Algebra Integral
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    • ℹ️Intro
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  • ⬆️Changes v1.2.1
  • Algebra V1 / Technical Reference
    • 🔏Contracts
      • API Reference v1.0
        • V1.0 - Core
          • AlgebraFactory
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          • IAlgebraFactory
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          • IWNativeToken
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          • NFTDescriptor
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          • PeripheryImmutableState
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          • Quoter
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        • V1.0 - Tokenomics
          • AlgebraEternalFarming
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          • IAlgebraFactory
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          • IAlgebraLimitVirtualPool
          • IAlgebraPoolActions
          • IAlgebraPoolDeployer
          • IAlgebraPoolDerivedState
          • IAlgebraPoolEvents
          • IAlgebraPoolImmutables
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          • IAlgebraVirtualPoolBase
          • IDataStorageOperator
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          • IERC721Enumerable
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          • IPeripheryImmutableState
          • IPoolInitializer
          • ISwapRouter
          • IWNativeToken
          • LimitVirtualPool
          • Multicall
          • PeripheryPayments
      • API Reference v1.9
        • V1.9 - Core
          • AlgebraFactory
          • AlgebraPool
          • AlgebraPoolDeployer
          • DataStorage
          • DataStorageOperator
          • IAlgebraFactory
          • IAlgebraFlashCallback
          • IAlgebraMintCallback
          • IAlgebraPoolActions
          • IAlgebraPoolDeployer
          • IAlgebraPoolDerivedState
          • IAlgebraPoolEvents
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          • IAlgebraPoolPermissionedActions
          • IAlgebraPoolState
          • IAlgebraSwapCallback
          • IAlgebraVirtualPool
          • IDataStorageOperator
          • IERC20Minimal
          • PoolImmutables
          • PoolState
        • V1.9 - Periphery
          • ERC721Permit
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          • IERC20Metadata
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          • IERC1271
          • IMulticall
          • INonfungiblePositionManager
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        • V1.9 - Tokenomics
          • AlgebraFarming
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      • API Reference v1.9 - Directional Fees
        • V1.9 (Directional Fees) - Core
          • AlgebraFactory
          • AlgebraPool
          • AlgebraPoolDeployer
          • DataStorage
          • DataStorageOperator
          • IAlgebraFactory
          • IAlgebraFlashCallback
          • IAlgebraMintCallback
          • IAlgebraPoolActions
          • IAlgebraPoolDeployer
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        • V1.9 (Directional Fees) - Periphery
          • AlgebraInterfaceMulticall
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          • IAlgebraVirtualPoolBase
          • IERC20Minimal
          • IFarmingCenterVault
          • IFarmingCenter
          • LimitVirtualPool
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      • API Reference v2.0
        • V2.0 - Core
          • AlgebraCommunityVault
          • AlgebraFactory
          • AlgebraFeeConfiguration
          • AlgebraPool
          • AlgebraPoolBase
          • AlgebraPoolDeployer
          • DataStorage
          • DataStorageOperator
          • DerivedState
          • IAlgebraFactory
          • IAlgebraFlashCallback
          • IAlgebraMintCallback
          • IAlgebraPoolActions
          • IAlgebraPoolDeployer
          • IAlgebraPoolDerivedState
          • IAlgebraPoolErrors
          • IAlgebraPoolEvents
          • IAlgebraPoolImmutables
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          • IAlgebraPoolState
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          • IAlgebraVirtualPool
          • IDataStorageOperator
          • IERC20Minimal
          • Positions
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        • V2.0 - Periphery
          • AlgebraInterfaceMulticall
          • ERC721Permit
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          • IERC20PermitAllowed
          • IERC721Permit
          • IERC1271
          • ILimitOrderManager
          • IMulticall
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          • INonfungibleTokenPositionDescriptor
          • IPeripheryImmutableState
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          • IPeripheryPaymentsWithFee
          • IPoolInitializer
          • IPositionFollower
          • IQuoter
          • IQuoterV2
