// SPDX-License-Identifier: LGPL-3.0-only
pragma solidity ^0.6.0;

/// @title Proxied - indicates that a contract will be proxied. Also defines storage requirements for Proxy.
/// @author Alan Lu - <alan@gnosis.pm>
contract Proxied {
    address public masterCopy;
}

/// @title Proxy - Generic proxy contract allows to execute all transactions applying the code of a master contract.
/// @author Stefan George - <stefan@gnosis.pm>
contract Proxy is Proxied {
    /// @dev Constructor function sets address of master copy contract.
    /// @param _masterCopy Master copy address.
    constructor(address _masterCopy) public {
        require(_masterCopy != address(0), "The master copy is required");
        masterCopy = _masterCopy;
    }

    /// @dev Fallback function forwards all transactions and returns all received return data.
    function _fallback() internal {
        address _masterCopy = masterCopy;
        assembly {
            calldatacopy(0, 0, calldatasize())
            let success := delegatecall(not(0), _masterCopy, 0, calldatasize(), 0, 0)
            returndatacopy(0, 0, returndatasize())
            switch success
                case 0 {
                    revert(0, returndatasize())
                }
                default {
                    return(0, returndatasize())
                }
        }
    }

    /**
     * @dev Fallback function that delegates calls to the masterCopy. 
     * Runs when no other function in the contract matches the call data.
     */
    fallback () external payable {
        _fallback();
    }

    /**
     * @dev Fallback function that receives ether and delegates calls to masterCopy. 
     * Runs when call data is empty.
     */
    receive () external payable {
        _fallback();
    }
}