Abehjati/update-eth-contract-prev-price (#252)

* Set prev* to current* when price gets stale

* Add new solidity sdk

* Add migration files for this update

* rename diff to absDiff

Strangely, although you cannot use parent private method, you cannot
define a method with same name

* Add a comment to explain the prevPrice replacement

Author: ali-behjati

ethereum/contracts/pyth/Pyth.sol

@@ -223,19 +223,27 @@ abstract contract Pyth is PythGetters, PythSetters, AbstractPyth {
 
         // Check that there is not a significant difference between this chain's time
         // and the price publish time.
-        if (diff(block.timestamp, info.priceFeed.publishTime) > VALID_TIME_PERIOD_SECS) {
+        if (info.priceFeed.status == PythStructs.PriceStatus.TRADING && 
+            absDiff(block.timestamp, info.priceFeed.publishTime) > VALID_TIME_PERIOD_SECS) {
             info.priceFeed.status = PythStructs.PriceStatus.UNKNOWN;
+            // getLatestAvailablePrice* gets prevPrice when status is
+            // unknown. So, now that status is being set to unknown,
+            // we should move the current price to the previous
+            // price to ensure getLatestAvailablePrice* works
+            // as intended.
+            info.priceFeed.prevPrice = info.priceFeed.price;
+            info.priceFeed.prevConf = info.priceFeed.conf;
+            info.priceFeed.prevPublishTime = info.priceFeed.publishTime;
         }
 
         return info.priceFeed;
     }
 
-    function diff(uint x, uint y) private pure returns (uint) {
+    function absDiff(uint x, uint y) private pure returns (uint) {
         if (x > y) {
             return x - y;
         } else {
             return y - x;
         }
     }
-
 }

ethereum/migrations/prod-receiver/6_pyth_update_interface_add_latest_methods.js

@@ -0,0 +1,16 @@
+require('dotenv').config({ path: "../.env" });
+
+const PythUpgradable = artifacts.require("PythUpgradable");
+
+const { upgradeProxy } = require("@openzeppelin/truffle-upgrades");
+
+/**
+ * This change:
+ * - Updates the interface, removes `getPrevPriceUnsafe` and adds two functions
+ *   `getLatestAvailablePriceUnsafe` and `getLatestAvailablePriceWithinDuration`
+ *   to replace its behaviour in a more elegant way.
+ */
+module.exports = async function (deployer) {
+    const proxy = await PythUpgradable.deployed();
+    await upgradeProxy(proxy.address, PythUpgradable, { deployer });
+}

ethereum/migrations/prod/5_pyth_update_interface_add_latest_methods.js

@@ -0,0 +1,16 @@
+require('dotenv').config({ path: "../.env" });
+
+const PythUpgradable = artifacts.require("PythUpgradable");
+
+const { upgradeProxy } = require("@openzeppelin/truffle-upgrades");
+
+/**
+ * This change:
+ * - Updates the interface, removes `getPrevPriceUnsafe` and adds two functions
+ *   `getLatestAvailablePriceUnsafe` and `getLatestAvailablePriceWithinDuration`
+ *   to replace its behaviour in a more elegant way.
+ */
+module.exports = async function (deployer) {
+    const proxy = await PythUpgradable.deployed();
+    await upgradeProxy(proxy.address, PythUpgradable, { deployer });
+}

ethereum/migrations/test/6_pyth_update_interface_add_latest_methods.js

@@ -0,0 +1,16 @@
+require('dotenv').config({ path: "../.env" });
+
+const PythUpgradable = artifacts.require("PythUpgradable");
+
+const { upgradeProxy } = require("@openzeppelin/truffle-upgrades");
+
+/**
+ * This change:
+ * - Updates the interface, removes `getPrevPriceUnsafe` and adds two functions
+ *   `getLatestAvailablePriceUnsafe` and `getLatestAvailablePriceWithinDuration`
+ *   to replace its behaviour in a more elegant way.
+ */
+module.exports = async function (deployer) {
+    const proxy = await PythUpgradable.deployed();
+    await upgradeProxy(proxy.address, PythUpgradable, { deployer });
+}

ethereum/package-lock.json

@@ -30,7 +30,7 @@
   "dependencies": {
     "@openzeppelin/contracts": "^4.5.0",
     "@openzeppelin/contracts-upgradeable": "^4.5.2",
-    "@pythnetwork/pyth-sdk-solidity": "^0.4.0",
+    "@pythnetwork/pyth-sdk-solidity": "^0.5.0",
     "dotenv": "^10.0.0",
     "elliptic": "^6.5.2",
     "ganache-cli": "^6.12.1",