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fix comment error #577

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fix comment error #577

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71 changes: 35 additions & 36 deletions packages/contracts/contracts/PriceFeed.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ import "./Dependencies/LiquityMath.sol";
import "./Dependencies/console.sol";

/*
* PriceFeed for mainnet deployment, to be connected to Chainlink's live ETH:USD aggregator reference
* PriceFeed for mainnet deployment, to be connected to Chainlink's live ETH:USD aggregator reference
* contract, and a wrapper contract TellorCaller, which connects to TellorMaster contract.
*
* The PriceFeed uses Chainlink as primary oracle, and Tellor as fallback. It contains logic for
Expand All @@ -35,16 +35,16 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
uint constant public ETHUSD_TELLOR_REQ_ID = 1;

// Use to convert a price answer to an 18-digit precision uint
uint constant public TARGET_DIGITS = 18;
uint constant public TARGET_DIGITS = 18;
uint constant public TELLOR_DIGITS = 6;

// Maximum time period allowed since Chainlink's latest round data timestamp, beyond which Chainlink is considered frozen.
uint constant public TIMEOUT = 14400; // 4 hours: 60 * 60 * 4

// Maximum deviation allowed between two consecutive Chainlink oracle prices. 18-digit precision.
uint constant public MAX_PRICE_DEVIATION_FROM_PREVIOUS_ROUND = 5e17; // 50%

/*
/*
* The maximum relative price difference between two oracle responses allowed in order for the PriceFeed
* to return to using the Chainlink oracle. 18-digit precision.
*/
Expand All @@ -69,10 +69,10 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
}

enum Status {
chainlinkWorking,
usingTellorChainlinkUntrusted,
chainlinkWorking,
usingTellorChainlinkUntrusted,
bothOraclesUntrusted,
usingTellorChainlinkFrozen,
usingTellorChainlinkFrozen,
usingChainlinkTellorUntrusted
}

Expand All @@ -83,7 +83,7 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
event PriceFeedStatusChanged(Status newStatus);

// --- Dependency setters ---

function setAddresses(
address _priceAggregatorAddress,
address _tellorCallerAddress
Expand All @@ -93,7 +93,7 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
{
checkContract(_priceAggregatorAddress);
checkContract(_tellorCallerAddress);

priceAggregator = AggregatorV3Interface(_priceAggregatorAddress);
tellorCaller = ITellorCaller(_tellorCallerAddress);

Expand All @@ -103,8 +103,8 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
// Get an initial price from Chainlink to serve as first reference for lastGoodPrice
ChainlinkResponse memory chainlinkResponse = _getCurrentChainlinkResponse();
ChainlinkResponse memory prevChainlinkResponse = _getPrevChainlinkResponse(chainlinkResponse.roundId, chainlinkResponse.decimals);
require(!_chainlinkIsBroken(chainlinkResponse, prevChainlinkResponse) && !_chainlinkIsFrozen(chainlinkResponse),

require(!_chainlinkIsBroken(chainlinkResponse, prevChainlinkResponse) && !_chainlinkIsFrozen(chainlinkResponse),
"PriceFeed: Chainlink must be working and current");

_storeChainlinkPrice(chainlinkResponse);
Expand All @@ -122,7 +122,7 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
*
* Non-view function - it stores the last good price seen by Liquity.
*
* Uses a main oracle (Chainlink) and a fallback oracle (Tellor) in case Chainlink fails. If both fail,
* Uses a main oracle (Chainlink) and a fallback oracle (Tellor) in case Chainlink fails. If both fail,
* it uses the last good price seen by Liquity.
*
*/
Expand All @@ -139,7 +139,7 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
// If Tellor is broken then both oracles are untrusted, so return the last good price
if (_tellorIsBroken(tellorResponse)) {
_changeStatus(Status.bothOraclesUntrusted);
return lastGoodPrice;
return lastGoodPrice;
}
/*
* If Tellor is only frozen but otherwise returning valid data, return the last good price.
Expand All @@ -149,23 +149,23 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
_changeStatus(Status.usingTellorChainlinkUntrusted);
return lastGoodPrice;
}

// If Chainlink is broken and Tellor is working, switch to Tellor and return current Tellor price
_changeStatus(Status.usingTellorChainlinkUntrusted);
return _storeTellorPrice(tellorResponse);
}

// If Chainlink is frozen, try Tellor
if (_chainlinkIsFrozen(chainlinkResponse)) {
if (_chainlinkIsFrozen(chainlinkResponse)) {
// If Tellor is broken too, remember Tellor broke, and return last good price
if (_tellorIsBroken(tellorResponse)) {
_changeStatus(Status.usingChainlinkTellorUntrusted);
return lastGoodPrice;
return lastGoodPrice;
}

// If Tellor is frozen or working, remember Chainlink froze, and switch to Tellor
_changeStatus(Status.usingTellorChainlinkFrozen);

if (_tellorIsFrozen(tellorResponse)) {return lastGoodPrice;}

// If Tellor is working, use it
Expand All @@ -177,22 +177,22 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
// If Tellor is broken, both oracles are untrusted, and return last good price
if (_tellorIsBroken(tellorResponse)) {
_changeStatus(Status.bothOraclesUntrusted);
return lastGoodPrice;
return lastGoodPrice;
}

