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📌 Simple Chat Messaging Simulator

A modern JavaFX-based WhatsApp-style chat simulator showcasing clean architecture, multithreading, and advanced Software Engineering design patterns.

Build Status

🚀 Features

Chat List Screen

  • Shows Chats: Mano, Yusra, Rabail

  • Each item displays:

    • Contact name
    • Last message preview
    • Unread message badge (● N)

  • Clicking a chat opens a dedicated chat window for that contact

  • List updates live when:

    • A new message arrives
    • Unread count changes
    • Last message changes

(Implemented via ChatListController + ChatObserver + ChatEngine.)

🧩 Overview

The Simple Chat Messaging Simulator is a desktop application built with JavaFX, designed to simulate realistic two-way chat conversations. The system integrates multiple design patterns including Factory, Builder, Decorator, Observer, Singleton, and multithreading.

It features:

  • Chat list screen
  • Per-contact chat windows
  • Human-like bot replies
  • Typing indicators
  • Message previews
  • Unread counters
  • Personality-based auto-replies

✨ Features

Chat UI

  • WhatsApp-style layout
  • User + bot message bubbles
  • Timestamps via decorator
  • Auto-scroll
  • Clean FXML-driven UI

🤖 Personality-Based Bot

Each contact has a unique texting style:

  • Mano – dramatic, playful
  • Yusra – chaotic, meme-texting
  • Rabail – soft, sweet, teasing

Smart reply engine supports:

  • Keyword detection
  • Personality-based responses
  • Emoji-rich fallback replies

⌨ Realistic Typing Simulation

Typing delay calculation:

0.8s + (messageLength × 40ms)
Max ≈ 2.8 seconds

Bot shows:

  • “Typing…” bubble
  • Human-like delay
  • Then sends reply

Bot only replies when the user sends a message.

📬 Chat List Features

  • Last message preview
  • Automatic unread count updates
  • Observer pattern implementation
  • Smooth UI refresh

🧠 Design Patterns Implemented

Pattern Where Used Purpose
Factory MessageFactory Create Message objects (currently TextMessage)
Builder ChatSession / session builder (initializer) Build initial session data / configure startup chat content
Decorator MessageDecorator, StyleDecorator, TimestampDecorator Add timestamp and visual style to messages without changing core Message
Observer ChatObserver, IncomingMessageSimulator, ChatListController Notify chat list when unread counts / last message change; simulate incoming messages
Singleton ChatEngine Central manager for chat logs, active contact, UI hooks, routing & typing state

📁 Project Structure

Simple-Chat-Messaging-Simulator/
│
├── pom.xml
├── README.md
├── Report.pdf
├── screenshots/
│      ├── chat_list.png
│      └── chat_window_1.png
│      └── chat_window_2.png
├── src/
│   └── main/
│       ├── java/
│       │   └── com/chatapp/
│       │        ├── Main.java
│       │        ├── controllers/
│       │        │      ├── ChatController.java
│       │        │      └── ChatListController.java
│       │        ├── engine/
│       │        │      └── ChatEngine.java
│       │        ├── messages/
│       │        │      ├── Message.java
│       │        │      ├── TextMessage.java
│       │        │      └── MessageFactory.java
│       │        ├── builder/
│       │        │      └── ChatSession.java   (or ChatSessionBuilder)
│       │        ├── decorator/
│       │        │      ├── MessageDecorator.java
│       │        │      ├── StyleDecorator.java
│       │        │      └── TimestampDecorator.java
│       │        └── observer/
│       │               ├── ChatObserver.java
│       │               └── IncomingMessageSimulator.java
│       └── resources/
│            └── ui/
│                 ├── chat.fxml
│                 └── chat_list.fxml

🛠 Technologies Used

  • Java 23
  • JavaFX 23 / 21+
  • Maven
  • FXML UI Layout
  • Object-Oriented Design + GoF Patterns

⚙ How to Run

1️⃣ Install JDK & JavaFX

Download JavaFX SDK: 👉 https://gluonhq.com/products/javafx/

2️⃣ Clone Repo

git clone https://github.com/yourname/Simple-Chat-Messaging-Simulator.git
cd Simple-Chat-Messaging-Simulator

3️⃣ Run in IntelliJ

Add VM options (Run Configuration → VM options):

--module-path "C:/Program Files/javafx-sdk/lib" --add-modules javafx.controls,javafx.fxml

(Adjust path to your JavaFX SDK.)

4️⃣ Run Main Class

Main class: com.chatapp.Main

🧠 Core Logic Overview

🔹 ChatEngine (Singleton)

  • Stores chat logs per contact

  • Tracks active contact

  • Handles:

    • Sending & receiving messages
    • Adding message bubbles to the UI
    • Scroll-to-bottom behavior
    • Typing indicator (showTyping / hideTyping)
    • Unread counters + last message preview for chat list

  • Notifies ChatObserver (implemented by ChatListController) when:

    • Unread count changes
    • Last message changes

🔹 Typing Indicator Flow

  1. User sends message via ChatController

  2. ChatEngine.sendMessageTo(contact, msg):

    • Adds user bubble
    • Notifies IncomingMessageSimulator.onUserMessage(contact, text)

  3. Simulator thread:

    • Calls ChatEngine.showTyping(contact)
    • Sleeps ~1–2 seconds
    • Calls ChatEngine.hideTyping(contact)
    • Generates personality-based reply
    • Calls ChatEngine.receiveMessage(contact, msg)

🔹 Reply Logic Overview

  • Keyword-based layer

    • If message contains words like "hi", "hello", "how are", "busy", "wyd", "thanks" → reply with a relevant canned sentence.

  • Personality layer

    • If no keyword matches, pick from that contact’s own reply set:

      • Mano → playful / dramatic replies
      • Yusra → chaotic / meme replies
      • Rabail → calm / sweet / teasing replies

  • All replies are English, with casual texting + emojis.

🔄 Chat Flow

  1. User sends message
  2. ChatEngine logs + displays it
  3. IncomingMessageSimulator triggers typing
  4. Delay based on content length
  5. Bot reply generated
  6. Chat list updates

📸 Results



🧪 Extensibility

You can extend:

  • Message types (image, audio)
  • Contacts & personalities
  • AI chatbot backend
  • Database persistence
  • WhatsApp-style ticks
  • Urdu texting mode
  • Dark mode UI

⚠ Limitations

  • In-memory chat only
  • No media messages
  • Rule-based bot logic

⭐ Future Enhancements

  • LLM integration
  • Persistent SQLite storage
  • Voice note bubbles
  • Custom themes
  • Animation transitions
  • Online/offline indicators