          • ISelfPermit
          • ISwapRouter
          • ITickLens
          • IV3Migrator
          • IWNativeToken
          • LimitOrderManagement
          • LimitOrderManager
          • LiquidityManagement
          • Multicall
          • NFTDescriptor
          • NonfungiblePositionManager
          • NonfungibleTokenPositionDescriptor
          • PeripheryImmutableState
          • PeripheryPayments
          • PeripheryPaymentsWithFee
          • PoolInitializer
          • Quoter
          • QuoterV2
          • SelfPermit
          • SwapRouter
          • TickLens
          • V3Migrator
        • V2.0 - Tokenomics
          • AlgebraEternalFarming
          • EternalVirtualPool
          • FarmingCenter
          • IAccessControl
          • IAlgebraEternalFarming
          • IAlgebraEternalVirtualPool
          • IFarmingCenter
          • IncentiveKey
          • VirtualTickStructure
      • API Reference v2.0 - Directional Fees
        • V2.0 (Directional Fees) - Core
          • AlgebraCommunityVault
          • AlgebraFactory
          • AlgebraFeeConfiguration
          • AlgebraPool
          • AlgebraPoolBase
          • AlgebraPoolDeployer
          • DataStorage
          • DataStorageOperator
          • DerivedState
          • IAlgebraFactory
          • IAlgebraFlashCallback
          • IAlgebraMintCallback
          • IAlgebraPoolActions
          • IAlgebraPoolDeployer
          • IAlgebraPoolDerivedState
          • IAlgebraPoolErrors
          • IAlgebraPoolEvents
          • IAlgebraPoolImmutables
          • IAlgebraPoolPermissionedActions
          • IAlgebraPoolState
          • IAlgebraSwapCallback
          • IAlgebraVirtualPool
          • IDataStorageOperator
          • IERC20Minimal
          • Positions
          • ReservesManager
        • V2.0 (Directional Fees) - Periphery
          • AlgebraInterfaceMulticall
          • ERC721Permit
          • IERC20Metadata
          • IERC20PermitAllowed
          • IERC721Permit
          • IERC1271
          • ILimitOrderManager
          • IMulticall
          • INonfungiblePositionManager
          • INonfungibleTokenPositionDescriptor
          • IPeripheryImmutableState
          • IPeripheryPayments
          • IPeripheryPaymentsWithFee
          • IPoolInitializer
          • IPositionFollower
          • IQuoter
          • IQuoterV2
          • ISelfPermit
          • ISwapRouter
          • ITickLens
          • IV3Migrator
          • IWNativeToken
          • LimitOrderManagement
          • LimitOrderManager
          • LiquidityManagement
          • Multicall
          • NFTDescriptor
          • NonfungiblePositionManager
          • NonfungibleTokenPositionDescriptor
          • PeripheryImmutableState
          • PeripheryPayments
          • PeripheryPaymentsWithFee
          • PoolInitializer
          • QuoterV2
          • Quoter
          • SelfPermit
          • SwapRouter
          • TickLens
          • V3Migrator
        • V2.0 (Directional Fees) - Tokenomics
          • AlgebraEternalFarming
          • EternalVirtualPool
          • FarmingCenter
          • IAccessControl
          • IAlgebraEternalFarming
          • IAlgebraEternalVirtualPool
          • IFarmingCenter
          • IncentiveKey
          • VirtualTickStructure
      • Adaptive Fee
        • Adaptive Fee
        • How to set up specific formula behaviour
        • How to tweak formula behaviour
      • Contracts Setup
        • Deployment
          • Contracts Deployment
          • Deployment Scripts
        • Misc
          • POOL_INIT_CODE_HASH
          • Code Audits
          • Deployment Addresses
      • The Algebra Guides
        • Flash Integrations
          • The Full Contract
          • Calling Flash
          • Flash Callback
          • Inheritance constructor
        • Liquidity Mining
          • Liquidity Mining Overview
        • Providing Liquidity
          • Collecting fees
          • Decrease liquidity
          • Increase Liquidity Within The Current Range
          • Mint a new position
          • Set up your contract
          • The full contract
        • Swaps
          • Multihop swaps
          • Single swaps
    • 📊Subgraph
      • Query Examples
        • Query Examples
      • GraphQL Schema
        • Farming GraphQL Schema
        • Algebra GraphQL Schema
      • Subgraph Setup
        • Subgraph Settings
        • Subgraph Deployment
    • 🖥️Frontend
      • Admin Panel
        • Contracts
          • Admin Panel
          • Changing Subgraph
        • Eternal Farmings
          • Create Eternal Farming
          • Managing Eternal Farming
        • Limit Farmings
          • Create Limit Farming
    • ⚙️Backend
      • Backend Setup
    • ⛑️Guides
      • Step by Step Deployment
  • Other
    • 📦Archived Documentation
    • ❗Link Awareness Notice
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On this page
  1. Algebra Integral / Technical Reference
  2. Integration Process
  3. Technical Guides
  4. Flashloans

