// SPDX-License-Identifier: MIT

pragma solidity ^0.7.1;
pragma experimental ABIEncoderV2;


// 
/******************************************************************************\
* Author: Nick Mudge <nick@perfectabstractions.com> (https://twitter.com/mudgen)
/******************************************************************************/
interface IDiamondCut {
    enum FacetCutAction {Add, Replace, Remove}

    struct FacetCut {
        address facetAddress;
        FacetCutAction action;
        bytes4[] functionSelectors;
    }

    /// @notice Add/replace/remove any number of functions and optionally execute
    ///         a function with delegatecall
    /// @param _diamondCut Contains the facet addresses and function selectors
    /// @param _init The address of the contract or facet to execute _calldata
    /// @param _calldata A function call, including function selector and arguments
    ///                  _calldata is executed with delegatecall on _init
    function diamondCut(
        FacetCut[] calldata _diamondCut,
        address _init,
        bytes calldata _calldata
    ) external;

    event DiamondCut(FacetCut[] _diamondCut, address _init, bytes _calldata);
}

// 
/******************************************************************************\
* Author: Nick Mudge <nick@perfectabstractions.com> (https://twitter.com/mudgen)
*
* Implementation of internal diamondCut function.
/******************************************************************************/
library LibDiamond {
    bytes32 constant DIAMOND_STORAGE_POSITION = keccak256("diamond.standard.diamond.storage");

    struct FacetAddressAndPosition {
        address facetAddress;
        uint16 functionSelectorPosition; // position in facetFunctionSelectors.functionSelectors array
    }

    struct FacetFunctionSelectors {
        bytes4[] functionSelectors;
        uint16 facetAddressPosition; // position of facetAddress in facetAddresses array
    }

    struct DiamondStorage {
        // maps function selector to the facet address and
        // the position of the selector in the facetFunctionSelectors.selectors array
        mapping(bytes4 => FacetAddressAndPosition) selectorToFacetAndPosition;
        // maps facet addresses to function selectors
        mapping(address => FacetFunctionSelectors) facetFunctionSelectors;
        // facet addresses
        address[] facetAddresses;
        // Used to query if a contract implements an interface.
        // Used to implement ERC-165.
        mapping(bytes4 => bool) supportedInterfaces;
        // owner of the contract
        address contractOwner;
    }

    function diamondStorage() internal pure returns (DiamondStorage storage ds) {
        bytes32 position = DIAMOND_STORAGE_POSITION;
        assembly {
            ds.slot := position
        }
    }

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    function setContractOwner(address _newOwner) internal {
        DiamondStorage storage ds = diamondStorage();
        address previousOwner = ds.contractOwner;
        ds.contractOwner = _newOwner;
        emit OwnershipTransferred(previousOwner, _newOwner);
    }

    function contractOwner() internal view returns (address contractOwner_) {
        contractOwner_ = diamondStorage().contractOwner;
    }

    function enforceIsContractOwner() internal view {
        require(msg.sender == diamondStorage().contractOwner, "LibDiamond: Must be contract owner");
    }

    modifier onlyOwner {
        require(msg.sender == diamondStorage().contractOwner, "LibDiamond: Must be contract owner");
        _;
    }

    event DiamondCut(IDiamondCut.FacetCut[] _diamondCut, address _init, bytes _calldata);

    // Internal function version of diamondCut
    // This code is almost the same as the external diamondCut,
    // except it is using 'FacetCut[] memory _diamondCut' instead of
    // 'FacetCut[] calldata _diamondCut'.
    // The code is duplicated to prevent copying calldata to memory which
    // causes an error for a two dimensional array.
    function diamondCut(
        IDiamondCut.FacetCut[] memory _diamondCut,
        address _init,
        bytes memory _calldata
    ) internal {
        for (uint256 facetIndex; facetIndex < _diamondCut.length; facetIndex++) {
            addReplaceRemoveFacetSelectors(
                _diamondCut[facetIndex].facetAddress,
                _diamondCut[facetIndex].action,
                _diamondCut[facetIndex].functionSelectors
            );
        }
        emit DiamondCut(_diamondCut, _init, _calldata);
        initializeDiamondCut(_init, _calldata);
    }

