Router Types

The IU2U Protocol supports multiple router types, each optimized for different trading scenarios and requirements. This document explains the various router implementations and their use cases.

Overview

IU2U Protocol implements several router types to handle different trading patterns:

1. Simple Router - Direct swaps on single DEXes

2. Multi-hop Router - Complex routes through multiple pools

3. Cross-chain Router - Routes spanning multiple blockchains

4. Aggregation Router - Combines multiple DEXes for optimal execution

5. Split Router - Divides large orders across multiple routes

6. Flash Router - Atomic multi-step operations using flash loans

Router Architecture

Base Router Interface

All routers implement a common interface for consistency:

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

import "./interfaces/IIU2URouter.sol";

interface IIU2URouter {
    struct SwapParams {
        address tokenIn;
        address tokenOut;
        uint256 amountIn;
        uint256 amountOutMin;
        address[] pools;
        uint256 deadline;
        address recipient;
        bytes extraData;
    }

    struct Route {
        address[] tokens;
        address[] pools;
        uint256[] fees;
        bytes[] swapData;
    }

    function swapExactTokensForTokens(
        SwapParams calldata params
    ) external payable returns (uint256 amountOut);

    function getAmountsOut(
        uint256 amountIn,
        Route calldata route
    ) external view returns (uint256[] memory amounts);

    function quote(
        address tokenA,
        address tokenB,
        uint256 amountIn
    ) external view returns (uint256 amountOut, Route memory optimalRoute);

    function getSupportedDEXes() external view returns (address[] memory);
    function getRouterType() external pure returns (string memory);
}

Router Registry

contract IU2URouterRegistry {
    mapping(string => address) public routers;
    mapping(address => bool) public authorizedRouters;
    address public governance;

    event RouterRegistered(string indexed routerType, address indexed router);
    event RouterUpdated(string indexed routerType, address indexed oldRouter, address indexed newRouter);

    modifier onlyGovernance() {
        require(msg.sender == governance, "Not authorized");
        _;
    }

    constructor(address _governance) {
        governance = _governance;
    }

    function registerRouter(string calldata routerType, address router) external onlyGovernance {
        require(router != address(0), "Invalid router address");
        
        address oldRouter = routers[routerType];
        routers[routerType] = router;
        authorizedRouters[router] = true;
        
        if (oldRouter != address(0)) {
            authorizedRouters[oldRouter] = false;
            emit RouterUpdated(routerType, oldRouter, router);
        } else {
            emit RouterRegistered(routerType, router);
        }
    }

    function getRouter(string calldata routerType) external view returns (address) {
        return routers[routerType];
    }

    function isAuthorizedRouter(address router) external view returns (bool) {
        return authorizedRouters[router];
    }
}

1. Simple Router

The Simple Router handles direct swaps on single DEXes with minimal complexity:

contract IU2USimpleRouter is IIU2URouter {
    using SafeERC20 for IERC20;

    struct DEXConfig {
        address router;
        uint256 fee;
        bytes4 swapSelector;
        bool isActive;
    }

    mapping(string => DEXConfig) public dexConfigs;
    mapping(address => mapping(address => address)) public pairAddresses;
    
    address public immutable WETH;
    uint256 public constant MAX_SLIPPAGE = 500; // 5%

    constructor(address _weth) {
        WETH = _weth;
        _initializeDEXes();
    }

    function swapExactTokensForTokens(
        SwapParams calldata params
    ) external payable override returns (uint256 amountOut) {
        require(params.deadline >= block.timestamp, "Expired");
        require(params.pools.length == 1, "Simple router supports single pool only");
        
        address pool = params.pools[0];
        string memory dexName = _getDEXName(pool);
        DEXConfig memory config = dexConfigs[dexName];
        
        require(config.isActive, "DEX not active");

        // Handle native ETH
        if (params.tokenIn == address(0)) {
            require(msg.value >= params.amountIn, "Insufficient ETH");
            return _swapETHForTokens(config, params);
        } else if (params.tokenOut == address(0)) {
            return _swapTokensForETH(config, params);
        } else {
            return _swapTokensForTokens(config, params);
        }
    }

    function _swapTokensForTokens(
        DEXConfig memory config,
        SwapParams calldata params
    ) internal returns (uint256 amountOut) {
        IERC20(params.tokenIn).safeTransferFrom(
            msg.sender,
            address(this),
            params.amountIn
        );

