// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.15;

import "@openzeppelin/contracts/interfaces/IERC1271.sol";
import "@openzeppelin/contracts/utils/Address.sol";

library Signature {
    function recover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address) {
        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
        // the valid range for s in (301): 0 < s < secp256k1n ÷ 2 + 1, and for v in (302): v ∈ {27, 28}. Most
        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
        //
        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
        // these malleable signatures as well.
        require(
            uint256(s) <= 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0,
            "LEVX: INVALID_SIGNATURE_S_VALUE"
        );
        require(v == 27 || v == 28, "LEVX: INVALID_SIGNATURE_V_VALUE");

        // If the signature is valid (and not malleable), return the signer address
        address signer = ecrecover(hash, v, r, s);
        require(signer != address(0), "LEVX: INVALID_SIGNATURE");

        return signer;
    }

    function verify(
        bytes32 hash,
        address signer,
        uint8 v,
        bytes32 r,
        bytes32 s,
        bytes32 domainSeparator
    ) internal view {
        bytes32 digest = keccak256(abi.encodePacked("\x19\x01", domainSeparator, hash));
        if (Address.isContract(signer)) {
            require(
                IERC1271(signer).isValidSignature(digest, abi.encodePacked(r, s, v)) == 0x1626ba7e,
                "LEVX: UNAUTHORIZED"
            );
        } else {
            require(recover(digest, v, r, s) == signer, "LEVX: UNAUTHORIZED");
        }
    }
}