    function addReplaceRemoveFacetSelectors(
        address _newFacetAddress,
        IDiamondCut.FacetCutAction _action,
        bytes4[] memory _selectors
    ) internal {
        DiamondStorage storage ds = diamondStorage();
        require(_selectors.length > 0, "LibDiamondCut: No selectors in facet to cut");
        // add or replace functions
        if (_newFacetAddress != address(0)) {
            uint256 facetAddressPosition = ds.facetFunctionSelectors[_newFacetAddress].facetAddressPosition;
            // add new facet address if it does not exist
            if (facetAddressPosition == 0 && ds.facetFunctionSelectors[_newFacetAddress].functionSelectors.length == 0) {
                enforceHasContractCode(_newFacetAddress, "LibDiamondCut: New facet has no code");
                facetAddressPosition = ds.facetAddresses.length;
                ds.facetAddresses.push(_newFacetAddress);
                ds.facetFunctionSelectors[_newFacetAddress].facetAddressPosition = uint16(facetAddressPosition);
            }
            // add or replace selectors
            for (uint256 selectorIndex; selectorIndex < _selectors.length; selectorIndex++) {
                bytes4 selector = _selectors[selectorIndex];
                address oldFacetAddress = ds.selectorToFacetAndPosition[selector].facetAddress;
                // add
                if (_action == IDiamondCut.FacetCutAction.Add) {
                    require(oldFacetAddress == address(0), "LibDiamondCut: Can't add function that already exists");
                    addSelector(_newFacetAddress, selector);
                } else if (_action == IDiamondCut.FacetCutAction.Replace) {
                    // replace
                    require(oldFacetAddress != _newFacetAddress, "LibDiamondCut: Can't replace function with same function");
                    removeSelector(oldFacetAddress, selector);
                    addSelector(_newFacetAddress, selector);
                } else {
                    revert("LibDiamondCut: Incorrect FacetCutAction");
                }
            }
        } else {
            require(_action == IDiamondCut.FacetCutAction.Remove, "LibDiamondCut: action not set to FacetCutAction.Remove");
            // remove selectors
            for (uint256 selectorIndex; selectorIndex < _selectors.length; selectorIndex++) {
                bytes4 selector = _selectors[selectorIndex];
                removeSelector(ds.selectorToFacetAndPosition[selector].facetAddress, selector);
            }
        }
    }

    function addSelector(address _newFacet, bytes4 _selector) internal {
        DiamondStorage storage ds = diamondStorage();
        uint256 selectorPosition = ds.facetFunctionSelectors[_newFacet].functionSelectors.length;
        ds.facetFunctionSelectors[_newFacet].functionSelectors.push(_selector);
        ds.selectorToFacetAndPosition[_selector].facetAddress = _newFacet;
        ds.selectorToFacetAndPosition[_selector].functionSelectorPosition = uint16(selectorPosition);
    }

    function removeSelector(address _oldFacetAddress, bytes4 _selector) internal {
        DiamondStorage storage ds = diamondStorage();
        // if function does not exist then do nothing and return
        require(_oldFacetAddress != address(0), "LibDiamondCut: Can't remove or replace function that doesn't exist");
        require(_oldFacetAddress != address(this), "LibDiamondCut: Can't remove or replace immutable function");
        // replace selector with last selector, then delete last selector
        uint256 selectorPosition = ds.selectorToFacetAndPosition[_selector].functionSelectorPosition;
        uint256 lastSelectorPosition = ds.facetFunctionSelectors[_oldFacetAddress].functionSelectors.length - 1;
        // if not the same then replace _selector with lastSelector
        if (selectorPosition != lastSelectorPosition) {
            bytes4 lastSelector = ds.facetFunctionSelectors[_oldFacetAddress].functionSelectors[lastSelectorPosition];
            ds.facetFunctionSelectors[_oldFacetAddress].functionSelectors[selectorPosition] = lastSelector;
            ds.selectorToFacetAndPosition[lastSelector].functionSelectorPosition = uint16(selectorPosition);
        }
        // delete the last selector
        ds.facetFunctionSelectors[_oldFacetAddress].functionSelectors.pop();
        delete ds.selectorToFacetAndPosition[_selector];

        // if no more selectors for facet address then delete the facet address
        if (lastSelectorPosition == 0) {
            // replace facet address with last facet address and delete last facet address
            uint256 lastFacetAddressPosition = ds.facetAddresses.length - 1;
            uint256 facetAddressPosition = ds.facetFunctionSelectors[_oldFacetAddress].facetAddressPosition;
            if (facetAddressPosition != lastFacetAddressPosition) {
                address lastFacetAddress = ds.facetAddresses[lastFacetAddressPosition];
                ds.facetAddresses[facetAddressPosition] = lastFacetAddress;
                ds.facetFunctionSelectors[lastFacetAddress].facetAddressPosition = uint16(facetAddressPosition);
            }
            ds.facetAddresses.pop();
            delete ds.facetFunctionSelectors[_oldFacetAddress];
        }
    }

    function initializeDiamondCut(address _init, bytes memory _calldata) internal {
        if (_init == address(0)) {
            require(_calldata.length == 0, "LibDiamondCut: _init is address(0) but_calldata is not empty");
        } else {
            require(_calldata.length > 0, "LibDiamondCut: _calldata is empty but _init is not address(0)");
            if (_init != address(this)) {
                enforceHasContractCode(_init, "LibDiamondCut: _init address has no code");
            }
            (bool success, bytes memory error) = _init.delegatecall(_calldata);
            if (!success) {
                if (error.length > 0) {
                    // bubble up the error
                    revert(string(error));
                } else {
                    revert("LibDiamondCut: _init function reverted");
                }
            }
        }
    }

    function enforceHasContractCode(address _contract, string memory _errorMessage) internal view {
        uint256 contractSize;
        assembly {
            contractSize := extcodesize(_contract)
        }
        require(contractSize > 0, _errorMessage);
    }
}

