// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/// @author: manifold.xyz

/**
 * ENS Registry Interface
 */
interface ENS {
    function resolver(bytes32 node) external view returns (address);
}

/**
 * ENS Resolver Interface
 */
interface Resolver {
    function addr(bytes32 node) external view returns (address);
    function name(bytes32 node) external view returns (string memory);
    function text(bytes32 node, string calldata key) external view returns (string memory);
}

/**
 * Validate a signing address is associtaed with a linked address
 */
library LinkedAddress {
    /**
     * Validate that the message sender is an authentication address for mainAddress
     *
     * @param ensRegistry    Address of ENS registry
     * @param mainAddress     The main address we want to authenticate for.
     * @param mainENSNodeHash The main ENS Node Hash
     * @param authKey         The TEXT record of the authKey we are using for validation
     * @param authENSNodeHash The auth ENS Node Hash
     */
    function validateSender(
        address ensRegistry,
        address mainAddress,
        bytes32 mainENSNodeHash,
        string calldata authKey,
        bytes32 authENSNodeHash
    ) internal view returns (bool) {
        return validate(ensRegistry, mainAddress, mainENSNodeHash, authKey, msg.sender, authENSNodeHash);
    }

    /**
     * Validate that the authAddress is an authentication address for mainAddress
     *
     * @param ensRegistry     Address of ENS registry
     * @param mainAddress     The main address we want to authenticate for.
     * @param mainENSNodeHash The main ENS Node Hash
     * @param authAddress     The address of the authentication wallet
     * @param authENSNodeHash The auth ENS Node Hash
     */
    function validate(
        address ensRegistry,
        address mainAddress,
        bytes32 mainENSNodeHash,
        string calldata authKey,
        address authAddress,
        bytes32 authENSNodeHash
    ) internal view returns (bool) {
        _verifyMainENS(ensRegistry, mainAddress, mainENSNodeHash, authKey, authAddress);
        _verifyAuthENS(ensRegistry, mainAddress, authKey, authAddress, authENSNodeHash);

        return true;
    }

    // *********************
    //   Helper Functions
    // *********************
    function _verifyMainENS(
        address ensRegistry,
        address mainAddress,
        bytes32 mainENSNodeHash,
        string calldata authKey,
        address authAddress
    ) private view {
        // Check if the ENS nodes resolve correctly to the provided addresses
        address mainResolver = ENS(ensRegistry).resolver(mainENSNodeHash);
        require(mainResolver != address(0), "Main ENS not registered");
        require(mainAddress == Resolver(mainResolver).addr(mainENSNodeHash), "Main address is wrong");

        // Verify the authKey TEXT record is set to authAddress by mainENS
        string memory authText = Resolver(mainResolver).text(mainENSNodeHash, string(abi.encodePacked("eip5131:", authKey)));
        require(
            keccak256(bytes(authText)) == keccak256(bytes(_addressToString(authAddress))),
            "Invalid auth address"
        );
    }

    function _verifyAuthENS(
        address ensRegistry,
        address mainAddress,
        string memory authKey,
        address authAddress,
        bytes32 authENSNodeHash
    ) private view {
        // Check if the ENS nodes resolve correctly to the provided addresses
        address authResolver = ENS(ensRegistry).resolver(authENSNodeHash);
        require(authResolver != address(0), "Auth ENS not registered");
        require(authAddress == Resolver(authResolver).addr(authENSNodeHash), "Auth address is wrong");

        // Verify the TEXT record is appropriately set by authENS
        string memory vaultText = Resolver(authResolver).text(authENSNodeHash, "eip5131:vault");
        require(
            keccak256(abi.encodePacked(authKey, ":", _addressToString(mainAddress))) ==
                keccak256(bytes(vaultText)),
            "Invalid auth text record"
        );
    }

    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";

    function sha3HexAddress(address addr) private pure returns (bytes32 ret) {
        uint256 value = uint256(uint160(addr));
        bytes memory buffer = new bytes(40);
        for (uint256 i = 39; i > 1; --i) {
            buffer[i] = _HEX_SYMBOLS[value & 0xf];
            value >>= 4;
        }
        return keccak256(buffer);
    }

    function _addressToString(address addr) private pure returns (string memory ptr) {
        // solhint-disable-next-line no-inline-assembly
        assembly {
            ptr := mload(0x40)

            // Adjust mem ptr and keep 32 byte aligned
            // 32 bytes to store string length; address is 42 bytes long
            mstore(0x40, add(ptr, 96))

            // Store (string length, '0', 'x') (42, 48, 120)
            // Single write by offsetting across 32 byte boundary
            ptr := add(ptr, 2)
            mstore(ptr, 0x2a3078)

            // Write string backwards
            for {
                // end is at 'x', ptr is at lsb char
                let end := add(ptr, 31)
                ptr := add(ptr, 71)
            } gt(ptr, end) {
                ptr := sub(ptr, 1)
                addr := shr(4, addr)
            } {
                let v := and(addr, 0xf)
                // if > 9, use ascii 'a-f' (no conditional required)
                v := add(v, mul(gt(v, 9), 39))
                // Add ascii for '0'
                v := add(v, 48)
                mstore8(ptr, v)
            }

            // return ptr to point to length (32 + 2 for '0x' - 1)
            ptr := sub(ptr, 33)
        }

        return string(ptr);
    }
}