feat: adds mta redeemer

contracts/shared/MetaTokenRedeemer.sol

@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+pragma solidity 0.8.6;
+
+import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
+
+/**
+ * @notice  Allows to redeem MTA for WETH at a fixed rate.
+ * @author  mStable
+ * @dev     VERSION: 1.0
+ *          DATE:    2023-03-08
+ */
+contract MetaTokenRedeemer {
+    using SafeERC20 for IERC20;
+
+    address public immutable MTA;
+    address public immutable WETH;
+    uint256 public immutable PERIOD_DURATION;
+    uint256 public periodStart;
+    uint256 public periodEnd;
+    uint256 public totalFunded;
+    uint256 public totalRegistered;
+    mapping(address => uint256) public balances;
+
+    /**
+     * @notice Emitted when the redeemer is funded.
+     */
+    event Funded(address indexed sender, uint256 amount);
+    /**
+     * @notice Emitted when a user register MTA.
+     */
+    event Register(address indexed sender, uint256 amount);
+
+    /**
+     * @notice Emitted when a user claims WETH for the registered amount.
+     */
+    event Redeemed(address indexed sender, uint256 registeredAmount, uint256 redeemedAmount);
+
+    /**
+     * @notice Crates a new instance of the contract
+     * @param _mta MTA Token Address
+     * @param _weth WETH Token Address
+     * @param _periodDuration The lenght of the registration period.
+     */
+    constructor(
+        address _mta,
+        address _weth,
+        uint256 _periodDuration
+    ) {
+        MTA = _mta;
+        WETH = _weth;
+        PERIOD_DURATION = _periodDuration;
+    }
+
+    /**
+     * @notice Funds the contract with WETH, and initialize the funding period.
+     * It only allows to fund during the funding period.
+     * @param amount The Amount of WETH to be transfer to the contract
+     */
+    function fund(uint256 amount) external {
+        require(periodStart == 0 || block.timestamp <= periodEnd, "Funding period ended");
+
+        IERC20(WETH).safeTransferFrom(msg.sender, address(this), amount);
+        if (periodStart == 0) {
+            periodStart = block.timestamp;
+            periodEnd = periodStart + PERIOD_DURATION;
+        }
+        totalFunded += amount;
+
+        emit Funded(msg.sender, amount);
+    }
+
+    /**
+     * @notice Allos user to register and transfer a given amount of MTA
+     * It only allows to register during the registration period.
+     * @param amount The Amount of MTA to register.
+     */
+    function register(uint256 amount) external {
+        require(periodStart > 0, "Registration period not started");
+        require(block.timestamp <= periodEnd, "Registration period ended");
+
+        IERC20(MTA).safeTransferFrom(msg.sender, address(this), amount);
+        balances[msg.sender] += amount;
+        totalRegistered += amount;
+        emit Register(msg.sender, amount);
+    }
+
+    /// @notice Redeems all user MTA balance for WETH at a fixed rate.
+    /// @return redeemedAmount The amount of WETH to receive.
+    function redeem() external returns (uint256 redeemedAmount) {
+        require(periodEnd <= block.timestamp, "Redeem period not started");
+        uint256 registeredAmount = balances[msg.sender];
+        require(registeredAmount > 0, "No balance");
+
+        // MTA and WETH both have 18 decimal points, no need for scaling.
+        redeemedAmount = (registeredAmount * totalRegistered) / totalFunded;
+        balances[msg.sender] = 0;
+
+        IERC20(WETH).safeTransfer(msg.sender, redeemedAmount);
+
+        emit Redeemed(msg.sender, registeredAmount, redeemedAmount);
+    }
+}

tasks/deployShared.ts

@@ -0,0 +1,32 @@
+import "ts-node/register"
+import "tsconfig-paths/register"
+import { task, types } from "hardhat/config"
+import { MetaTokenRedeemer__factory } from "types/generated"
+import { BigNumber } from "ethers"
+import { deployContract } from "./utils/deploy-utils"
+import { getSigner } from "./utils/signerFactory"
+import { verifyEtherscan } from "./utils/etherscan"
+import { MTA } from "./utils"
+import { getChain, getChainAddress } from "./utils/networkAddressFactory"
+
+task("deploy-MetaTokenRedeemer")
+    .addParam("duration", "Registration period duration, default value 90 days (7776000)", 7776000, types.int)
+    .addOptionalParam("speed", "Defender Relayer speed param: 'safeLow' | 'average' | 'fast' | 'fastest'", "fast", types.string)
+    .setAction(async (taskArgs, hre) => {
+        const signer = await getSigner(hre, taskArgs.speed)
+        const chain = getChain(hre)
+        const mtaAddr = MTA.address
+        const wethAddr = getChainAddress("UniswapEthToken", chain)
+
+        const metaTokenRedeemer = await deployContract(new MetaTokenRedeemer__factory(signer), "MetaTokenRedeemer", [
+            mtaAddr,
+            wethAddr,
+            BigNumber.from(taskArgs.duration),
+        ])
+
+        await verifyEtherscan(hre, {
+            address: metaTokenRedeemer.address,
+            contract: "contracts/shared/MetaTokenRedeemer.sol:MetaTokenRedeemer",
+        })
+    })
+module.exports = {}

