# --- Step 1: Base Build Stage ---
# Use an official Python slim image for a lightweight foundation
FROM python:3.11-slim as builder

# Set build-time environment variables
ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1

# Set the working directory inside the container
WORKDIR /app

# Install minimal system-level dependencies required for building/running certain wheels
# (Even with headless OpenCV, some underlying OS libraries are helpful)
RUN apt-get update && apt-get install -y --no-install-recommends \
    build-essential \
    curl \
    && rm -rf /var/lib/apt/lists/*

# Copy only the requirements file first to maximize Docker layer caching
COPY requirements.txt .

# Install dependencies into a local deployment wheelhouse/directory
# We use --no-cache-dir to minimize final image size
RUN pip install --upgrade pip && \
    pip install --no-cache-dir -r requirements.txt

# --- Step 2: Final Runtime Stage ---
FROM python:3.11-slim

WORKDIR /app

# Set runtime environment parameters
ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1
ENV PORT=8000

# Copy installed dependencies from the builder stage
COPY --from=builder /usr/local/lib/python3.11/site-packages /usr/local/lib/python3.11/site-packages
COPY --from=builder /usr/local/bin /usr/local/bin

# Copy the application source code into the execution environment
COPY . .

# Expose the internal port that Uvicorn will listen on
EXPOSE ${PORT}

# Healthcheck to verify the container is alive and responding
HEALTHCHECK --interval=30s --timeout=30s --start-period=5s --retries=3 \
  CMD curl -f http://localhost:${PORT}/docs || exit 1

# Launch the Uvicorn application server
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]