// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

abstract contract Initializable {
    uint8 private _initialized;

    bool private _initializing;

    event Initialized(uint8 version);

    modifier initializer() {
        bool isTopLevelCall = !_initializing;
        require(
            (isTopLevelCall && _initialized < 1) ||
                (!Address.isContract(address(this)) && _initialized == 1),
            "Initializable: contract is already initialized"
        );
        _initialized = 1;
        if (isTopLevelCall) {
            _initializing = true;
        }
        _;
        if (isTopLevelCall) {
            _initializing = false;
            emit Initialized(1);
        }
    }

    modifier reinitializer(uint8 version) {
        require(
            !_initializing && _initialized < version,
            "Initializable: contract is already initialized"
        );
        _initialized = version;
        _initializing = true;
        _;
        _initializing = false;
        emit Initialized(version);
    }

    modifier onlyInitializing() {
        require(_initializing, "Initializable: contract is not initializing");
        _;
    }

    function _disableInitializers() internal virtual {
        require(!_initializing, "Initializable: contract is initializing");
        if (_initialized != type(uint8).max) {
            _initialized = type(uint8).max;
            emit Initialized(type(uint8).max);
        }
    }

    function _getInitializedVersion() internal view returns (uint8) {
        return _initialized;
    }

    function _isInitializing() internal view returns (bool) {
        return _initializing;
    }
}

contract Implementation4 is Initializable {
    uint256 internal _value;

    function initialize() public initializer {}

    function setValue(uint256 _number) public {
        _value = _number;
    }

    function getValue() public view returns (uint256) {
        return _value;
    }

    fallback() external {
        _value = 1;
    }
}

contract Implementation2 is Initializable {
    uint256 internal _value;

    function initialize() public initializer {}

    function setValue(uint256 _number) public {
        _value = _number;
    }

    function getValue() public view returns (uint256) {
        return _value;
    }
}

abstract contract Proxy {
    function _delegate(address implementation) internal virtual {
        assembly {
            calldatacopy(0, 0, calldatasize())

            let result := delegatecall(
                gas(),
                implementation,
                0,
                calldatasize(),
                0,
                0
            )

            returndatacopy(0, 0, returndatasize())

            switch result
            case 0 {
                revert(0, returndatasize())
            }
            default {
                return(0, returndatasize())
            }
        }
    }

    function _implementation() internal view virtual returns (address);

    function _fallback() internal virtual {
        _beforeFallback();
        _delegate(_implementation());
    }

    fallback() external payable virtual {
        _fallback();
    }

    receive() external payable virtual {
        _fallback();
    }

    function _beforeFallback() internal virtual {}
}

interface IBeacon {
    function implementation() external view returns (address);
}

interface IERC1822Proxiable {
    function proxiableUUID() external view returns (bytes32);
}

library Address {
    function isContract(address account) internal view returns (bool) {
        return account.code.length > 0;
    }

    function sendValue(address payable recipient, uint256 amount) internal {
        require(
            address(this).balance >= amount,
            "Address: insufficient balance"
        );

        (bool success, ) = recipient.call{value: amount}("");
        require(
            success,
            "Address: unable to send value, recipient may have reverted"
        );
    }

    function functionCall(
        address target,
        bytes memory data
    ) internal returns (bytes memory) {
        return
            functionCallWithValue(
                target,
                data,
                0,
                "Address: low-level call failed"
            );
    }

    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return
            functionCallWithValue(
                target,
                data,
                value,
                "Address: low-level call with value failed"
            );
    }

    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(
            address(this).balance >= value,
            "Address: insufficient balance for call"
        );
        (bool success, bytes memory returndata) = target.call{value: value}(
            data
        );
        return
            verifyCallResultFromTarget(
                target,
                success,
                returndata,
                errorMessage
            );
    }

    function functionStaticCall(
        address target,
        bytes memory data
    ) internal view returns (bytes memory) {
        return
            functionStaticCall(
                target,
                data,
                "Address: low-level static call failed"
            );
    }

