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Fix decimals on ratio outputs #176

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Sep 15, 2020
Merged

Fix decimals on ratio outputs #176

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f7847f9
Fix decimals on ratio outputs
tomlinton Sep 15, 2020
45905f5
Fix divisor
tomlinton Sep 15, 2020
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31 changes: 19 additions & 12 deletions contracts/contracts/vault/Vault.sol
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Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
pragma solidity 0.5.11;

/*
The Vault contract stores assets. On a deposit, OUSD will be minted and sent to
the depositor. On a withdrawal, OUSD will be burned and assets will be sent to
Expand Down Expand Up @@ -594,6 +593,7 @@ contract Vault is Initializable, InitializableGovernable {
internal
returns (uint256[] memory outputs)
{
uint256 totalBalance = _checkBalance();
uint256 totalOutputValue = 0; // Running total of USD value of assets
uint256 combinedAssetValue = 0;
uint256 assetCount = getAssetCount();
Expand All @@ -602,20 +602,22 @@ contract Vault is Initializable, InitializableGovernable {
// Initialise arrays
// Price of each asset in USD in 1e18
uint256[] memory assetPrices = new uint256[](assetCount);
uint256[] memory assetDecimals = new uint256[](assetCount);
outputs = new uint256[](assetCount);

for (uint256 i = 0; i < allAssets.length; i++) {
uint256 assetDecimals = Helpers.getDecimals(allAssets[i]);
assetDecimals[i] = Helpers.getDecimals(allAssets[i]);
// Get all the USD prices of the asset in 1e18
assetPrices[i] = _priceUSDMax(
allAssets[i],
uint256(1).scaleBy(int8(assetDecimals))
uint256(1).scaleBy(int8(assetDecimals[i]))
);

// Get the proportional amount of this token for the redeem in 1e18
uint256 proportionalAmount = _checkBalance(allAssets[i])
.scaleBy(int8(18 - assetDecimals))
.scaleBy(int8(18 - assetDecimals[i]))
.mul(_amount)
.div(_checkBalance());
.div(totalBalance);

if (proportionalAmount > 0) {
// Non zero output means this asset is contributing to the
Expand All @@ -629,7 +631,7 @@ contract Vault is Initializable, InitializableGovernable {
);
// Save the output amount in the decimals of the asset
outputs[i] = proportionalAmount.scaleBy(
int8(assetDecimals - 18)
int8(assetDecimals[i] - 18)
);
}
}
Expand All @@ -642,14 +644,19 @@ contract Vault is Initializable, InitializableGovernable {
for (uint256 i = 0; i < outputs.length; i++) {
if (outputs[i] == 0) continue;

uint256 adjustment = 0;
if (outputValueDiff < 0) {
outputs[i] -= uint256(-outputValueDiff)
.divPrecisely(combinedAssetValue)
.div(redeemAssetCount);
adjustment = uint256(-outputValueDiff)
.div(combinedAssetValue)
.divPrecisely(redeemAssetCount)
.scaleBy(int8(assetDecimals[i] - 18));
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Is there any circumstance where combinedAssetValue would be greater than outputValueDiff?

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Yes, I had this wrong though, should be updated now

outputs[i] -= adjustment;
} else if (outputValueDiff > 0) {
outputs[i] += uint256(outputValueDiff)
.divPrecisely(combinedAssetValue)
.div(redeemAssetCount);
adjustment = uint256(outputValueDiff)
.div(combinedAssetValue)
.divPrecisely(redeemAssetCount)
.scaleBy(int8(assetDecimals[i] - 18));
outputs[i] += adjustment;
}
}
}
Expand Down
31 changes: 23 additions & 8 deletions contracts/test/vault/redeem.js
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Original file line number Diff line number Diff line change
Expand Up @@ -143,10 +143,10 @@ describe("Vault Redeem", function () {
await vault.connect(anna).redeemAll();

// 100 USDC and 350 DAI in contract
// 100/450 * 250 USDC + existing 1000
// 350/450 * 250 DAI + existing 1000
await expect(anna).has.an.approxBalanceOf("1044.44", dai);
// (1000-100) + 100/450 * 250 USDC
// (1000-150) + 350/450 * 250 DAI
await expect(anna).has.an.approxBalanceOf("955.55", usdc);
await expect(anna).has.an.approxBalanceOf("1044.44", dai);
});

it("Should redeem entire OUSD balance, with a higher oracle price", async () => {
Expand All @@ -166,18 +166,33 @@ describe("Vault Redeem", function () {
await vault.connect(anna).mint(dai.address, daiUnits("150.0"));
await expect(anna).has.a.balanceOf("250.00", ousd);

await setOracleTokenPriceUsd("DAI", "1.20");
await setOracleTokenPriceUsd("USDC", "1.30");
await setOracleTokenPriceUsd("DAI", "1.20");
await vault.connect(governor).rebase();

// Anna's share of OUSD is 200/450
// Vault has 100 USDC and 350 DAI total
// 200/450 * 100 * 1.3 + 350 * 1.2
await expect(anna).has.an.approxBalanceOf("305.55", ousd);

// Withdraw all
await ousd.connect(anna).approve(vault.address, ousdUnits("250.0"));
await vault.connect(anna).redeemAll();

// 100 USDC and 350 DAI in contract
// 100/450 * 250 USDC + existing 1000
// 350/450 * 250 DAI + existing 1000
await expect(anna).has.an.approxBalanceOf("1", dai); // To be mathed out
await expect(anna).has.an.approxBalanceOf("1", usdc); // To be mathed out
// 100 * 1.30 = 130 USD value for USDC
// 350 * 1.20 = 420 USD value for DAI
// 100/450 * 305.5555555 = 67.9012345556 USDC
// 350/450 * 305.5555555 = 237.654320944 DAI
// Difference between output value and redeem value is:
// 305.5555555 - (67.9012345556 * 1.3 + 237.654320944 * 1.20) = -67.9012345551
// Remove 67.9012345551/2.5/2 from USDC
// Remove 67.9012345551/2.5/2 from DAI
// (1000-100) + 100/450 * 305.5555555 - 67.9012345551/2.5/2 USDC
// (1000-150) + 350/450 * 305.5555555 - 67.9012345551/2.5/2 DAI
await expect(anna).has.an.approxBalanceOf("954.32", usdc); // To be mathed out
await expect(anna).has.an.approxBalanceOf("1074.07", dai); // To be mathed out
});

it("Should redeem entire OUSD balance, with a lower oracle price");
});