        IERC20(params.tokenIn).safeApprove(config.router, params.amountIn);

        if (config.swapSelector == IUniswapV2Router.swapExactTokensForTokens.selector) {
            return _executeUniswapV2Swap(config, params);
        } else if (config.swapSelector == IUniswapV3Router.exactInputSingle.selector) {
            return _executeUniswapV3Swap(config, params);
        } else {
            revert("Unsupported DEX");
        }
    }

    function _executeUniswapV2Swap(
        DEXConfig memory config,
        SwapParams calldata params
    ) internal returns (uint256 amountOut) {
        address[] memory path = new address[](2);
        path[0] = params.tokenIn;
        path[1] = params.tokenOut;

        uint256[] memory amounts = IUniswapV2Router(config.router)
            .swapExactTokensForTokens(
                params.amountIn,
                params.amountOutMin,
                path,
                params.recipient,
                params.deadline
            );

        return amounts[amounts.length - 1];
    }

    function _executeUniswapV3Swap(
        DEXConfig memory config,
        SwapParams calldata params
    ) internal returns (uint256 amountOut) {
        IUniswapV3Router.ExactInputSingleParams memory swapParams = 
            IUniswapV3Router.ExactInputSingleParams({
                tokenIn: params.tokenIn,
                tokenOut: params.tokenOut,
                fee: uint24(config.fee),
                recipient: params.recipient,
                deadline: params.deadline,
                amountIn: params.amountIn,
                amountOutMinimum: params.amountOutMin,
                sqrtPriceLimitX96: 0
            });

        return IUniswapV3Router(config.router).exactInputSingle(swapParams);
    }

    function quote(
        address tokenA,
        address tokenB,
        uint256 amountIn
    ) external view override returns (uint256 amountOut, Route memory optimalRoute) {
        address bestPool;
        uint256 bestOutput = 0;
        string memory bestDEX;

        // Check all configured DEXes
        string[] memory dexNames = _getAllDEXNames();
        
        for (uint256 i = 0; i < dexNames.length; i++) {
            DEXConfig memory config = dexConfigs[dexNames[i]];
            if (!config.isActive) continue;

            try this.getAmountOut(tokenA, tokenB, amountIn, dexNames[i]) returns (uint256 output) {
                if (output > bestOutput) {
                    bestOutput = output;
                    bestPool = _getPoolAddress(tokenA, tokenB, dexNames[i]);
                    bestDEX = dexNames[i];
                }
            } catch {
                // Skip failed quotes
            }
        }

        require(bestOutput > 0, "No liquidity found");

        optimalRoute.tokens = new address[](2);
        optimalRoute.tokens[0] = tokenA;
        optimalRoute.tokens[1] = tokenB;
        
        optimalRoute.pools = new address[](1);
        optimalRoute.pools[0] = bestPool;
        
        optimalRoute.fees = new uint256[](1);
        optimalRoute.fees[0] = dexConfigs[bestDEX].fee;

        return (bestOutput, optimalRoute);
    }

    function getAmountOut(
        address tokenA,
        address tokenB,
        uint256 amountIn,
        string calldata dexName
    ) external view returns (uint256 amountOut) {
        DEXConfig memory config = dexConfigs[dexName];
        require(config.isActive, "DEX not active");

        if (config.swapSelector == IUniswapV2Router.swapExactTokensForTokens.selector) {
            return _getUniswapV2AmountOut(tokenA, tokenB, amountIn, config);
        } else if (config.swapSelector == IUniswapV3Router.exactInputSingle.selector) {
            return _getUniswapV3AmountOut(tokenA, tokenB, amountIn, config);
        } else {
            revert("Unsupported DEX");
        }
    }

    function _initializeDEXes() internal {
        // Uniswap V2
        dexConfigs["UNISWAP_V2"] = DEXConfig({
            router: 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D,
            fee: 3000, // 0.3%
            swapSelector: IUniswapV2Router.swapExactTokensForTokens.selector,
            isActive: true
        });

        // Uniswap V3
        dexConfigs["UNISWAP_V3"] = DEXConfig({
            router: 0xE592427A0AEce92De3Edee1F18E0157C05861564,
            fee: 3000, // 0.3% default
            swapSelector: IUniswapV3Router.exactInputSingle.selector,
            isActive: true
        });

        // SushiSwap
        dexConfigs["SUSHISWAP"] = DEXConfig({
            router: 0xd9e1cE17f2641f24aE83637ab66a2cca9C378B9F,
            fee: 3000, // 0.3%
            swapSelector: IUniswapV2Router.swapExactTokensForTokens.selector,
            isActive: true
        });
    }

    function getRouterType() external pure override returns (string memory) {
        return "SIMPLE";
    }
}

2. Multi-hop Router

The Multi-hop Router enables complex routing through multiple intermediary tokens:

contract IU2UMultiHopRouter is IIU2URouter {
    using SafeERC20 for IERC20;

    struct HopData {
        address pool;
        address tokenIn;
        address tokenOut;
        uint256 fee;
        bytes swapData;
    }

    uint256 public constant MAX_HOPS = 4;
    mapping(address => bool) public authorizedCallers;

    event MultiHopSwap(
        address indexed user,
        address indexed tokenIn,
        address indexed tokenOut,
        uint256 amountIn,
        uint256 amountOut,
        uint256 hops
    );

    function swapExactTokensForTokens(
        SwapParams calldata params
    ) external payable override returns (uint256 amountOut) {
        require(params.deadline >= block.timestamp, "Expired");
        require(params.pools.length <= MAX_HOPS, "Too many hops");
        require(params.pools.length > 0, "No pools specified");

