// SPDX-License-Identifier: MIT
// WARNING! This smart contract and the associated zk-SNARK verifiers have not been audited.
// DO NOT USE THIS CONTRACT FOR PRODUCTION
pragma solidity ^0.8.12;

// Original source: https://github.com/hamdiallam/Solidity-RLP/blob/master/contracts/RLPReader.sol
// Commit:          e3c1e3d

/*
 * @author Hamdi Allam hamdi.allam97@gmail.com
 * Please reach out with any questions or concerns
 */

library RLPReader {
    uint8 constant STRING_SHORT_START = 0x80;
    uint8 constant STRING_LONG_START = 0xb8;
    uint8 constant LIST_SHORT_START = 0xc0;
    uint8 constant LIST_LONG_START = 0xf8;
    uint8 constant WORD_SIZE = 32;

    struct RLPItem {
        uint256 len;
        uint256 memPtr;
    }

    struct Iterator {
        RLPItem item; // Item that's being iterated over.
        uint256 nextPtr; // Position of the next item in the list.
    }

    /*
     * @dev Returns the next element in the iteration. Reverts if it has not next element.
     * @param self The iterator.
     * @return The next element in the iteration.
     */
    function next(Iterator memory self) internal pure returns (RLPItem memory) {
        require(hasNext(self));

        uint256 ptr = self.nextPtr;
        uint256 itemLength = _itemLength(ptr);
        self.nextPtr = ptr + itemLength;

        return RLPItem(itemLength, ptr);
    }

    /*
     * @dev Returns true if the iteration has more elements.
     * @param self The iterator.
     * @return true if the iteration has more elements.
     */
    function hasNext(Iterator memory self) internal pure returns (bool) {
        RLPItem memory item = self.item;
        return self.nextPtr < item.memPtr + item.len;
    }

    /*
     * @param item RLP encoded bytes
     */
    function toRlpItem(bytes memory item) internal pure returns (RLPItem memory) {
        uint256 memPtr;
        assembly {
            memPtr := add(item, 0x20)
        }

        return RLPItem(item.length, memPtr);
    }

    /*
     * @dev Create an iterator. Reverts if item is not a list.
     * @param self The RLP item.
     * @return An 'Iterator' over the item.
     */
    function iterator(RLPItem memory self) internal pure returns (Iterator memory) {
        require(isList(self));

        uint256 ptr = self.memPtr + _payloadOffset(self.memPtr);
        return Iterator(self, ptr);
    }

    /*
     * @param the RLP item.
     */
    function rlpLen(RLPItem memory item) internal pure returns (uint256) {
        return item.len;
    }

    /*
     * @param the RLP item.
     * @return (memPtr, len) pair: location of the item's payload in memory.
     */
    function payloadLocation(RLPItem memory item) internal pure returns (uint256, uint256) {
        uint256 offset = _payloadOffset(item.memPtr);
        uint256 memPtr = item.memPtr + offset;
        uint256 len = item.len - offset; // data length
        return (memPtr, len);
    }

    /*
     * @param the RLP item.
     */
    function payloadLen(RLPItem memory item) internal pure returns (uint256) {
        (, uint256 len) = payloadLocation(item);
        return len;
    }

    /*
     * @param the RLP item containing the encoded list.
     */
    function toList(RLPItem memory item) internal pure returns (RLPItem[] memory) {
        require(isList(item));

        uint256 items = numItems(item);
        RLPItem[] memory result = new RLPItem[](items);

        uint256 memPtr = item.memPtr + _payloadOffset(item.memPtr);
        uint256 dataLen;
        for (uint256 i = 0; i < items; i++) {
            dataLen = _itemLength(memPtr);
            result[i] = RLPItem(dataLen, memPtr);
            memPtr = memPtr + dataLen;
        }

        return result;
    }

    // @return indicator whether encoded payload is a list. negate this function call for isData.
    function isList(RLPItem memory item) internal pure returns (bool) {
        if (item.len == 0) return false;

        uint8 byte0;
        uint256 memPtr = item.memPtr;
        assembly {
            byte0 := byte(0, mload(memPtr))
        }

        if (byte0 < LIST_SHORT_START) return false;
        return true;
    }

    /*
     * @dev A cheaper version of keccak256(toRlpBytes(item)) that avoids copying memory.
     * @return keccak256 hash of RLP encoded bytes.
     */
    function rlpBytesKeccak256(RLPItem memory item) internal pure returns (bytes32) {
        uint256 ptr = item.memPtr;
        uint256 len = item.len;
        bytes32 result;
        assembly {
            result := keccak256(ptr, len)
        }
        return result;
    }

    /*
     * @dev A cheaper version of keccak256(toBytes(item)) that avoids copying memory.
     * @return keccak256 hash of the item payload.
     */
    function payloadKeccak256(RLPItem memory item) internal pure returns (bytes32) {
        (uint256 memPtr, uint256 len) = payloadLocation(item);
        bytes32 result;
        assembly {
            result := keccak256(memPtr, len)
        }
        return result;
    }

