Added native eth guide support (#824)

docs/contracts/v4/guides/09-swap-routing.mdx

@@ -136,19 +136,32 @@ First, let’s define our function signature:
 
 ```solidity
 function swapExactInputSingle(
-    PoolKey calldata key,
-    uint128 amountIn,
-    uint128 minAmountOut
+    PoolKey calldata key, // PoolKey struct that identifies the v4 pool
+    uint128 amountIn, // Exact amount of tokens to swap
+    uint128 minAmountOut // Minimum amount of output tokens expected
 ) external returns (uint256 amountOut) {
     // Implementation will follow
 }
 ```
+**Important note:**
 
-The function takes:
+When swapping tokens involving native ETH, we use `Currency.wrap(address(0))` to represent ETH in the `PoolKey` struct.
 
-- `key`: The PoolKey struct that identifies the v4 pool
-- `amountIn`: The exact amount of tokens to swap
-- `minAmountOut`: The minimum amount of output tokens expected
+```solidity
+struct PoolKey {
+    /// @notice The lower currency of the pool, sorted numerically.
+    ///         For native ETH, Currency currency0 = Currency.wrap(address(0));
+    Currency currency0;
+    /// @notice The higher currency of the pool, sorted numerically
+    Currency currency1;
+    /// @notice The pool LP fee, capped at 1_000_000. If the highest bit is 1, the pool has a dynamic fee and must be exactly equal to 0x800000
+    uint24 fee;
+    /// @notice Ticks that involve positions must be a multiple of tick spacing
+    int24 tickSpacing;
+    /// @notice The hooks of the pool
+    IHooks hooks;
+}
+```
 
 ### 3.2: Encoding the Swap Command
 

docs/contracts/v4/quickstart/02-manage-liquidity/00-setup-liquidity.mdx

@@ -46,6 +46,5 @@ After cloning the repository, and installing foundry, developers can manually se
     forge-std/=lib/v4-core/lib/forge-std/src/
     permit2/=lib/v4-periphery/lib/permit2/
     solmate/=lib/v4-core/lib/solmate/
-    v4-core/=lib/v4-core/
     v4-periphery/=lib/v4-periphery/
     ```

docs/contracts/v4/quickstart/02-manage-liquidity/01-mint-position.mdx

@@ -60,6 +60,10 @@ The `MINT_POSITION` action requires the following parameters:
 | `hookData`   | _bytes_   | arbitrary data that will be forwarded to hook functions        |
 
 ```solidity
+Currency currency0 = Currency.wrap(<tokenAddress1>); // tokenAddress1 = 0 for native ETH
+Currency currency1 = Currency.wrap(<tokenAddress2>);
+PoolKey poolKey = PoolKey(currency0, currency1, 3000, 60, IHooks(hook));
+
 params[0] = abi.encode(poolKey, tickLower, tickUpper, liquidity, amount0Max, amount1Max, recipient, hookData);
 ```
 
@@ -79,7 +83,9 @@ The entrypoint for all liquidity operations is `modifyLiquidities()`
 ```solidity
 uint256 deadline = block.timestamp + 60;
 
-posm.modifyLiquidities(
+uint256 valueToPass = currency0.isAddressZero() ? amount0Max : 0;
+
+posm.modifyLiquidities{value: valueToPass}(
     abi.encode(actions, params),
     deadline
 );

docs/contracts/v4/quickstart/02-manage-liquidity/02-increase-liquidity.mdx

@@ -102,6 +102,8 @@ The `SETTLE_PAIR` action requires the following parameters:
 In the above case, the parameter encoding is:
 
 ```solidity
+Currency currency0 = Currency.wrap(<tokenAddress1>); // tokenAddress1 = 0 for native ETH
+Currency currency1 = Currency.wrap(<tokenAddress2>);
 params[1] = abi.encode(currency0, currency1);
 ``` 
 
@@ -131,7 +133,10 @@ The entrypoint for all liquidity operations is `modifyLiquidities()`.
 