// If Tellor is frozen, switch to Tellor and return last good price
if (_tellorIsFrozen(tellorResponse)) {
// If Tellor is frozen, switch to Tellor and return last good price
if (_tellorIsFrozen(tellorResponse)) {
_changeStatus(Status.usingTellorChainlinkUntrusted);
return lastGoodPrice;
}

/*
/*
* If Tellor is live and both oracles have a similar price, conclude that Chainlink's large price deviation between
* two consecutive rounds was likely a legitmate market price movement, and so continue using Chainlink
* two consecutive rounds was likely a legitmate market price movement, and so continue using Chainlink
*/
if (_bothOraclesSimilarPrice(chainlinkResponse, tellorResponse)) {
return _storeChainlinkPrice(chainlinkResponse);
}
}

// If Tellor is live but the oracles differ too much in price, conclude that Chainlink's initial price deviation was
// an oracle failure. Switch to Tellor, and use Tellor price
Expand All @@ -202,16 +202,16 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {

// If Chainlink is working and Tellor is broken, remember Tellor is broken
if (_tellorIsBroken(tellorResponse)) {
_changeStatus(Status.usingChainlinkTellorUntrusted);
}
_changeStatus(Status.usingChainlinkTellorUntrusted);
}

// If Chainlink is working, return Chainlink current price (no status change)
return _storeChainlinkPrice(chainlinkResponse);
}


// --- CASE 2: The system fetched last price from Tellor ---
if (status == Status.usingTellorChainlinkUntrusted) {
// --- CASE 2: The system fetched last price from Tellor ---
if (status == Status.usingTellorChainlinkUntrusted) {
// If both Tellor and Chainlink are live, unbroken, and reporting similar prices, switch back to Chainlink
if (_bothOraclesLiveAndUnbrokenAndSimilarPrice(chainlinkResponse, prevChainlinkResponse, tellorResponse)) {
_changeStatus(Status.chainlinkWorking);
Expand All @@ -220,15 +220,15 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {

if (_tellorIsBroken(tellorResponse)) {
_changeStatus(Status.bothOraclesUntrusted);
return lastGoodPrice;
return lastGoodPrice;
}

/*
* If Tellor is only frozen but otherwise returning valid data, just return the last good price.
* Tellor may need to be tipped to return current data.
*/
if (_tellorIsFrozen(tellorResponse)) {return lastGoodPrice;}

// Otherwise, use Tellor price
return _storeTellorPrice(tellorResponse);
}
Expand All @@ -242,7 +242,7 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
if (_bothOraclesLiveAndUnbrokenAndSimilarPrice(chainlinkResponse, prevChainlinkResponse, tellorResponse)) {
_changeStatus(Status.chainlinkWorking);
return _storeChainlinkPrice(chainlinkResponse);
}
}

// Otherwise, return the last good price - both oracles are still untrusted (no status change)
return lastGoodPrice;
Expand Down Expand Up @@ -320,14 +320,14 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
return _storeChainlinkPrice(chainlinkResponse);
}

// If Chainlink is live but deviated >50% from it's previous price and Tellor is still untrusted, switch
// If Chainlink is live but deviated >50% from it's previous price and Tellor is still untrusted, switch
// to bothOraclesUntrusted and return last good price
if (_chainlinkPriceChangeAboveMax(chainlinkResponse, prevChainlinkResponse)) {
_changeStatus(Status.bothOraclesUntrusted);
return lastGoodPrice;
}

// Otherwise if Chainlink is live and deviated <50% from it's previous price and Tellor is still untrusted,
// Otherwise if Chainlink is live and deviated <50% from it's previous price and Tellor is still untrusted,
// return Chainlink price (no status change)
return _storeChainlinkPrice(chainlinkResponse);
}
Expand Down Expand Up @@ -432,7 +432,7 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
uint percentPriceDifference = maxPrice.sub(minPrice).mul(DECIMAL_PRECISION).div(minPrice);

/*
* Return true if the relative price difference is <= 3%: if so, we assume both oracles are probably reporting
* Return true if the relative price difference is <= 5%: if so, we assume both oracles are probably reporting
* the honest market price, as it is unlikely that both have been broken/hacked and are still in-sync.
*/
return percentPriceDifference <= MAX_PRICE_DIFFERENCE_BETWEEN_ORACLES;
Expand Down Expand Up @@ -542,12 +542,12 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {

function _getPrevChainlinkResponse(uint80 _currentRoundId, uint8 _currentDecimals) internal view returns (ChainlinkResponse memory prevChainlinkResponse) {
/*
* NOTE: Chainlink only offers a current decimals() value - there is no way to obtain the decimal precision used in a
* NOTE: Chainlink only offers a current decimals() value - there is no way to obtain the decimal precision used in a
* previous round. We assume the decimals used in the previous round are the same as the current round.
*/

// Try to get the price data from the previous round:
try priceAggregator.getRoundData(_currentRoundId - 1) returns
try priceAggregator.getRoundData(_currentRoundId - 1) returns
(
uint80 roundId,
int256 answer,
Expand All @@ -569,4 +569,3 @@ contract PriceFeed is Ownable, CheckContract, BaseMath, IPriceFeed {
}
}
}