Escrow Contract

assignments/Class/.gitignore

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+# Node modules
+/node_modules
+
+# Compilation output
+/dist
+
+# pnpm deploy output
+/bundle
+
+# Hardhat Build Artifacts
+/artifacts
+
+# Hardhat compilation (v2) support directory
+/cache
+
+# Typechain output
+/types
+
+# Hardhat coverage reports
+/coverage

assignments/Class/README.md

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+## MilestoneEscrow
+
+A simple and secure milestone-based escrow smart contract that enables a client to fund a project upfront and release payments to a freelancer per milestone as work is completed and approved.
+This contract is designed for freelance or contractor workflows where payments are tied to deliverables instead of a single lump-sum transfer.
+
+Contract Address: 0x5DBE332243125b5E8E71F8A59bEEC7C9EccF49Fc
+
+Etherscan Verification:
+(etherscan_link)[https://sepolia.etherscan.io/address/0x5DBE332243125b5E8E71F8A59bEEC7C9EccF49Fc]
+
+### Overview
+
+MilestoneEscrow allows:
+A client to deposit the full project payment upfront
+A freelancer to mark milestones as completed
+The client (or anyone after timeout) to approve and release payments
+Automatic approval after a timeout period
+Cancellation with refund of remaining funds
+Dispute signaling via events
+Each milestone has a fixed payment amount, and funds are released incrementally.
+
+### Roles
+
+- Client
+  Deploys and funds the contract
+  Approves milestones
+  Can cancel the contract and reclaim remaining funds
+- Freelancer
+  Marks milestones as completed
+  Receives milestone payments

assignments/Class/contracts/Factory.sol

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+
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.28;
+
+import "./MilestoneEscrow.sol";
+
+contract MilestoneEscrowFactory {
+
+    address[] public allEscrows;
+
+    // user => escrows they are involved in
+    mapping(address => address[]) public userEscrows;
+
+    event EscrowCreated(
+        address indexed client,
+        address indexed freelancer,
+        address escrow,
+        uint256 milestones,
+        uint256 amountPerMilestone
+    );
+
+    function createEscrow(
+        address _freelancer,
+        uint256 _milestoneCount,
+        uint256 _amountPerMilestone
+    ) external payable returns (address) {
+
+        require(_freelancer != address(0), "Invalid freelancer");
+        require(_freelancer != msg.sender, "Self-hire not allowed");
+        require(_milestoneCount > 0, "Milestones = 0");
+        require(_amountPerMilestone > 0, "Amount = 0");
+
+        uint256 totalCost = _milestoneCount * _amountPerMilestone;
+        require(msg.value == totalCost, "Wrong ETH sent");
+
+        MilestoneEscrow escrow = new MilestoneEscrow{value: msg.value}(
+            _freelancer,
+            _milestoneCount,
+            _amountPerMilestone
+        );
+
+        address escrowAddr = address(escrow);
+
+        allEscrows.push(escrowAddr);
+
+        userEscrows[msg.sender].push(escrowAddr);
+        userEscrows[_freelancer].push(escrowAddr);
+
+        emit EscrowCreated(
+            msg.sender,
+            _freelancer,
+            escrowAddr,
+            _milestoneCount,
+            _amountPerMilestone
+        );
+
+        return escrowAddr;
+    }
+
+    function getUserEscrows(address user)
+        external
+        view
+        returns (address[] memory)
+    {
+        return userEscrows[user];
+    }
+
+    function getAllEscrows()
+        external
+        view
+        returns (address[] memory)
+    {
+        return allEscrows;
+    }
+}
+

