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Documentation Index

Fetch the complete documentation index at: https://tech.ramses.xyz/llms.txt

Use this file to discover all available pages before exploring further.

Ramses V3 uses interfaces compatible with Uniswap V3, so you can use the @uniswap/v3-periphery and @uniswap/v3-core npm packages for interface definitions. The callback function names (uniswapV3FlashCallback, etc.) remain the same for compatibility.
This guide builds a contract that calls flash on a Ramses V3 pool and arbitrages the price difference between pools with different fee tiers for the same token pair.

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Flash Transactions Overview

flash withdraws specified amounts of both token0 and token1 to a recipient. The withdrawn amount plus fees must be repaid by the end of the transaction. A data parameter allows passing arbitrary abi-encoded data to the callback. 
    function flash(
        address recipient,
        uint256 amount0,
        uint256 amount1,
        bytes calldata data
    ) external override lock noDelegateCall {

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The Flash Callback

Inside flash, the pool calls back into msg.sender: 
IUniswapV3FlashCallback(msg.sender).uniswapV3FlashCallback(fee0, fee1, data);
This is where you implement your custom logic. Three callbacks exist: uniswapV3SwapCallback, uniswapV3MintCallback, and uniswapV3FlashCallback.

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Contract Setup

Inherit IUniswapV3FlashCallback and PeripheryPayments. PeripheryPayments extends other contracts we need, including LowGasSafeMath. 
pragma solidity =0.7.6;
pragma abicoder v2;

import '@uniswap/v3-core/contracts/interfaces/callback/IUniswapV3FlashCallback.sol';
import '@uniswap/v3-core/contracts/libraries/LowGasSafeMath.sol';

import '@uniswap/v3-periphery/contracts/base/PeripheryPayments.sol';
import '@uniswap/v3-periphery/contracts/base/PeripheryImmutableState.sol';
import '@uniswap/v3-periphery/contracts/libraries/PoolAddress.sol';
import '@uniswap/v3-periphery/contracts/libraries/CallbackValidation.sol';
import '@uniswap/v3-periphery/contracts/libraries/TransferHelper.sol';
import '@uniswap/v3-periphery/contracts/interfaces/ISwapRouter.sol';

contract PairFlash is IUniswapV3FlashCallback, PeripheryPayments {
    using LowGasSafeMath for uint256;
    using LowGasSafeMath for int256;

    ISwapRouter public immutable swapRouter;

    constructor(
        ISwapRouter _swapRouter,
        address _factory,
        address _WETH9
    ) PeripheryImmutableState(_factory, _WETH9) {
        swapRouter = _swapRouter;
    }
}