radionica3d/backend/services/pricing.py

from typing import List
import db
import config

def calculate_estimated_price(material_id: int, file_sizes: List[int], file_quantities: List[int] = None, return_details=False) -> float:
    """
    Internal logic to estimate price per file based on file size (proxy for volume)
    and print time (proxy for machine wear/energy).
    """
    material = db.execute_query("""
        SELECT m.price_per_cm3, 
               COALESCE(NULLIF(m.price_per_hour, 0), s.price_per_hour, %s) as price_per_hour,
               m.speed_coeff
        FROM materials m
        LEFT JOIN services s ON m.service_id = s.id
        WHERE m.id = %s
    """, (config.DEFAULT_PRINTER_HOUR_PRICE, material_id))
    if not material:
        return (0.0, []) if return_details else 0.0
    
    price_per_cm3 = float(material[0]['price_per_cm3'])
    price_per_hour = float(material[0]['price_per_hour'])
    speed_coeff = float(material[0]['speed_coeff'] or 1.0)
    
    if file_quantities is None or len(file_quantities) != len(file_sizes):
        file_quantities = [1] * len(file_sizes)
        
    # Volume discount: 5% for each next item, max 20% total
    total_qty = sum(file_quantities)
    discount_multiplier = 1.0
    discount_percent = 0.0
    if total_qty > 1:
        discount_percent = min((total_qty - 1) * 0.05, 0.20)
        discount_multiplier = 1.0 - discount_percent

    for size, qty in zip(file_sizes, file_quantities):
        total_size_mb = size / (1024 * 1024)
        # Empirical conversion: ~8cm3 per 1MB of STL (binary)
        estimated_volume_cm3 = total_size_mb * 8.0 
        
        # Estimate printing time (same logic as in slicer_utils.py: volume_mm3 / 10.0)
        # Apply speed_coeff to adjust time based on material difficulty
        estimated_hours = ((estimated_volume_cm3 * 100.0) / 3600.0) * speed_coeff
        
        material_cost = estimated_volume_cm3 * price_per_cm3
        operation_cost = estimated_hours * price_per_hour
        
        # Apply volume discount to unit price
        file_cost = round((base_fee + material_cost + operation_cost) * discount_multiplier, 2)
        file_costs.append(file_cost)
        estimated_total += file_cost * qty
    
    metadata = {
        "price_per_cm3": price_per_cm3,
        "price_per_hour": price_per_hour,
        "speed_coeff": speed_coeff,
        "base_fee": base_fee,
        "discount_percent": round(discount_percent * 100, 0),
        "total_qty": total_qty
    }

    if return_details:
        return round(estimated_total, 2), file_costs, metadata
    return round(estimated_total, 2)