        Route memory route = _decodeRoute(params);
        return _executeMultiHopSwap(route, params);
    }

    function _executeMultiHopSwap(
        Route memory route,
        SwapParams calldata params
    ) internal returns (uint256 finalAmount) {
        uint256 currentAmount = params.amountIn;
        
        // Transfer initial tokens
        if (params.tokenIn != address(0)) {
            IERC20(params.tokenIn).safeTransferFrom(
                msg.sender,
                address(this),
                params.amountIn
            );
        }

        // Execute each hop
        for (uint256 i = 0; i < route.pools.length; i++) {
            currentAmount = _executeHop(
                route.tokens[i],
                route.tokens[i + 1],
                route.pools[i],
                currentAmount,
                route.swapData[i],
                i == route.pools.length - 1 ? params.recipient : address(this)
            );
        }

        require(currentAmount >= params.amountOutMin, "Insufficient output");
        
        emit MultiHopSwap(
            msg.sender,
            params.tokenIn,
            params.tokenOut,
            params.amountIn,
            currentAmount,
            route.pools.length
        );

        return currentAmount;
    }

    function _executeHop(
        address tokenIn,
        address tokenOut,
        address pool,
        uint256 amountIn,
        bytes memory swapData,
        address recipient
    ) internal returns (uint256 amountOut) {
        string memory dexType = _getDEXType(pool);
        
        if (keccak256(abi.encodePacked(dexType)) == keccak256("UNISWAP_V2")) {
            return _executeUniswapV2Hop(tokenIn, tokenOut, pool, amountIn, recipient);
        } else if (keccak256(abi.encodePacked(dexType)) == keccak256("UNISWAP_V3")) {
            return _executeUniswapV3Hop(tokenIn, tokenOut, pool, amountIn, swapData, recipient);
        } else if (keccak256(abi.encodePacked(dexType)) == keccak256("CURVE")) {
            return _executeCurveHop(tokenIn, tokenOut, pool, amountIn, swapData, recipient);
        } else {
            revert("Unsupported DEX type");
        }
    }

    function _executeUniswapV2Hop(
        address tokenIn,
        address tokenOut,
        address pool,
        uint256 amountIn,
        address recipient
    ) internal returns (uint256 amountOut) {
        IUniswapV2Pair pair = IUniswapV2Pair(pool);
        
        (uint256 reserve0, uint256 reserve1,) = pair.getReserves();
        bool token0IsInput = tokenIn < tokenOut;
        
        (uint256 reserveIn, uint256 reserveOut) = token0IsInput 
            ? (reserve0, reserve1) 
            : (reserve1, reserve0);

        amountOut = _getAmountOut(amountIn, reserveIn, reserveOut);
        
        IERC20(tokenIn).safeTransfer(pool, amountIn);
        
        (uint256 amount0Out, uint256 amount1Out) = token0IsInput 
            ? (uint256(0), amountOut) 
            : (amountOut, uint256(0));
            
        pair.swap(amount0Out, amount1Out, recipient, "");
        
        return amountOut;
    }

    function _executeUniswapV3Hop(
        address tokenIn,
        address tokenOut,
        address pool,
        uint256 amountIn,
        bytes memory swapData,
        address recipient
    ) internal returns (uint256 amountOut) {
        // Decode fee from swap data
        uint24 fee = abi.decode(swapData, (uint24));
        
        IUniswapV3Pool v3Pool = IUniswapV3Pool(pool);
        
        bool zeroForOne = tokenIn < tokenOut;
        
        IERC20(tokenIn).safeTransfer(pool, amountIn);
        
        (int256 amount0, int256 amount1) = v3Pool.swap(
            recipient,
            zeroForOne,
            int256(amountIn),
            zeroForOne ? TickMath.MIN_SQRT_RATIO + 1 : TickMath.MAX_SQRT_RATIO - 1,
            ""
        );
        
        amountOut = uint256(-(zeroForOne ? amount1 : amount0));
        return amountOut;
    }

    function _executeCurveHop(
        address tokenIn,
        address tokenOut,
        address pool,
        uint256 amountIn,
        bytes memory swapData,
        address recipient
    ) internal returns (uint256 amountOut) {
        // Decode token indices for Curve
        (int128 i, int128 j, uint256 minAmountOut) = abi.decode(swapData, (int128, int128, uint256));
        
        IERC20(tokenIn).safeApprove(pool, amountIn);
        
