FROM python:3.10.14-slim

# Prevent Python from buffering stdout/stderr (important for logging)
ENV PYTHONUNBUFFERED=1
ENV PYTHONDONTWRITEBYTECODE=1

WORKDIR /app

# System dependencies required by librosa / soundfile / audioread.
#  - libsndfile1 → WAV / FLAC / OGG decoding
#  - ffmpeg     → AAC / MP4 / M4A decoding (Apple Music previews, iTunes,
#                 and m4a mic recordings from iOS — REQUIRED)
# Note: HF Spaces ignores packages.txt when a Dockerfile is present, so
# every system package must be declared here.
RUN apt-get update && apt-get install -y --no-install-recommends \
    libsndfile1 \
    ffmpeg \
    && rm -rf /var/lib/apt/lists/*

# Install Python dependencies
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Copy application code
COPY . .

# Create non-root user (HF Spaces best practice)
RUN useradd --create-home --shell /bin/bash appuser \
    && chown -R appuser:appuser /app
USER appuser

# Expose the HF Spaces port
EXPOSE 7860

# Health check — hit the /health endpoint every 30s
HEALTHCHECK --interval=30s --timeout=10s --start-period=120s --retries=3 \
    CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:7860/health')" || exit 1

# Uvicorn flags — set explicitly because the defaults are unsafe for SSE.
#
#   --timeout-keep-alive 120
#       Default is 5 seconds. The /analyze endpoint downloads up to 5 MB
#       from Apple Music CDNs with a 10-second client-side timeout, and
#       SSE streams may not emit their first event for ~30 seconds on a
#       cold-start container. With keep-alive=5 the connection is closed
#       before the first event reaches the client — exactly the
#       "backend never finalises" symptom Apple cited.
#
#   --limit-concurrency 32
#       Connection-level cap. Lets uvicorn 503 incoming connections it
#       cannot serve instead of accepting them and parking them.
#       Complements the application-level Semaphore(2) — that handles
#       inference fairness; this handles socket-level backpressure.
CMD ["uvicorn", "main:app", \
     "--host", "0.0.0.0", \
     "--port", "7860", \
     "--timeout-keep-alive", "120", \
     "--limit-concurrency", "32"]