Factory.sol

// SPDX-License-Identifier: CAL
pragma solidity =0.8.10;

import {IFactory} from "./IFactory.sol";
// solhint-disable-next-line max-line-length
import {ReentrancyGuard} from "@openzeppelin/contracts/security/ReentrancyGuard.sol";

/// @title Factory
/// @notice Base contract for deploying and registering child contracts.
abstract contract Factory is IFactory, ReentrancyGuard {
    /// @dev state to track each deployed contract address. A `Factory` will
    /// never lie about deploying a child, unless `isChild` is overridden to do
    /// so.
    mapping(address => bool) private contracts;

    /// Implements `IFactory`.
    ///
    /// `_createChild` hook must be overridden to actually create child
    /// contract.
    ///
    /// Implementers may want to overload this function with a typed equivalent
    /// to expose domain specific structs etc. to the compiled ABI consumed by
    /// tooling and other scripts. To minimise gas costs for deployment it is
    /// expected that the tooling will consume the typed ABI, then encode the
    /// arguments and pass them to this function directly.
    ///
    /// @param data_ ABI encoded data to pass to child contract constructor.
    function _createChild(bytes calldata data_)
        internal
        virtual
        returns (address)
    {} // solhint-disable-line no-empty-blocks

    /// Implements `IFactory`.
    ///
    /// Calls the `_createChild` hook that inheriting contracts must override.
    /// Registers child contract address such that `isChild` is `true`.
    /// Emits `NewChild` event.
    ///
    /// @param data_ Encoded data to pass down to child contract constructor.
    /// @return New child contract address.
    function createChild(bytes calldata data_)
        external
        virtual
        override
        nonReentrant
        returns (address)
    {
        // Create child contract using hook.
        address child_ = _createChild(data_);
        // Ensure the child at this address has not previously been deployed.
        require(!contracts[child_], "DUPLICATE_CHILD");
        // Register child contract address to `contracts` mapping.
        contracts[child_] = true;
        // Emit `NewChild` event with child contract address.
        emit IFactory.NewChild(msg.sender, child_);
        return child_;
    }

    /// Implements `IFactory`.
    ///
    /// Checks if address is registered as a child contract of this factory.
    ///
    /// @param maybeChild_ Address of child contract to look up.
    /// @return Returns `true` if address is a contract created by this
    /// contract factory, otherwise `false`.
    function isChild(address maybeChild_)
        external
        view
        virtual
        override
        returns (bool)
    {
        return contracts[maybeChild_];
    }
}