Contract Source Code:

// SPDX-License-Identifier: MIT
pragma solidity 0.8.16;

interface IDiamondCut {
    enum FacetCutAction {
        Add,
        Replace,
        Remove
    }
    // Add=0, Replace=1, Remove=2

    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);
}

// SPDX-License-Identifier: MIT
pragma solidity 0.8.16;

import { IDiamondCut } from "../interfaces/IDiamondCut.sol";
import { OnlyContractOwner } from "../utils/Errors.sol";

/// Implementation of EIP-2535 Diamond Standard
/// https://eips.ethereum.org/EIPS/eip-2535
library LibDiamond {
    /// @dev keccak256("diamond.standard.diamond.storage");
    bytes32 internal constant DIAMOND_STORAGE_POSITION = hex"c8fcad8db84d3cc18b4c41d551ea0ee66dd599cde068d998e57d5e09332c131c";

    // Diamond specific errors
    error IncorrectFacetCutAction();
    error NoSelectorsInFace();
    error FunctionAlreadyExists();
    error FacetAddressIsZero();
    error FacetAddressIsNotZero();
    error FacetContainsNoCode();
    error FunctionDoesNotExist();
    error FunctionIsImmutable();
    error InitZeroButCalldataNotEmpty();
    error CalldataEmptyButInitNotZero();
    error InitReverted();
    // ----------------

    struct FacetAddressAndPosition {
        address facetAddress;
        uint96 functionSelectorPosition; // position in facetFunctionSelectors.functionSelectors array
    }

    struct FacetFunctionSelectors {
        bytes4[] functionSelectors;
        uint256 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;
        // solhint-disable-next-line no-inline-assembly
        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 {
        if (msg.sender != diamondStorage().contractOwner) revert OnlyContractOwner();
    }

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

    // Internal function version of diamondCut
    function diamondCut(
        IDiamondCut.FacetCut[] memory _diamondCut,
        address _init,
        bytes memory _calldata
    ) internal {
        for (uint256 facetIndex; facetIndex < _diamondCut.length; ) {
            IDiamondCut.FacetCutAction action = _diamondCut[facetIndex].action;
            if (action == IDiamondCut.FacetCutAction.Add) {
                addFunctions(_diamondCut[facetIndex].facetAddress, _diamondCut[facetIndex].functionSelectors);
            } else if (action == IDiamondCut.FacetCutAction.Replace) {
                replaceFunctions(_diamondCut[facetIndex].facetAddress, _diamondCut[facetIndex].functionSelectors);
            } else if (action == IDiamondCut.FacetCutAction.Remove) {
                removeFunctions(_diamondCut[facetIndex].facetAddress, _diamondCut[facetIndex].functionSelectors);
            } else {
                revert IncorrectFacetCutAction();
            }
            unchecked {
                ++facetIndex;
            }
        }
        emit DiamondCut(_diamondCut, _init, _calldata);
        initializeDiamondCut(_init, _calldata);
    }

    function addFunctions(address _facetAddress, bytes4[] memory _functionSelectors) internal {
        if (_functionSelectors.length == 0) {
            revert NoSelectorsInFace();
        }
        DiamondStorage storage ds = diamondStorage();
        if (_facetAddress == address(0)) {
            revert FacetAddressIsZero();
        }
        uint96 selectorPosition = uint96(ds.facetFunctionSelectors[_facetAddress].functionSelectors.length);
        // add new facet address if it does not exist
        if (selectorPosition == 0) {
            addFacet(ds, _facetAddress);
        }
        for (uint256 selectorIndex; selectorIndex < _functionSelectors.length; ) {
            bytes4 selector = _functionSelectors[selectorIndex];
            address oldFacetAddress = ds.selectorToFacetAndPosition[selector].facetAddress;
            if (oldFacetAddress != address(0)) {
                revert FunctionAlreadyExists();
            }
            addFunction(ds, selector, selectorPosition, _facetAddress);
            unchecked {
                ++selectorPosition;
                ++selectorIndex;
            }
        }
    }

