add foundry and hardhat guides for DF getting started

foundry.toml

@@ -9,6 +9,11 @@ out = ".test/artifacts"
 cache_path = ".test/cache"
 libs = ["lib", "node_modules"]
 
+# Foundry deploy scripts (e.g. public/samples/DataFeeds/Foundry/*.s.sol) are
+# meant to run inside a user's Foundry project where forge-std and a src/ layout
+# are available. They cannot compile in this repo, so skip them.
+skip = ["*/DataFeeds/Foundry/*"]
+
 optimizer = true
 optimizer_runs = 1_000_000
 

public/samples/DataFeeds/Foundry/DeployAndReadDataConsumerV3.s.sol

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.7;
+
+/* solhint-disable no-console */
+
+import {DataConsumerV3} from "../../src/DataFeeds/DataConsumerV3.sol";
+import {AggregatorV3Interface} from "@chainlink/contracts/src/v0.8/shared/interfaces/AggregatorV3Interface.sol";
+import {Script} from "forge-std/Script.sol";
+import {console2} from "forge-std/console2.sol";
+
+/**
+ * THIS IS EXAMPLE CODE THAT USES HARDCODED VALUES FOR CLARITY.
+ * THIS IS EXAMPLE CODE THAT USES UN-AUDITED CODE.
+ * DO NOT USE THIS CODE IN PRODUCTION.
+ *
+ * Deploy DataConsumerV3 and read the latest BTC/USD price on Sepolia.
+ *
+ * Usage:
+ *   forge script script/DataFeeds/DeployAndReadDataConsumerV3.s.sol \
+ *     --rpc-url $SEPOLIA_RPC_URL \
+ *     --broadcast \
+ *     --private-key $PRIVATE_KEY
+ */
+contract DeployAndReadDataConsumerV3 is Script {
+  // Sepolia BTC / USD price feed proxy address
+  address public constant SEPOLIA_BTC_USD = 0x1b44F3514812d835EB1BDB0acB33d3fA3351Ee43;
+
+  function run() public {
+    vm.startBroadcast();
+
+    // 1. Deploy the consumer contract
+    DataConsumerV3 consumer = new DataConsumerV3();
+    console2.log("DataConsumerV3 deployed at:", address(consumer));
+
+    vm.stopBroadcast();
+
+    // 2. Read the latest price through the consumer
+    int256 answer = consumer.getChainlinkDataFeedLatestAnswer();
+    console2.log("Latest answer (raw):", uint256(answer));
+
+    // 3. Read decimals directly from the feed to scale the answer
+    uint8 decimals = AggregatorV3Interface(SEPOLIA_BTC_USD).decimals();
+    console2.log("Decimals:", decimals);
+    console2.log("Latest price (scaled): %s", _scale(answer, decimals));
+  }
+
+  function _scale(
+    int256 answer,
+    uint8 decimals
+  ) internal pure returns (string memory) {
+    // Convert the integer answer to a human-readable price string.
+    // For 8 decimals, 3030914000000 -> "30309.14000000"
+    uint256 magnitude = uint256(answer);
+    uint256 base = 10 ** decimals;
+    uint256 whole = magnitude / base;
+    uint256 fraction = magnitude % base;
+    return string.concat(vm.toString(whole), ".", vm.toString(fraction));
+  }
+}

public/samples/DataFeeds/Hardhat/DeployAndReadDataConsumerV3.js

@@ -0,0 +1,47 @@
+import { network } from "hardhat"
+
+/**
+ * THIS IS EXAMPLE CODE THAT USES HARDCODED VALUES FOR CLARITY.
+ * THIS IS EXAMPLE CODE THAT USES UN-AUDITED CODE.
+ * DO NOT USE THIS CODE IN PRODUCTION.
+ */
+
+const { ethers } = await network.create()
+
+async function main() {
+  // 1. Deploy the DataConsumerV3 contract
+  const consumer = await ethers.deployContract("DataConsumerV3")
+  await consumer.waitForDeployment()
+
+  const consumerAddress = await consumer.getAddress()
+  console.log("DataConsumerV3 deployed at:", consumerAddress)
+
+  // 2. Read the latest price through the consumer contract
+  const answer = await consumer.getChainlinkDataFeedLatestAnswer()
+  console.log("Latest answer (raw):", answer.toString())
+
+  // 3. Read decimals directly from the feed to scale the answer
+  // Sepolia BTC / USD price feed proxy address
+  const feedAddress = "0x1b44F3514812d835EB1BDB0acB33d3fA3351Ee43"
+  const AggregatorV3Interface = [
+    {
+      inputs: [],
+      name: "decimals",
+      outputs: [{ internalType: "uint8", name: "", type: "uint8" }],
+      stateMutability: "view",
+      type: "function",
+    },
+  ]
+  const feed = await ethers.getContractAt(AggregatorV3Interface, feedAddress)
+  const decimals = await feed.decimals()
+  console.log("Decimals:", decimals)
+
+  // 4. Scale and print the human-readable price
+  const scaled = Number(answer) / 10 ** Number(decimals)
+  console.log("Latest price (USD):", scaled)
+}
+
+main().catch((error) => {
+  console.error(error)
+  process.exit(1)
+})