# 🧪 Mock OpenAI Chat API Server

This project simulates the OpenAI `/v1/chat/completions` API using a local FastAPI server.  
It logs all incoming requests and returns a dummy response using `"Lorem Ipsum..."` content for debugging and development purposes.

---

## ✅ Features

- Local server that mimics OpenAI ChatCompletion endpoint
- Logs full request (headers + body) to `requests_log.json`
- Returns a dummy OpenAI-style response
- Plug-in replacement for `openai.ChatCompletion.create(...)`

---

## ⚙️ Requirements

- Python 3.7+
- FastAPI
- Uvicorn

---

## 📦 Installation & Setup

### 1. Clone or copy this project into a local folder

### 2. Create and activate a virtual environment

```bash
python -m venv venv
```

Then activate it:

- **Windows:**

```bash
venv\Scripts\activate
```

- **macOS/Linux:**

```bash
source venv/bin/activate
```

### 3. Install dependencies

```bash
pip install fastapi uvicorn
```

---

## 🚀 How to Start the Server

Use this command to launch the mock API server:

```bash
python -m uvicorn mock_openai_server:app --reload --port 8000
```

It will be available at:

```
http://localhost:8000/v1/chat/completions
```

---

## 🧪 How to Use with OpenAI Python SDK

Update your client to point to the mock server:

```python
import openai

openai.api_key = "sk-dummy"
openai.api_base = "http://localhost:8000"

response = openai.ChatCompletion.create(
    model="gpt-4",
    messages=[
        {"role": "user", "content": "Hello!"}
    ]
)

print(response)
```

---

## 📄 Example Dummy Response

```text
ID:            chatcmpl-mock123
Model:         gpt-4
Created:       <current timestamp>
Role:          assistant
Message:       Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Finish reason: stop
Tokens used:   prompt=10, completion=12, total=22
```

---

## 📝 Output Logs

All requests and responses are logged to `requests_log.json`.  
Each log entry contains:

- Timestamp
- Headers (sent by client)
- JSON body (messages, model, etc.)
- Dummy response

You can use this log to debug what your app sends to OpenAI.

---

## 📂 Project Structure

```
.
├── mock_openai_server.py    # FastAPI mock server
├── requests_log.json        # Saved request/response logs
└── README.md                # Documentation
```

---

## 🧰 Optional: Save Installed Packages

To track your environment:

```bash
pip freeze > requirements.txt
```

Later, you can restore it with:

```bash
pip install -r requirements.txt
```

---

## 📌 Notes

- No actual API calls are made to OpenAI
- Great for debugging payload formats, headers, and SDK integrations
- For local development only

---

## 🪪 License

MIT License