Dryja-Poon Channel

import { Script } from '@scure/btc-signer';
import { hex } from '@scure/base';
import {
  RestArkProvider,
  MnemonicIdentity,
  VtxoScript,
  networks
} from '@arkade-os/sdk';

// Setup
const arkProvider = new RestArkProvider('https://arkade.computer');
const info = await arkProvider.getInfo();
const serverPubkey = hex.decode(info.signerPubkey).slice(1); // x-only
const exitDelay = BigInt(info.exitDelay);

// Channel participants
const alice = MnemonicIdentity.fromMnemonic("abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about");
const bob = MnemonicIdentity.fromMnemonic("zoo zoo zoo zoo zoo zoo zoo zoo zoo zoo zoo wrong");
const alicePubkey = await alice.xOnlyPublicKey();
const bobPubkey = await bob.xOnlyPublicKey();

// Standard Lightning CSV delay for to_local
const toLocalDelay = 144n; // ~1 day in blocks

Collaborative: <alicePubkey> OP_CHECKSIGVERIFY <bobPubkey> OP_CHECKSIGVERIFY <serverPubkey> OP_CHECKSIG
Unilateral:    <exitDelay> OP_CSV OP_DROP <alicePubkey> OP_CHECKSIGVERIFY <bobPubkey> OP_CHECKSIG

// Collaborative: aliceSig + bobSig + serverSig
const fundingCollaborative = Script.encode([
  alicePubkey,
  'CHECKSIGVERIFY',
  bobPubkey,
  'CHECKSIGVERIFY',
  serverPubkey,
  'CHECKSIG'
]);

// Unilateral: after exitDelay, aliceSig + bobSig
const fundingUnilateral = Script.encode([
  exitDelay,
  'CHECKSEQUENCEVERIFY',
  'DROP',
  alicePubkey,
  'CHECKSIGVERIFY',
  bobPubkey,
  'CHECKSIG'
]);

const fundingScript = new VtxoScript([fundingCollaborative, fundingUnilateral]);
const fundingAddress = fundingScript.address(networks.bitcoin.hrp, serverPubkey).encode();

console.log('Funding address:', fundingAddress);

Revocation: <revocationPubkey> OP_CHECKSIG
Normal:     <toLocalDelay> OP_CSV OP_DROP <localPubkey> OP_CHECKSIG

// Revocation keys are derived per commitment (simplified here)
function buildToLocalScript(
  localPubkey: Uint8Array,
  revocationPubkey: Uint8Array,
  delay: bigint
) {
  // Revocation path: counterparty can punish old state
  const revocationPath = Script.encode([
    revocationPubkey,
    'CHECKSIG'
  ]);

  // Normal path: broadcaster claims after delay
  const normalPath = Script.encode([
    delay,
    'CHECKSEQUENCEVERIFY',
    'DROP',
    localPubkey,
    'CHECKSIG'
  ]);

  // Ark unilateral exit variant
  const unilateralPath = Script.encode([
    exitDelay,
    'CHECKSEQUENCEVERIFY',
    'DROP',
    delay,
    'CHECKSEQUENCEVERIFY',
    'DROP',
    localPubkey,
    'CHECKSIG'
  ]);

  return new VtxoScript([revocationPath, normalPath, unilateralPath]);
}

// Alice's to_local in her commitment
const aliceRevocationPubkey = /* derived from Bob's revocation basepoint */;
const aliceToLocal = buildToLocalScript(alicePubkey, aliceRevocationPubkey, toLocalDelay);

Normal:     <remotePubkey> OP_CHECKSIG
Unilateral: <exitDelay> OP_CSV OP_DROP <remotePubkey> OP_CHECKSIG

function buildToRemoteScript(remotePubkey: Uint8Array) {
  // Normal: counterparty claims immediately
  const normalPath = Script.encode([
    remotePubkey,
    'CHECKSIG'
  ]);

  // Ark unilateral exit
  const unilateralPath = Script.encode([
    exitDelay,
    'CHECKSEQUENCEVERIFY',
    'DROP',
    remotePubkey,
    'CHECKSIG'
  ]);

  return new VtxoScript([normalPath, unilateralPath]);
}

// Bob's to_remote in Alice's commitment
const bobToRemote = buildToRemoteScript(bobPubkey);

Taproot tree:
├── <standard lightning script>
└── <exitDelay> OP_CSV OP_DROP <standard lightning script>