swap fee information

forge-test/SwapFee.t.sol

@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.19;
+
+import "forge-std/Test.sol";
+import {IHooks} from "v4-core/interfaces/IHooks.sol";
+import {Hooks} from "v4-core/libraries/Hooks.sol";
+import {TickMath} from "v4-core/libraries/TickMath.sol";
+import {IPoolManager} from "v4-core/interfaces/IPoolManager.sol";
+import {PoolKey} from "v4-core/types/PoolKey.sol";
+import {BalanceDelta} from "v4-core/types/BalanceDelta.sol";
+import {PoolId, PoolIdLibrary} from "v4-core/types/PoolId.sol";
+import {Constants} from "v4-core/../test/utils/Constants.sol";
+import {CurrencyLibrary, Currency} from "v4-core/types/Currency.sol";
+import {HookTest} from "@v4-by-example/utils/HookTest.sol";
+import {HookMiner} from "./utils/HookMiner.sol";
+import {GasSnapshot} from "forge-gas-snapshot/GasSnapshot.sol";
+import {PoolSwapTest} from "v4-core/test/PoolSwapTest.sol";
+
+contract SwapFeeTest is HookTest, GasSnapshot {
+    using PoolIdLibrary for PoolKey;
+    using CurrencyLibrary for Currency;
+
+    PoolKey poolKey;
+    PoolId poolId;
+
+    function setUp() public {
+        // creates the pool manager, test tokens, and other utility routers
+        HookTest.initHookTestEnv();
+
+        // Create the pool
+        poolKey =
+            PoolKey(Currency.wrap(address(token0)), Currency.wrap(address(token1)), 3000, 60, IHooks(address(0x0)));
+        poolId = poolKey.toId();
+        initializeRouter.initialize(poolKey, Constants.SQRT_RATIO_1_1, ZERO_BYTES);
+
+        // Provide liquidity to the pool
+        modifyPositionRouter.modifyLiquidity(poolKey, IPoolManager.ModifyLiquidityParams(-60, 60, 10 ether), ZERO_BYTES);
+        modifyPositionRouter.modifyLiquidity(
+            poolKey, IPoolManager.ModifyLiquidityParams(-120, 120, 10 ether), ZERO_BYTES
+        );
+        modifyPositionRouter.modifyLiquidity(
+            poolKey,
+            IPoolManager.ModifyLiquidityParams(TickMath.minUsableTick(60), TickMath.maxUsableTick(60), 10 ether),
+            ZERO_BYTES
+        );
+    }
+
+    function test_zeroForOne_exactInput() public {
+        uint256 balance0Before = token0.balanceOf(address(this));
+        uint256 balance1Before = token1.balanceOf(address(this));
+
+        // Perform a test swap //
+        int256 amount = 1e18;
+        bool zeroForOne = true;
+        BalanceDelta swapDelta = swap(poolKey, amount, zeroForOne, ZERO_BYTES);
+        // ------------------- //
+
+        uint256 balance0After = token0.balanceOf(address(this));
+        uint256 balance1After = token1.balanceOf(address(this));
+
+        assertEq(balance0Before - balance0After, 1e18);
+        assertApproxEqAbs(balance1After - balance1Before, 1e18, 0.1e18); // fee on output token
+    }
+
+    function test_zeroForOne_exactOutput() public {
+        uint256 balance0Before = token0.balanceOf(address(this));
+        uint256 balance1Before = token1.balanceOf(address(this));
+
+        // Perform a test swap //
+        int256 amount = -1e18;
+        bool zeroForOne = true;
+        BalanceDelta swapDelta = swap(poolKey, amount, zeroForOne, ZERO_BYTES);
+        // ------------------- //
+
+        uint256 balance0After = token0.balanceOf(address(this));
+        uint256 balance1After = token1.balanceOf(address(this));
+
+        assertApproxEqAbs(balance0Before - balance0After, 1e18, 0.1e18); // fee on input token
+        assertEq(balance1After - balance1Before, 1e18);
+    }
+
+    function test_oneForZero_exactInput() public {
+        uint256 balance0Before = token0.balanceOf(address(this));
+        uint256 balance1Before = token1.balanceOf(address(this));
+
+        // Perform a test swap //
+        int256 amount = 1e18;
+        bool zeroForOne = false;
+        BalanceDelta swapDelta = swap(poolKey, amount, zeroForOne, ZERO_BYTES);
+        // ------------------- //
+
+        uint256 balance0After = token0.balanceOf(address(this));
+        uint256 balance1After = token1.balanceOf(address(this));
+
+        // fee on output token 0
+        assertEq(balance1Before - balance1After, 1e18);
+        assertApproxEqAbs(balance0After - balance0Before, 1e18, 0.1e18);
+    }
+
+    function test_oneForZero_exactOutput() public {
+        uint256 balance0Before = token0.balanceOf(address(this));
+        uint256 balance1Before = token1.balanceOf(address(this));
+
+        // Perform a test swap //
+        int256 amount = -1e18;
+        bool zeroForOne = false;
+        BalanceDelta swapDelta = swap(poolKey, amount, zeroForOne, ZERO_BYTES);
+        // ------------------- //
+
+        uint256 balance0After = token0.balanceOf(address(this));
+        uint256 balance1After = token1.balanceOf(address(this));
+
+        // fee on input token
+        assertApproxEqAbs(balance1Before - balance1After, 1e18, 0.1e18);
+        assertEq(balance0After - balance0Before, 1e18);
+    }
+}