    /** RLPItem conversions into data types **/

    // @returns raw rlp encoding in bytes
    function toRlpBytes(RLPItem memory item) internal pure returns (bytes memory) {
        bytes memory result = new bytes(item.len);
        if (result.length == 0) return result;

        uint256 ptr;
        assembly {
            ptr := add(0x20, result)
        }

        copy(item.memPtr, ptr, item.len);
        return result;
    }

    // any non-zero byte except "0x80" is considered true
    function toBoolean(RLPItem memory item) internal pure returns (bool) {
        require(item.len == 1);
        uint256 result;
        uint256 memPtr = item.memPtr;
        assembly {
            result := byte(0, mload(memPtr))
        }

        // SEE Github Issue #5.
        // Summary: Most commonly used RLP libraries (i.e Geth) will encode
        // "0" as "0x80" instead of as "0". We handle this edge case explicitly
        // here.
        if (result == 0 || result == STRING_SHORT_START) {
            return false;
        } else {
            return true;
        }
    }

    function toAddress(RLPItem memory item) internal pure returns (address) {
        // 1 byte for the length prefix
        require(item.len == 21);

        return address(uint160(toUint(item)));
    }

    function toUint(RLPItem memory item) internal pure returns (uint256) {
        require(item.len > 0 && item.len <= 33);

        (uint256 memPtr, uint256 len) = payloadLocation(item);

        uint256 result;
        assembly {
            result := mload(memPtr)

            // shift to the correct location if neccesary
            if lt(len, 32) {
                result := div(result, exp(256, sub(32, len)))
            }
        }

        return result;
    }

    // enforces 32 byte length
    function toUintStrict(RLPItem memory item) internal pure returns (uint256) {
        // one byte prefix
        require(item.len == 33);

        uint256 result;
        uint256 memPtr = item.memPtr + 1;
        assembly {
            result := mload(memPtr)
        }

        return result;
    }

    function toBytes(RLPItem memory item) internal pure returns (bytes memory) {
        require(item.len > 0);

        (uint256 memPtr, uint256 len) = payloadLocation(item);
        bytes memory result = new bytes(len);

        uint256 destPtr;
        assembly {
            destPtr := add(0x20, result)
        }

        copy(memPtr, destPtr, len);
        return result;
    }

    /*
     * Private Helpers
     */

    // @return number of payload items inside an encoded list.
    function numItems(RLPItem memory item) private pure returns (uint256) {
        if (item.len == 0) return 0;

        uint256 count = 0;
        uint256 currPtr = item.memPtr + _payloadOffset(item.memPtr);
        uint256 endPtr = item.memPtr + item.len;
        while (currPtr < endPtr) {
            currPtr = currPtr + _itemLength(currPtr); // skip over an item
            count++;
        }

        return count;
    }

    // @return entire rlp item byte length
    function _itemLength(uint256 memPtr) private pure returns (uint256) {
        uint256 itemLen;
        uint256 byte0;
        assembly {
            byte0 := byte(0, mload(memPtr))
        }

        if (byte0 < STRING_SHORT_START) {
            itemLen = 1;
        } else if (byte0 < STRING_LONG_START) {
            itemLen = byte0 - STRING_SHORT_START + 1;
        } else if (byte0 < LIST_SHORT_START) {
            assembly {
                let byteLen := sub(byte0, 0xb7) // # of bytes the actual length is
                memPtr := add(memPtr, 1) // skip over the first byte

                /* 32 byte word size */
                let dataLen := div(mload(memPtr), exp(256, sub(32, byteLen))) // right shifting to get the len
                itemLen := add(dataLen, add(byteLen, 1))
            }
        } else if (byte0 < LIST_LONG_START) {
            itemLen = byte0 - LIST_SHORT_START + 1;
        } else {
            assembly {
                let byteLen := sub(byte0, 0xf7)
                memPtr := add(memPtr, 1)

                let dataLen := div(mload(memPtr), exp(256, sub(32, byteLen))) // right shifting to the correct length
                itemLen := add(dataLen, add(byteLen, 1))
            }
        }

        return itemLen;
    }

    // @return number of bytes until the data
    function _payloadOffset(uint256 memPtr) private pure returns (uint256) {
        uint256 byte0;
        assembly {
            byte0 := byte(0, mload(memPtr))
        }

        if (byte0 < STRING_SHORT_START) {
            return 0;
        } else if (byte0 < STRING_LONG_START || (byte0 >= LIST_SHORT_START && byte0 < LIST_LONG_START)) {
            return 1;
        } else if (byte0 < LIST_SHORT_START) {
            // being explicit
            return byte0 - (STRING_LONG_START - 1) + 1;
        } else {
            return byte0 - (LIST_LONG_START - 1) + 1;
        }
    }

    /*
     * @param src Pointer to source
     * @param dest Pointer to destination
     * @param len Amount of memory to copy from the source
     */
    function copy(uint256 src, uint256 dest, uint256 len) private pure {
        if (len == 0) return;

