# Router Exercises In this exercise, you'll learn how to swap tokens with the [`PoolManager`](https://github.com/Uniswap/v4-core/blob/main/src/PoolManager.sol) contract. The starter code for this exercise is provided in [`foundry/src/exercises/Router.sol`](https://github.com/Cyfrin/defi-uniswap-v4/blob/main/foundry/src/exercises/Router.sol) Solution is in [`foundry/src/solutions/Router.sol`](https://github.com/Cyfrin/defi-uniswap-v4/blob/main/foundry/src/solutions/Router.sol) ## Task 1 - Single hop swap exact input ```solidity function swapExactInputSingle(ExactInputSingleParams calldata params) external payable setAction(SWAP_EXACT_IN_SINGLE) returns (uint256 amountOut) { // Write your code here } ``` Implement this function so it performs a swap against a single pool in the `PoolManager` contract. - Swap the full amount of the input currency specified by `ExactInputSingleParams.amountIn` for the maximum possible amount of the other currency in the pool. - Revert if the received output amount is less than `ExactInputSingleParams.amountOutMin`. - Return any unused tokens back to the caller. - Return the amount of currency out (`amountOut`). ## Task 2 - Single hop swap exact output ```solidity function swapExactOutputSingle(ExactOutputSingleParams calldata params) external payable setAction(SWAP_EXACT_OUT_SINGLE) returns (uint256 amountIn) { // Write your code here } ``` Implement this function so it performs a swap against a single pool in the `PoolManager` contract. - Swap the minimum amount of the input currency for the exact amount of output specified by `ExactOutputSingleParams.amountOut` of the other currency in the pool. - Revert if the input amount is greater than `ExactOutputSingleParams.amountInMax`. - Return any unused tokens back to the caller. - Return the amount of currency in (`amountIn`) ## Task 3 - Multi hops swap exact input ```solidity function swapExactInput(ExactInputParams calldata params) external payable setAction(SWAP_EXACT_IN) returns (uint256 amountOut) { // Write your code here } ``` Implement this function so it performs a swap against multiple pools in the `PoolManager` contract. - Swap the full amount of the input currency specified by `ExactInputParams.amountIn` for the maximum possible amount of the final currency specified in the last element of `ExactInputParams.path`. - Revert if the received output amount is less than `ExactInputParams.amountOutMin`. - Return any unused tokens back to the caller. - Return the amount of currency out (`amountOut`). ## Task 4 - Multi hops swap exact output ```solidity function swapExactOutput(ExactOutputParams calldata params) external payable setAction(SWAP_EXACT_OUT) returns (uint256 amountIn) { // Write your code here } ``` Implement this function so it performs a swap against multiple pools in the `PoolManager` contract. - Swap the minimum amount of the input currency for the exact amount of output specified by `ExactOutputParams.amountOut` of the final currency specified in `ExactOutputParams.currencyOut`. - Revert if the input amount is greater than `ExactOutputParams.amountInMax`. - Return any unused tokens back to the caller. - Return the amount of currency in (`amountIn`) ## Test ```shell forge test --fork-url $FORK_URL --fork-block-number $FORK_BLOCK_NUM --match-path test/Router.test.sol -vvv ```