DuoPay

/*
 * DuoPay — 2-of-2 Co-Buyer Escrow
 * Left  → release: both buyers sign → seller paid
 * Right → timeout: expiry passed + both sign → refund
 *
 * Parameters set at compile time via param:: namespace:
 *   BUYER_A_PUBKEY, BUYER_B_PUBKEY — BIP-340 public keys
 *   EXPIRY_TIME                    — block height for refund unlock
 *   BUYER_A_AMOUNT, BUYER_B_AMOUNT — deposits in satoshis
 */

fn get_output_explicit_amount(index: u32) -> u64 {
    let pair: (Asset1, Amount1) = unwrap(jet::output_amount(index));
    let (_, amount): (Asset1, Amount1) = pair;
    let amount: u64 = unwrap_right::<(u1, u256)>(amount);
    amount
}

fn check_signature(pubkey: Pubkey, sig: Signature) {
    let msg: u256 = jet::sig_all_hash();
    jet::bip_0340_verify((pubkey, msg), sig);
}

fn release_path(sig_a: Signature, sig_b: Signature) {
    check_signature(param::BUYER_A_PUBKEY, sig_a);
    check_signature(param::BUYER_B_PUBKEY, sig_b);
    let (carry, total): (bool, u64) =
        jet::add_64(param::BUYER_A_AMOUNT, param::BUYER_B_AMOUNT);
    assert!(jet::eq_1(<bool>::into(carry), 0));
    assert!(jet::eq_64(get_output_explicit_amount(0), total));
}

fn timeout_path(sig_a: Signature, sig_b: Signature) {
    jet::check_lock_time(param::EXPIRY_TIME);
    check_signature(param::BUYER_A_PUBKEY, sig_a);
    check_signature(param::BUYER_B_PUBKEY, sig_b);
    assert!(jet::eq_64(get_output_explicit_amount(0), param::BUYER_A_AMOUNT));
    assert!(jet::eq_64(get_output_explicit_amount(1), param::BUYER_B_AMOUNT));
}

fn main() {
    let sig_a: Signature = witness::SIG_A;
    let sig_b: Signature = witness::SIG_B;
    match witness::PATH {
        Left(params: ())  => release_path(sig_a, sig_b),
        Right(params: ()) => timeout_path(sig_a, sig_b),
    }
}