test/shared/meta-token-redeemer.spec.ts

@@ -0,0 +1,173 @@
+import { simpleToExactAmount } from "@utils/math"
+import { ethers } from "hardhat"
+import { ERC20, MetaTokenRedeemer, MetaTokenRedeemer__factory, MockERC20__factory } from "types/generated"
+import { expect } from "chai"
+import { Signer } from "ethers"
+import { ONE_DAY, ZERO } from "@utils/constants"
+import { getTimestamp, increaseTime } from "@utils/time"
+
+describe("MetaTokenRedeemer", () => {
+    let redeemer: MetaTokenRedeemer
+    let deployer: Signer
+    let alice: Signer
+    let bob: Signer
+    let aliceAddress: string
+    let mta: ERC20
+    let weth: ERC20
+
+    before(async () => {
+        const accounts = await ethers.getSigners()
+        deployer = accounts[0]
+        alice = accounts[1]
+        bob = accounts[2]
+        aliceAddress = await alice.getAddress()
+        mta = await new MockERC20__factory(deployer).deploy(
+            "Meta Token",
+            "mta",
+            18,
+            await deployer.getAddress(),
+            simpleToExactAmount(10_000_000),
+        )
+        weth = await new MockERC20__factory(deployer).deploy(
+            "WETH Token",
+            "weth",
+            18,
+            await deployer.getAddress(),
+            simpleToExactAmount(1_000_000),
+        )
+        redeemer = await new MetaTokenRedeemer__factory(deployer).deploy(mta.address, weth.address, ONE_DAY.mul(90))
+        // send mta to alice
+        mta.transfer(aliceAddress, simpleToExactAmount(10_000))
+        mta.transfer(await bob.getAddress(), simpleToExactAmount(10_000))
+    })
+    it("constructor parameters are correct", async () => {
+        expect(await redeemer.MTA(), "MTA").to.be.eq(mta.address)
+        expect(await redeemer.WETH(), "WETH").to.be.eq(weth.address)
+        expect(await redeemer.PERIOD_DURATION(), "PERIOD_DURATION").to.be.eq(ONE_DAY.mul(90))
+        expect(await redeemer.periodStart(), "periodStart").to.be.eq(ZERO)
+        expect(await redeemer.periodEnd(), "periodEnd").to.be.eq(ZERO)
+        expect(await redeemer.totalFunded(), "totalFunded").to.be.eq(ZERO)
+        expect(await redeemer.totalRegistered(), "totalRegistered").to.be.eq(ZERO)
+        expect(await redeemer.balances(aliceAddress), "balances").to.be.eq(ZERO)
+    })
+    it("fails to register if period has not started", async () => {
+        expect(await redeemer.periodStart(), "periodStart").to.be.eq(ZERO)
+
+        await expect(redeemer.register(ZERO), "register").to.be.revertedWith("Registration period not started")
+    })
+    it("funds WETH into redeemer", async () => {
+        const wethAmount = await weth.balanceOf(await deployer.getAddress())
+        const redeemerWethBalance = await weth.balanceOf(redeemer.address)
+        await weth.approve(redeemer.address, wethAmount)
+        const now = await getTimestamp()
+        const tx = await redeemer.fund(wethAmount.div(2))
+        expect(tx)
+            .to.emit(redeemer, "Funded")
+            .withArgs(await deployer.getAddress(), wethAmount.div(2))
+        // Check total funded increases
+        expect(await redeemer.totalFunded(), "total funded").to.be.eq(wethAmount.div(2))
+        expect(await weth.balanceOf(redeemer.address), "weth balance").to.be.eq(redeemerWethBalance.add(wethAmount.div(2)))
+        // Fist time it is invoked , period details are set
+        expect(await redeemer.periodStart(), "period start").to.be.eq(now.add(1))
+        expect(await redeemer.periodEnd(), "period end").to.be.eq(now.add(1).add(await redeemer.PERIOD_DURATION()))
+    })
+    it("funds again WETH into redeemer", async () => {
+        const wethAmount = await weth.balanceOf(await deployer.getAddress())
+
+        const periodStart = await redeemer.periodStart()
+        const periodEnd = await redeemer.periodEnd()
+        const totalFunded = await redeemer.totalFunded()
+        const redeemerWethBalance = await weth.balanceOf(redeemer.address)
+
+        await weth.approve(redeemer.address, wethAmount)
+        const tx = await redeemer.fund(wethAmount)
+        expect(tx)
+            .to.emit(redeemer, "Funded")
+            .withArgs(await deployer.getAddress(), wethAmount)
+        // Check total funded increases
+        expect(await redeemer.totalFunded(), "total funded").to.be.eq(totalFunded.add(wethAmount))
+        expect(await weth.balanceOf(redeemer.address), "weth balance").to.be.eq(redeemerWethBalance.add(wethAmount))