Final contract

// SPDX-License-Identifier: GPL-2.0-or-later
pragma solidity =0.8.20;

import '@cryptoalgebra/integral-core/contracts/interfaces/callback/IAlgebraFlashCallback.sol';

import '@cryptoalgebra/integral-periphery/contracts/base/PeripheryPayments.sol';
import '@cryptoalgebra/integral-periphery/contracts/base/PeripheryImmutableState.sol';
import '@cryptoalgebra/integral-periphery/contracts/libraries/PoolAddress.sol';
import '@cryptoalgebra/integral-periphery/contracts/libraries/CallbackValidation.sol';
import '@cryptoalgebra/integral-periphery/contracts/libraries/TransferHelper.sol';
import '@cryptoalgebra/integral-periphery/contracts/interfaces/ISwapRouter.sol';

/// @title Flash contract implementation
/// @notice An example contract using the Algebra flash function
contract PairFlash is IAlgebraFlashCallback, PeripheryImmutableState, PeripheryPayments {
    ISwapRouter public immutable swapRouter;

    constructor(
        ISwapRouter _swapRouter,
        address _factory,
        address _WMATIC,
        address _poolDeployer
    ) PeripheryImmutableState(_factory, _WMATIC, _poolDeployer) {
        swapRouter = _swapRouter;
    }

    /// @param fee0 The fee from calling flash for token0
    /// @param fee1 The fee from calling flash for token1
    /// @param data The data needed in the callback passed as FlashCallbackData from `initFlash`
    /// @notice implements the callback called from flash
    /// @dev fails if the flash is not profitable, meaning the amountOut from the flash is less than the amount borrowed
    function IAlgebraFlashCallback(
        uint256 fee0,
        uint256 fee1,
        bytes calldata data
    ) external override {
        FlashCallbackData memory decoded = abi.decode(data, (FlashCallbackData));
        CallbackValidation.verifyCallback(poolDeployer, decoded.poolKey);

        address token0 = decoded.poolKey.token0;
        address token1 = decoded.poolKey.token1;

        TransferHelper.safeApprove(token0, address(swapRouter), decoded.amount0);
        TransferHelper.safeApprove(token1, address(swapRouter), decoded.amount1);

        // profitable check
        // exactInputSingle will fail if this amount not met
        uint256 amount1Min = decoded.amount1 + fee1;
        uint256 amount0Min = decoded.amount0 + fee0;

        // call exactInputSingle for swapping token1 for token0 in pool
        uint256 amountOut0 =
            swapRouter.exactInputSingle(
                ISwapRouter.ExactInputSingleParams({
                    tokenIn: token1,
                    tokenOut: token0,
                    recipient: address(this),
                    deadline: block.timestamp,
                    amountIn: decoded.amount1,
                    amountOutMinimum: amount0Min,
                    sqrtPriceLimitX96: 0
                })
            );

        // call exactInputSingle for swapping token0 for token 1 in pool
        uint256 amountOut1 =
            swapRouter.exactInputSingle(
                ISwapRouter.ExactInputSingleParams({
                    tokenIn: token0,
                    tokenOut: token1,
                    recipient: address(this),
                    deadline: block.timestamp,
                    amountIn: decoded.amount0,
                    amountOutMinimum: amount1Min,
                    sqrtPriceLimitX96: 0
                })
            );

        // end up with amountOut0 of token0 from first swap and amountOut1 of token1 from second swap
        uint256 amount0Owed = decoded.amount0 + fee0;
        uint256 amount1Owed = decoded.amount1 + fee1;

        TransferHelper.safeApprove(token0, address(this), amount0Owed);
        TransferHelper.safeApprove(token1, address(this), amount1Owed);

        if (amount0Owed > 0) pay(token0, address(this), msg.sender, amount0Owed);
        if (amount1Owed > 0) pay(token1, address(this), msg.sender, amount1Owed);

        // if profitable pay profits to payer
        if (amountOut0 > amount0Owed) {
            uint256 profit0 = amountOut0 - amount0Owed;

            TransferHelper.safeApprove(token0, address(this), profit0);
            pay(token0, address(this), decoded.payer, profit0);
        }
        if (amountOut1 > amount1Owed) {
            uint256 profit1 = amountOut1 - amount1Owed;
            TransferHelper.safeApprove(token0, address(this), profit1);
            pay(token1, address(this), decoded.payer, profit1);
        }
    }

    struct FlashParams {
        address token0;
        address token1;
        uint256 amount0;
        uint256 amount1;
    }

    struct FlashCallbackData {
        uint256 amount0;
        uint256 amount1;
        address payer;
        PoolAddress.PoolKey poolKey;
    }

    /// @param params The parameters necessary for flash and the callback, passed in as FlashParams
    /// @notice Calls the pools flash function with data needed in `algebraFlashCallback`
    function initFlash(FlashParams memory params) external {
        PoolAddress.PoolKey memory poolKey =
            PoolAddress.PoolKey({token0: params.token0, token1: params.token1});
        IAlgebraPool pool = IAlgebraPool(PoolAddress.computeAddress(poolDeployer, poolKey));
        // recipient of borrowed amounts
        // amount of token0 requested to borrow
        // amount of token1 requested to borrow
        // need amount 0 and amount1 in callback to pay back pool
        // recipient of flash should be THIS contract
        pool.flash(
            address(this),
            params.amount0,
            params.amount1,
            abi.encode(
                FlashCallbackData({
                    amount0: params.amount0,
                    amount1: params.amount1,
                    payer: msg.sender,
                    poolKey: poolKey,
                })
            )
        );
    }
}
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