Add contract for MOO compensation with startTime

contracts/MerkleDistributorWithStartTime.sol

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity =0.8.11;
+
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";
+import "@openzeppelin/contracts/access/Ownable.sol";
+import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Pausable.sol";
+
+contract AccumulatingMerkleDistributor is Ownable {
+    uint public immutable timeout;
+    uint public immutable startTime;
+    address public immutable token;
+    bytes32 public merkleRoot;
+
+    // This is a packed array of booleans.
+    mapping(address => uint256) public claimedAmount;
+
+    event Claimed(uint256 index, address account, uint256 amount);
+    event RootUpdated(bytes32 newRoot);
+
+    constructor(address token_, bytes32 merkleRoot_, address owner_, uint timeout_, uint startTime_) {
+        transferOwnership(owner_);
+        token = token_;
+        merkleRoot = merkleRoot_;
+        timeout = timeout_;
+        startTime = startTime_;
+    }
+
+    function claim(uint256 index, address account, uint256 amount, bytes32[] calldata merkleProof) external claimStarted {
+        uint claimed = claimedAmount[account];
+        require(claimed < amount, 'AccumulatingMerkleDistributor: Drop already claimed.');
+
+        // Verify the merkle proof.
+        bytes32 node = keccak256(abi.encodePacked(index, account, amount));
+        require(MerkleProof.verify(merkleProof, merkleRoot, node), 'AccumulatingMerkleDistributor: Invalid proof.');
+
+        // Mark it claimed and send the token.
+        claimedAmount[account] = amount;
+        require(IERC20(token).transfer(account, amount - claimed), 'AccumulatingMerkleDistributor: Transfer failed.');
+
+        emit Claimed(index, account, amount);
+    }
+
+    // New root should include all old recipients plus new ones.
+    function updateRoot(bytes32 newRoot) public onlyOwner() {
+        merkleRoot = newRoot;
+        emit RootUpdated(newRoot);
+    }
+
+    function recover(address to, bytes calldata data) external onlyOwner() returns(bool, bytes memory) {
+        if (to == token) {
+            require(block.timestamp > timeout, 'AccumulatingMerkleDistributor: not timed out yet.');
+        }
+        return to.call(data);
+    }
+
+    modifier claimStarted() {
+        require(block.timestamp > startTime, 'Claiming has not started yet.');
+        _;
+    }
+}