src/app.py

"""
Flask application entrypoint.

Routes
  GET   /                     — main UI (index.html)
  GET   /healthz              — liveness probe
  POST  /api/scrape           — scrape a product URL
  POST  /api/predict          — run BERT QA on (question, context)
  GET   /api/history          — list stored Q&A entries
  DELETE /api/history/<id>    — remove a single entry
  DELETE /api/history         — clear all entries
"""
import logging
import os
from pathlib import Path

from flask import Flask, jsonify, render_template, request

from . import config, db
from .model import init_model, predict_qa
from .scraper import scrape_url

FORMAT = "%(asctime)s [%(levelname)s] %(name)s — %(message)s"
logging.basicConfig(format=FORMAT, level=logging.INFO)
logger = logging.getLogger(__name__)

_PROJECT_ROOT = Path(__file__).resolve().parent.parent


def create_app() -> Flask:
    app = Flask(
        __name__,
        template_folder=str(_PROJECT_ROOT / "templates"),
        static_folder=str(_PROJECT_ROOT / "static"),
    )

    # ── Rate limiting (optional) ────────────────────────────────
    limiter = None
    if config.RATE_LIMIT_ENABLED:
        try:
            from flask_limiter import Limiter
            from flask_limiter.util import get_remote_address

            limiter = Limiter(
                get_remote_address,
                app=app,
                default_limits=[config.RATE_LIMIT_DEFAULT],
                storage_uri="memory://",
                strategy="fixed-window",
            )
            logger.info("Rate limiting enabled")
        except ImportError:
            logger.warning("flask-limiter not installed; rate limiting disabled")

    def _limit(rule: str):
        """Decorator that applies a limit only if the limiter is active."""
        if limiter is None:
            def noop(fn):
                return fn
            return noop
        return limiter.limit(rule)

    # ── Init DB early so any failure surfaces at boot, not at first write ──
    db.init_db()

    # ── Routes ──────────────────────────────────────────────────

    @app.get("/")
    def index():
        return render_template("index.html")

    @app.get("/healthz")
    def healthz():
        return jsonify({"status": "ok", "model": config.MODEL_NAME}), 200

    @app.post("/api/scrape")
    @_limit(config.RATE_LIMIT_SCRAPE)
    def api_scrape():
        payload = request.get_json(silent=True) or {}
        url = (payload.get("url") or "").strip()
        if not url:
            return jsonify({"error": "URL is required."}), 400
        try:
            result = scrape_url(url)
            if result.get("error"):
                return jsonify(result), 400
            return jsonify(result)
        except Exception as e:  # noqa: BLE001 — top-level safety net
            logger.exception("Scraping failed")
            return jsonify({"error": f"Unexpected error: {e}"}), 500

    @app.post("/api/predict")
    @_limit(config.RATE_LIMIT_PREDICT)
    def api_predict():
        payload = request.get_json(silent=True) or {}
        question = (payload.get("question") or "").strip()
        context = (payload.get("context") or "").strip()
        source_url = (payload.get("source_url") or "").strip() or None
        source_type = (payload.get("source_type") or "").strip() or None
        product_title = (payload.get("product_title") or "").strip() or None

        if not question or not context:
            return jsonify({"error": "Both question and context are required."}), 400
        if len(context) < 20:
            return jsonify({"error": "Context is too short (minimum 20 characters)."}), 400
        if len(question) > 500:
            return jsonify({"error": "Question is too long (max 500 characters)."}), 400

        try:
            result = predict_qa(question, context)
        except ValueError as e:
            return jsonify({"error": str(e)}), 400
        except Exception as e:  # noqa: BLE001
            logger.exception("Prediction failed")
            return jsonify({"error": f"Inference error: {e}"}), 500

        # Persist — failure here must NOT break the user's response
        try:
            entry_id = db.save_qa(
                question=question,
                answer=result["answer"],
                confidence=result["confidence"],
                confidence_level=result["confidence_level"],
                inference_ms=result["inference_time_ms"],
                source_url=source_url,
                source_type=source_type,
                product_title=product_title,
            )
            result["history_id"] = entry_id
        except Exception:
            logger.exception("Failed to persist Q&A — continuing")

        return jsonify(result)

    @app.get("/api/history")
    def api_history():
        limit = request.args.get("limit", type=int) or config.HISTORY_LIMIT
        limit = max(1, min(limit, 500))
        try:
            return jsonify({"items": db.list_history(limit=limit)})
        except Exception as e:  # noqa: BLE001
            logger.exception("History listing failed")
            return jsonify({"error": str(e)}), 500

    @app.delete("/api/history/<int:entry_id>")
    def api_history_delete(entry_id: int):
        try:
            ok = db.delete_entry(entry_id)
            return jsonify({"deleted": ok, "id": entry_id}), (200 if ok else 404)
        except Exception as e:  # noqa: BLE001
            logger.exception("History delete failed")
            return jsonify({"error": str(e)}), 500

    @app.delete("/api/history")
    def api_history_clear():
        try:
            n = db.clear_history()
            return jsonify({"cleared": n})
        except Exception as e:  # noqa: BLE001
            logger.exception("History clear failed")
            return jsonify({"error": str(e)}), 500

    # ── Model load at import-time so gunicorn workers are warm ─────
    logger.info("Initializing BERT QA model…")
    init_model()
    logger.info("Model ready.")

    return app


# Gunicorn entry: `gunicorn src.app:app`
app = create_app()


if __name__ == "__main__":
    app.run(host="0.0.0.0", port=config.PORT, debug=config.DEBUG)