fix: fee calculation logic (#10)

Co-authored-by: Kay <kehiiiiya@gmail.com>

.github/workflows/unit-test.yml

@@ -28,4 +28,4 @@ jobs:
       run: npm install
 
     - name: Run Hardhat tests
-      run: npx hardhat test
+      run: npm run test

README.md

@@ -4,7 +4,7 @@ Welcome to the repository for Wrapped PAC (WPAC) token. WPAC is a wrapped token
 
 ## Project Overview
 
-WPAC tokens are wrapped tokens of the Teleport Protocol contracts. The token contract is implemented in Solidity and follows the OpenZeppelin Contracts upgradeable pattern. It allows users to bridge PAC tokens from one blockchain to another by locking the tokens in the contract and minting WPAC tokens on the destination chain.
+WPAC tokens are wrapped tokens of the Wrapto contracts. The token contract is implemented in Solidity and follows the OpenZeppelin Contracts upgradeable pattern. It allows users to bridge PAC tokens from one blockchain to another by locking the tokens in the contract and minting WPAC tokens on the destination chain.
 
 ## Getting Started
 
@@ -42,7 +42,8 @@ In the project directory, you can run the following scripts:
 
 ## Contract Overview
 
-The main contract file is `WrappedPAC.sol` which implements the ERC20 interface. It also integrates functionalities for bridging PAC tokens from one blockchain to another. The contract is upgradeable and follows the Ownable and Pausable patterns for security and control.
+The main contract file is `wpac.sol` which implements the ERC20 interface. It also integrates functionalities for bridging PAC tokens from one blockchain to another. The contract is upgradeable and follows the Ownable and Pausable patterns for security and control.
+
 
 ## Project Structure
 
@@ -57,7 +58,7 @@ The main project files and directories are structured as follows:
 
 ## License
 
-This project is licensed under the [MIT License](LICENSE).
+Wrapto is released under [MIT License](LICENSE).
 
 ---
 

contracts/wpac.sol

@@ -7,6 +7,7 @@ import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
 import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
 import "@openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";
 import "@openzeppelin/contracts-upgradeable/security/PausableUpgradeable.sol";
+import "@openzeppelin/contracts/utils/math/Math.sol";
 
 contract WrappedPAC is Initializable, OwnableUpgradeable, PausableUpgradeable, ERC20Upgradeable, UUPSUpgradeable {
 	struct BridgeEvent {
@@ -15,7 +16,8 @@ contract WrappedPAC is Initializable, OwnableUpgradeable, PausableUpgradeable, E
 		string destinationAddress;
 		uint256 fee;
 	}
-	uint256 public constant FEE = 1_000_000_000; // 1wpac
+	uint256 public constant MIN_FEE = 1_000_000_000; // 1wpac
+	uint256 public constant MAX_FEE = 5_000_000_000; // 5wpac
 	mapping(uint256 => BridgeEvent) public bridged;
 	uint256 public counter;
 	event Bridge(address indexed sender, uint256 amount, string destinationAddress, uint256 fee);
@@ -39,13 +41,30 @@ contract WrappedPAC is Initializable, OwnableUpgradeable, PausableUpgradeable, E
 		_mint(to, amount);
 	}
 
+	function getFee(uint256 amount) public pure returns (uint256) {
+		uint256 f = Math.ceilDiv(amount, 200); // 0.5%
+
+		if (f <= MIN_FEE) {
+			return MIN_FEE;
+		} 
+
+		if (f >= MAX_FEE) {
+			return MAX_FEE;
+		}
+
+		return f;
+	}
+
 	function bridge(string memory destinationAddress, uint256 value) public whenNotPaused {
 		require(value > (1 * 1e9), "Bridge: value is low.");
-		_transfer(_msgSender(), address(this), FEE); //fee
+
+		_transfer(_msgSender(), address(this), getFee(value)); //fee
+
 		_burn(_msgSender(), value);
-		emit Bridge(_msgSender(), value, destinationAddress, FEE);
+
+		emit Bridge(_msgSender(), value, destinationAddress, getFee(value));
 		counter++;
-		bridged[counter] = BridgeEvent(_msgSender(), value - FEE, destinationAddress, FEE);
+		bridged[counter] = BridgeEvent(_msgSender(), value , destinationAddress, getFee(value));
 	}
 
 	function adminBridge(string memory destinationAddress, uint256 value) public whenNotPaused onlyOwner {

