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

import {Encoding} from "./Encoding.sol";
import {Types} from "./Types.sol";

/// @title Hashing
/// @notice Hashing handles Optimism's various different hashing schemes.
library Hashing {
    /// @notice Computes the hash of the RLP encoded L2 transaction that would be generated when a
    ///         given deposit is sent to the L2 system. Useful for searching for a deposit in the L2
    ///         system.
    /// @param _tx User deposit transaction to hash.
    /// @return Hash of the RLP encoded L2 deposit transaction.
    function hashDepositTransaction(Types.UserDepositTransaction memory _tx) internal pure returns (bytes32) {
        return keccak256(Encoding.encodeDepositTransaction(_tx));
    }

    /// @notice Computes the deposit transaction's "source hash", a value that guarantees the hash
    ///         of the L2 transaction that corresponds to a deposit is unique and is
    ///         deterministically generated from L1 transaction data.
    /// @param _l1BlockHash Hash of the L1 block where the deposit was included.
    /// @param _logIndex    The index of the log that created the deposit transaction.
    /// @return Hash of the deposit transaction's "source hash".
    function hashDepositSource(bytes32 _l1BlockHash, uint256 _logIndex) internal pure returns (bytes32) {
        bytes32 depositId = keccak256(abi.encode(_l1BlockHash, _logIndex));
        return keccak256(abi.encode(bytes32(0), depositId));
    }

    /// @notice Hashes the cross domain message based on the version that is encoded into the
    ///         message nonce.
    /// @param _nonce    Message nonce with version encoded into the first two bytes.
    /// @param _sender   Address of the sender of the message.
    /// @param _target   Address of the target of the message.
    /// @param _value    ETH value to send to the target.
    /// @param _gasLimit Gas limit to use for the message.
    /// @param _data     Data to send with the message.
    /// @return Hashed cross domain message.
    function hashCrossDomainMessage(
        uint256 _nonce,
        address _sender,
        address _target,
        uint256 _value,
        uint256 _gasLimit,
        bytes memory _data
    )
    internal
    pure
    returns (bytes32)
    {
        (, uint16 version) = Encoding.decodeVersionedNonce(_nonce);
        if (version == 0) {
            return hashCrossDomainMessageV0(_target, _sender, _data, _nonce);
        } else if (version == 1) {
            return hashCrossDomainMessageV1(_nonce, _sender, _target, _value, _gasLimit, _data);
        } else {
            revert("Hashing: unknown cross domain message version");
        }
    }

    /// @notice Hashes a cross domain message based on the V0 (legacy) encoding.
    /// @param _target Address of the target of the message.
    /// @param _sender Address of the sender of the message.
    /// @param _data   Data to send with the message.
    /// @param _nonce  Message nonce.
    /// @return Hashed cross domain message.
    function hashCrossDomainMessageV0(
        address _target,
        address _sender,
        bytes memory _data,
        uint256 _nonce
    )
    internal
    pure
    returns (bytes32)
    {
        return keccak256(Encoding.encodeCrossDomainMessageV0(_target, _sender, _data, _nonce));
    }

    /// @notice Hashes a cross domain message based on the V1 (current) encoding.
    /// @param _nonce    Message nonce.
    /// @param _sender   Address of the sender of the message.
    /// @param _target   Address of the target of the message.
    /// @param _value    ETH value to send to the target.
    /// @param _gasLimit Gas limit to use for the message.
    /// @param _data     Data to send with the message.
    /// @return Hashed cross domain message.
    function hashCrossDomainMessageV1(
        uint256 _nonce,
        address _sender,
        address _target,
        uint256 _value,
        uint256 _gasLimit,
        bytes memory _data
    )
    internal
    pure
    returns (bytes32)
    {
        return keccak256(Encoding.encodeCrossDomainMessageV1(_nonce, _sender, _target, _value, _gasLimit, _data));
    }

    /// @notice Derives the withdrawal hash according to the encoding in the L2 Withdrawer contract
    /// @param _tx Withdrawal transaction to hash.
    /// @return Hashed withdrawal transaction.
    function hashWithdrawal(Types.WithdrawalTransaction memory _tx) internal pure returns (bytes32) {
        return keccak256(abi.encode(_tx.nonce, _tx.sender, _tx.target, _tx.value, _tx.gasLimit, _tx.data));
    }

    /// @notice Hashes the various elements of an output root proof into an output root hash which
    ///         can be used to check if the proof is valid.
    /// @param _outputRootProof Output root proof which should hash to an output root.
    /// @return Hashed output root proof.
    function hashOutputRootProof(Types.OutputRootProof memory _outputRootProof) internal pure returns (bytes32) {
        return keccak256(
            abi.encode(
                _outputRootProof.version,
                _outputRootProof.stateRoot,
                _outputRootProof.messagePasserStorageRoot,
                _outputRootProof.latestBlockhash
            )
        );
    }
}