// SPDX-License-Identifier: ISC
pragma solidity ^0.8.19;

struct VaultAccount {
    uint128 amount; // Total amount, analogous to market cap
    uint128 shares; // Total shares, analogous to shares outstanding
}

/// @title VaultAccount Library
/// @author Drake Evans (Frax Finance) github.com/drakeevans, modified from work by @Boring_Crypto github.com/boring_crypto
/// @notice Provides a library for use with the VaultAccount struct, provides convenient math implementations
/// @dev Uses uint128 to save on storage
library VaultAccountingLibrary {
    /// @notice Calculates the shares value in relationship to `amount` and `total`
    /// @dev Given an amount, return the appropriate number of shares
    function toShares(VaultAccount memory total, uint256 amount, bool roundUp) internal pure returns (uint256 shares) {
        if (total.amount == 0) {
            shares = amount;
        } else {
            shares = (amount * total.shares) / total.amount;
            if (roundUp && (shares * total.amount) / total.shares < amount) {
                shares = shares + 1;
            }
        }
    }

    /// @notice Calculates the amount value in relationship to `shares` and `total`
    /// @dev Given a number of shares, returns the appropriate amount
    function toAmount(VaultAccount memory total, uint256 shares, bool roundUp) internal pure returns (uint256 amount) {
        if (total.shares == 0) {
            amount = shares;
        } else {
            amount = (shares * total.amount) / total.shares;
            if (roundUp && (amount * total.shares) / total.amount < shares) {
                amount = amount + 1;
            }
        }
    }
}