// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

/// @notice Library for accessing block hashes way beyond the 256-block limit.
/// @author Solady (https://github.com/vectorized/solady/blob/main/src/utils/BlockHashLib.sol)
/// @author Modified from OpenZeppelin (https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Blockhash.sol)
library BlockHashLib {
    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
    /*                         CONSTANTS                          */
    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

    /// @dev Address of the EIP-2935 history storage contract.
    /// See: https://eips.ethereum.org/EIPS/eip-2935
    address internal constant HISTORY_STORAGE_ADDRESS = 0x0000F90827F1C53a10cb7A02335B175320002935;

    /*´:°•.°+.*•´.*:˚.°*.˚•´.°:°•.°•.*•´.*:˚.°*.˚•´.°:°•.°+.*•´.*:*/
    /*                         OPERATIONS                         */
    /*.•°:°.´+˚.*°.˚:*.´•*.+°.•°:´*.´•*.•°.•°:°.´:•˚°.*°.˚:*.´+°.•*/

    /// @dev Retrieves the block hash for any historical block within the supported range.
    /// The function gracefully handles future blocks and blocks beyond the history window by returning zero,
    /// consistent with the EVM's native `BLOCKHASH` behavior.
    function blockHash(uint256 blockNumber) internal view returns (bytes32 result) {
        unchecked {
            // If `blockNumber + 256` overflows:
            // - Typical chain height (`block.number > 255`) -> `staticcall` -> 0.
            // - Very early chain (`block.number <= 255`) -> `blockhash` -> 0.
            if (block.number <= blockNumber + 256) return blockhash(blockNumber);
        }
        /// @solidity memory-safe-assembly
        assembly {
            mstore(0x20, blockNumber)
            mstore(0x00, 0)
            pop(staticcall(gas(), HISTORY_STORAGE_ADDRESS, 0x20, 0x20, 0x00, 0x20))
            result := mload(0x00)
        }
    }
}