Init backend

backend/.gitignore

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+node_modules
+.env
+
+# Hardhat files
+/cache
+/artifacts
+
+# TypeChain files
+/typechain
+/typechain-types
+
+# solidity-coverage files
+/coverage
+/coverage.json
+
+# Hardhat Ignition default folder for deployments against a local node
+ignition/deployments/chain-31337

backend/README.md

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+# Sample Hardhat Project
+
+This project demonstrates a basic Hardhat use case. It comes with a sample contract, a test for that contract, and a Hardhat Ignition module that deploys that contract.
+
+Try running some of the following tasks:
+
+```shell
+npx hardhat help
+npx hardhat test
+REPORT_GAS=true npx hardhat test
+npx hardhat node
+npx hardhat ignition deploy ./ignition/modules/Lock.ts
+```

backend/contracts/Lock.sol

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+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.24;
+
+// Uncomment this line to use console.log
+// import "hardhat/console.sol";
+
+contract Lock {
+    uint public unlockTime;
+    address payable public owner;
+
+    event Withdrawal(uint amount, uint when);
+
+    constructor(uint _unlockTime) payable {
+        require(
+            block.timestamp < _unlockTime,
+            "Unlock time should be in the future"
+        );
+
+        unlockTime = _unlockTime;
+        owner = payable(msg.sender);
+    }
+
+    function withdraw() public {
+        // Uncomment this line, and the import of "hardhat/console.sol", to print a log in your terminal
+        // console.log("Unlock time is %o and block timestamp is %o", unlockTime, block.timestamp);
+
+        require(block.timestamp >= unlockTime, "You can't withdraw yet");
+        require(msg.sender == owner, "You aren't the owner");
+
+        emit Withdrawal(address(this).balance, block.timestamp);
+
+        owner.transfer(address(this).balance);
+    }
+}

backend/hardhat.config.ts

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+import { HardhatUserConfig } from "hardhat/config";
+import "@nomicfoundation/hardhat-toolbox";
+
+const config: HardhatUserConfig = {
+  solidity: "0.8.24",
+};
+
+export default config;

backend/ignition/modules/Lock.ts

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+import { buildModule } from "@nomicfoundation/hardhat-ignition/modules";
+
+const JAN_1ST_2030 = 1893456000;
+const ONE_GWEI: bigint = 1_000_000_000n;
+
+const LockModule = buildModule("LockModule", (m) => {
+  const unlockTime = m.getParameter("unlockTime", JAN_1ST_2030);
+  const lockedAmount = m.getParameter("lockedAmount", ONE_GWEI);
+
+  const lock = m.contract("Lock", [unlockTime], {
+    value: lockedAmount,
+  });
+
+  return { lock };
+});
+
+export default LockModule;