vout }]), JSON.stringify({ [to]: out }));
    const signed = cliJSON(NODES.M, 'signrawtransactionwithwallet', raw);
    if (!signed.complete) throw new Error('sign incomplete');
    return signed.hex;
  };
  const TRV = mk(addrB); // pays the vendor
  const TRA = mk(addrC); // double-spends to the attacker
  return { TRV, TRA };
}

const txid = (node, hex) => cli(node, 'decoderawtransaction', hex).length ? cliJSON(node, 'decoderawtransaction', hex).txid : '';

/** Did the vendor node receive a DSProof for the conflicted coin? */
function dsproofOnVendor() {
  const r = cliTry(NODES.V, 'getdsprooflist', '2', 'true');
  if (!r.ok) return { supported: false, present: false, note: r.error.slice(0, 80) };
  let list;
  try { list = JSON.parse(r.value); } catch { return { supported: true, present: false }; }
  return { supported: true, present: Array.isArray(list) && list.length > 0, count: Array.isArray(list) ? list.length : 0 };
}

/** One experimental run. `targeted` = Variant A (TRV→V, TRA→M) vs B (both→M). */
async function runVariant(targeted, addrB, addrC) {
  const label = targeted ? 'A · TARGETED topology (TRV→vendor, TRA→miner)' : 'B · SAME-NODE (both → miner)';
  line('-');
  console.log(`VARIANT ${label}`);
  line('-');

  const coin = freshCoin();
  // sync the funding so V also knows the coin exists before we conflict it
  await sleep(800);
  const { TRV, TRA } = buildConflict(coin, addrB, addrC);
  const idV = txid(NODES.M, TRV);
  const idA = txid(NODES.M, TRA);
  console.log(`  coin   ${coin.txid.slice(0, 16)}…:${coin.vout}  (${coin.amount} BCH)`);
  console.log(`  TRV→B  ${idV.slice(0, 16)}…   TRA→C  ${idA.slice(0, 16)}…  (same input)`);

  let rTRV, rTRA;
  if (targeted) {
    rTRV = cliTry(NODES.V, 'sendrawtransaction', TRV); // vendor sees TRV first
    rTRA = cliTry(NODES.M, 'sendrawtransaction', TRA); // miner sees TRA first
  } else {
    rTRV = cliTry(NODES.M, 'sendrawtransaction', TRV);
    rTRA = cliTry(NODES.M, 'sendrawtransaction', TRA); // same node → first-seen should reject
  }
  console.log(`  send TRV → ${targeted ? 'V' : 'M'}: ${rTRV.ok ? 'ACCEPTED' : 'REJECTED ' + rTRV.error.slice(0, 60)}`);
  console.log(`  send TRA → M: ${rTRA.ok ? 'ACCEPTED' : 'REJECTED ' + rTRA.error.slice(0, 60)}`);

  await sleep(1500); // let gossip + DSProof propagate
  const ds = dsproofOnVendor();
  const vendorPool = cliJSON(NODES.V, 'getrawmempool');
  const vendorHasTRV = vendorPool.includes(idV);

  // miner confirms its view
  const mAddr = cli(NODES.M, 'getnewaddress');
  cli(NODES.M, 'generatetoaddress', '1', mAddr);
  await sleep(1000);

  const confirmed = (id) => {
    const r = cliTry(NODES.V, 'getrawtransaction', id, 'true');
    if (!r.ok) return 0;
    try { return JSON.parse(r.value).confirmations ?? 0; } catch { return 0; }
  };
  const cTRV = confirmed(idV);
  const cTRA = confirmed(idA);

  const merchantFooled = targeted && vendorHasTRV && cTRA >= 1 && cTRV === 0;
  console.log('');
  console.log(`  vendor mempool held TRV (merchant would release goods): ${vendorHasTRV ? 'YES' : 'no'}`);
  console.log(`  after 1 block:  TRV conf=${cTRV}   TRA conf=${cTRA}`);
  console.log(`  DSProof on vendor for the conflict: ${ds.supported ? (ds.present ? `YES (${ds.count}) — a waiting merchant is WARNED` : 'none seen') : 'RPC unsupported: ' + (ds.note || '')}`);
  if (!targeted) {
    const firstSeenHeld = rTRV.ok && !rTRA.ok;
    console.log(`  ⇒ result: ${firstSeenHeld ? 'first-seen REJECTED the double-spend (attack fails without topology control)' : rTRV.ok && rTRA.ok ? 'BOTH accepted — first-seen VIOLATED (unexpected!)' : 'inconclusive'}`);
  } else {
    console.log(`  ⇒ result: ${merchantFooled ? 'naive-merchant FOOLED (TRA confirmed, TRV evaporated) — KAC mechanism reproduced' : 'attack did NOT achieve the divergence'}`);
    console.log(`            a DSProof-aware merchant who waited ~1–2s would have ${ds.present ? 'DECLINED' : 'had no warning'}.`);
  }
  return { variant: targeted ? 'A' : 'B', idV, idA, vendorHasTRV, cTRV, cTRA, ds, merchantFooled };
}

async function main() {
  if (process.argv.includes('--help')) {
    console.log('Topology × first-seen × DSProof double-spend sweep (regtest, stock BCHN).');
    console.log('Set BCHN_BIN_DIR to your BCHN bin folder, then: npm run regtest:dsweep');
    process.exit(0);
  }
  line();
  console.log('REGTEST DOUBLE-SPEND SWEEP — KAC 2012 reproduction on stock BCHN');
  line();
  preflight();

  console.log('Launching vendor + miner regtest nodes…');
  launch(NODES.V); launch(NODES.M);
  try {
    await waitReady(NODES.V); await waitReady(NODES.M);
    peer(); await waitConnected();
    console.log('Nodes up and peered.\n');

    const addrB = (cliTry(NODES.V, 'createwallet', 'wv'), cli(NODES.V, 'getnewaddress')); // vendor's payout addr
    const addrC = cli(NODES.M, 'getnewaddress'); // attacker's addr

    const results = [];
    results.push(await runVariant(false, addrB, addrC)); // B: same-node first-seen
    results.push(await runVariant(true, addrB, addrC));  // A: targeted topology

    line();
    console.log('SWEEP SUMMARY');
    for (const r of results) {
      console.log(`  Variant ${r.variant}: TRV=${r.idV.slice(0, 12)}… TRA=${r.idA.slice(0, 12)}…  ` +
        `merchantFooled=${r.merchantFooled}  dsproof=${r.ds.present ? 'fired' : (r.ds.supported ? 'none' : 'n/a')}`);
    }
    console.log('\n  Interpretation:');
    console.log('   • B fails  + A succeeds  ⇒ the race needs TOPOLOGY CONTROL, not a code hack;');
    console.log('     first-seen alone stops the naive case; DSProof is what warns the vendor in A.');
    console.log('   • A fails too           ⇒ even targeted, the race did not divide vendor/miner here.');
    line();
  } finally {
    console.log('Tearing down nodes…');
    for (const n of Object.values(NODES)) {
      try { cli(n, 'stop'); } catch { /* ignore */ }
    }
    await sleep(1500);
    for (const n of Object.values(NODES)) {
      try { n.proc?.kill(); } catch { /* ignore */ }
      try { if (n.dir) rmSync(n.dir, { recursive: true, force: true }); } catch { /* ignore */ }
    }
  }
  process.exit(0);
}

main().catch((e) => { console.error('FAILED:', e?.message ?? e); process.exit(1); });