Building a Custom Fee Calculator

hyro_protocol · fund op  ->  charge_fees
        |  FeeCalculationInput
fee_collection · dispatcher & VaultFees ledger
        |  CALCULATE_FEES_DISCRIMINATOR ‖ input
fee_calc_program · calculate_fees  (your program)
        ^  FeeCalculationOutput (via return-data)

pub enum FeeType { Lp, Manager, Protocol, Performance } // u8

pub struct FeeAmounts { pub lp: u64, pub manager: u64, pub protocol: u64, pub performance: u64 }

pub struct FeeCalculationInput {   // core -> calculator
    pub operation: FeeOperation,
    pub amount: u64,               // notional of the triggering op
    pub total_balance: i64,        // signed: a vault may carry venue debt
    pub timestamp: i64,
    pub last_fee_timestamp: i64,   // for time-based accrual
    pub high_water_mark: u64,      // for performance fees
}

pub struct FeeCalculationOutput {  // calculator -> core (via return-data)
    pub fees: FeeAmounts,
    pub new_high_water_mark: Option<u64>,
}

use anchor_lang::prelude::*;
use fee_sdk::{FeeCalculationInput, FeeCalculationOutput};

declare_id!("Examp1eFeeCa1c1111111111111111111111111111111");

#[program]
pub mod my_fee_calc {
    use super::*;

    // name == "calculate_fees" => discriminator == CALCULATE_FEES_DISCRIMINATOR
    pub fn calculate_fees(_ctx: Context<Calc>, input: FeeCalculationInput) -> Result<()> {
        let mut out = FeeCalculationOutput::default();
        out.fees.protocol = input.amount / 100; // flat 1% to protocol — your logic here
        anchor_lang::solana_program::program::set_return_data(&out.try_to_vec()?);
        Ok(())
    }
}

#[derive(Accounts)]
pub struct Calc<'info> {
    /// CHECK: account[0] is the read-only vault
    pub vault: UncheckedAccount<'info>,
    // add your own config PDA(s) here as needed
}