# Start with a slim and secure Python base image
FROM python:3.9-slim

# --- Environment Variables ---
# Prevents Python from writing .pyc files to disc
ENV PYTHONDONTWRITEBYTECODE 1
# Ensures Python output is sent straight to the terminal without buffering
ENV PYTHONUNBUFFERED 1
# Set the MPLCONFIGDIR to a writable directory to avoid matplotlib warnings
ENV MPLCONFIGDIR /tmp/matplotlib

# --- System Dependencies ---
# First, update the package lists and install system libraries required by OpenCV.
# Combining these into a single RUN layer reduces image size.
# libglib2.0-0 is essential to fix the "libgthread-2.0.so.0" error.
RUN apt-get update && \
    apt-get install -y --no-install-recommends \
    libgl1-mesa-glx \
    libglib2.0-0 && \
    # Clean up the apt cache to reduce image size
    rm -rf /var/lib/apt/lists/*

# --- Python Dependencies ---
# Set the working directory
WORKDIR /app

# Copy only the requirements file first to leverage Docker's layer caching.
# This layer will only be re-run if requirements.txt changes.
COPY requirements.txt .

# Install Python dependencies from the requirements file.
# --no-cache-dir reduces image size.
RUN pip install --no-cache-dir -r requirements.txt

# --- Application Code ---
# Now, copy the rest of the application code into the container.
# This layer will be rebuilt on code changes, but the dependencies above will not.
COPY . .

# --- Port and Command ---
# Expose the port the application will run on
EXPOSE 7860

# The command to run the application
# Using a list format is the recommended way to write CMD
CMD ["uvicorn", "predict:app", "--host", "0.0.0.0", "--port", "7860"]