src/keywords.json

@@ -45,6 +45,13 @@
     "custom curve",
     "custom accounting"
   ],
+  "/fees/swap-fee": [
+    "fees",
+    "swap",
+    "swap fee",
+    "lp fee",
+    "fee tier"
+  ],
   "/fees/fixed-hook-fee": [
     "hook",
     "hooks",

src/nav.ts

@@ -45,6 +45,10 @@ export const HOOK_ROUTES: Route[] = [
 ]
 
 const FEE_ROUTES: Route[] = [
+  {
+    path: "swap-fee",
+    title: "Swap Fee"
+  },
   {
     path: "fixed-hook-fee",
     title: "Static Hook Fee"

src/pages/fees/swap-fee/SetSwapFee.solsnippet

@@ -0,0 +1,12 @@
+uint24 swapFee = 500; // 0.05% swap fee, 3000 = 0.30%
+
+// ----------------------------------------------- //
+
+PoolKey memory pool = PoolKey({
+    currency0: Currency.wrap(token0),
+    currency1: Currency.wrap(token1),
+    fee: swapFee,                     // <-- Setting the Swap Fee -- //
+    tickSpacing: tickSpacing,
+    hooks: IHooks(address(0x0))
+});
+initializeRouter.initialize(pool, ...);

src/pages/fees/swap-fee/index.html.ts

@@ -0,0 +1,60 @@
+// metadata
+export const version = "0.8.20"
+export const title = "Swap Fees"
+export const description = "Swap Fees in v4"
+
+export const keywords = [
+    "fees",
+    "swap",
+    "swap fee",
+    "lp fee",
+    "fee tier",
+]
+
+export const codes = [
+    {
+        fileName: "SetSwapFee.sol",
+        code: "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",
+    },
+]
+
+const html = `<p>Swap fees are accrued to liquidity providers and paid by swappers. The core logic and accrual design is exactly the same as v3.</p>
+<p>In v3, there were four fixed fee-tiers <code>0.01%, 0.05%, 0.30%, and 1.0%</code>. In v4, fee-tiers are continuous</p>
+<h3>Fee Charging</h3>
+<p>Swap fees are charged on the "open" side of a trade</p>
+<ul>
+<li>exact-input: fees are taken from the output token</li>
+<li>exact-output: fees are taken on the input token</li>
+</ul>
+<p>Example:</p>
+<ul>
+<li><strong>Exact Input</strong>: User is swapping exactly 100 USDC into ETH: fee is taken from the <strong>ETH output</strong></li>
+<li><strong>Exact Output</strong>: User is willing to pay USDC for 0.01 ETH: fee is taken from the <strong>USDC input</strong></li>
+</ul>
+<h3>Note on Protocol Fee</h3>
+<p>The protocol fee is <strong>not</strong> currently enabled. However, it is expressed as a percentage of the swap fee and <em>taken</em> from the swap fee</p>
+<p>Example:</p>
+<ul>
+<li>swap fee 0.30%, protocol fee 0.10%</li>
+<li>A swapper pays 1e18 in fees (0.30% of their swap size)</li>
+<li>0.001e18 token (0.10% of 1e18) is taken for the protocol</li>
+<li>0.999e18 token (99.9% of 1e18) is given the liquidity providers</li>
+</ul>
+<hr>
+<h2>Example: Setting a Swap Fee</h2>
+<p>The swap fee is set during pool creation, as defined in its <code>PoolKey</code></p>
+<pre><code class="language-solidity"><span class="hljs-keyword">uint24</span> swapFee <span class="hljs-operator">=</span> <span class="hljs-number">500</span>; <span class="hljs-comment">// 0.05% swap fee, 3000 = 0.30%</span>
+
+<span class="hljs-comment">// ----------------------------------------------- //</span>
+
+PoolKey <span class="hljs-keyword">memory</span> pool <span class="hljs-operator">=</span> PoolKey({
+    currency0: Currency.<span class="hljs-built_in">wrap</span>(token0),
+    currency1: Currency.<span class="hljs-built_in">wrap</span>(token1),
+    fee: swapFee,                     <span class="hljs-comment">// &lt;-- Setting the Swap Fee -- //</span>
+    tickSpacing: tickSpacing,
+    hooks: IHooks(<span class="hljs-keyword">address</span>(<span class="hljs-number">0x0</span>))
+});
+initializeRouter.initialize(pool, ...);
+</code></pre>`
+
+export default html

