// contracts/NFT.sol
// SPDX-License-Identifier: MIT OR Apache-2.0
pragma solidity ^0.8.3;

import "@openzeppelin/contracts/access/Ownable.sol";


contract UnicornAdmin is Ownable {
    mapping(address => uint256) addressToUnicornCreatorId;
    address[] UnicornCreators;

    event UnicornCreatorAdded(address creator);
    event UnicornCreatorRemoved(address creator);

    constructor()  {
        // placeholder to reserve ID zero as an invalid value
        _addUnicornCreator(address(0));

        // the owner should be allowed to create kitties
        _addUnicornCreator(owner());
    }

    modifier onlyUnicornCreator() {
        require(isUnicornCreator(msg.sender), "must be a Unicorn creator");
        _;
    }

    function isUnicornCreator(address _address) public view returns (bool) {
        return addressToUnicornCreatorId[_address] != 0;
    }

    function addUnicornCreator(address _address) external onlyOwner {
        require(_address != address(this), "contract address");
        require(_address != address(0), "zero address");

        _addUnicornCreator(_address);
    }

    function _addUnicornCreator(address _address) internal {
        addressToUnicornCreatorId[_address] = UnicornCreators.length;
        UnicornCreators.push(_address);

        emit UnicornCreatorAdded(_address);
    }

    function removeUnicornCreator(address _address) external onlyOwner {
        uint256 id = addressToUnicornCreatorId[_address];
        delete addressToUnicornCreatorId[_address];
        delete UnicornCreators[id];

        emit UnicornCreatorRemoved(_address);
    }

    function getUnicornCreators() external view returns (address[] memory) {
        return UnicornCreators;
    }
}