        ICurvePool curvePool = ICurvePool(pool);
        
        uint256 balanceBefore = IERC20(tokenOut).balanceOf(recipient);
        curvePool.exchange(i, j, amountIn, minAmountOut);
        uint256 balanceAfter = IERC20(tokenOut).balanceOf(recipient);
        
        amountOut = balanceAfter - balanceBefore;
        return amountOut;
    }

    function quote(
        address tokenA,
        address tokenB,
        uint256 amountIn
    ) external view override returns (uint256 amountOut, Route memory optimalRoute) {
        // Find optimal multi-hop route
        Route[] memory candidateRoutes = _findCandidateRoutes(tokenA, tokenB, amountIn);
        
        uint256 bestOutput = 0;
        uint256 bestRouteIndex = 0;

        for (uint256 i = 0; i < candidateRoutes.length; i++) {
            try this.getAmountsOut(amountIn, candidateRoutes[i]) returns (uint256[] memory amounts) {
                uint256 output = amounts[amounts.length - 1];
                if (output > bestOutput) {
                    bestOutput = output;
                    bestRouteIndex = i;
                }
            } catch {
                // Skip failed routes
            }
        }

        require(bestOutput > 0, "No viable route found");
        
        return (bestOutput, candidateRoutes[bestRouteIndex]);
    }

    function _findCandidateRoutes(
        address tokenA,
        address tokenB,
        uint256 amountIn
    ) internal view returns (Route[] memory routes) {
        // Implementation would use graph algorithms to find optimal paths
        // This is simplified for demonstration
        
        address[] memory intermediateTokens = _getPopularIntermediateTokens();
        routes = new Route[](intermediateTokens.length + 1);
        
        // Direct route
        routes[0] = _createDirectRoute(tokenA, tokenB);
        
        // Routes through intermediate tokens
        for (uint256 i = 0; i < intermediateTokens.length; i++) {
            routes[i + 1] = _create2HopRoute(tokenA, tokenB, intermediateTokens[i]);
        }
        
        return routes;
    }

    function getRouterType() external pure override returns (string memory) {
        return "MULTI_HOP";
    }
}

3. Cross-chain Router

The Cross-chain Router handles swaps across different blockchains:

contract IU2UCrossChainRouter is IIU2URouter {
    using SafeERC20 for IERC20;

    struct CrossChainParams {
        uint256 sourceChain;
        uint256 destinationChain;
        address bridgeAdapter;
        bytes bridgeData;
        address destinationRouter;
        bytes destinationSwapData;
    }

    mapping(uint256 => mapping(address => bool)) public supportedTokens;
    mapping(address => bool) public authorizedBridges;
    mapping(uint256 => address) public chainRouters;

    event CrossChainSwapInitiated(
        address indexed user,
        uint256 indexed sourceChain,
        uint256 indexed destinationChain,
        address tokenIn,
        address tokenOut,
        uint256 amountIn,
        bytes32 swapId
    );

    function swapExactTokensForTokens(
        SwapParams calldata params
    ) external payable override returns (uint256 amountOut) {
        CrossChainParams memory crossChainParams = abi.decode(
            params.extraData,
            (CrossChainParams)
        );
        
        return _executeCrossChainSwap(params, crossChainParams);
    }

    function _executeCrossChainSwap(
        SwapParams calldata params,
        CrossChainParams memory crossChainParams
    ) internal returns (uint256 amountOut) {
        require(
            authorizedBridges[crossChainParams.bridgeAdapter],
            "Unauthorized bridge"
        );
        
        bytes32 swapId = keccak256(
            abi.encodePacked(
                msg.sender,
                params.tokenIn,
                params.tokenOut,
                params.amountIn,
                block.timestamp
            )
        );

        // Step 1: Handle source chain operations
        if (params.tokenIn != _getBridgeToken(crossChainParams.sourceChain)) {
            // Swap to bridge token on source chain
            uint256 bridgeAmount = _swapToBridgeToken(
                params.tokenIn,
                params.amountIn,
                crossChainParams.sourceChain
            );
            params.amountIn = bridgeAmount;
        }

        // Step 2: Initiate bridge transfer
        IBridgeAdapter bridge = IBridgeAdapter(crossChainParams.bridgeAdapter);
        
        IERC20(params.tokenIn).safeApprove(crossChainParams.bridgeAdapter, params.amountIn);
        
        uint256 bridgeFee = bridge.calculateFee(
            crossChainParams.sourceChain,
            crossChainParams.destinationChain,
            params.amountIn
        );
        
        bridge.bridgeTokens{value: bridgeFee}(
            params.tokenIn,
            params.amountIn,
            crossChainParams.destinationChain,
            params.recipient,
            crossChainParams.bridgeData
        );

        emit CrossChainSwapInitiated(
            msg.sender,
            crossChainParams.sourceChain,
            crossChainParams.destinationChain,
            params.tokenIn,
            params.tokenOut,
            params.amountIn,
            swapId
        );

