Milestone-Based Fund Release

What it does:
A smart contract that releases funds in stages based on predefined milestones being completed and approved, ensuring money is only paid when real progress is made.

Why it matters:
Whether for startups, freelancers, grants, or DAOs, this contract prevents misuse of funds and aligns incentives by enforcing pay-for-performance on-chain.

How it works:

A funder deposits the full budget into escrow.
The project is divided into milestones with specific payout amounts.
The project owner submits milestone completion proofs.
An approver (or DAO) verifies and approves each milestone.
Funds are released incrementally as milestones are approved.

      // SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

/**
 * @title MilestoneBasedFundRelease
 * @author Nam
 * @notice Escrow contract that releases funds per approved milestone
 */
contract MilestoneBasedFundRelease {

    // -------------------- DATA STRUCTURES --------------------

    enum MilestoneStatus { Pending, Submitted, Approved, Paid }

    struct Milestone {
        string description;   // Description or IPFS hash
        uint256 amount;       // Payout amount
        MilestoneStatus status;
    }

    Milestone[] public milestones;

    address public funder;
    address public recipient;
    address public approver;

    uint256 public totalBudget;
    uint256 public totalPaid;

    // -------------------- EVENTS --------------------

    event Funded(uint256 amount);
    event MilestoneSubmitted(uint256 indexed index);
    event MilestoneApproved(uint256 indexed index);
    event MilestonePaid(uint256 indexed index, uint256 amount);

    // -------------------- MODIFIERS --------------------

    modifier onlyFunder() {
        require(msg.sender == funder, "Not funder");
        _;
    }

    modifier onlyRecipient() {
        require(msg.sender == recipient, "Not recipient");
        _;
    }

    modifier onlyApprover() {
        require(msg.sender == approver, "Not approver");
        _;
    }

    // -------------------- CONSTRUCTOR --------------------

    constructor(
        address _recipient,
        address _approver
    ) {
        require(_recipient != address(0), "Invalid recipient");
        require(_approver != address(0), "Invalid approver");

        funder = msg.sender;
        recipient = _recipient;
        approver = _approver;
    }

    // -------------------- FUNDING --------------------

    /**
     * @notice Fund the escrow contract
     */
    function fund() external payable onlyFunder {
        require(msg.value &gt; 0, "Zero funding");
        totalBudget += msg.value;
        emit Funded(msg.value);
    }

    // -------------------- MILESTONE SETUP --------------------

    /**
     * @notice Add milestones before work begins
     */
    function addMilestone(
        string calldata _description,
        uint256 _amount
    ) external onlyFunder {
        require(_amount &gt; 0, "Invalid amount");
        require(
            totalPaid + _amount = m.amount,
            "Insufficient balance"
        );

        m.status = MilestoneStatus.Paid;
        totalPaid += m.amount;

        payable(recipient).transfer(m.amount);
        emit MilestonePaid(_index, m.amount);
    }

    // -------------------- VIEW FUNCTIONS --------------------

    /**
     * @notice Total milestones count
     */
    function milestoneCount() external view returns (uint256) {
        return milestones.length;
    }
}