        // copy as many word sizes as possible
        for (; len >= WORD_SIZE; len -= WORD_SIZE) {
            assembly {
                mstore(dest, mload(src))
            }

            src += WORD_SIZE;
            dest += WORD_SIZE;
        }

        if (len > 0) {
            // left over bytes. Mask is used to remove unwanted bytes from the word
            uint256 mask = 256**(WORD_SIZE - len) - 1;
            assembly {
                let srcpart := and(mload(src), not(mask)) // zero out src
                let destpart := and(mload(dest), mask) // retrieve the bytes
                mstore(dest, or(destpart, srcpart))
            }
        }
    }
}

// WARNING! This smart contract and the associated zk-SNARK verifiers have not been audited.
// DO NOT USE THIS CONTRACT FOR PRODUCTION

interface IAxiomV0 {
    // historicalRoots(startBlockNumber) is 0 unless (startBlockNumber % 1024 == 0)
    // historicalRoots(startBlockNumber) holds the hash of
    //   prevHash || root || numFinal
    // where
    // - prevHash is the parent hash of block startBlockNumber
    // - root is the partial Merkle root of blockhashes of block numbers
    //   [startBlockNumber, startBlockNumber + 1024)
    //   where unconfirmed block hashes are 0's
    // - numFinal is the number of confirmed consecutive roots in [startBlockNumber, startBlockNumber + 1024)
    function historicalRoots(uint32 startBlockNumber) external view returns (bytes32);

    event UpdateEvent(uint32 startBlockNumber, bytes32 prevHash, bytes32 root, uint32 numFinal);

    struct BlockHashWitness {
        uint32 blockNumber;
        bytes32 claimedBlockHash;
        bytes32 prevHash;
        uint32 numFinal;
        bytes32[10] merkleProof;
    }

    // returns Merkle root of a tree of depth `depth` with 0's as leaves
    function getEmptyHash(uint256 depth) external pure returns (bytes32);

    // update blocks in the "backward" direction, anchoring on a "recent" end blockhash that is within last 256 blocks
    // * startBlockNumber must be a multiple of 1024
    // * roots[idx] is the root of a Merkle tree of height 2**(10 - idx) in a Merkle mountain
    //   range which stores block hashes in the interval [startBlockNumber, endBlockNumber]
    function updateRecent(bytes calldata proofData) external;

    // update older blocks in "backwards" direction, anchoring on more recent trusted blockhash
    // must be batch of 1024 blocks
    function updateOld(bytes32 nextRoot, uint32 nextNumFinal, bytes calldata proofData) external;

    // Update older blocks in "backwards" direction, anchoring on more recent trusted blockhash
    // Must be batch of 128 * 1024 blocks
    // `roots` should contain 128 merkle roots, one per batch of 1024 blocks
    // For all except the last batch of 1024 blocks, a Merkle inclusion proof of the `endHash` of the batch
    // must be provided, with respect to the corresponding Merkle root in `roots`
    function updateHistorical(
        bytes32 nextRoot,
        uint32 nextNumFinal,
        bytes32[128] calldata roots,
        bytes32[11][127] calldata endHashProofs,
        bytes calldata proofData
    ) external;

    function isRecentBlockHashValid(uint32 blockNumber, bytes32 claimedBlockHash) external view returns (bool);
    function isBlockHashValid(BlockHashWitness calldata witness) external view returns (bool);
}

// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

contract RandaoV02 is Ownable {
    string public constant VERSION = "0.2";

    using RLPReader for RLPReader.RLPItem;
    using RLPReader for bytes;

    address public axiomAddress;
    uint32 MERGE_BLOCK = 15537393;

    // mapping between blockNumber and prevRandao
    mapping(uint32 => uint256) public prevRandaos;

    event RandaoProof(uint32 blockNumber, uint256 prevRandao);

    event UpdateAxiomAddress(address newAddress);

    constructor(address _axiomAddress) {
        axiomAddress = _axiomAddress;
    }

    function updateAxiomAddress(address _axiomAddress) external onlyOwner {
        axiomAddress = _axiomAddress;
        emit UpdateAxiomAddress(_axiomAddress);
    }

    function verifyRandao(IAxiomV0.BlockHashWitness calldata witness, bytes calldata header) external {
        if (block.number - witness.blockNumber <= 256) {
            require(
                IAxiomV0(axiomAddress).isRecentBlockHashValid(witness.blockNumber, witness.claimedBlockHash),
                "Block hash was not validated in cache"
            );
        } else {
            require(IAxiomV0(axiomAddress).isBlockHashValid(witness), "Block hash was not validated in cache");
        }

        require(keccak256(header) == witness.claimedBlockHash, "Block hash does not match witness hash");

        require(witness.blockNumber > MERGE_BLOCK, "prevRandao is not valid before merge block");

        RLPReader.RLPItem[] memory headerItems = header.toRlpItem().toList();
        uint256 prevRandao = headerItems[13].toUint();

        prevRandaos[witness.blockNumber] = prevRandao;
        emit RandaoProof(witness.blockNumber, prevRandao);
    }
}