        // Return estimated output (actual output depends on destination chain execution)
        return _estimateCrossChainOutput(params, crossChainParams);
    }

    function _swapToBridgeToken(
        address tokenIn,
        uint256 amountIn,
        uint256 chainId
    ) internal returns (uint256 bridgeAmount) {
        address bridgeToken = _getBridgeToken(chainId);
        
        if (tokenIn == bridgeToken) {
            return amountIn;
        }

        // Use simple router to swap to bridge token
        IIU2URouter simpleRouter = IIU2URouter(chainRouters[chainId]);
        
        SwapParams memory swapParams = SwapParams({
            tokenIn: tokenIn,
            tokenOut: bridgeToken,
            amountIn: amountIn,
            amountOutMin: 0, // Will calculate proper minimum
            pools: new address[](1),
            deadline: block.timestamp + 300,
            recipient: address(this),
            extraData: ""
        });
        
        // Get best pool for swap
        (, Route memory route) = simpleRouter.quote(tokenIn, bridgeToken, amountIn);
        swapParams.pools[0] = route.pools[0];
        swapParams.amountOutMin = _calculateMinOutput(route, amountIn);

        return simpleRouter.swapExactTokensForTokens(swapParams);
    }

    function quote(
        address tokenA,
        address tokenB,
        uint256 amountIn
    ) external view override returns (uint256 amountOut, Route memory optimalRoute) {
        // For cross-chain quotes, we need to estimate the full journey
        CrossChainParams memory params = _getOptimalCrossChainRoute(tokenA, tokenB);
        
        // Estimate source chain swap (if needed)
        uint256 bridgeAmount = amountIn;
        if (tokenA != _getBridgeToken(params.sourceChain)) {
            (, Route memory sourceRoute) = IIU2URouter(chainRouters[params.sourceChain])
                .quote(tokenA, _getBridgeToken(params.sourceChain), amountIn);
            uint256[] memory sourceAmounts = IIU2URouter(chainRouters[params.sourceChain])
                .getAmountsOut(amountIn, sourceRoute);
            bridgeAmount = sourceAmounts[sourceAmounts.length - 1];
        }

        // Estimate bridge fee
        IBridgeAdapter bridge = IBridgeAdapter(params.bridgeAdapter);
        uint256 bridgeFee = bridge.calculateFee(
            params.sourceChain,
            params.destinationChain,
            bridgeAmount
        );
        uint256 destinationAmount = bridgeAmount - bridgeFee;

        // Estimate destination chain swap (if needed)
        uint256 finalAmount = destinationAmount;
        if (_getBridgeToken(params.destinationChain) != tokenB) {
            (, Route memory destRoute) = IIU2URouter(chainRouters[params.destinationChain])
                .quote(_getBridgeToken(params.destinationChain), tokenB, destinationAmount);
            uint256[] memory destAmounts = IIU2URouter(chainRouters[params.destinationChain])
                .getAmountsOut(destinationAmount, destRoute);
            finalAmount = destAmounts[destAmounts.length - 1];
        }

        // Build cross-chain route representation
        optimalRoute = _buildCrossChainRoute(tokenA, tokenB, params);
        
        return (finalAmount, optimalRoute);
    }

    function getRouterType() external pure override returns (string memory) {
        return "CROSS_CHAIN";
    }
}

4. Aggregation Router

The Aggregation Router combines quotes from multiple DEXes for optimal pricing:

contract IU2UAggregationRouter is IIU2URouter {
    using SafeERC20 for IERC20;

    struct AggregationResult {
        address[] dexes;
        uint256[] amounts;
        uint256[] expectedOutputs;
        uint256 totalOutput;
        bytes[] swapData;
    }

    mapping(address => uint256) public dexWeights;
    uint256 public constant PRECISION = 1e18;
    uint256 public maxSlippageAggregation = 300; // 3%

    function swapExactTokensForTokens(
        SwapParams calldata params
    ) external payable override returns (uint256 totalAmountOut) {
        AggregationResult memory result = abi.decode(params.extraData, (AggregationResult));
        
        require(result.dexes.length > 0, "No DEXes specified");
        require(result.amounts.length == result.dexes.length, "Mismatched arrays");
        
        // Transfer tokens from user
        IERC20(params.tokenIn).safeTransferFrom(
            msg.sender,
            address(this),
            params.amountIn
        );

        // Execute swaps across multiple DEXes
        for (uint256 i = 0; i < result.dexes.length; i++) {
            if (result.amounts[i] == 0) continue;
            
            uint256 outputAmount = _executeAggregatedSwap(
                result.dexes[i],
                params.tokenIn,
                params.tokenOut,
                result.amounts[i],
                result.swapData[i]
            );
            
            totalAmountOut += outputAmount;
        }

        require(totalAmountOut >= params.amountOutMin, "Insufficient output");

        // Transfer final tokens to recipient
        IERC20(params.tokenOut).safeTransfer(params.recipient, totalAmountOut);
        
        return totalAmountOut;
    }

    function _executeAggregatedSwap(
        address dex,
        address tokenIn,
        address tokenOut,
        uint256 amountIn,
        bytes memory swapData
    ) internal returns (uint256 amountOut) {
        uint256 balanceBefore = IERC20(tokenOut).balanceOf(address(this));
        
