// SPDX-License-Identifier: GPL-3.0-or-later
pragma solidity ^0.8.17;

import {V3Path} from './V3Path.sol';
import {BytesLib} from './BytesLib.sol';
import {SafeCast} from '@uniswap/v3-core/contracts/libraries/SafeCast.sol';
import {IUniswapV3Pool} from '@uniswap/v3-core/contracts/interfaces/IUniswapV3Pool.sol';
import {IUniswapV3SwapCallback} from '@uniswap/v3-core/contracts/interfaces/callback/IUniswapV3SwapCallback.sol';
import {Constants} from '../../../libraries/Constants.sol';
import {Permit2Payments} from '../../Permit2Payments.sol';
import {UniswapImmutables} from '../UniswapImmutables.sol';
import {Constants} from '../../../libraries/Constants.sol';
import {ERC20} from 'solmate/src/tokens/ERC20.sol';

/// @title Router for Uniswap v3 Trades
abstract contract V3SwapRouter is UniswapImmutables, Permit2Payments, IUniswapV3SwapCallback {
    using V3Path for bytes;
    using BytesLib for bytes;
    using SafeCast for uint256;

    error V3InvalidSwap();
    error V3TooLittleReceived();
    error V3TooMuchRequested();
    error V3InvalidAmountOut();
    error V3InvalidCaller();

    /// @dev Used as the placeholder value for maxAmountIn, because the computed amount in for an exact output swap
    /// can never actually be this value
    uint256 private constant DEFAULT_MAX_AMOUNT_IN = type(uint256).max;

    /// @dev Transient storage variable used for checking slippage
    uint256 private maxAmountInCached = DEFAULT_MAX_AMOUNT_IN;

    /// @dev The minimum value that can be returned from #getSqrtRatioAtTick. Equivalent to getSqrtRatioAtTick(MIN_TICK)
    uint160 internal constant MIN_SQRT_RATIO = 4295128739;

    /// @dev The maximum value that can be returned from #getSqrtRatioAtTick. Equivalent to getSqrtRatioAtTick(MAX_TICK)
    uint160 internal constant MAX_SQRT_RATIO = 1461446703485210103287273052203988822378723970342;

    function uniswapV3SwapCallback(int256 amount0Delta, int256 amount1Delta, bytes calldata data) external {
        if (amount0Delta <= 0 && amount1Delta <= 0) revert V3InvalidSwap(); // swaps entirely within 0-liquidity regions are not supported
        (, address payer) = abi.decode(data, (bytes, address));
        bytes calldata path = data.toBytes(0);

        // because exact output swaps are executed in reverse order, in this case tokenOut is actually tokenIn
        (address tokenIn, uint24 fee, address tokenOut) = path.decodeFirstPool();

        if (computePoolAddress(tokenIn, tokenOut, fee) != msg.sender) revert V3InvalidCaller();

        (bool isExactInput, uint256 amountToPay) =
            amount0Delta > 0 ? (tokenIn < tokenOut, uint256(amount0Delta)) : (tokenOut < tokenIn, uint256(amount1Delta));

        if (isExactInput) {
            // Pay the pool (msg.sender)
            payOrPermit2Transfer(tokenIn, payer, msg.sender, amountToPay);
        } else {
            // either initiate the next swap or pay
            if (path.hasMultiplePools()) {
                // this is an intermediate step so the payer is actually this contract
                path = path.skipToken();
                _swap(-amountToPay.toInt256(), msg.sender, path, payer, false);
            } else {
                if (amountToPay > maxAmountInCached) revert V3TooMuchRequested();
                // note that because exact output swaps are executed in reverse order, tokenOut is actually tokenIn
                payOrPermit2Transfer(tokenOut, payer, msg.sender, amountToPay);
            }
        }
    }

