ds_message.sol

pragma solidity ^0.4.23;

contract DSMath {
    function add(uint x, uint y) internal pure returns (uint z) {
        require((z = x + y) >= x, "ds-math-add-overflow");
    }
    function sub(uint x, uint y) internal pure returns (uint z) {
        require((z = x - y) <= x, "ds-math-sub-underflow");
    }
    function mul(uint x, uint y) internal pure returns (uint z) {
        require(y == 0 || (z = x * y) / y == x, "ds-math-mul-overflow");
    }

    function min(uint x, uint y) internal pure returns (uint z) {
        return x <= y ? x : y;
    }
    function max(uint x, uint y) internal pure returns (uint z) {
        return x >= y ? x : y;
    }
    function imin(int x, int y) internal pure returns (int z) {
        return x <= y ? x : y;
    }
    function imax(int x, int y) internal pure returns (int z) {
        return x >= y ? x : y;
    }

    uint constant WAD = 10 ** 18;
    uint constant RAY = 10 ** 27;

    function wmul(uint x, uint y) internal pure returns (uint z) {
        z = add(mul(x, y), WAD / 2) / WAD;
    }
    function rmul(uint x, uint y) internal pure returns (uint z) {
        z = add(mul(x, y), RAY / 2) / RAY;
    }
    function wdiv(uint x, uint y) internal pure returns (uint z) {
        z = add(mul(x, WAD), y / 2) / y;
    }
    function rdiv(uint x, uint y) internal pure returns (uint z) {
        z = add(mul(x, RAY), y / 2) / y;
    }

    // This famous algorithm is called "exponentiation by squaring"
    // and calculates x^n with x as fixed-point and n as regular unsigned.
    //
    // It's O(log n), instead of O(n) for naive repeated multiplication.
    //
    // These facts are why it works:
    //
    //  If n is even, then x^n = (x^2)^(n/2).
    //  If n is odd,  then x^n = x * x^(n-1),
    //   and applying the equation for even x gives
    //    x^n = x * (x^2)^((n-1) / 2).
    //
    //  Also, EVM division is flooring and
    //    floor[(n-1) / 2] = floor[n / 2].
    //
    function rpow(uint x, uint n) internal pure returns (uint z) {
        z = n % 2 != 0 ? x : RAY;

        for (n /= 2; n != 0; n /= 2) {
            x = rmul(x, x);

            if (n % 2 != 0) {
                z = rmul(z, x);
            }
        }
    }
}

contract DSNote {
    event LogNote(
        bytes4   indexed  sig,
        address  indexed  guy,
        bytes32  indexed  foo,
        bytes32  indexed  bar,
        uint256           wad,
        bytes             fax
    ) anonymous;

    modifier note {
        bytes32 foo;
        bytes32 bar;
        uint256 wad;

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

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

        _;
    }
}

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(address(authority));
    }

    modifier auth {
        require(isAuthorized(msg.sender, msg.sig), "ds-auth-unauthorized");
        _;
    }

    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, address(this), sig);
        }
    }
}


contract DSThing is DSAuth, DSNote, DSMath {
    function S(string memory s) internal pure returns (bytes4) {
        return bytes4(keccak256(abi.encodePacked(s)));
    }

}


contract DSValue is DSThing {
    bool    has;
    bytes32 val;
    function peek() public view returns (bytes32, bool) {
        return (val,has);
    }
    function read() public view returns (bytes32) {
        bytes32 wut; bool haz;
        (wut, haz) = peek();
        require(haz, "haz-not");
        return wut;
    }
    function poke(bytes32 wut) public note auth {
        val = wut;
        has = true;
    }
    function void() public note auth {  // unset the value
        has = false;
    }
}


contract DSMessage is DSThing {
    struct Message {
        bool    has;
        bytes32 val;
    }

    // message array from users
    Message[] Messages;

    // top of authorized index position
    uint256 private indexTobePost;

    function getLength() public view returns (uint256) {
        return Messages.length;
    }

    function setPost() public note {
        for (uint Pos = Messages.length; Pos > 0; Pos--) {
            if (Messages[Pos-1].has == true) {
                // Anyone can update recent confirmed message
                // if does not, next line should be.
                // setPostManually(Pos-1);
                indexTobePost = Pos;
                break;
            }
        }
    }

    // this function should be private
    function setPostManually(uint256 Pos) public note auth{
        require(Messages[Pos].has == true);
        indexTobePost = Pos;
    }

    function getPost() public view returns (uint256, bytes32) {
        return (indexTobePost, Messages[indexTobePost].val);
    }

    // Send Message to ethcon board
    function poke(bytes32 wut) public note auth {
        Messages.push(Message(false, wut));
    }

    // this function should be private
    // Just confirm lastest message, should be carefully.
    function lastConfirm() public auth {
        confirm(Messages.length -1);
    }

    // this function should be private
    function confirm(uint msgNum) public auth {
        Messages[msgNum].has = true;
    }

    // this function should be private
    function unconfirm(uint msgNum) public auth {
        Messages[msgNum].has = false;
    }

    function peek(uint msgNum) public view returns (bytes32, bool) {
        return (Messages[msgNum].val, Messages[msgNum].has);
    }

}