 ```solidity
 uint256 deadline = block.timestamp + 60;
-posm.modifyLiquidities(
+
+uint256 valueToPass = currency0.isAddressZero() ? amount0Max : 0;
+
+posm.modifyLiquidities{value: valueToPass}(
     abi.encode(actions, params),
     deadline
 );

docs/contracts/v4/quickstart/02-manage-liquidity/03-decrease-liquidity.mdx

@@ -95,6 +95,8 @@ The `TAKE_PAIR` action requires the following parameters:
 In the above case, the parameter encoding is:
 
 ```solidity
+Currency currency0 = Currency.wrap(<tokenAddress1>); // tokenAddress1 = 0 for native ETH
+Currency currency1 = Currency.wrap(<tokenAddress2>);
 params[1] = abi.encode(currency0, currency1, recipient);
 ``` 
 
@@ -116,7 +118,10 @@ The entrypoint for all liquidity operations is `modifyLiquidities()`.
 
 ```solidity
 uint256 deadline = block.timestamp + 60;
-posm.modifyLiquidities(
+
+uint256 valueToPass = currency0.isAddressZero() ? amount0Max : 0;
+
+posm.modifyLiquidities{value: valueToPass}(
     abi.encode(actions, params),
     deadline
 );

docs/contracts/v4/quickstart/02-manage-liquidity/04-collect.mdx

@@ -64,6 +64,8 @@ The `TAKE_PAIR` action requires the following parameters:
 * `recipient` - _address_, destination of the fee revenue for both tokens
 
 ```solidity
+Currency currency0 = Currency.wrap(<tokenAddress1>); // tokenAddress1 = 0 for native ETH
+Currency currency1 = Currency.wrap(<tokenAddress2>);
 params[1] = abi.encode(currency0, currency1, recipient);
 ```
 
@@ -73,7 +75,10 @@ The entrypoint for all liquidity operations is `modifyLiquidities()`.
 
 ```solidity
 uint256 deadline = block.timestamp + 60;
-posm.modifyLiquidities(
+
+uint256 valueToPass = currency0.isAddressZero() ? amount0Max : 0;
+
+posm.modifyLiquidities{value: valueToPass}(
     abi.encode(actions, params),
     deadline
 );

docs/contracts/v4/quickstart/03-swap.mdx

@@ -68,16 +68,6 @@ In this step, we’re importing the necessary contracts and interfaces:
 - `IPermit2`: This interface allows us to interact with the Permit2 contract, which provides enhanced token approval functionality.
 - `StateLibrary`: This provides optimized functions for interacting with the PoolManager’s state. By using `StateLibrary`, we can more efficiently read and manipulate pool states, which is crucial for many operations in Uniswap v4.
 
-**Important note:**
-
-To use the Universal Router imports, you'll need to set up remappings in your project. This can be done using a `remappings.txt` file:
-
-```
-@uniswap/universal-router/=lib/universal-router/
-
-[...]
-```
-
 ## Step 2: Implement Token Approval with Permit2
 
 `UniversalRouter` integrates with [Permit2](https://github.com/Uniswap/permit2), to enable users to have more safety, flexibility, and control over their ERC20 token approvals.
@@ -107,19 +97,32 @@ First, let’s define our function signature:
 
 ```solidity
 function swapExactInputSingle(
-    PoolKey calldata key,
-    uint128 amountIn,
-    uint128 minAmountOut
+    PoolKey calldata key, // PoolKey struct that identifies the v4 pool
+    uint128 amountIn, // Exact amount of tokens to swap
+    uint128 minAmountOut // Minimum amount of output tokens expected
 ) external returns (uint256 amountOut) {
     // Implementation will follow
 }
 ```
+**Important note:**
 
-The function takes:
+When swapping tokens involving native ETH, we use `Currency.wrap(address(0))` to represent ETH in the `PoolKey` struct.
 
-- `key`: The [PoolKey](https://github.com/Uniswap/v4-core/blob/main/src/types/PoolKey.sol) struct that identifies the v4 pool
-- `amountIn`: The exact amount of tokens to swap
-- `minAmountOut`: The minimum amount of output tokens expected
+```solidity
+struct PoolKey {
+    /// @notice The lower currency of the pool, sorted numerically.
+    ///         For native ETH, Currency currency0 = Currency.wrap(address(0));
+    Currency currency0;
+    /// @notice The higher currency of the pool, sorted numerically
+    Currency currency1;
+    /// @notice The pool LP fee, capped at 1_000_000. If the highest bit is 1, the pool has a dynamic fee and must be exactly equal to 0x800000
+    uint24 fee;
+    /// @notice Ticks that involve positions must be a multiple of tick spacing
+    int24 tickSpacing;
+    /// @notice The hooks of the pool
+    IHooks hooks;
+}
+```
 
 ### 3.2: Encoding the Swap Command