    function replaceFunctions(address _facetAddress, bytes4[] memory _functionSelectors) internal {
        if (_functionSelectors.length == 0) {
            revert NoSelectorsInFace();
        }
        DiamondStorage storage ds = diamondStorage();
        if (_facetAddress == address(0)) {
            revert FacetAddressIsZero();
        }
        uint96 selectorPosition = uint96(ds.facetFunctionSelectors[_facetAddress].functionSelectors.length);
        // add new facet address if it does not exist
        if (selectorPosition == 0) {
            addFacet(ds, _facetAddress);
        }
        for (uint256 selectorIndex; selectorIndex < _functionSelectors.length; ) {
            bytes4 selector = _functionSelectors[selectorIndex];
            address oldFacetAddress = ds.selectorToFacetAndPosition[selector].facetAddress;
            if (oldFacetAddress == _facetAddress) {
                revert FunctionAlreadyExists();
            }
            removeFunction(ds, oldFacetAddress, selector);
            addFunction(ds, selector, selectorPosition, _facetAddress);
            unchecked {
                ++selectorPosition;
                ++selectorIndex;
            }
        }
    }

    function removeFunctions(address _facetAddress, bytes4[] memory _functionSelectors) internal {
        if (_functionSelectors.length == 0) {
            revert NoSelectorsInFace();
        }
        DiamondStorage storage ds = diamondStorage();
        // if function does not exist then do nothing and return
        if (_facetAddress != address(0)) {
            revert FacetAddressIsNotZero();
        }
        for (uint256 selectorIndex; selectorIndex < _functionSelectors.length; ) {
            bytes4 selector = _functionSelectors[selectorIndex];
            address oldFacetAddress = ds.selectorToFacetAndPosition[selector].facetAddress;
            removeFunction(ds, oldFacetAddress, selector);
            unchecked {
                ++selectorIndex;
            }
        }
    }

    function addFacet(DiamondStorage storage ds, address _facetAddress) internal {
        enforceHasContractCode(_facetAddress);
        ds.facetFunctionSelectors[_facetAddress].facetAddressPosition = ds.facetAddresses.length;
        ds.facetAddresses.push(_facetAddress);
    }

    function addFunction(
        DiamondStorage storage ds,
        bytes4 _selector,
        uint96 _selectorPosition,
        address _facetAddress
    ) internal {
        ds.selectorToFacetAndPosition[_selector].functionSelectorPosition = _selectorPosition;
        ds.facetFunctionSelectors[_facetAddress].functionSelectors.push(_selector);
        ds.selectorToFacetAndPosition[_selector].facetAddress = _facetAddress;
    }

    function removeFunction(
        DiamondStorage storage ds,
        address _facetAddress,
        bytes4 _selector
    ) internal {
        if (_facetAddress == address(0)) {
            revert FunctionDoesNotExist();
        }
        // an immutable function is a function defined directly in a diamond
        if (_facetAddress == address(this)) {
            revert FunctionIsImmutable();
        }
        // replace selector with last selector, then delete last selector
        uint256 selectorPosition = ds.selectorToFacetAndPosition[_selector].functionSelectorPosition;
        uint256 lastSelectorPosition = ds.facetFunctionSelectors[_facetAddress].functionSelectors.length - 1;
        // if not the same then replace _selector with lastSelector
        if (selectorPosition != lastSelectorPosition) {
            bytes4 lastSelector = ds.facetFunctionSelectors[_facetAddress].functionSelectors[lastSelectorPosition];
            ds.facetFunctionSelectors[_facetAddress].functionSelectors[selectorPosition] = lastSelector;
            ds.selectorToFacetAndPosition[lastSelector].functionSelectorPosition = uint96(selectorPosition);
        }
        // delete the last selector
        ds.facetFunctionSelectors[_facetAddress].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[_facetAddress].facetAddressPosition;
            if (facetAddressPosition != lastFacetAddressPosition) {
                address lastFacetAddress = ds.facetAddresses[lastFacetAddressPosition];
                ds.facetAddresses[facetAddressPosition] = lastFacetAddress;
                ds.facetFunctionSelectors[lastFacetAddress].facetAddressPosition = facetAddressPosition;
            }
            ds.facetAddresses.pop();
            delete ds.facetFunctionSelectors[_facetAddress].facetAddressPosition;
        }
    }

