Burning Tokens

pragma language_version >= 0.17.0;

import CompactStandardLibrary;

// Account balances
export ledger balances: Map<Either<ZswapCoinPublicKey, ContractAddress>, Uint<128>>;

// Total token supply
export ledger totalSupply: Uint<128>;

// Get total circulating supply
export circuit getTotalSupply(): Uint<128> {
    return totalSupply;
}

// Burn your own tokens
export circuit burn(amount: Uint<128>): [] {
    const account = left<ZswapCoinPublicKey, ContractAddress>(ownPublicKey());
    _burn(account, amount);
}

// Burn tokens from another account (with approval)
export circuit burnFrom(
    account: Either<ZswapCoinPublicKey, ContractAddress>,
    amount: Uint<128>
): [] {
    const spender = left<ZswapCoinPublicKey, ContractAddress>(ownPublicKey());

    // Check and spend allowance (requires approval system)
    _spendAllowance(account, spender, amount);

    _burn(account, amount);
}

// Internal: Burn tokens
circuit _burn(
    account: Either<ZswapCoinPublicKey, ContractAddress>,
    amount: Uint<128>
): [] {
    // Get current balance
    const currentBalance = getBalance(account);

    // Check sufficient balance
    assert(currentBalance >= amount, "Burn amount exceeds balance");

    // Decrease account balance
    balances.insert(disclose(account), disclose(currentBalance - amount));

    // Decrease total supply
    totalSupply = disclose(totalSupply - amount);
}

// Helper: Get balance
circuit getBalance(account: Either<ZswapCoinPublicKey, ContractAddress>): Uint<128> {
    if (!balances.member(disclose(account))) {
        return 0;
    }
    return balances.lookup(disclose(account));
}

// Helper: Spend allowance (simplified - see Approval tutorial for full implementation)
circuit _spendAllowance(
    owner: Either<ZswapCoinPublicKey, ContractAddress>,
    spender: Either<ZswapCoinPublicKey, ContractAddress>,
    amount: Uint<128>
): [] {
    // Check allowance and decrease it
    // See Approval & Allowance tutorial for complete implementation
}