// SPDX-License-Identifier: MIT

pragma solidity ^0.6.12;

/*
 * @dev Solidity implementation of the ENS namehash algorithm.
 *
 * Warning! Does not normalize or validate names before hashing.
 * Original version can be found here https://github.com/JonahGroendal/ens-namehash/
 */
library ENSNamehash {
    function namehash(bytes memory domain) internal pure returns (bytes32) {
        return namehash(domain, 0);
    }

    function namehash(bytes memory domain, uint256 i) internal pure returns (bytes32) {
        if (domain.length <= i) return 0x0000000000000000000000000000000000000000000000000000000000000000;

        uint256 len = labelLength(domain, i);

        return keccak256(abi.encodePacked(namehash(domain, i + len + 1), keccak(domain, i, len)));
    }

    function labelLength(bytes memory domain, uint256 i) private pure returns (uint256) {
        uint256 len;
        while (i + len != domain.length && domain[i + len] != 0x2e) {
            len++;
        }
        return len;
    }

    function keccak(bytes memory data, uint256 offset, uint256 len) private pure returns (bytes32 ret) {
        require(offset + len <= data.length);
        assembly {
            ret := keccak256(add(add(data, 32), offset), len)
        }
    }
}