***rDAI donation integration***

[andersonmmi]

• Create a SimpleStaking contract
• UI shows how much DAI is staked
• UI shows how much you've donated through staking (total)
• Funding Component accepts DAI, converts to rDAI behind the scenes
• User can withdraw their DAI stake at any time

[andersonmmi]

SimpleStaking contract so far:

pragma solidity >=0.5.0 <0.6.0;

/* 
    I have been using eth.build to explore the rDaiContract. A copy of my work so far can be found at
    https://eth.build/build#d18e4814da12b791f0fac8c0fc7740edb582bb4d9964d7fe0619dbb61e573fe2
    Make sure your metamask is set to Kovan when you use it.
*/

contract SimpleStaking {
    // address public myAddress = this.address;
    address public owner;
    address constant public alfredDao = 0x9ED8057F7A1fe5EFbb4fdd6a57f8bF919Dd68DB1;
    address constant public rDaiContract = 0x462303f77a3f17Dbd95eb7bab412FE4937F9B9CB; // Kovan
    address constant public mcdContract = 0x4F96Fe3b7A6Cf9725f59d353F723c1bDb64CA6Aa; // Kovan
    mapping(address => uint) public balances;

    constructor() public{
        owner = msg.sender;
        /* set rDai hat to beneficiary address */
        rDaiContract.createHat(alfredDao, [1]);
    }
    
    /* fallback function reverts by default */
    function () external {
        revert();
    }

    /* stake function recieves DAI, converts to rDai, and incriments sender's balance*/
    function stake (uint ammount) payable public returns (bool){
        // check to make sure that only MCD is being sent, else revert and return false
        
        // accept DAI, call mint on rDaiContract passing in this ammount of DAI
        
        // balances += ammount
        return true;
    }
    
    /* redeem function redeems msg.sender's total balance from rDai contract 
    (paying interest to alfredDao) and sends DAI to msg.sender   */
    function redeem () payable public returns (bool){
        // check to make sure msg.sender balance > 0, else return false
        
        // call redeem on rDaiContract passing in msg.sender's balances.total
        
        // call transfer mcdContract passing in msg.sender's balances.total and msg.sender.address
        
        // balances -= balances.total
        return true;
    }
}

[morganstar]

Revised, compiles and passes basic testing
(codeblock formatting of pasted code is weird, not sure why):

`pragma solidity >=0.5.0 <0.6.0;

/*
I have been using eth.build to explore the rDaiContract. A copy of my work so far can be found at
https://eth.build/build#d18e4814da12b791f0fac8c0fc7740edb582bb4d9964d7fe0619dbb61e573fe2
Make sure your metamask is set to Kovan when you use it.
*/

import './IRToken.sol';
import './IERC20.sol';

contract SimpleStaking {
// Largest integer, for setting token allowance
uint constant MAX_UINT = 2**256 - 1;

address public owner;
address constant public alfredDao = 0x9ED8057F7A1fe5EFbb4fdd6a57f8bF919Dd68DB1;
address constant public rDaiContract = 0x462303f77a3f17Dbd95eb7bab412FE4937F9B9CB; // Kovan rDAI
address constant public mcdContract = 0x4F96Fe3b7A6Cf9725f59d353F723c1bDb64CA6Aa; // Kovan DAI
mapping(address => uint) public balances;

// --- Math ---
function add(uint x, uint y) internal pure returns (uint z) {
    require((z = x + y) >= x);
}
function sub(uint x, uint y) internal pure returns (uint z) {
    require((z = x - y) <= x);
}

constructor() public{
    // owner = msg.sender;
    /* set rDai hat to beneficiary address */
    address[] memory recipients = new address[](1);
    uint32[] memory proportions = new uint32[](1);
    recipients[0] = alfredDao;
    proportions[0] = 1;
    IRToken(rDaiContract).createHat(recipients, proportions, true);
    // approve rDai contract to transfer DAI on behalf of this contract
    IERC20(mcdContract).approve(rDaiContract, MAX_UINT);
}

/* fallback function reverts by default */
function () external {
    revert();
}

/* Stake function recieves DAI, converts to rDai, and incriments sender's balance
   User must first .approve this contract to spend DAI on their behalf */
function stake (uint amount) payable public returns (bool){
    // Accept DAI
    require(IERC20(mcdContract).transferFrom(msg.sender, address(this), amount), 'Transfering DAI failed');
    // Mint rDai
    require(IRToken(rDaiContract).mint(amount), 'Minting rDai failed');
    // Track user balance
    balances[msg.sender] = add(balances[msg.sender], amount);

    return true;
}

/* redeem function redeems msg.sender's total balance from rDai contract 
(paying interest to alfredDao) and sends DAI to msg.sender   */
function redeem () payable public returns (bool){
    // check to make sure msg.sender balance > 0, else revert
    uint256 amount = balances[msg.sender];
    require((amount > 0), 'No balance to redeem');

    // Redeem all of user's balance worth of DAI and transfer it back to them
    require(IRToken(rDaiContract).redeemAndTransfer(msg.sender, amount), 'Redeeming DAI failed');

    // Set user's balance to zero
    balances[msg.sender] = 0;

    // Trigger interest payout
    IRToken(rDaiContract).payInterest(alfredDao);

    return true;
}

}`

[morganstar]

Included files:

https://github.com/rtoken-project/rtoken-contracts/blob/master/contracts/IRToken.sol
https://github.com/OpenZeppelin/openzeppelin-contracts/blob/7552af95e4ec6fccd64a95b206f59a1b4ff91517/contracts/token/ERC20/IERC20.sol

[morganstar]

Need these too to get it to compile:

https://github.com/rtoken-project/rtoken-contracts/blob/master/contracts/IAllocationStrategy.sol
https://github.com/rtoken-project/rtoken-contracts/blob/master/contracts/RTokenStructs.sol

[morganstar]

Test copy deployed on Kovan at 0xf871EFEFB58aE7C72f646416B91115F379eFd5f5