From 230a9560a54e9a02f58c2ae7edbb21643739e507 Mon Sep 17 00:00:00 2001
From: Alexander Daichendt <git@daichendt.one>
Date: Wed, 12 Feb 2025 12:29:16 +0100
Subject: [PATCH] feat: add system messages

---
 client/src/components/ChatProvider.tsx   |  6 ++--
 client/src/components/MessageDisplay.tsx | 42 ++++++++++++++++++++----
 client/src/contexts/ChatContext.tsx      | 18 +++++++---
 client/src/hooks/useWebSocket.ts         |  6 ++--
 4 files changed, 55 insertions(+), 17 deletions(-)

diff --git a/client/src/components/ChatProvider.tsx b/client/src/components/ChatProvider.tsx
index d250e83..b98ee68 100644
--- a/client/src/components/ChatProvider.tsx
+++ b/client/src/components/ChatProvider.tsx
@@ -1,6 +1,6 @@
 import React, { useReducer } from "react";
-import { ChatMessage, User } from "../../../shared";
-import { ChatContext } from "../contexts/ChatContext";
+import { User } from "../../../shared";
+import { ChatContext, Message } from "../contexts/ChatContext";
 import { chatReducer } from "../reducers/chatReducers";
 
 export function ChatProvider({ children }: { children: React.ReactNode }) {
@@ -14,7 +14,7 @@ export function ChatProvider({ children }: { children: React.ReactNode }) {
     state,
     dispatch,
     actions: {
-      addMessage: (message: ChatMessage) =>
+      addMessage: (message: Message) =>
         dispatch({ type: "ADD_MESSAGE", payload: message }),
       setUser: (user: User) => dispatch({ type: "SET_USER", payload: user }),
       setConnected: (isConnected: boolean) =>
diff --git a/client/src/components/MessageDisplay.tsx b/client/src/components/MessageDisplay.tsx
index 177f0ed..e0a837d 100644
--- a/client/src/components/MessageDisplay.tsx
+++ b/client/src/components/MessageDisplay.tsx
@@ -1,4 +1,5 @@
 import React from "react";
+import { ServerMessage } from "../../../shared";
 import { useChatState } from "../contexts/ChatContext";
 import ChatMessage from "./ChatMessage";
 
@@ -6,13 +7,40 @@ function ChatMessages() {
   const { state } = useChatState();
   const userId = state.currentUser?.userId;
 
-  return (
-    <>
-      {state.messages.map((message) => (
-        <ChatMessage message={message} userId={userId} />
-      ))}
-    </>
-  );
+  function renderMessage(message: ServerMessage) {
+    switch (message.type) {
+      case "CHAT_MESSAGE":
+        return (
+          <ChatMessage
+            message={message.payload}
+            userId={userId}
+            key={message.payload.id}
+          />
+        );
+      case "USER_JOINED":
+        return (
+          <div
+            className="text-center text-gray-500 my-2"
+            key={`join-${message.payload.user.name}-${new Date()}`}
+          >
+            {message.payload.user.name} joined!
+          </div>
+        );
+      case "USER_LEFT":
+        return (
+          <div
+            className="text-center text-gray-500 my-2"
+            key={`leave-${message.payload.user.name}-${new Date()}`}
+          >
+            {message.payload.user.name} left!
+          </div>
+        );
+      default:
+        return null;
+    }
+  }
+
+  return <>{state.messages.map(renderMessage)}</>;
 }
 
 export default React.memo(ChatMessages);
diff --git a/client/src/contexts/ChatContext.tsx b/client/src/contexts/ChatContext.tsx
index 771f464..8d2288a 100644
--- a/client/src/contexts/ChatContext.tsx
+++ b/client/src/contexts/ChatContext.tsx
@@ -1,20 +1,30 @@
 import { createContext, useContext, Dispatch } from "react";
-import { ChatMessage, User } from "../../../shared";
+import {
+  ServerChatMessage,
+  ServerUserJoinedMessage,
+  ServerUserLeftMessage,
+  User,
+} from "../../../shared";
+
+export type Message =
+  | ServerChatMessage
+  | ServerUserJoinedMessage
+  | ServerUserLeftMessage;
 
 export type ChatState = {
-  messages: ChatMessage[];
+  messages: Message[];
   currentUser: User | null;
   isConnected: boolean;
 };
 
 export type ChatAction =
-  | { type: "ADD_MESSAGE"; payload: ChatMessage }
+  | { type: "ADD_MESSAGE"; payload: Message }
   | { type: "SET_USER"; payload: User }
   | { type: "SET_CONNECTED"; payload: boolean }
   | { type: "CLEAR_MESSAGES" };
 
 export type ChatActions = {
-  addMessage: (message: ChatMessage) => void;
+  addMessage: (message: Message) => void;
   setUser: (user: User) => void;
   setConnected: (isConnected: boolean) => void;
 };
diff --git a/client/src/hooks/useWebSocket.ts b/client/src/hooks/useWebSocket.ts
index c805b3b..f9ef96d 100644
--- a/client/src/hooks/useWebSocket.ts
+++ b/client/src/hooks/useWebSocket.ts
@@ -21,11 +21,11 @@ export function useWebSocket(roomId: string) {
           actions.setUser(message.payload.user);
           break;
 
+        // intentional fallthrough
         case "USER_JOINED":
-          break;
-
+        case "USER_LEFT":
         case "CHAT_MESSAGE":
-          actions.addMessage(message.payload);
+          actions.addMessage(message);
           break;
 
         default: