CPMM fees

// Paraphrased from raydium-cp-swap/programs/cp-swap/src/curve/{calculator,fees}.rs.
// The actual code branches on `is_creator_fee_on_input`; both branches preserve the
// invariant that creator_fee is its own rate, never a slice of trade_fee.

const FEE_RATE_DENOMINATOR_VALUE: u64 = 1_000_000;

pub struct FeeBreakdown {
    pub amount_in_after_fees: u64,    // input minus all fees taken on the input side
    pub amount_out_after_fees: u64,   // output minus any creator fee taken on the output side
    pub trade_fee:    u64,            // → split into LP / protocol / fund buckets below
    pub protocol_fee: u64,            // share of trade_fee
    pub fund_fee:     u64,            // share of trade_fee
    pub creator_fee:  u64,            // independent bucket (input or output side)
}

fn take_fees_on_input(
    amount_in: u64,
    trade_rate: u64,
    creator_rate: u64,
    protocol_rate: u64,
    fund_rate: u64,
) -> (u64 /* trade_fee */, u64 /* creator_fee */, u64 /* amount_in_after_fees */) {
    // The two rates are added so we round once on the combined fee, then split
    // proportionally — this is purely a rounding/efficiency trick. The split
    // honours the rates exactly: creator_fee/trade_fee == creator_rate/trade_rate.
    let total_fee = ((amount_in as u128) * ((trade_rate + creator_rate) as u128))
        .div_ceil(FEE_RATE_DENOMINATOR_VALUE as u128) as u64;

    let creator_fee = ((total_fee as u128) * (creator_rate as u128)
                       / ((trade_rate + creator_rate) as u128)) as u64;
    let trade_fee   = total_fee - creator_fee;

    (trade_fee, creator_fee, amount_in - total_fee)
}

fn take_creator_fee_on_output(amount_out_swapped: u64, creator_rate: u64) -> (u64, u64) {
    // When creator_fee_on routes the creator fee to the output side,
    // trade_fee is taken on input as a single rate, and creator_fee
    // is computed against the curve output.
    let creator_fee = ((amount_out_swapped as u128) * (creator_rate as u128))
        .div_ceil(FEE_RATE_DENOMINATOR_VALUE as u128) as u64;
    (amount_out_swapped - creator_fee, creator_fee)
}

fn split_trade_fee(
    trade_fee: u64,
    protocol_rate: u64,
    fund_rate: u64,
) -> (u64 /* protocol_fee */, u64 /* fund_fee */) {
    let protocol_fee = (trade_fee as u128 * protocol_rate as u128
                        / FEE_RATE_DENOMINATOR_VALUE as u128) as u64;
    let fund_fee     = (trade_fee as u128 * fund_rate as u128
                        / FEE_RATE_DENOMINATOR_VALUE as u128) as u64;
    (protocol_fee, fund_fee)
}

raw_vault_0_balance = getTokenAccountBalance(vault_0).amount
                    = lp_entitled + protocol_fees_token0
                      + fund_fees_token0 + creator_fees_token0

curve_x = raw_vault_0_balance − (protocol_fees_token0
                                  + fund_fees_token0
                                  + creator_fees_token0)

// Off-chain: current accrued fees in each bucket
const pool = await connection.getAccountInfo(poolStatePda);
const decoded = PoolState.decode(pool.data);
console.log(
  "Protocol accrued:",
  decoded.protocolFeesToken0.toString(),
  decoded.protocolFeesToken1.toString(),
);
console.log(
  "Fund accrued:",
  decoded.fundFeesToken0.toString(),
  decoded.fundFeesToken1.toString(),
);
console.log(
  "Creator accrued:",
  decoded.creatorFeesToken0.toString(),
  decoded.creatorFeesToken1.toString(),
);

// Off-chain: effective rates today.
// trade_fee_rate, creator_fee_rate are fractions of volume (denominator 1e6).
// protocol_fee_rate, fund_fee_rate are fractions of the *trade fee* (same denominator).
const config = await fetch("https://api-v3.raydium.io/main/cpmm-config")
  .then((r) => r.json());
const tier = config.data.find((t) => t.index === decoded.ammConfigIndex);

const tradeFeeOfVolume   = tier.tradeFeeRate / 1_000_000;
const protocolOfTradeFee = tier.protocolFeeRate / 1_000_000;
const fundOfTradeFee     = tier.fundFeeRate / 1_000_000;
const lpOfTradeFee       = 1 - protocolOfTradeFee - fundOfTradeFee;

console.log("LP fee effective:",       (tradeFeeOfVolume * lpOfTradeFee * 100).toFixed(4), "%");
console.log("Protocol fee effective:", (tradeFeeOfVolume * protocolOfTradeFee * 100).toFixed(4), "%");
console.log("Fund fee effective:",     (tradeFeeOfVolume * fundOfTradeFee * 100).toFixed(4), "%");
console.log(
  "Creator fee effective:",
  decoded.enableCreatorFee
    ? ((tier.creatorFeeRate / 1_000_000) * 100).toFixed(4) + " %"
    : "0 % (disabled on this pool)",
);