    function initializeDiamondCut(address _init, bytes memory _calldata) internal {
        if (_init == address(0)) {
            if (_calldata.length != 0) {
                revert InitZeroButCalldataNotEmpty();
            }
        } else {
            if (_calldata.length == 0) {
                revert CalldataEmptyButInitNotZero();
            }
            if (_init != address(this)) {
                enforceHasContractCode(_init);
            }
            // solhint-disable-next-line avoid-low-level-calls
            (bool success, bytes memory error) = _init.delegatecall(_calldata);
            if (!success) {
                if (error.length > 0) {
                    // bubble up the error
                    revert(string(error));
                } else {
                    revert InitReverted();
                }
            }
        }
    }

    function enforceHasContractCode(address _contract) internal view {
        uint256 contractSize;
        // solhint-disable-next-line no-inline-assembly
        assembly {
            contractSize := extcodesize(_contract)
        }
        if (contractSize == 0) {
            revert FacetContainsNoCode();
        }
    }
}

// SPDX-License-Identifier: MIT
pragma solidity 0.8.16;

import { LibDiamond } from "../libraries/LibDiamond.sol";
import { IDiamondCut } from "../interfaces/IDiamondCut.sol";

contract RangoDiamond {
    constructor(address _contractOwner, address _diamondCutFacet) payable {
        LibDiamond.setContractOwner(_contractOwner);

        // Add the diamondCut external function from the diamondCutFacet
        IDiamondCut.FacetCut[] memory cut = new IDiamondCut.FacetCut[](1);
        bytes4[] memory functionSelectors = new bytes4[](1);
        functionSelectors[0] = IDiamondCut.diamondCut.selector;
        cut[0] = IDiamondCut.FacetCut({
            facetAddress: _diamondCutFacet,
            action: IDiamondCut.FacetCutAction.Add,
            functionSelectors: functionSelectors
        });
        LibDiamond.diamondCut(cut, address(0), "");
    }

    // Find facet for function that is called and execute the
    // function if a facet is found and return any value.
    // solhint-disable-next-line no-complex-fallback
    fallback() external payable {
        LibDiamond.DiamondStorage storage ds;
        bytes32 position = LibDiamond.DIAMOND_STORAGE_POSITION;

        // get diamond storage
        // solhint-disable-next-line no-inline-assembly
        assembly {
            ds.slot := position
        }

        // get facet from function selector
        address facet = ds.selectorToFacetAndPosition[msg.sig].facetAddress;

        if (facet == address(0)) {
            revert LibDiamond.FunctionDoesNotExist();
        }

        // Execute external function from facet using delegatecall and return any value.
        // solhint-disable-next-line no-inline-assembly
        assembly {
            // copy function selector and any arguments
            calldatacopy(0, 0, calldatasize())
            // execute function call using the facet
            let result := delegatecall(gas(), facet, 0, calldatasize(), 0, 0)
            // get any return value
            returndatacopy(0, 0, returndatasize())
            // return any return value or error back to the caller
            switch result
            case 0 {
                revert(0, returndatasize())
            }
            default {
                return(0, returndatasize())
            }
        }
    }

    // Able to receive ether
    // solhint-disable-next-line no-empty-blocks
    receive() external payable {}
}

// SPDX-License-Identifier: MIT
pragma solidity 0.8.16;

error OnlyContractOwner();