// SPDX-License-Identifier: Apache-2.0
pragma solidity 0.8.18;

import "../interfaces/IERC1271Wallet.sol";

import "./LibBytes.sol";

/**
 * @dev Contains logic for signature validation.
 * Signatures from wallet contracts assume ERC-1271 support (https://github.com/ethereum/EIPs/blob/master/EIPS/eip-1271.md)
 * Notes: Methods are strongly inspired by contracts in https://github.com/0xProject/0x-monorepo/blob/development/
 */
library SignatureValidator {
  // Errors
  error InvalidSignatureLength(bytes _signature);
  error EmptySignature();
  error InvalidSValue(bytes _signature, bytes32 _s);
  error InvalidVValue(bytes _signature, uint256 _v);
  error UnsupportedSignatureType(bytes _signature, uint256 _type, bool _recoverMode);
  error SignerIsAddress0(bytes _signature);

  using LibBytes for bytes;

  /***********************************|
  |             Variables             |
  |__________________________________*/

  // bytes4(keccak256("isValidSignature(bytes,bytes)"))
  bytes4 constant internal ERC1271_MAGICVALUE = 0x20c13b0b;

  // bytes4(keccak256("isValidSignature(bytes32,bytes)"))
  bytes4 constant internal ERC1271_MAGICVALUE_BYTES32 = 0x1626ba7e;

  // Allowed signature types.
  uint256 private constant SIG_TYPE_EIP712 = 1;
  uint256 private constant SIG_TYPE_ETH_SIGN = 2;
  uint256 private constant SIG_TYPE_WALLET_BYTES32 = 3;

  /***********************************|
  |        Signature Functions        |
  |__________________________________*/

 /**
   * @notice Recover the signer of hash, assuming it's an EOA account
   * @dev Only for SignatureType.EIP712 and SignatureType.EthSign signatures
   * @param _hash      Hash that was signed
   *   encoded as (bytes32 r, bytes32 s, uint8 v, ... , SignatureType sigType)
   */
  function recoverSigner(
    bytes32 _hash,
    bytes calldata _signature
  ) internal pure returns (address signer) {
    if (_signature.length != 66) revert InvalidSignatureLength(_signature);
    uint256 signatureType = _signature.readUint8(_signature.length - 1);

    // Variables are not scoped in Solidity.
    uint8 v = _signature.readUint8(64);
    bytes32 r = _signature.readBytes32(0);
    bytes32 s = _signature.readBytes32(32);

    // 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 (281): 0 < s < secp256k1n ÷ 2 + 1, and for v in (282): 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.
    //
    // Source OpenZeppelin
    // https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/cryptography/ECDSA.sol

    if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
      revert InvalidSValue(_signature, s);
    }

    if (v != 27 && v != 28) {
      revert InvalidVValue(_signature, v);
    }

    // Signature using EIP712
    if (signatureType == SIG_TYPE_EIP712) {
      signer = ecrecover(_hash, v, r, s);

    // Signed using web3.eth_sign() or Ethers wallet.signMessage()
    } else if (signatureType == SIG_TYPE_ETH_SIGN) {
      signer = ecrecover(
        keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", _hash)),
        v,
        r,
        s
      );

    } else {
      // We cannot recover the signer for any other signature type.
      revert UnsupportedSignatureType(_signature, signatureType, true);
    }

    // Prevent signer from being 0x0
    if (signer == address(0x0)) revert SignerIsAddress0(_signature);

    return signer;
  }

 /**
   * @notice Returns true if the provided signature is valid for the given signer.
   * @dev Supports SignatureType.EIP712, SignatureType.EthSign, and ERC1271 signatures
   * @param _hash      Hash that was signed
   * @param _signer    Address of the signer candidate
   * @param _signature Signature byte array
   */
  function isValidSignature(
    bytes32 _hash,
    address _signer,
    bytes calldata _signature
  ) internal view returns (bool valid) {
    if (_signature.length == 0) {
      revert EmptySignature();
    }

    uint256 signatureType = uint8(_signature[_signature.length - 1]);
    if (signatureType == SIG_TYPE_EIP712 || signatureType == SIG_TYPE_ETH_SIGN) {
      // Recover signer and compare with provided
      valid = recoverSigner(_hash, _signature) == _signer;

    } else if (signatureType == SIG_TYPE_WALLET_BYTES32) {
      // Remove signature type before calling ERC1271, restore after call
      valid = ERC1271_MAGICVALUE_BYTES32 == IERC1271Wallet(_signer).isValidSignature(_hash, _signature[0:_signature.length - 1]);

    } else {
      // We cannot validate any other signature type.
      // We revert because we can say nothing about its validity.
      revert UnsupportedSignatureType(_signature, signatureType, false);
    }
  }
}