+        // After first time, period details do not change
+        expect(await redeemer.periodStart(), "period start").to.be.eq(periodStart)
+        expect(await redeemer.periodEnd(), "period end").to.be.eq(periodEnd)
+    })
+    const registerTests = [{ user: "alice" }, { user: "bob" }]
+    registerTests.forEach((test, i) =>
+        it(`${test.user} can register MTA multiple times`, async () => {
+            const accounts = await ethers.getSigners()
+            const signer = accounts[i + 1]
+            const signerAddress = await signer.getAddress()
+            const signerBalanceBefore = await mta.balanceOf(signerAddress)
+            const redeemerMTABalance = await mta.balanceOf(redeemer.address)
+
+            const amount = signerBalanceBefore.div(2)
+            expect(signerBalanceBefore, "balance").to.be.gt(ZERO)
+            await mta.connect(signer).approve(redeemer.address, ethers.constants.MaxUint256)
+
+            const tx1 = await redeemer.connect(signer).register(amount)
+            expect(tx1).to.emit(redeemer, "Register").withArgs(signerAddress, amount)
+
+            const tx2 = await redeemer.connect(signer).register(amount)
+            expect(tx2).to.emit(redeemer, "Register").withArgs(signerAddress, amount)
+
+            const signerBalanceAfter = await mta.balanceOf(signerAddress)
+            const redeemerMTABalanceAfter = await mta.balanceOf(redeemer.address)
+
+            expect(signerBalanceAfter, "user mta balance").to.be.eq(ZERO)
+            expect(redeemerMTABalanceAfter, "redeemer mta balance").to.be.eq(redeemerMTABalance.add(signerBalanceBefore))
+        }),
+    )
+    it("fails to redeem if Redeem period not started", async () => {
+        const now = await getTimestamp()
+        const periodEnd = await redeemer.periodEnd()
+
+        expect(now, "now < periodEnd").to.be.lt(periodEnd)
+
+        await expect(redeemer.redeem(), "redeem").to.be.revertedWith("Redeem period not started")
+    })
+    it("fails to fund or register if register period ended", async () => {
+        await increaseTime(ONE_DAY.mul(91))
+        const periodEnd = await redeemer.periodEnd()
+        const now = await getTimestamp()
+
+        expect(now, "now > periodEnd").to.be.gt(periodEnd)
+
+        await expect(redeemer.fund(ZERO), "fund").to.be.revertedWith("Funding period ended")
+        await expect(redeemer.register(ZERO), "register").to.be.revertedWith("Registration period ended")
+    })
+
+    it("anyone can redeem WETH", async () => {
+        const aliceWethBalanceBefore = await weth.balanceOf(aliceAddress)
+        const redeemerWethBalanceBefore = await weth.balanceOf(redeemer.address)
+        const redeemerMTABalanceBefore = await mta.balanceOf(redeemer.address)
+        const registeredAmount = await redeemer.balances(aliceAddress)
+
+        const totalRegistered = await redeemer.totalRegistered()
+        const totalFunded = await redeemer.totalFunded()
+
+        const expectedWeth = registeredAmount.mul(totalRegistered).div(totalFunded)
+
+        expect(registeredAmount, "registeredAmount").to.be.gt(ZERO)
+
+        const tx = await redeemer.connect(alice).redeem()
+        expect(tx).to.emit(redeemer, "Redeemed").withArgs(aliceAddress, registeredAmount, expectedWeth)
+
+        const redeemerMTABalanceAfter = await mta.balanceOf(redeemer.address)
+        const aliceWethBalanceAfter = await weth.balanceOf(aliceAddress)
+        const redeemerWethBalanceAfter = await weth.balanceOf(redeemer.address)
+        const registeredAmountAfter = await redeemer.balances(aliceAddress)
+
+        expect(registeredAmountAfter, "alice register balance").to.be.eq(ZERO)
+        expect(aliceWethBalanceAfter, "alice weth balance").to.be.eq(aliceWethBalanceBefore.add(expectedWeth))
+        expect(redeemerWethBalanceAfter, "redeemer weth balance").to.be.eq(redeemerWethBalanceBefore.sub(expectedWeth))
+        // invariants
+        expect(redeemerMTABalanceAfter, "no mta is transferred").to.be.eq(redeemerMTABalanceBefore)
+        expect(totalRegistered, "register amount").to.be.eq(await redeemer.totalRegistered())
+        expect(totalFunded, "funded amount ").to.be.eq(await redeemer.totalFunded())
+    })
+    it("fails if sender did not register", async () => {
+        const registeredAmount = await redeemer.balances(await deployer.getAddress())
+        expect(registeredAmount).to.be.eq(ZERO)
+        await expect(redeemer.connect(deployer).redeem()).to.be.revertedWith("No balance")
+    })
+})