// SPDX-License-Identifier: MIT
// Gearbox Protocol. Generalized leverage for DeFi protocols
// (c) Gearbox Holdings, 2022
pragma solidity ^0.8.10;

struct Balance {
    address token;
    uint256 balance;
}

library BalanceOps {
    error UnknownToken(address);

    function copyBalance(Balance memory b)
        internal
        pure
        returns (Balance memory)
    {
        return Balance({ token: b.token, balance: b.balance });
    }

    function addBalance(
        Balance[] memory b,
        address token,
        uint256 amount
    ) internal pure {
        b[getIndex(b, token)].balance += amount;
    }

    function subBalance(
        Balance[] memory b,
        address token,
        uint256 amount
    ) internal pure {
        b[getIndex(b, token)].balance -= amount;
    }

    function getBalance(Balance[] memory b, address token)
        internal
        pure
        returns (uint256 amount)
    {
        return b[getIndex(b, token)].balance;
    }

    function setBalance(
        Balance[] memory b,
        address token,
        uint256 amount
    ) internal pure {
        b[getIndex(b, token)].balance = amount;
    }

    function getIndex(Balance[] memory b, address token)
        internal
        pure
        returns (uint256 index)
    {
        for (uint256 i; i < b.length; ) {
            if (b[i].token == token) {
                return i;
            }

            unchecked {
                ++i;
            }
        }
        revert UnknownToken(token);
    }

    function copy(Balance[] memory b, uint256 len)
        internal
        pure
        returns (Balance[] memory res)
    {
        res = new Balance[](len);
        for (uint256 i; i < len; ) {
            res[i] = copyBalance(b[i]);
            unchecked {
                ++i;
            }
        }
    }

    function clone(Balance[] memory b)
        internal
        pure
        returns (Balance[] memory)
    {
        return copy(b, b.length);
    }

    function getModifiedAfterSwap(
        Balance[] memory b,
        address tokenFrom,
        uint256 amountFrom,
        address tokenTo,
        uint256 amountTo
    ) internal pure returns (Balance[] memory res) {
        res = copy(b, b.length);
        setBalance(res, tokenFrom, getBalance(b, tokenFrom) - amountFrom);
        setBalance(res, tokenTo, getBalance(b, tokenTo) + amountTo);
    }
}