BTC

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./interfaces/IBRC20Factory.sol";

contract BRC20 {
    string public name;
    string public symbol;
    uint8 public immutable decimals;
    address public immutable factory;
    uint256 public totalSupply;
    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;
    mapping(address => uint256) public nonces;

    bytes32 public DOMAIN_SEPARATOR;
    bytes32 public constant PERMIT_TYPEHASH =
        keccak256(
            "Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"
        );
    bytes32 public constant DOMAIN_TYPEHASH =
        keccak256(
            "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
        );

    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
    event Transfer(address indexed from, address indexed to, uint256 value);

    constructor() {
        (name, symbol, decimals) = IBRC20Factory(msg.sender).parameters();

        factory = msg.sender;

        uint256 chainId;
        assembly {
            chainId := chainid()
        }
        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                DOMAIN_TYPEHASH,
                keccak256(bytes(name)),
                keccak256(bytes("1")),
                chainId,
                address(this)
            )
        );
    }

    function mint(address to, uint256 amount) external {
        require(msg.sender == factory, "unauthorized");
        _mint(to, amount);
    }

    function burn(uint256 amount) external {
        require(msg.sender == factory, "unauthorized");
        _burn(msg.sender, amount);
    }

    function approve(address spender, uint256 amount) external returns (bool) {
        allowance[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }

    function transfer(address to, uint256 amount) external returns (bool) {
        balanceOf[msg.sender] -= amount;

        unchecked {
            balanceOf[to] += amount;
        }

        emit Transfer(msg.sender, to, amount);
        return true;
    }

    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool) {
        uint256 allowed = allowance[from][msg.sender];

        if (allowed != type(uint256).max)
            allowance[from][msg.sender] = allowed - amount;

        balanceOf[from] -= amount;

        unchecked {
            balanceOf[to] += amount;
        }

        emit Transfer(from, to, amount);
        return true;
    }

    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external {
        require(deadline >= block.timestamp, "EXPIRED");
        unchecked {
            bytes32 digest = keccak256(
                abi.encodePacked(
                    "\x19\x01",
                    DOMAIN_SEPARATOR,
                    keccak256(
                        abi.encode(
                            PERMIT_TYPEHASH,
                            owner,
                            spender,
                            value,
                            nonces[owner]++,
                            deadline
                        )
                    )
                )
            );
            address recoveredAddress = ecrecover(digest, v, r, s);
            require(
                recoveredAddress != address(0) && recoveredAddress == owner,
                "INVALID_SIGNATURE"
            );
            allowance[recoveredAddress][spender] = value;
        }
        emit Approval(owner, spender, value);
    }

    function _mint(address to, uint256 amount) internal {
        totalSupply += amount;

        unchecked {
            balanceOf[to] += amount;
        }

        emit Transfer(address(0), to, amount);
    }

    function _burn(address from, uint256 amount) internal {
        balanceOf[from] -= amount;

        unchecked {
            totalSupply -= amount;
        }

        emit Transfer(from, address(0), amount);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

interface IBRC20Factory {
    function parameters()
        external
        view
        returns (string memory name, string memory symbol, uint8 decimals);
}

{
  "compilationTarget": {
    "contracts/bridge/BRC20.sol": "BRC20"
  },
  "evmVersion": "paris",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}