Unidirectional payment channel

unidirectional_payment_channel/.env.example

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+ALCHEMY_API_KEY=
+ROPSTEN_PRIVATE_KEY=

unidirectional_payment_channel/.gitignore

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+node_modules
+.env
+
+#Hardhat files
+cache
+artifacts
+dist
+typechain

unidirectional_payment_channel/.prettierrc

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+{
+  "overrides": [
+    {
+      "files": "*.sol",
+      "options": {
+        "printWidth": 120,
+        "tabWidth": 2,
+        "useTabs": false,
+        "singleQuote": false,
+        "bracketSpacing": false,
+        "explicitTypes": "always",
+        "semi": true
+      }
+    }
+  ]
+}

unidirectional_payment_channel/contracts/PaymentChannel.sol

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+// SPDX-License-Identifier: GPL-3.0
+pragma solidity ^0.8.7;
+
+import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
+import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
+
+contract PaymentChannel is ReentrancyGuard {
+  using ECDSA for bytes32;
+
+  address payable public payer;
+  address payable public receiver;
+
+  uint256 private constant DURATION = 7 * 24 * 60 * 60;
+  uint256 public immutable expiresAt;
+
+  constructor(address payable _receiver) {
+    require(_receiver != address(0), "receiver is zero address");
+    payer = payable(msg.sender);
+    receiver = _receiver;
+    expiresAt = block.timestamp + DURATION;
+  }
+
+  receive() external payable {}
+
+  function getHash(uint256 amount) public view returns (bytes32) {
+    return keccak256(abi.encodePacked(address(this), amount));
+  }
+
+  function getEthSignedHash(uint256 amount) public view returns (bytes32) {
+    return getHash(amount).toEthSignedMessageHash();
+  }
+
+  function verify(uint256 amount, bytes memory signature) public view returns (bool) {
+    return getEthSignedHash(amount).recover(signature) == payer;
+  }
+
+  function close(uint256 amount, bytes memory signature) external nonReentrant {
+    require(msg.sender == receiver, "!receiver");
+    require(verify(amount, signature), "invalid signature");
+
+    receiver.transfer(amount);
+
+    selfdestruct(payer);
+  }
+
+  function cancel() external {
+    require(msg.sender == payer, "!payer");
+    require(block.timestamp >= expiresAt, "channel not expired yet");
+
+    selfdestruct(payer);
+  }
+}

unidirectional_payment_channel/hardhat.config.ts

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+import { config as dotenvConfig } from "dotenv";
+import "@typechain/hardhat";
+import "@nomiclabs/hardhat-ethers";
+import "@nomiclabs/hardhat-waffle";
+import "@nomiclabs/hardhat-etherscan";
+import "solidity-coverage";
+import "hardhat-gas-reporter";
+import { HardhatUserConfig } from "hardhat/types/config";
+
+dotenvConfig();
+
+const gasPrice = parseInt(process.env.GAS_PRICE || "1000000000");
+
+const config: HardhatUserConfig = {
+  solidity: {
+    compilers: [
+      {
+        version: "0.8.10",
+        settings: {
+          optimizer: {
+            enabled: true,
+            runs: 200,
+          },
+        },
+      },
+    ],
+  },
+  networks: {
+    hardhat: {
+      initialBaseFeePerGas: 0,
+    },
+    rinkeby: {
+      url: process.env.RINKEBY_URL || "",
+      accounts:
+        process.env.PRIVATE_KEY !== undefined ? [process.env.PRIVATE_KEY] : [],
+      gasPrice,
+    },
+    mainnet: {
+      url: process.env.MAINNET_URL || "",
+      accounts:
+        process.env.PRIVATE_KEY !== undefined ? [process.env.PRIVATE_KEY] : [],
+      gasPrice,
+    },
+  },
+  gasReporter: {
+    enabled: process.env.REPORT_GAS !== undefined,
+    currency: "USD",
+    gasPrice: 120,
+    coinmarketcap: process.env.COINMARKETCAP_API_KEY,
+  },
+  etherscan: {
+    apiKey: process.env.ETHERSCAN_API_KEY,
+  },
+};
+
+export default config;