src/pages/fees/swap-fee/index.md

@@ -0,0 +1,43 @@
+---
+title: Swap Fees
+version: 0.8.20
+description: Swap Fees in v4
+keywords: [fees, swap, swap fee, lp fee, fee tier]
+---
+
+Swap fees are accrued to liquidity providers and paid by swappers. The core logic and accrual design is exactly the same as v3.
+
+In v3, there were four fixed fee-tiers `0.01%, 0.05%, 0.30%, and 1.0%`. In v4, fee-tiers are continuous
+
+### Fee Charging
+
+Swap fees are charged on the "open" side of a trade
+
+- exact-input: fees are taken from the output token
+- exact-output: fees are taken on the input token
+
+Example:
+
+- **Exact Input**: User is swapping exactly 100 USDC into ETH: fee is taken from the **ETH output**
+- **Exact Output**: User is willing to pay USDC for 0.01 ETH: fee is taken from the **USDC input**
+
+### Note on Protocol Fee
+
+The protocol fee is **not** currently enabled. However, it is expressed as a percentage of the swap fee and _taken_ from the swap fee
+
+Example:
+
+- swap fee 0.30%, protocol fee 0.10%
+- A swapper pays 1e18 in fees (0.30% of their swap size)
+- 0.001e18 token (0.10% of 1e18) is taken for the protocol
+- 0.999e18 token (99.9% of 1e18) is given the liquidity providers
+
+---
+
+## Example: Setting a Swap Fee
+
+The swap fee is set during pool creation, as defined in its `PoolKey`
+
+```solidity
+{{{SetSwapFee}}}
+```

src/pages/fees/swap-fee/index.tsx

@@ -0,0 +1,29 @@
+import React from "react"
+import Example from "../../../components/Example"
+import html, { version, title, description, codes } from "./index.html"
+
+interface Path {
+  path: string
+  title: string
+}
+
+interface Props {
+  prev: Path | null
+  next: Path | null
+}
+
+const ExamplePage: React.FC<Props> = ({ prev, next }) => {
+  return (
+    <Example
+      version={version}
+      title={title}
+      description={description}
+      html={html}
+      prev={prev}
+      next={next}
+      codes={codes}
+    />
+  )
+}
+
+export default ExamplePage

src/pages/index.tsx

@@ -8,7 +8,7 @@ import styles from "./index.module.css"
 import youTube from "../components/youtube.png"
 import { ROUTES, ROUTES_BY_CATEGORY, TRANSLATIONS } from "../nav"
 
-const UPDATES = ["2024/01/31 - msg.sender", "2024/01/23 - Dynamic Fees", "2024/01/08 - Quoter", "2023/12/15 - Update v4", "2023/12/11 - Custom Curves", "2023/12/03 - Static Hook Fee", "2023/11/28 - Updated pool initialization", "2023/11/28 - NoOp", "2023/11/13 - Make snippets concise", "2023/10/18 - Initial V4 Snippets"]
+const UPDATES = ["2024/02/01 - Swap Fee", "2024/01/31 - msg.sender", "2024/01/23 - Dynamic Fees", "2024/01/08 - Quoter", "2023/12/15 - Update v4", "2023/12/11 - Custom Curves", "2023/12/03 - Static Hook Fee", "2023/11/28 - Updated pool initialization", "2023/11/28 - NoOp", "2023/11/13 - Make snippets concise", "2023/10/18 - Initial V4 Snippets"]
 
 export default function HomePage() {
   const [query, setQuery] = useState("")

src/routes.tsx

@@ -1,6 +1,7 @@
 import component_create_liquidity from "./pages/create-liquidity"
 import component_fees_dynamic_fee from "./pages/fees/dynamic-fee"
 import component_fees_fixed_hook_fee from "./pages/fees/fixed-hook-fee"
+import component_fees_swap_fee from "./pages/fees/swap-fee"
 import component_hooks_custom_curve from "./pages/hooks/custom-curve"
 import component_hooks_msg_sender from "./pages/hooks/msg-sender"
 import component_hooks_no_op from "./pages/hooks/no-op"
@@ -38,6 +39,10 @@ const routes: Route[] = [
         path: "/fees/fixed-hook-fee",
         component: component_fees_fixed_hook_fee
     },
+    {
+        path: "/fees/swap-fee",
+        component: component_fees_swap_fee
+    },
     {
         path: "/hooks/custom-curve",
         component: component_hooks_custom_curve

src/search.json

@@ -1,7 +1,8 @@
 {
   "swap": [
     "/swap",
-    "/hooks/no-op"
+    "/hooks/no-op",
+    "/fees/swap-fee"
   ],
   "trade": [
     "/swap"
@@ -89,6 +90,19 @@
   "custom accounting": [
     "/hooks/custom-curve"
   ],
+  "fees": [
+    "/fees/swap-fee",
+    "/fees/dynamic-fee"
+  ],
+  "swap fee": [
+    "/fees/swap-fee"
+  ],
+  "lp fee": [
+    "/fees/swap-fee"
+  ],
+  "fee tier": [
+    "/fees/swap-fee"
+  ],
   "fee": [
     "/fees/fixed-hook-fee",
     "/fees/dynamic-fee"
@@ -99,9 +113,6 @@
   "hook fee": [
     "/fees/fixed-hook-fee"
   ],
-  "fees": [
-    "/fees/dynamic-fee"
-  ],
   "dynamic fee": [
     "/fees/dynamic-fee"
   ],