import datetime
from flask import Blueprint, jsonify
from flask_jwt_extended import jwt_required, get_jwt_identity
from .database import db, MilkBatch, User
from sqlalchemy import func # For sum

overview_bp = Blueprint('overview', __name__, url_prefix='/api/overview')

@overview_bp.route('', methods=['GET'])
@jwt_required()
def get_overview():
    current_user_id = get_jwt_identity()
    user = User.query.get(current_user_id)
    if not user: return jsonify({"error": "User not found"}), 404

    # Find active (not deleted, not empty, not expired) batches
    active_batches = MilkBatch.query.filter(
        MilkBatch.user_id == current_user_id,
        MilkBatch.is_deleted == False,
        MilkBatch.remaining_volume > 0.001,
        MilkBatch.expiry_date >= datetime.date.today()
    ).order_by(MilkBatch.expiry_date.asc()).all()

    total_volume_ml = 0
    total_items_approx = 0
    nearest_expiry_info = None

    for batch in active_batches:
        # Sum total volume in ml
        if batch.volume_unit == 'L':
            total_volume_ml += batch.remaining_volume * 1000
        else: # Assumed ml
            total_volume_ml += batch.remaining_volume

        total_items_approx += batch.remaining_items_approx

        # Capture the first one (soonest expiry)
        if not nearest_expiry_info:
            nearest_expiry_info = batch.to_dict()

    total_quantity_liters = total_volume_ml / 1000.0

    # Basic low stock check (can be enhanced in push notification logic)
    is_low_stock = False
    if user.low_stock_threshold_value is not None and user.low_stock_threshold_unit:
        threshold_value = user.low_stock_threshold_value
        threshold_unit = user.low_stock_threshold_unit
        try:
            if threshold_unit == 'items':
                 if total_items_approx <= threshold_value: is_low_stock = True
            else: # ml or L
                 # Convert threshold to ml if needed
                 threshold_ml = convert_volume(threshold_value, threshold_unit, 'ml')
                 if total_volume_ml <= threshold_ml: is_low_stock = True
        except ValueError:
            print(f"Warning: Invalid low stock threshold units for user {current_user_id}")


    overview_data = {
        "totalQuantityLiters": round(total_quantity_liters, 2),
        "totalQuantityItemsApprox": round(total_items_approx),
        "nearestExpiry": nearest_expiry_info, # Full batch dict or null
        "isLowStock": is_low_stock, # Simple flag based on settings
        # "estimatedFinishDate": "N/A" # Requires historical analysis - skip for now
    }

    return jsonify(overview_data), 200