        IERC20(tokenIn).safeApprove(dex, amountIn);
        
        // Execute the swap using the DEX-specific data
        (bool success, bytes memory result) = dex.call(swapData);
        require(success, "Aggregated swap failed");
        
        uint256 balanceAfter = IERC20(tokenOut).balanceOf(address(this));
        amountOut = balanceAfter - balanceBefore;
        
        return amountOut;
    }

    function quote(
        address tokenA,
        address tokenB,
        uint256 amountIn
    ) external view override returns (uint256 amountOut, Route memory optimalRoute) {
        // Get quotes from all available DEXes
        address[] memory availableDEXes = getSupportedDEXes();
        uint256[] memory individualQuotes = new uint256[](availableDEXes.length);
        uint256[] memory liquidityWeights = new uint256[](availableDEXes.length);
        
        uint256 totalLiquidity = 0;
        
        for (uint256 i = 0; i < availableDEXes.length; i++) {
            try this._getIndividualQuote(availableDEXes[i], tokenA, tokenB, amountIn) 
                returns (uint256 quote, uint256 liquidity) {
                individualQuotes[i] = quote;
                liquidityWeights[i] = liquidity;
                totalLiquidity += liquidity;
            } catch {
                // DEX not available or no liquidity
                individualQuotes[i] = 0;
                liquidityWeights[i] = 0;
            }
        }

        // Calculate optimal distribution
        AggregationResult memory result = _calculateOptimalDistribution(
            availableDEXes,
            individualQuotes,
            liquidityWeights,
            amountIn,
            totalLiquidity
        );

        optimalRoute = _buildAggregationRoute(tokenA, tokenB, result);
        
        return (result.totalOutput, optimalRoute);
    }

    function _calculateOptimalDistribution(
        address[] memory dexes,
        uint256[] memory quotes,
        uint256[] memory weights,
        uint256 totalAmount,
        uint256 totalLiquidity
    ) internal pure returns (AggregationResult memory result) {
        result.dexes = dexes;
        result.amounts = new uint256[](dexes.length);
        result.expectedOutputs = new uint256[](dexes.length);
        result.swapData = new bytes[](dexes.length);
        
        // Simple distribution based on liquidity weights
        // More sophisticated algorithms could optimize for price impact
        for (uint256 i = 0; i < dexes.length; i++) {
            if (weights[i] > 0 && quotes[i] > 0) {
                result.amounts[i] = (totalAmount * weights[i]) / totalLiquidity;
                result.expectedOutputs[i] = (quotes[i] * result.amounts[i]) / totalAmount;
                result.totalOutput += result.expectedOutputs[i];
            }
        }
        
        return result;
    }

    function getRouterType() external pure override returns (string memory) {
        return "AGGREGATION";
    }
}

5. Split Router

The Split Router divides large orders to minimize price impact:

contract IU2USplitRouter is IIU2URouter {
    using SafeERC20 for IERC20;

    struct SplitOrder {
        uint256[] amounts;
        address[] pools;
        uint256[] delays;
        uint256 totalParts;
    }

    mapping(bytes32 => SplitOrder) public splitOrders;
    mapping(bytes32 => uint256) public executedParts;
    
    uint256 public constant MAX_SPLITS = 10;
    uint256 public constant MIN_SPLIT_DELAY = 60; // 1 minute

    event SplitOrderCreated(bytes32 indexed orderId, address indexed user, uint256 totalParts);
    event SplitOrderPartExecuted(bytes32 indexed orderId, uint256 part, uint256 amountOut);

    function createSplitOrder(
        SwapParams calldata params,
        uint256 splits,
        uint256 delayBetweenSplits
    ) external returns (bytes32 orderId) {
        require(splits <= MAX_SPLITS, "Too many splits");
        require(delayBetweenSplits >= MIN_SPLIT_DELAY, "Delay too short");
        
        orderId = keccak256(
            abi.encodePacked(
                msg.sender,
                params.tokenIn,
                params.tokenOut,
                params.amountIn,
                block.timestamp
            )
        );

        SplitOrder storage order = splitOrders[orderId];
        order.totalParts = splits;
        order.amounts = new uint256[](splits);
        order.pools = new address[](splits);
        order.delays = new uint256[](splits);

        // Calculate split amounts (could be optimized based on liquidity)
        uint256 baseAmount = params.amountIn / splits;
        uint256 remainder = params.amountIn % splits;

        for (uint256 i = 0; i < splits; i++) {
            order.amounts[i] = baseAmount + (i < remainder ? 1 : 0);
            order.pools[i] = params.pools[0]; // Simplified - could optimize per split
            order.delays[i] = i * delayBetweenSplits;
        }

