FROM python:3.9-slim-buster

WORKDIR /app

# Install build dependencies first and clean up afterwards in a single RUN command
# This minimizes layers and cleans up unused packages immediately.
RUN apt-get update && apt-get install -y --no-install-recommends gcc python3-dev && \
    rm -rf /var/lib/apt/lists/*

# Copy requirements.txt separately to leverage caching
# If only source code changes, pip install won't re-run
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Copy the rest of the application code
COPY . .

# Remove build dependencies
RUN apt-get purge -y --auto-remove gcc python3-dev

EXPOSE 8000

# Use gunicorn as a production-ready WSGI server
CMD ["gunicorn", "--bind", "0.0.0.0:8000", "your_project.wsgi:application"]