package.json

@@ -8,7 +8,7 @@
 		"packages/eslint-config"
 	],
 	"scripts": {
-		"node":"npx hardhat node",
+		"node": "npx hardhat node",
 		"compile": "cross-env TS_NODE_TRANSPILE_ONLY=true hardhat compile",
 		"clean": "shx rm -rf ./artifacts ./cache ./coverage ./src/types ./coverage.json && yarn typechain",
 		"lint:sol": "solhint --config ./.solhint.json --max-warnings 0 \"contracts/**/*.sol\"",
@@ -17,17 +17,17 @@
 		"typechain": "cross-env TS_NODE_TRANSPILE_ONLY=true hardhat typechain"
 	},
 	"devDependencies": {
-		"husky": "^8.0.3",
 		"@nomicfoundation/hardhat-toolbox": "^4.0.0",
-		"hardhat": "^2.21.0"
+		"hardhat": "^2.21.0",
+		"husky": "^8.0.3"
 	},
 	"keywords": [],
 	"author": "",
 	"license": "MIT",
 	"dependencies": {
-		"@openzeppelin/hardhat-upgrades": "^3.0.5",
 		"@openzeppelin/contracts": "^5.0.2",
 		"@openzeppelin/contracts-upgradeable": "^4.7.3",
+		"@openzeppelin/hardhat-upgrades": "^3.0.5",
 		"dotenv": "^16.4.5"
 	}
 }

test/bridge.ts

@@ -2,6 +2,7 @@ import { ethers, upgrades } from "hardhat"
 import { SignerWithAddress } from "@nomicfoundation/hardhat-ethers/signers"
 import { expect } from "chai"
 import { decimal } from "../utils/decimal"
+import { getFee } from "./utils/fee"
 
 export const shouldBehaveLikeBridge = async () => {
 	let wpac: any
@@ -42,10 +43,10 @@ export const shouldBehaveLikeBridge = async () => {
 		expect(await wpac.balanceOf(bob.address)).to.be.equal(decimal(92))
 		expect(b.destinationAddress).to.be.equal(pacAddr)
 		expect(b.sender).to.be.equal(bob.address)
-		expect(b.amount).to.be.equal(decimal(6))
-		expect(b.fee).to.be.equal(decimal(1))
+		expect(b.amount).to.be.equal(decimal(7))
+		expect(b.fee).to.be.equal(getFee(7))
 
-		expect(await wpac.balanceOf(wpac.target)).to.be.equal(decimal(1)) //Fee
+		expect(await wpac.balanceOf(wpac.target)).to.be.equal(getFee(7)) //Fee
 		expect(await wpac.totalSupply()).to.be.equal(decimal(93)) //burn
 		expect(await wpac.counter()).to.be.equal(1) //counter
 	})

test/fee.ts

@@ -0,0 +1,22 @@
+import { ethers, upgrades } from "hardhat"
+import { SignerWithAddress } from "@nomicfoundation/hardhat-ethers/signers"
+import { expect } from "chai"
+
+export const shouldBehaveLikeFee = async () => {
+	let wpac: any
+	let owner: SignerWithAddress
+
+	before(async () => {
+		const signers = await ethers.getSigners()
+		owner = signers[0]
+		const Factory = await ethers.getContractFactory("WrappedPAC")
+		const WPAC = await upgrades.deployProxy(Factory, undefined, { initializer: "initialize" })
+		wpac = await WPAC.waitForDeployment()
+	})
+
+	it("should calculate correct fee", async () => {
+		expect(await wpac.getFee(1_903_076_060_983)).to.be.equal(5_000_000_000)
+		expect(await wpac.getFee(2_874_345_000)).to.be.equal(1_000_000_000)
+		expect(await wpac.getFee(200e9)).to.be.equal(1e9)
+	})
+}

test/init.ts

@@ -17,7 +17,8 @@ export const shouldBehaveLikeInitialize = async () => {
 
 	it("should init correct", async () => {
 		expect(await wpac.owner()).to.be.equal(owner.address)
-		expect(await wpac.FEE()).to.be.equal(decimal(1))
+		expect(await wpac.MIN_FEE()).to.be.equal(decimal(1))
+		expect(await wpac.MAX_FEE()).to.be.equal(decimal(5))
 		expect(await wpac.counter()).to.be.equal(0)
 		expect(await wpac.decimals()).to.be.equal(9)
         expect(await wpac.paused()).to.be.equal(false)

test/main.ts

@@ -1,5 +1,6 @@
 import { shouldBehaveLikeAdminBridge } from "./adminBridge"
 import { shouldBehaveLikeBridge } from "./bridge"
+import { shouldBehaveLikeFee } from "./fee"
 import { shouldBehaveLikeInitialize } from "./init"
 import { shouldBehaveLikeMint } from "./mint"
 import { shouldBehaveLikeWithdrawFee } from "./withdrawFee"
@@ -23,4 +24,8 @@ describe("Wrapped PAC", function () {
 	describe("WithdrawFee", async function () {
 		shouldBehaveLikeWithdrawFee()
 	})
+
+	describe("Fee", async function () {
+		shouldBehaveLikeFee()
+	})
 })

test/utils/fee.ts

@@ -0,0 +1,15 @@
+import { decimal } from "../../utils/decimal"
+
+export function getFee(amount: number): bigint {
+	const f = amount / 200
+
+	if (f <= decimal(1)) {
+		return decimal(1)
+	}
+
+	if (f >= decimal(5)) {
+		return decimal(5)
+	}
+
+	return decimal(f)
+}