implement interest owed

contracts/compound/Compound.sol

@@ -2,7 +2,7 @@ pragma solidity ^0.5.3;
 import "../token/ERC20Token.sol";
 
 
-
+// DO NOT USE IN PRODUCTION
 // Contract to mock interactions with Compound.finance
 
 contract Compound {
@@ -35,7 +35,7 @@ contract Compound {
     uint supplyTime = supplyTimes[msg.sender];
     uint balance = supplyBalances[msg.sender];
     uint timeDelta = now - supplyTime;
-    uint accruedInterest = timeDelta * periodicRate;
+    uint accruedInterest = balance * timeDelta * periodicRate / percentBase;
     return accruedInterest + balance;
   }
 }

contracts/subscription.sol

@@ -30,6 +30,7 @@ contract Subscription {
     uint256 public totalBalances;
     uint256 constant base = 10 ** 18;
     uint256 constant percentBase = 100 * base;
+    uint256 public minDeposit = 12;
 
     constructor(
         address _compoundAddress,
@@ -110,6 +111,13 @@ contract Subscription {
       return target * percent/percentBase;
     }
 
+    function getInterestOwed(uint256 amountOwed) view public returns (uint256) {
+      uint256 totalAmount = compound.getSupplyBalance(address(this), daiAddress);
+      uint256 totalInterest = totalAmount - totalBalances;
+      uint256 interestOwed = totalInterest * amountOwed / totalBalances;
+      return interestOwed;
+    }
+
     function getAmountOwed(bytes32 agreementId) view public returns (uint256) {
       Agreement memory agreement = agreements[agreementId];
       //TODO check for enddate, use instead of now
@@ -156,7 +164,10 @@ contract Subscription {
       external
     {
       require(msg.sender == payor, "Agreement must be created by payor");
+      require(annualAmount > 0, "AnnualAmount can not be zero");
       bytes32 agreementId = keccak256(abi.encode(receiver, payor, token, annualAmount, startDate, description));
+      uint supplyAmount = annualAmount / minDeposit;
+      supply(supplyAmount);
       Agreement storage agreement = agreements[agreementId];
 
       agreement.receiver = receiver;

test/subscription_spec.js

@@ -85,6 +85,16 @@ contract("subscription", function () {
       assert.equal(owed, accrued, `Owned: ${owed} amount returned not equal to expected ${accrued}`)
     });
 
+    it('should get interest owed from compound', async function() {
+      const accrued = 1000 * 10 * (annualSalary / SECONDS_IN_A_YEAR)
+      const approxInterest = accrued * (0.04 / 12 / 30 / 24)
+      await utils.increaseTime(1000)
+      const owed = await Subscription.methods.getInterestOwed(
+        accrued.toString()
+      ).call({from: receiver})
+      assert(owed < approxInterest, "The amount owed is higher than expected")
+    })
+
     it('should allow a payor to supply token', async function() {
       const amount = toWei('100000')
       const supply = await Subscription.methods.supply(