assignments/Class/contracts/MilestoneEscrow.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.28;
+
+contract MilestoneEscrow {
+    address public immutable client;
+    address public immutable freelancer;
+
+    uint256 public immutable milestoneCount;
+    uint256 public immutable amountPerMilestone;
+
+    uint256 public approvedMilestones;   
+    uint256 public releasedMilestones;   
+
+    mapping(uint256 => bool) public completed;
+    mapping(uint256 => bool) public approved;
+    mapping(uint256 => uint256) public completionTime;  
+
+    bool public cancelled;
+
+    uint256 public constant AUTO_APPROVE_TIMEOUT = 14 days; 
+
+   event Funded(
+        address indexed client,
+        address indexed freelancer,
+        uint256 totalAmount,
+        uint256 milestoneCount,
+        uint256 amountPerMilestone
+    );
+
+    event MilestoneCompleted(
+        uint256 indexed milestoneId,
+        address indexed freelancer,
+        uint256 timestamp
+    );
+
+    event MilestoneApproved(
+        uint256 indexed milestoneId,
+        address indexed approver,           
+        uint256 amountReleased
+    );
+
+
+    event MilestoneAutoApproved(
+        uint256 indexed milestoneId,
+        uint256 timeoutTimestamp,
+        uint256 amountReleased
+    );
+
+
+    event ContractCancelled(
+        address indexed caller,
+        uint256 refundAmount,
+        uint256 timestamp
+    );
+
+
+    event DisputeRaised(
+        uint256 indexed milestoneId,
+        address indexed raiser,
+        string reason
+    );
+
+
+    event AllMilestonesReleased(
+      address indexed freelancer,
+      uint256 totalReleased
+    );
+
+    constructor(
+      address _freelancer,
+        uint256 _milestoneCount,
+        uint256 _amountPerMilestone
+    ) payable {
+        require(_freelancer != address(0), "Invalid freelancer address");
+        require(_freelancer != msg.sender, "Client cannot be freelancer");
+        require(_milestoneCount > 0, "At least one milestone required");
+        require(_amountPerMilestone > 0, "Amount per milestone must be > 0");
+
+        uint256 expectedDeposit = _milestoneCount * _amountPerMilestone;
+        require(msg.value == expectedDeposit, "Must fund all milestones");
+
+        client = msg.sender;
+        freelancer = _freelancer;
+
+        milestoneCount = _milestoneCount;
+        amountPerMilestone = _amountPerMilestone;
+
+        emit Funded(
+            msg.sender,
+            _freelancer,
+            msg.value,
+            _milestoneCount,
+            _amountPerMilestone
+        );
+    }
+
+    function markCompleted(uint256 id) public {
+        require(msg.sender == freelancer, "Only freelancer can mark complete");
+        require(id < milestoneCount, "Invalid milestone id");
+        require(!completed[id], "Already marked as completed");
+        require(!cancelled, "Contract is cancelled");
+
+        completed[id] = true;
+        completionTime[id] = block.timestamp;   
+
+        emit MilestoneCompleted(id, msg.sender, block.timestamp);
+    }
+
+
+    function approveMilestone(uint256 id) external {
+        _requireCanApprove(id);
+
+        approved[id] = true;
+        approvedMilestones++;
+        releasedMilestones++;
+
+        _safeTransfer(freelancer, amountPerMilestone);
+
+        emit MilestoneApproved(id, msg.sender, amountPerMilestone);
+
+        if (releasedMilestones == milestoneCount) {
+            emit AllMilestonesReleased(freelancer, address(this).balance);
+        }
+    }
+
+
+    function autoApprove(uint256 id) external {
+        _requireCanApprove(id);
+
+        require(
+            block.timestamp >= completionTime[id] + AUTO_APPROVE_TIMEOUT,
+            "Timeout not reached yet"
+        );
+
+        approved[id] = true;
+        approvedMilestones++;
+        releasedMilestones++;
+
+        _safeTransfer(freelancer, amountPerMilestone);
+
+        emit MilestoneAutoApproved(id, block.timestamp, amountPerMilestone);
+        emit MilestoneApproved(id, address(0), amountPerMilestone); 
+
+        if (releasedMilestones == milestoneCount) {
+            emit AllMilestonesReleased(freelancer, address(this).balance);
+        }
+    }
+
+
+    function cancel() external {
+        require(msg.sender == client, "Only client can cancel");
+        require(!cancelled, "Already cancelled");
+
+        cancelled = true;
+
+        uint256 remaining = address(this).balance;
+        if (remaining > 0) {
+            _safeTransfer(client, remaining);
+        }
+
+        emit ContractCancelled(msg.sender, remaining, block.timestamp);
+    }
+
+    //TODO: Internal Helpers
+    function _requireCanApprove(uint256 id) internal view {
+        require(id < milestoneCount, "Invalid milestone id");
+        require(completed[id], "Milestone not completed yet");
+        require(!approved[id], "Already approved");
+        require(!cancelled, "Contract is cancelled");
+    }
+
+
+    function _safeTransfer(address to, uint256 value) internal {
+        (bool success, ) = to.call{value: value}("");
+        require(success, "ETH transfer failed");
+    }
+
+    function isFullyReleased() external view returns (bool) {
+        return releasedMilestones == milestoneCount;
+    }
+
+    function getRemainingBalance() external view returns (uint256) {
+        return address(this).balance;
+    }
+
+    function canAutoApprove(uint256 id) external view returns (bool) {
+        if (id >= milestoneCount || !completed[id] || approved[id]) return false;
+        return block.timestamp >= completionTime[id] + AUTO_APPROVE_TIMEOUT;
+    }
+
+    function raiseDispute(uint256 id, string calldata reason) external {
+        require(msg.sender == client || msg.sender == freelancer);
+        require(completed[id], "Not completed yet");
+        require(!approved[id], "Already approved");
+
+        emit DisputeRaised(id, msg.sender, reason);
+    }
+}

assignments/Class/hardhat.config.ts

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+import hardhatToolboxMochaEthersPlugin from "@nomicfoundation/hardhat-toolbox-mocha-ethers";
+import { configVariable, defineConfig } from "hardhat/config";
+import "dotenv/config";
+
+export default defineConfig({
+  plugins: [hardhatToolboxMochaEthersPlugin],
+  solidity: {
+    profiles: {
+      default: {
+        version: "0.8.28",
+      },
+      production: {
+        version: "0.8.28",
+        settings: {
+          optimizer: {
+            enabled: true,
+            runs: 200,
+          },
+        },
+      },
+    },
+  },
+  networks: {
+    hardhatMainnet: {
+      type: "edr-simulated",
+      chainType: "l1",
+    },
+    hardhatOp: {
+      type: "edr-simulated",
+      chainType: "op",
+    },
+    sepolia: {
+      type: "http",
+      chainType: "l1",
+      url: configVariable("SEPOLIA_RPC_URL"),
+      accounts: [configVariable("SEPOLIA_PRIVATE_KEY")],
+    },
+  },
+  verify: {
+    etherscan: {
+      apiKey: configVariable("ETHERSCAN_API_KEY"),
+    },
+  },
+});