// Contract: IndigenaNFTMarketplace
// Target function: function upgradeTo(address _impl)
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

/**
 * @dev This abstract contract provides a fallback function that delegates all calls to another contract using the EVM
 * instruction `delegatecall`. We refer to the second contract as the _implementation_ behind the proxy, and it has to
 * be specified by overriding the virtual {_implementation} function.
 *
 * Additionally, delegation to the implementation can be triggered manually through the {_fallback} function, or to a
 * different contract through the {_delegate} function.
 *
 * The success and return data of the delegated call will be returned back to the caller of the proxy.
 */
abstract contract Proxy {
    /**
     * @dev Delegates the current call to `implementation`.
     *
     * This function does not return to its internall call site, it will return directly to the external caller.
     */
    function _delegate(address implementation) internal virtual {
        assembly {
            // Copy msg.data. We take full control of memory in this inline assembly
            // block because it will not return to Solidity code. We overwrite the
            // Solidity scratch pad at memory position 0.
            calldatacopy(0, 0, calldatasize())

            // Call the implementation.
            // out and outsize are 0 because we don't know the size yet.
            let result := delegatecall(gas(), implementation, 0, calldatasize(), 0, 0)

            // Copy the returned data.
            returndatacopy(0, 0, returndatasize())

            switch result
            // delegatecall returns 0 on error.
            case 0 {
                revert(0, returndatasize())
            }
            default {
                return(0, returndatasize())
            }
        }
    }

    /**
     * @dev This is a virtual function that should be overriden so it returns the address to which the fallback function
     * and {_fallback} should delegate.
     */
    function _implementation() internal view virtual returns (address);

    /**
     * @dev Delegates the current call to the address returned by `_implementation()`.
     *
     * This function does not return to its internall call site, it will return directly to the external caller.
     */
    function _fallback() internal virtual {
        _beforeFallback();
        _delegate(_implementation());
    }

    /**
     * @dev Fallback function that delegates calls to the address returned by `_implementation()`. Will run if no other
     * function in the contract matches the call data.
     */
    fallback() external payable virtual {
        _fallback();
    }

    /**
     * @dev Fallback function that delegates calls to the address returned by `_implementation()`. Will run if call data
     * is empty.
     */
    receive() external payable virtual {
        _fallback();
    }

    /**
     * @dev Hook that is called before falling back to the implementation. Can happen as part of a manual `_fallback`
     * call, or as part of the Solidity `fallback` or `receive` functions.
     *
     * If overriden should call `super._beforeFallback()`.
     */
    function _beforeFallback() internal virtual {}
}
contract IndigenaNFTMarketplace is Proxy {
    
    // Storage position of the address of the current implementation
    bytes32 private constant implementationPosition = 
        keccak256("org.smartdefi.implementation.address");
    
    // Storage position of the owner of the contract
    bytes32 private constant proxyOwnerPosition = 
        keccak256("org.smartdefi.proxy.owner");
    
    /**
    * @dev Throws if called by any account other than the owner.
    */
    modifier onlyProxyOwner() {
        require (msg.sender == proxyOwner(), "Not Proxy owner");
        _;
    }

    /**
    * @dev the constructor sets owner
    */
    constructor() {
        _setUpgradeabilityOwner(msg.sender);
    }

    /**
     * @dev Allows the current owner to transfer ownership
     * @param _newOwner The address to transfer ownership to
     */
    function transferProxyOwnership(address _newOwner) 
        public onlyProxyOwner 
    {
        require(_newOwner != address(0));
        _setUpgradeabilityOwner(_newOwner);
    }