        // Transfer all tokens upfront
        IERC20(params.tokenIn).safeTransferFrom(
            msg.sender,
            address(this),
            params.amountIn
        );

        emit SplitOrderCreated(orderId, msg.sender, splits);
        
        return orderId;
    }

    function executeSplitOrderPart(
        bytes32 orderId,
        uint256 partIndex,
        SwapParams calldata params
    ) external returns (uint256 amountOut) {
        SplitOrder storage order = splitOrders[orderId];
        require(partIndex < order.totalParts, "Invalid part index");
        require(
            block.timestamp >= order.delays[partIndex],
            "Part not ready for execution"
        );
        
        // Check if part already executed
        require(
            (executedParts[orderId] & (1 << partIndex)) == 0,
            "Part already executed"
        );

        // Mark part as executed
        executedParts[orderId] |= (1 << partIndex);

        // Execute the swap for this part
        amountOut = _executeSingleSplit(
            order.pools[partIndex],
            params.tokenIn,
            params.tokenOut,
            order.amounts[partIndex],
            params.recipient
        );

        emit SplitOrderPartExecuted(orderId, partIndex, amountOut);
        
        return amountOut;
    }

    function _executeSingleSplit(
        address pool,
        address tokenIn,
        address tokenOut,
        uint256 amountIn,
        address recipient
    ) internal returns (uint256 amountOut) {
        // Get the appropriate router for this pool
        IIU2URouter router = _getRouterForPool(pool);
        
        IERC20(tokenIn).safeApprove(address(router), amountIn);
        
        SwapParams memory splitParams = SwapParams({
            tokenIn: tokenIn,
            tokenOut: tokenOut,
            amountIn: amountIn,
            amountOutMin: 0, // Calculate based on current market
            pools: new address[](1),
            deadline: block.timestamp + 300,
            recipient: recipient,
            extraData: ""
        });
        splitParams.pools[0] = pool;

        return router.swapExactTokensForTokens(splitParams);
    }

    function getRouterType() external pure override returns (string memory) {
        return "SPLIT";
    }
}

6. Flash Router

The Flash Router enables atomic multi-step operations using flash loans:

contract IU2UFlashRouter is IIU2URouter, IFlashLoanReceiver {
    using SafeERC20 for IERC20;

    struct FlashOperation {
        address[] tokens;
        uint256[] amounts;
        address[] pools;
        bytes[] swapData;
        address finalRecipient;
        uint256 expectedProfit;
    }

    mapping(address => bool) public authorizedFlashProviders;
    uint256 public constant MAX_FLASH_FEE = 100; // 1%

    event FlashSwapExecuted(
        address indexed user,
        address indexed tokenIn,
        address indexed tokenOut,
        uint256 amountIn,
        uint256 amountOut,
        uint256 profit
    );

    function swapExactTokensForTokens(
        SwapParams calldata params
    ) external payable override returns (uint256 amountOut) {
        FlashOperation memory operation = abi.decode(params.extraData, (FlashOperation));
        
        // Initiate flash loan
        IFlashLoanProvider provider = _getBestFlashProvider(operation.tokens[0], operation.amounts[0]);
        
        require(
            authorizedFlashProviders[address(provider)],
            "Unauthorized flash provider"
        );

        provider.flashLoan(
            operation.tokens[0],
            operation.amounts[0],
            abi.encode(operation, msg.sender)
        );

        return operation.expectedProfit; // Return expected profit from arbitrage
    }

    function executeOperation(
        address asset,
        uint256 amount,
        uint256 fee,
        bytes calldata params
    ) external override returns (bool) {
        require(authorizedFlashProviders[msg.sender], "Unauthorized caller");
        
        (FlashOperation memory operation, address originalCaller) = abi.decode(
            params,
            (FlashOperation, address)
        );

        uint256 totalOwed = amount + fee;
        uint256 currentAmount = amount;

        // Execute the operation steps
        for (uint256 i = 0; i < operation.pools.length; i++) {
            currentAmount = _executeFlashStep(
                operation.tokens[i],
                operation.tokens[i + 1],
                operation.pools[i],
                currentAmount,
                operation.swapData[i]
            );
        }

        // Ensure we have enough to repay the flash loan + profit
        require(currentAmount > totalOwed, "Insufficient profit from flash operation");
        
        uint256 profit = currentAmount - totalOwed;

        // Repay flash loan
        IERC20(asset).safeTransfer(msg.sender, totalOwed);
        
