pragma solidity ^0.4.23;

contract DSAuthority {
    function canCall(address src, address dst, bytes4 sig) public view returns (bool);
}

contract DSAuthEvents {
    event LogSetAuthority (address indexed authority);
    event LogSetOwner     (address indexed owner);
}

contract DSAuth is DSAuthEvents {
    DSAuthority  public  authority;
    address      public  owner;

    constructor() public {
        owner = msg.sender;
        emit LogSetOwner(msg.sender);
    }

    function setOwner(address owner_)
        public
        auth
    {
        owner = owner_;
        emit LogSetOwner(owner);
    }

    function setAuthority(DSAuthority authority_)
        public
        auth
    {
        authority = authority_;
        emit LogSetAuthority(authority);
    }

    modifier auth {
        require(isAuthorized(msg.sender, msg.sig));
        _;
    }

    function isAuthorized(address src, bytes4 sig) internal view returns (bool) {
        if (src == address(this)) {
            return true;
        } else if (src == owner) {
            return true;
        } else if (authority == DSAuthority(0)) {
            return false;
        } else {
            return authority.canCall(src, this, sig);
        }
    }
}

contract DSNote {
    event LogNote(
        bytes4   indexed  sig,
        address  indexed  guy,
        bytes32  indexed  foo,
        bytes32  indexed  bar,
        uint              wad,
        bytes             fax
    ) anonymous;

    modifier note {
        bytes32 foo;
        bytes32 bar;

        assembly {
            foo := calldataload(4)
            bar := calldataload(36)
        }

        emit LogNote(msg.sig, msg.sender, foo, bar, msg.value, msg.data);

        _;
    }
}

// DSProxy
// Allows code execution using a persistant identity This can be very
// useful to execute a sequence of atomic actions. Since the owner of
// the proxy can be changed, this allows for dynamic ownership models
// i.e. a multisig
contract DSProxy is DSAuth, DSNote {
    DSProxyCache public cache;  // global cache for contracts

    constructor(address _cacheAddr) public {
        setCache(_cacheAddr);
    }

    function() external payable {
    }

    // use the proxy to execute calldata _data on contract _code
    function execute(bytes memory _code, bytes memory _data)
        public
        payable
        returns (address target, bytes memory response)
    {
        target = cache.read(_code);
        if (target == address(0)) {
            // deploy contract & store its address in cache
            target = cache.write(_code);
        }

        response = execute(target, _data);
    }

    function execute(address _target, bytes memory _data)
        public
        auth
        note
        payable
        returns (bytes memory response)
    {
        require(_target != address(0), "ds-proxy-target-address-required");

        // call contract in current context
        assembly {
            let succeeded := delegatecall(sub(gas, 5000), _target, add(_data, 0x20), mload(_data), 0, 0)
            let size := returndatasize

            response := mload(0x40)
            mstore(0x40, add(response, and(add(add(size, 0x20), 0x1f), not(0x1f))))
            mstore(response, size)
            returndatacopy(add(response, 0x20), 0, size)

            switch iszero(succeeded)
            case 1 {
                // throw if delegatecall failed
                revert(add(response, 0x20), size)
            }
        }
    }

    //set new cache
    function setCache(address _cacheAddr)
        public
        auth
        note
        returns (bool)
    {
        require(_cacheAddr != address(0), "ds-proxy-cache-address-required");
        cache = DSProxyCache(_cacheAddr);  // overwrite cache
        return true;
    }
}

// DSProxyCache
// This global cache stores addresses of contracts previously deployed
// by a proxy. This saves gas from repeat deployment of the same
// contracts and eliminates blockchain bloat.

// By default, all proxies deployed from the same factory store
// contracts in the same cache. The cache a proxy instance uses can be
// changed.  The cache uses the sha3 hash of a contract's bytecode to
// lookup the address
contract DSProxyCache {
    mapping(bytes32 => address) cache;

    function read(bytes memory _code) public view returns (address) {
        bytes32 hash = keccak256(_code);
        return cache[hash];
    }

    function write(bytes memory _code) public returns (address target) {
        assembly {
            target := create(0, add(_code, 0x20), mload(_code))
            switch iszero(extcodesize(target))
            case 1 {
                // throw if contract failed to deploy
                revert(0, 0)
            }
        }
        bytes32 hash = keccak256(_code);
        cache[hash] = target;
    }
}