FROM python:3.12-slim

WORKDIR /app

# Pillow needs these to build/run; python:3.12-slim's manylinux wheels cover
# most of it, but libjpeg/zlib runtime libs are still needed at import time.
RUN apt-get update && apt-get install -y --no-install-recommends \
    libjpeg62-turbo \
    zlib1g \
    && rm -rf /var/lib/apt/lists/*

COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

COPY . .

RUN mkdir -p instance uploads

EXPOSE 5000

# instance/ (sqlite db) and uploads/ (receipt photos) should be mounted as
# volumes - see docker-compose.yml - so they survive a container rebuild.
#
# NOTE: this app does not support running as multiple processes. Login Flow
# v2's in-flight state (app/auth.py _pending_flows) is a plain in-memory
# dict, not shared across processes/machines - it only works because every
# request within a login attempt is guaranteed to hit the same process.
# Scaling this out (more gunicorn workers, multiple replicas, etc.) would
# need that state moved to somewhere shared (the sqlite db, redis, ...)
# first.
#
# --workers 1: with >1 worker, /auth/login/start and the follow-up
# /auth/login/poll calls can land on different worker processes, which
# never see each other's flow_id, so login intermittently/always times out.
# Single worker (+ threads for concurrency) keeps that state actually
# shared. Fine for this scale (household tool, already SQLite-backed).
CMD ["gunicorn", "--bind", "0.0.0.0:5000", "--workers", "1", "--threads", "4", "--timeout", "60", "run:app"]