        // Send profit to original caller
        if (profit > 0) {
            IERC20(operation.tokens[operation.tokens.length - 1])
                .safeTransfer(originalCaller, profit);
        }

        emit FlashSwapExecuted(
            originalCaller,
            operation.tokens[0],
            operation.tokens[operation.tokens.length - 1],
            amount,
            currentAmount,
            profit
        );

        return true;
    }

    function _executeFlashStep(
        address tokenIn,
        address tokenOut,
        address pool,
        uint256 amountIn,
        bytes memory swapData
    ) internal returns (uint256 amountOut) {
        // Determine pool type and execute appropriate swap
        string memory poolType = _getPoolType(pool);
        
        if (keccak256(abi.encodePacked(poolType)) == keccak256("UNISWAP_V2")) {
            return _executeUniswapV2Flash(tokenIn, tokenOut, pool, amountIn);
        } else if (keccak256(abi.encodePacked(poolType)) == keccak256("UNISWAP_V3")) {
            return _executeUniswapV3Flash(tokenIn, tokenOut, pool, amountIn, swapData);
        } else {
            revert("Unsupported pool type for flash operation");
        }
    }

    function quote(
        address tokenA,
        address tokenB,
        uint256 amountIn
    ) external view override returns (uint256 amountOut, Route memory optimalRoute) {
        // For flash router, we look for arbitrage opportunities
        return _findArbitrageOpportunity(tokenA, tokenB, amountIn);
    }

    function _findArbitrageOpportunity(
        address tokenA,
        address tokenB,
        uint256 amountIn
    ) internal view returns (uint256 profit, Route memory route) {
        // Look for triangular arbitrage opportunities
        address[] memory intermediateTokens = _getArbitrageTokens();
        
        uint256 bestProfit = 0;
        Route memory bestRoute;

        for (uint256 i = 0; i < intermediateTokens.length; i++) {
            // A -> Intermediate -> B -> A
            uint256 step1Out = _getQuickQuote(tokenA, intermediateTokens[i], amountIn);
            if (step1Out == 0) continue;
            
            uint256 step2Out = _getQuickQuote(intermediateTokens[i], tokenB, step1Out);
            if (step2Out == 0) continue;
            
            uint256 step3Out = _getQuickQuote(tokenB, tokenA, step2Out);
            if (step3Out <= amountIn) continue;
            
            uint256 arbitrageProfit = step3Out - amountIn;
            
            if (arbitrageProfit > bestProfit) {
                bestProfit = arbitrageProfit;
                bestRoute = _buildArbitrageRoute(tokenA, tokenB, intermediateTokens[i]);
            }
        }

        return (bestProfit, bestRoute);
    }

    function getRouterType() external pure override returns (string memory) {
        return "FLASH";
    }
}

Router Selection Strategy

class RouterSelector {
    constructor() {
        this.routerTypes = [
            'SIMPLE',
            'MULTI_HOP', 
            'CROSS_CHAIN',
            'AGGREGATION',
            'SPLIT',
            'FLASH'
        ];
    }

    selectOptimalRouter(request) {
        const {
            fromToken,
            toToken,
            fromChain,
            toChain,
            amountIn,
            userPreferences
        } = request;

        // Cross-chain requirement
        if (fromChain !== toChain) {
            return 'CROSS_CHAIN';
        }

        // Large order optimization
        if (amountIn > this.getLargeOrderThreshold(fromToken)) {
            if (userPreferences.minimizeSlippage) {
                return 'SPLIT';
            } else if (userPreferences.optimizeForPrice) {
                return 'AGGREGATION';
            }
        }

        // Arbitrage opportunity
        if (userPreferences.enableArbitrage && this.hasArbitrageOpportunity(fromToken, toToken)) {
            return 'FLASH';
        }

        // Direct pair availability
        if (this.hasDirectPair(fromToken, toToken)) {
            return 'SIMPLE';
        }

        // Default to multi-hop for complex routes
        return 'MULTI_HOP';
    }

    getLargeOrderThreshold(token) {
        // Dynamic thresholds based on token liquidity
        const liquidityTiers = {
            'ETH': 50,     // 50 ETH
            'USDC': 100000, // 100k USDC
            'USDT': 100000, // 100k USDT
            'WBTC': 5,      // 5 WBTC
            'default': 10000 // $10k USD equivalent
        };

        return liquidityTiers[token] || liquidityTiers.default;
    }
}

Performance Comparison

Router Type	Best Use Case	Avg Gas Cost	Execution Time	Complexity
Simple	Direct swaps	150k gas	1-2 blocks	Low
Multi-hop	No direct pair	300k gas	1-2 blocks	Medium
Cross-chain	Different chains	400k+ gas	5-30 minutes	High
Aggregation	Best price	500k gas	2-3 blocks	Medium
Split	Large orders	200k per split	Variable	Medium
Flash	Arbitrage	600k gas	1 block	High

Best Practices

1. Router Selection: Choose based on trade characteristics and user preferences

2. Gas Optimization: Consider gas costs relative to trade size

3. Slippage Management: Set appropriate slippage tolerances for each router type

4. Error Handling: Implement robust fallback mechanisms

5. Security: Validate all external calls and user inputs

Resources

• DEX Aggregation Overview

• Supported DEXes

• Routing Algorithm

• Quote System

• Integration Examples