    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return
            verifyCallResultFromTarget(
                target,
                success,
                returndata,
                errorMessage
            );
    }

    function functionDelegateCall(
        address target,
        bytes memory data
    ) internal returns (bytes memory) {
        return
            functionDelegateCall(
                target,
                data,
                "Address: low-level delegate call failed"
            );
    }

    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return
            verifyCallResultFromTarget(
                target,
                success,
                returndata,
                errorMessage
            );
    }

    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(
        bytes memory returndata,
        string memory errorMessage
    ) private pure {
        if (returndata.length > 0) {
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

library StorageSlot {
    struct AddressSlot {
        address value;
    }

    struct BooleanSlot {
        bool value;
    }

    struct Bytes32Slot {
        bytes32 value;
    }

    struct Uint256Slot {
        uint256 value;
    }

    function getAddressSlot(
        bytes32 slot
    ) internal pure returns (AddressSlot storage r) {
        assembly {
            r.slot := slot
        }
    }

    function getBooleanSlot(
        bytes32 slot
    ) internal pure returns (BooleanSlot storage r) {
        assembly {
            r.slot := slot
        }
    }

    function getBytes32Slot(
        bytes32 slot
    ) internal pure returns (Bytes32Slot storage r) {
        assembly {
            r.slot := slot
        }
    }

    function getUint256Slot(
        bytes32 slot
    ) internal pure returns (Uint256Slot storage r) {
        assembly {
            r.slot := slot
        }
    }
}

abstract contract ERC1967Upgrade {
    bytes32 private constant _ROLLBACK_SLOT =
        0x4910fdfa16fed3260ed0e7147f7cc6da11a60208b5b9406d12a635614ffd9143;

    bytes32 internal constant _IMPLEMENTATION_SLOT =
        0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;

    event Upgraded(address indexed implementation);

    function _getImplementation() internal view returns (address) {
        return StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value;
    }

    function _setImplementation(address newImplementation) private {
        require(
            Address.isContract(newImplementation),
            "ERC1967: new implementation is not a contract"
        );
        StorageSlot
            .getAddressSlot(_IMPLEMENTATION_SLOT)
            .value = newImplementation;
    }

    function _upgradeTo(address newImplementation) internal {
        _setImplementation(newImplementation);
        emit Upgraded(newImplementation);
    }

    function _upgradeToAndCall(
        address newImplementation,
        bytes memory data,
        bool forceCall
    ) internal {
        _upgradeTo(newImplementation);
        if (data.length > 0 || forceCall) {
            Address.functionDelegateCall(newImplementation, data);
        }
    }

    function _upgradeToAndCallUUPS(
        address newImplementation,
        bytes memory data,
        bool forceCall
    ) internal {
        if (StorageSlot.getBooleanSlot(_ROLLBACK_SLOT).value) {
            _setImplementation(newImplementation);
        } else {
            try IERC1822Proxiable(newImplementation).proxiableUUID() returns (
                bytes32 slot
            ) {
                require(
                    slot == _IMPLEMENTATION_SLOT,
                    "ERC1967Upgrade: unsupported proxiableUUID"
                );
            } catch {
                revert("ERC1967Upgrade: new implementation is not UUPS");
            }
            _upgradeToAndCall(newImplementation, data, forceCall);
        }
    }

    bytes32 internal constant _ADMIN_SLOT =
        0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103;

    event AdminChanged(address previousAdmin, address newAdmin);

    function _getAdmin() internal view returns (address) {
        return StorageSlot.getAddressSlot(_ADMIN_SLOT).value;
    }

    function _setAdmin(address newAdmin) private {
        require(
            newAdmin != address(0),
            "ERC1967: new admin is the zero address"
        );
        StorageSlot.getAddressSlot(_ADMIN_SLOT).value = newAdmin;
    }

