feat: implemented an OffChainVerification example

test/OffChainVerificationExample.js

@@ -0,0 +1,58 @@
+const sdk = require("@redstone-finance/sdk");
+const { expect } = require("chai");
+const { BigNumber } = require("ethers");
+const { hexlify } = require("ethers/lib/utils");
+
+describe("OffChainVerificationExample", () => {
+  it("Get data packages and extract signers", async () => {
+    const oracleStateWithSigners = await sdk.getOracleRegistryState();
+    console.log(`== RedStone oracles state ==`);
+    console.log(JSON.stringify(oracleStateWithSigners, null, 2));
+
+    const dataPackagesResponse = await sdk.requestDataPackages({
+      dataFeeds: ["TON", "USDC", "USDT"],
+      dataServiceId: "redstone-primary-prod",
+      uniqueSignersCount: 3,
+      urls: [
+        "https://oracle-gateway-1.a.redstone.finance",
+        "https://oracle-gateway-2.a.redstone.finance",
+      ],
+    });
+
+    for (const [dataFeedId, dataPackages] of Object.entries(
+      dataPackagesResponse
+    )) {
+      console.log(`\n\n== Data packages for ${dataFeedId} ==\n`);
+      for (const signedDataPackage of dataPackages) {
+        const signerAddress = signedDataPackage.recoverSignerAddress();
+        // The `getDataServiceIdForSigner` function logic is very simple
+        // You can check it here: https://github.com/redstone-finance/redstone-oracles-monorepo/blob/main/packages/sdk/src/index.ts#L72
+        const dataServiceBySigner = sdk.getDataServiceIdForSigner(
+          oracleStateWithSigners,
+          signerAddress
+        );
+        const valueBytes = signedDataPackage.dataPackage.dataPoints[0].value;
+        const valueAsBigNumber = BigNumber.from(hexlify(valueBytes));
+        console.log(`Value (BigNumber): ${valueAsBigNumber.toString()}`);
+        console.log(
+          `Value (formatted): ${
+            valueAsBigNumber.toNumber() / 10 ** 8
+          }`
+        );
+        console.log(`Signer address: ${signerAddress}`);
+        console.log(`Data service id for signer: ${dataServiceBySigner}`);
+        console.log("------------------------------------");
+      }
+    }
+  });
+
+  it("Should fail trying to find an invalid signer", async () => {
+    const oracleStateWithSigners = await sdk.getOracleRegistryState();
+    const unauthorisedSigner = "0x3E1f4c6614cac82Ee6112114B37AB097d7693070";
+    expect(() =>
+      sdk.getDataServiceIdForSigner(oracleStateWithSigners, unauthorisedSigner)
+    ).to.throw(
+      "Data service not found for 0x3E1f4c6614cac82Ee6112114B37AB097d7693070"
+    );
+  });
+});