mango-v4/programs/mango-v4/src/state/token_bank.rs

use anchor_lang::prelude::*;
use fixed::types::I80F48;

use super::IndexedPosition;

#[account(zero_copy)]
pub struct TokenBank {
    /// native tokens deposited into or borrowed from this bank
    pub deposits: u64,
    pub borrows: u64,

    /// the index used to scale the value of an IndexedPosition
    pub deposit_index: I80F48,
    pub borrow_index: I80F48,
    // todo: multi-leg interest
    // pub optimal_util: I80F48,
    // pub optimal_rate: I80F48,
    // pub max_rate: I80F48,
}

impl TokenBank {
    pub fn deposit(&mut self, position: &mut IndexedPosition, amount: u64) {
        self.deposits = self.deposits.checked_add(amount).unwrap();
        // TODO: adjust position.value according to the indexes
    }
}