    function _changeAdmin(address newAdmin) internal {
        emit AdminChanged(_getAdmin(), newAdmin);
        _setAdmin(newAdmin);
    }

    bytes32 internal constant _BEACON_SLOT =
        0xa3f0ad74e5423aebfd80d3ef4346578335a9a72aeaee59ff6cb3582b35133d50;

    event BeaconUpgraded(address indexed beacon);

    function _getBeacon() internal view returns (address) {
        return StorageSlot.getAddressSlot(_BEACON_SLOT).value;
    }

    function _setBeacon(address newBeacon) private {
        require(
            Address.isContract(newBeacon),
            "ERC1967: new beacon is not a contract"
        );
        require(
            Address.isContract(IBeacon(newBeacon).implementation()),
            "ERC1967: beacon implementation is not a contract"
        );
        StorageSlot.getAddressSlot(_BEACON_SLOT).value = newBeacon;
    }

    function _upgradeBeaconToAndCall(
        address newBeacon,
        bytes memory data,
        bool forceCall
    ) internal {
        _setBeacon(newBeacon);
        emit BeaconUpgraded(newBeacon);
        if (data.length > 0 || forceCall) {
            Address.functionDelegateCall(
                IBeacon(newBeacon).implementation(),
                data
            );
        }
    }
}

contract ERC1967Proxy is Proxy, ERC1967Upgrade {
    constructor(address _logic, bytes memory _data) payable {
        _upgradeToAndCall(_logic, _data, false);
    }

    function _implementation()
        internal
        view
        virtual
        override
        returns (address impl)
    {
        return ERC1967Upgrade._getImplementation();
    }
}

contract TransparentUpgradeableProxy is ERC1967Proxy {
    constructor(address _logic) payable ERC1967Proxy(_logic, "") {
        _changeAdmin(msg.sender);
    }

    modifier ifAdmin() {
        if (msg.sender == _getAdmin()) {
            _;
        } else {
            _fallback();
        }
    }

    function admin() external payable ifAdmin returns (address admin_) {
        _requireZeroValue();
        admin_ = _getAdmin();
    }

    function implementation()
        external
        payable
        ifAdmin
        returns (address implementation_)
    {
        _requireZeroValue();
        implementation_ = _implementation();
    }

    function changeAdmin(address newAdmin) external payable virtual ifAdmin {
        _requireZeroValue();
        _changeAdmin(newAdmin);
    }

    function upgradeTo(address newImplementation) external payable ifAdmin {
        _requireZeroValue();
        _upgradeToAndCall(newImplementation, bytes(""), false);
    }

    function upgradeToAndCall(
        address newImplementation,
        bytes calldata data
    ) external payable ifAdmin {
        _upgradeToAndCall(newImplementation, data, true);
    }

    function _admin() internal view virtual returns (address) {
        return _getAdmin();
    }

    function _beforeFallback() internal virtual override {
        require(
            msg.sender != _getAdmin(),
            "TransparentUpgradeableProxy: admin cannot fallback to proxy target"
        );
        super._beforeFallback();
    }

    function _requireZeroValue() private {
        require(msg.value == 0);
    }
}

contract TestHelper {
    function getValue(address proxyAddress) public returns (uint256) {
        Implementation2 proxyInstance2 = Implementation2(proxyAddress);
        return proxyInstance2.getValue();
    }
}

contract TransparentUpgradeableProxyTestRunner {
    function test() public {
        assert(0 == getValue());
    }

    function getValue() public returns (uint256) {
        Implementation4 instance4 = new Implementation4();
        TransparentUpgradeableProxy proxy = new TransparentUpgradeableProxy(
            address(instance4)
        );
        Implementation2 instance2 = new Implementation2();
        proxy.upgradeTo(address(instance2));
        //use helper because proxy admin can't call getValue()
        TestHelper h = new TestHelper();
        return h.getValue(address(proxy));
    }
}