Add events (#3)

abi/omen_thumbnailmapping.abi.json

@@ -0,0 +1,64 @@
+[
+  {
+    "type": "function",
+    "name": "get",
+    "inputs": [
+      { "name": "marketAddress", "type": "address", "internalType": "address" }
+    ],
+    "outputs": [{ "name": "", "type": "bytes32", "internalType": "bytes32" }],
+    "stateMutability": "view"
+  },
+  {
+    "type": "function",
+    "name": "getLatestImageChanger",
+    "inputs": [
+      { "name": "marketAddress", "type": "address", "internalType": "address" }
+    ],
+    "outputs": [{ "name": "", "type": "address", "internalType": "address" }],
+    "stateMutability": "view"
+  },
+  {
+    "type": "function",
+    "name": "remove",
+    "inputs": [
+      { "name": "marketAddress", "type": "address", "internalType": "address" }
+    ],
+    "outputs": [],
+    "stateMutability": "nonpayable"
+  },
+  {
+    "type": "function",
+    "name": "set",
+    "inputs": [
+      { "name": "marketAddress", "type": "address", "internalType": "address" },
+      { "name": "image_hash", "type": "bytes32", "internalType": "bytes32" }
+    ],
+    "outputs": [],
+    "stateMutability": "nonpayable"
+  },
+  {
+    "type": "event",
+    "name": "ImageUpdated",
+    "inputs": [
+      {
+        "name": "marketAddress",
+        "type": "address",
+        "indexed": true,
+        "internalType": "address"
+      },
+      {
+        "name": "image_hash",
+        "type": "bytes32",
+        "indexed": false,
+        "internalType": "bytes32"
+      },
+      {
+        "name": "changer",
+        "type": "address",
+        "indexed": true,
+        "internalType": "address"
+      }
+    ],
+    "anonymous": false
+  }
+]

src/OmenThumbnailMapping.sol

@@ -5,24 +5,31 @@ import {IERC20} from "../lib/openzeppelin-contracts/contracts/interfaces/IERC20.
 
 /// @dev Mapping from market's address to image's IPFS hash
 contract OmenThumbnailMapping {
+    event ImageUpdated(address indexed marketAddress, bytes32 image_hash, address indexed changer);
+
     mapping(address => bytes32) private marketAddressToIPFSHash;
     mapping(address => address) private marketAddressToLatestImageChanger;
 
     /// @dev Get IPFS hash of thumbnail for the given market.
-    function get(address marketAddress) external view returns (bytes32) {
+    function get(address marketAddress) public view returns (bytes32) {
         return marketAddressToIPFSHash[marketAddress];
     }
 
     /// @dev Update IPFS hash of thumbnail for the given market.
-    function set(address marketAddress, bytes32 image_hash) external requireThatSenderCanChangeImage(marketAddress) {
+    function set(address marketAddress, bytes32 image_hash) public requireThatSenderCanChangeImage(marketAddress) {
         marketAddressToIPFSHash[marketAddress] = image_hash;
         marketAddressToLatestImageChanger[marketAddress] = msg.sender;
+        emit ImageUpdated(marketAddress, image_hash, msg.sender);
     }
 
     /// @dev Remove IPFS hash of thumbnail for the given market.
-    function remove(address marketAddress) external requireThatSenderCanChangeImage(marketAddress) {
-        delete marketAddressToIPFSHash[marketAddress];
-        marketAddressToLatestImageChanger[marketAddress] = msg.sender;
+    function remove(address marketAddress) public requireThatSenderCanChangeImage(marketAddress) {
+        set(marketAddress, bytes32(0));
+    }
+
+    /// @dev Get the address of the latest person who updated the image for the given market.
+    function getLatestImageChanger(address marketAddress) public view returns (address) {
+        return marketAddressToLatestImageChanger[marketAddress];
     }
 
     /// @dev Verify that sender is allowed to update IPFS hash for the given market.

test/OmenThumbnailMapping.t.sol

@@ -21,6 +21,8 @@ contract OmenThumbnailMappingTest is Test {
 
     function testCanUpdateImageWithAnyFundsInMarketIfThisIsFirstUpdater() public {
         productMarketMaker.mint(address(this), 1);
+        vm.expectEmit(true, true, true, true);
+        emit OmenThumbnailMapping.ImageUpdated(address(productMarketMaker), "Qm123", address(this));
         omenThumbnailMapping.set(address(productMarketMaker), "Qm123");
         assertEq(omenThumbnailMapping.get(address(productMarketMaker)), "Qm123");
     }
@@ -56,4 +58,27 @@ contract OmenThumbnailMappingTest is Test {
         omenThumbnailMapping.set(address(productMarketMaker), "Qm456");
         assertEq(omenThumbnailMapping.get(address(productMarketMaker)), "Qm456");
     }
+
+    function testNonSetImageIsEqualToNullBytes32() public {
+        assertEq(omenThumbnailMapping.get(address(productMarketMaker)), bytes32(0));
+    }
+
+    function testImageIsNullBytesAfterRemovalAndChangerIsUpdatedCorrectly() public {
+        productMarketMaker.mint(address(this), 1);
+        vm.expectEmit(true, true, true, true);
+        emit OmenThumbnailMapping.ImageUpdated(address(productMarketMaker), "Qm123", address(this));
+        omenThumbnailMapping.set(address(productMarketMaker), "Qm123");
+        assertEq(omenThumbnailMapping.get(address(productMarketMaker)), "Qm123");
+        assertEq(omenThumbnailMapping.getLatestImageChanger(address(productMarketMaker)), address(this));
+
+        address anotherUser = address(0x123);
+        productMarketMaker.mint(anotherUser, 2);
+        vm.expectEmit(true, true, true, true);
+        emit OmenThumbnailMapping.ImageUpdated(address(productMarketMaker), bytes32(0), anotherUser);
+        vm.prank(anotherUser);
+
+        omenThumbnailMapping.remove(address(productMarketMaker));
+        assertEq(omenThumbnailMapping.get(address(productMarketMaker)), bytes32(0));
+        assertEq(omenThumbnailMapping.getLatestImageChanger(address(productMarketMaker)), anotherUser);
+    }
 }