Architecture

System architecture, data flow, and component interactions

System Overview

ChatbotForCse consists of three independent subsystems communicating via REST APIs and a shared MongoDB database.

System Diagram

Components

Backend API

FastAPI handles logic, database access, and AI processing

WhatsApp Client

Node.js bridge listening to WhatsApp messages

Data Pipeline

Python scheduled jobs for web scraping

---

Layered Architecture

The backend follows a clean 4-layer architecture:

Layer Diagram

Responsibilities

Layer	Responsibility	Key Files
API	HTTP endpoints	api/routes/chat.py
Service	Business logic	services/chat_service.py
Domain	Core algorithms	llm_engine/, strategies/
Data Access	Database ops	db/mongo.py, clients/

---

Design Pattern Locations

Strategy Pattern

Files:

• llm_engine/classifiers/
• strategies/context_strategies.py

Factory Pattern

Files:

• llm_engine/classifier.py
• strategies/context_strategies.py

Singleton Pattern

Files:

• db/mongo.py
• clients/ollama_client.py

---

Chat Request Flow

1. User Message

   User sends “bugün menüde ne var?” via WhatsApp

2. Message Forwarding

   WhatsApp Client forwards to FastAPI backend

3. Intent Classification

   Factory returns HybridClassifier → classifies as “dining”

4. Context Fetching

   Factory returns DiningStrategy → fetches menu from MongoDB

5. LLM Response

   Gemini generates natural language response

6. Reply

   Response sent back to WhatsApp user

Sequence Diagram

View Full Sequence Diagram

---

Directory Structure

Full Project Structure

ChatbotForCse/
├── backend/
│   ├── app/
│   │   ├── api/routes/           # API endpoints
│   │   ├── core/                 # Settings & config
│   │   ├── db/                   # MongoDB Singleton
│   │   ├── llm_engine/
│   │   │   ├── classifiers/      # Strategy Pattern
│   │   │   └── clients/          # Singleton clients
│   │   ├── services/             # Business logic
│   │   └── strategies/           # Context Strategy Pattern
│   └── main.py
├── data-pipeline/
│   ├── crawlers/                 # SKS/CSE scrapers
│   ├── jobs/                     # Scheduled tasks
│   └── services/                 # Image processing
├── whatsapp/
│   └── src/                      # Node.js WPPConnect
└── documentation/                # Mintlify docs

---

Component Diagram

View Component Diagram