add Fund Me Foundry Smart Contract

fund-me/src/Counter.sol

@@ -1,14 +0,0 @@
-// SPDX-License-Identifier: UNLICENSED
-pragma solidity ^0.8.13;
-
-contract Counter {
-    uint256 public number;
-
-    function setNumber(uint256 newNumber) public {
-        number = newNumber;
-    }
-
-    function increment() public {
-        number++;
-    }
-}

fund-me/src/FundMe.sol

@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.18;
+
+// Note: The AggregatorV3Interface might be at a different location than what was in the video!
+import {AggregatorV3Interface} from "@chainlink/contracts/src/v0.8/shared/interfaces/AggregatorV3Interface.sol";
+import {PriceConverter} from "./PriceConverter.sol";
+
+error NotOwner();
+
+contract FundMe {
+    using PriceConverter for uint256;
+
+    // private is more gas efficient compared to public
+    mapping(address => uint256) private s_addressToAmountFunded;
+    address[] private s_funders;
+
+    // Could we make this constant?  /* hint: no! We should make it immutable! */
+    address private /* immutable */ i_owner;
+    uint256 public constant MINIMUM_USD = 5 * 10 ** 18;
+    AggregatorV3Interface private s_priceFeed;
+
+    constructor(address priceFeed) {
+        i_owner = msg.sender;
+	s_priceFeed = AggregatorV3Interface(priceFeed);
+    }
+
+    function fund() public payable {
+        require(msg.value.getConversionRate(s_priceFeed) >= MINIMUM_USD, "You need to spend more ETH!");
+        // require(PriceConverter.getConversionRate(msg.value) >= MINIMUM_USD, "You need to spend more ETH!");
+        s_addressToAmountFunded[msg.sender] += msg.value;
+        s_funders.push(msg.sender);
+    }
+
+    function getVersion() public view returns (uint256) {
+        return s_priceFeed.version();
+    }
+
+    modifier onlyOwner() {
+        // require(msg.sender == owner);
+        if (msg.sender != i_owner) revert NotOwner();
+        _;
+    }
+
+    function withdraw() public onlyOwner {
+        for (uint256 funderIndex = 0; funderIndex < s_funders.length; funderIndex++) {
+            address funder = s_funders[funderIndex];
+            s_addressToAmountFunded[funder] = 0;
+        }
+        s_funders = new address[](0);
+        // // transfer
+        // payable(msg.sender).transfer(address(this).balance);
+
+        // // send
+        // bool sendSuccess = payable(msg.sender).send(address(this).balance);
+        // require(sendSuccess, "Send failed");
+
+        // call
+        (bool callSuccess,) = payable(msg.sender).call{value: address(this).balance}("");
+        require(callSuccess, "Call failed");
+    }
+
+    function cheaperWithdraw() public onlyOwner {
+    	uint256 fundersLength = s_funders.length;
+	for (uint256 funderIndex = 0; funderIndex < fundersLength; funderIndex++) {
+	    address funder = s_funders[funderIndex];
+	    s_addressToAmountFunded[funder] = 0;
+	}
+	s_funders = new address[](0);
+
+	(bool callSuccess,) = payable(msg.sender).call{value: address(this).balance}("");
+	require(callSuccess, "Call failed");
+    }
+
+    // Explainer from: https://solidity-by-example.org/fallback/
+    // Ether is sent to contract
+    //      is msg.data empty?
+    //          /   \
+    //         yes  no
+    //         /     \
+    //    receive()?  fallback()
+    //     /   \
+    //   yes   no
+    //  /        \
+    //receive()  fallback()
+
+    fallback() external payable {
+        fund();
+    }
+
+    receive() external payable {
+        fund();
+    }
+
+    /**
+     * View / Pure Functions (Getters)
+     */
+    function getAddressToAmountFunded(
+	address fundingAddress
+    ) external view returns (uint256) {
+    	return s_addressToAmountFunded[fundingAddress];
+    }
+
+    function getFunder(uint256 funderIndex) external view returns (address) {
+    	return s_funders[funderIndex];
+    }
+
+    function getOwner() external view returns (address) {
+    	return i_owner;
+    }
+
+    function getPriceFeed() external view returns (AggregatorV3Interface) {
+    	return s_priceFeed;
+    }
+}
+
+// Concepts we didn't cover yet (will cover in later sections)
+// 1. Enum
+// 2. Events
+// 3. Try / Catch
+// 4. Function Selector
+// 5. abi.encode / decode
+// 6. Hash with keccak256
+// 7. Yul / Assembly

fund-me/src/PriceConverter.sol

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.18;
+
+import {AggregatorV3Interface} from "@chainlink/contracts/src/v0.8/shared/interfaces/AggregatorV3Interface.sol"; 
+
+// Why is this a library and not abstract?
+// Why not an interface?
+library PriceConverter {
+    // We could make this public, but then we'd have to deploy it
+    function getPrice(AggregatorV3Interface priceFeed) internal view returns (uint256) {
+        // Sepolia ETH / USD Address
+        // https://docs.chain.link/data-feeds/price-feeds/addresses
+        (, int256 answer, , , ) = priceFeed.latestRoundData();
+        // ETH/USD rate in 18 digit
+        return uint256(answer * 10000000000);
+    }
+
+    // 1000000000
+    function getConversionRate(
+        uint256 ethAmount,
+	AggregatorV3Interface priceFeed
+    ) internal view returns (uint256) {
+        uint256 ethPrice = getPrice(priceFeed);
+        uint256 ethAmountInUsd = (ethPrice * ethAmount) / 1000000000000000000;
+        // the actual ETH/USD conversion rate, after adjusting the extra 0s.
+        return ethAmountInUsd;
+    }
+}