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

contract EthTimeVault {
    uint256 public constant LOCK_TIME = 5324355200; // ~Jan 1, 2140
    bytes32 public merkleRoot;
    mapping(address => bool) public hasWithdrawn;

    constructor(bytes32 _merkleRoot) {
        merkleRoot = _merkleRoot;
    }

    function deposit() external payable {
        require(block.timestamp < LOCK_TIME, "Vault locked until 2140");
        // Contributors send ETH; contract aggregates toward 6M ETH target
    }

    function withdraw(bytes32[] memory proof, uint256 amount) external {
        require(block.timestamp >= LOCK_TIME, "Vault still locked");
        require(!hasWithdrawn[msg.sender], "Already withdrawn");
        bytes32 leaf = keccak256(abi.encodePacked(msg.sender, amount));
        require(verifyProof(leaf, proof), "Invalid Merkle proof");
        hasWithdrawn[msg.sender] = true;
        payable(msg.sender).transfer(amount);
    }

    function verifyProof(bytes32 leaf, bytes32[] memory proof) internal view returns (bool) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            computedHash = keccak256(abi.encodePacked(computedHash, proof[i]));
        }
        return computedHash == merkleRoot;
    }
}