// 
/******************************************************************************\
* Author: Nick Mudge <nick@perfectabstractions.com> (https://twitter.com/mudgen)
/******************************************************************************/
// A loupe is a small magnifying glass used to look at diamonds.
// These functions look at diamonds
interface IDiamondLoupe {
    /// These functions are expected to be called frequently
    /// by tools.

    struct Facet {
        address facetAddress;
        bytes4[] functionSelectors;
    }

    /// @notice Gets all facet addresses and their four byte function selectors.
    /// @return facets_ Facet
    function facets() external view returns (Facet[] memory facets_);

    /// @notice Gets all the function selectors supported by a specific facet.
    /// @param _facet The facet address.
    /// @return facetFunctionSelectors_
    function facetFunctionSelectors(address _facet) external view returns (bytes4[] memory facetFunctionSelectors_);

    /// @notice Get all the facet addresses used by a diamond.
    /// @return facetAddresses_
    function facetAddresses() external view returns (address[] memory facetAddresses_);

    /// @notice Gets the facet that supports the given selector.
    /// @dev If facet is not found return address(0).
    /// @param _functionSelector The function selector.
    /// @return facetAddress_ The facet address.
    function facetAddress(bytes4 _functionSelector) external view returns (address facetAddress_);
}

// 
/// @title ERC-173 Contract Ownership Standard
///  Note: the ERC-165 identifier for this interface is 0x7f5828d0
/* is ERC165 */
interface IERC173 {
    /// @dev This emits when ownership of a contract changes.
    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /// @notice Get the address of the owner
    /// @return owner_ The address of the owner.
    function owner() external view returns (address owner_);

    /// @notice Set the address of the new owner of the contract
    /// @dev Set _newOwner to address(0) to renounce any ownership.
    /// @param _newOwner The address of the new owner of the contract
    function transferOwnership(address _newOwner) external;
}

// 
interface IERC165 {
    /// @notice Query if a contract implements an interface
    /// @param interfaceId The interface identifier, as specified in ERC-165
    /// @dev Interface identification is specified in ERC-165. This function
    ///  uses less than 30,000 gas.
    /// @return `true` if the contract implements `interfaceID` and
    ///  `interfaceID` is not 0xffffffff, `false` otherwise
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// 
/******************************************************************************\
* Author: Nick Mudge
*
* Implementation of an example of a diamond.
/******************************************************************************/
contract Diamond {
    constructor(IDiamondCut.FacetCut[] memory _diamondCut, address _owner) payable {
        LibDiamond.diamondCut(_diamondCut, address(0), new bytes(0));
        LibDiamond.setContractOwner(_owner);

        LibDiamond.DiamondStorage storage ds = LibDiamond.diamondStorage();
                        
        // adding ERC165 data
        // ERC165
        ds.supportedInterfaces[IERC165.supportsInterface.selector] = true;

        // DiamondCut
        ds.supportedInterfaces[IDiamondCut.diamondCut.selector] = true;

        // DiamondLoupe        
        ds.supportedInterfaces[
            IDiamondLoupe.facets.selector ^
            IDiamondLoupe.facetFunctionSelectors.selector ^
            IDiamondLoupe.facetAddresses.selector ^
            IDiamondLoupe.facetAddress.selector
        ] = true;

        // ERC173
        ds.supportedInterfaces[
            IERC173.transferOwnership.selector ^ 
            IERC173.owner.selector
        ] = true;
    }

    // Find facet for function that is called and execute the
    // function if a facet is found and return any value.
    fallback() external payable {
        LibDiamond.DiamondStorage storage ds;
        bytes32 position = LibDiamond.DIAMOND_STORAGE_POSITION;
        assembly {
            ds.slot := position
        }
        address facet = ds.selectorToFacetAndPosition[msg.sig].facetAddress;
        require(facet != address(0), "Diamond: Function does not exist");
        assembly {
            calldatacopy(0, 0, calldatasize())
            let result := delegatecall(gas(), facet, 0, calldatasize(), 0, 0)
            returndatacopy(0, 0, returndatasize())
            switch result
                case 0 {
                    revert(0, returndatasize())
                }
                default {
                    return(0, returndatasize())
                }
        }
    }

    receive() external payable {}
}

// 
contract DiamondFactory {
  event DiamondCreated(address tokenAddress);

  function deployNewDiamond(
    address _owner,
    IDiamondCut.FacetCut[] memory diamondCut
  ) public returns (address) {
    Diamond d = new Diamond(diamondCut, _owner);
    emit DiamondCreated(address(d));
  }
}