Rollup.sol

//SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;

contract Rollup {


    // The address of the Ethereum mainchain
    address public mainchain;

    // The current state of the layer 2 chain
    mapping(address => uint256) public layer2Balances;

    // The current state of the layer 2 chain, as reported by the mainchain
    mapping(address => uint256) public mainchainBalances;

    constructor(address _mainchain) public {
        mainchain = _mainchain;
    }

    // Deposit funds into the layer 2 chain
    function deposit(address _to, uint256 _value) public payable {
        require(msg.value > 0, "Deposit amount must be greater than 0");
        layer2Balances[msg.sender] += msg.value;
        layer2Balances[_to] += _value;
    }

    // Withdraw funds from the layer 2 chain
function withdraw(address _from, uint256 _value) public {
        require(
            layer2Balances[_from] >= _value,
            "Insufficient funds in layer 2 balance"
        );
        layer2Balances[_from] -= _value;
        _from.transfer(_value);
    }

    // Batch and submit a group of layer 2 transactions to the Ethereum mainchain
function submitBatch() public {
        // Encode the batch data into a byte array
        bytes memory batchData = encodeBatchData();

        // Submit the batch data to the Ethereum mainchain
        mainchain.send(abi.encodeWithSignature("applyBatch(bytes)", batchData));
    }

    // Helper function to encode the batch data into a byte array
    function encodeBatchData() private returns (bytes memory) {
        // Example implementation: encode the layer2Balances mapping into a byte array
        uint256[] memory balances = new uint256[](layer2Balances.length);
        uint256 i = 0;
        for (uint256 j = 0; j < layer2Balances.length; j++) {
            address a = layer2Balances.keys[j];
            balances[i] = layer2Balances[a];
            i++;
        }

        return abi.encodePacked(balances);
    }

    // Verify and apply the results of a batch of layer 2 transactions

    // Code to verify and apply the results of a batch of layer 2 transactions
    // After the batch is applied, update the mainchainBalances mapping with the latest state

    // Code to extract the address and new balance from the batch data

function applyBatch(bytes memory _batch) public {
        // Verify the batch data using a fraud-proof mechanism
        require(verifyBatchData(_batch), "Batch verification failed");

        // Decode the batch data
        uint256[] memory balances = decodeBatchData(_batch);

        // Apply the results of the batch
        for (uint256 i = 0; i < balances.length; i++) {
            // Update the mainchainBalances mapping with the decoded balances
            mainchainBalances[layer2Addresses[i]] = balances[i];
        }
    }

    // Helper function to verify the batch data using a fraud-proof mechanism
    function verifyBatchData(bytes memory _batch) private view returns (bool) {
        // Example implementation: verify the batch data by checking the root of a Merkle tree
        

        //return true for now
        return true;
    }

    // Helper function to decode the batch data from a byte array
    function decodeBatchData(bytes memory _batch)
        private
        returns (uint256[] memory)
    {
        // Example implementation: decode the packed balances from the byte array
        return abi.decode(_batch, (uint256[]));
    }

    // Submit a fraud-proof to the mainchain, challenging a previous batch
function submitFraudProof(
    bytes memory _batch,
    uint256[] memory _challengedBalances
    ) public {
    // Verify that the challenged balances match the reported balances in the batch
    require(verifyChallengedBalances(_batch, _challengedBalances), "Challenged balances verification failed");

    // Store the fraud-proof data in the fraudProofs mapping
    fraudProofs[keccak256(_batch)] = FraudProof({
        batch: _batch,
        challengedBalances: _challengedBalances,
        reportedBalances: decodeBatchData(_batch),
        timestamp: now,
        resolved: false
    });

    // Emit a FraudProofSubmitted event
    emit FraudProofSubmitted(
        keccak256(_batch),
        _challengedBalances,
        decodeBatchData(_batch),
        now
    );
}

// Helper function to verify the challenged balances
function verifyChallengedBalances(
    bytes memory _batch,
    uint256[] memory _challengedBalances) private view returns (bool) {
    uint256[] memory reportedBalances = decodeBatchData(_batch);

    // Verify that the length of the challenged balances matches the length of the reported balances
    if (_challengedBalances.length != reportedBalances.length) {
        return false;
    }

    // Verify that the challenged balances match the reported balances
    for (uint256 i = 0; i < _challengedBalances.length; i++) {
        if (_challengedBalances[i] != reportedBalances[i]) {
            return false;
        }
    }

    return true;
}


    // Verify and process a fraud-proof submitted by a user
function processFraudProof(
        bytes memory _batch,
        uint256[] memory _challengedBalances
    ) public {
        // Verify that the batch and challenged balances match the current state on the mainchain
        for (uint256 i = 0; i < _challengedBalances.length; i++) {
            address a = addresses[i];
            require(
                mainchainBalances[a] == _challengedBalances[i],
                "Challenged balance does not match mainchain balance"
            );
        }

        // Revert the batch and update the layer2Balances mapping with the latest state
        for (uint256 i = 0; i < _batch.length; i++) {
            // Code to extract the address and new balance from the batch data
            layer2Balances[address] = oldBalance;
        }
    }
}