    /// @notice Performs a Uniswap v3 exact input swap
    /// @param recipient The recipient of the output tokens
    /// @param amountIn The amount of input tokens for the trade
    /// @param amountOutMinimum The minimum desired amount of output tokens
    /// @param path The path of the trade as a bytes string
    /// @param payer The address that will be paying the input
    function v3SwapExactInput(
        address recipient,
        uint256 amountIn,
        uint256 amountOutMinimum,
        bytes calldata path,
        address payer
    ) internal {
        // use amountIn == Constants.CONTRACT_BALANCE as a flag to swap the entire balance of the contract
        if (amountIn == Constants.CONTRACT_BALANCE) {
            address tokenIn = path.decodeFirstToken();
            amountIn = ERC20(tokenIn).balanceOf(address(this));
        }

        uint256 amountOut;
        while (true) {
            bool hasMultiplePools = path.hasMultiplePools();

            // the outputs of prior swaps become the inputs to subsequent ones
            (int256 amount0Delta, int256 amount1Delta, bool zeroForOne) = _swap(
                amountIn.toInt256(),
                hasMultiplePools ? address(this) : recipient, // for intermediate swaps, this contract custodies
                path.getFirstPool(), // only the first pool is needed
                payer, // for intermediate swaps, this contract custodies
                true
            );

            amountIn = uint256(-(zeroForOne ? amount1Delta : amount0Delta));

            // decide whether to continue or terminate
            if (hasMultiplePools) {
                payer = address(this);
                path = path.skipToken();
            } else {
                amountOut = amountIn;
                break;
            }
        }

        if (amountOut < amountOutMinimum) revert V3TooLittleReceived();
    }

    /// @notice Performs a Uniswap v3 exact output swap
    /// @param recipient The recipient of the output tokens
    /// @param amountOut The amount of output tokens to receive for the trade
    /// @param amountInMaximum The maximum desired amount of input tokens
    /// @param path The path of the trade as a bytes string
    /// @param payer The address that will be paying the input
    function v3SwapExactOutput(
        address recipient,
        uint256 amountOut,
        uint256 amountInMaximum,
        bytes calldata path,
        address payer
    ) internal {
        maxAmountInCached = amountInMaximum;
        (int256 amount0Delta, int256 amount1Delta, bool zeroForOne) =
            _swap(-amountOut.toInt256(), recipient, path, payer, false);

        uint256 amountOutReceived = zeroForOne ? uint256(-amount1Delta) : uint256(-amount0Delta);

        if (amountOutReceived != amountOut) revert V3InvalidAmountOut();

        maxAmountInCached = DEFAULT_MAX_AMOUNT_IN;
    }

    /// @dev Performs a single swap for both exactIn and exactOut
    /// For exactIn, `amount` is `amountIn`. For exactOut, `amount` is `-amountOut`
    function _swap(int256 amount, address recipient, bytes calldata path, address payer, bool isExactIn)
        private
        returns (int256 amount0Delta, int256 amount1Delta, bool zeroForOne)
    {
        (address tokenIn, uint24 fee, address tokenOut) = path.decodeFirstPool();

        zeroForOne = isExactIn ? tokenIn < tokenOut : tokenOut < tokenIn;

        (amount0Delta, amount1Delta) = IUniswapV3Pool(computePoolAddress(tokenIn, tokenOut, fee)).swap(
            recipient,
            zeroForOne,
            amount,
            (zeroForOne ? MIN_SQRT_RATIO + 1 : MAX_SQRT_RATIO - 1),
            abi.encode(path, payer)
        );
    }

    function computePoolAddress(address tokenA, address tokenB, uint24 fee) private view returns (address pool) {
        if (tokenA > tokenB) (tokenA, tokenB) = (tokenB, tokenA);
        pool = address(
            uint160(
                uint256(
                    keccak256(
                        abi.encodePacked(
                            hex'ff',
                            UNISWAP_V3_FACTORY,
                            keccak256(abi.encode(tokenA, tokenB, fee)),
                            UNISWAP_V3_POOL_INIT_CODE_HASH
                        )
                    )
                )
            )
        );
    }
}