<?php

namespace App\Services;

use App\Models\ShoppingOrder;
use InvalidArgumentException;

class DhlShipmentWeightCalculator
{
    public const DEFAULT_WEIGHT_KG = 1.0;

    public const DEFAULT_MAX_WEIGHT_KG = 31.5;

    public const PRODUCT_MAX_WEIGHTS_KG = [
        'V01PAK' => 31.5,
        'V53PAK' => 31.5,
        'V62KP' => 1.0,
    ];

    public function calculate(ShoppingOrder $order): float
    {
        $this->loadOrderItems($order);

        $baseWeightGrams = max((int) ($order->weight ?? 0), 0);
        $compensationWeightGrams = $this->calculateCompensationWeightGrams($order);
        $totalWeightGrams = $baseWeightGrams + $compensationWeightGrams;

        if ($totalWeightGrams <= 0) {
            return self::DEFAULT_WEIGHT_KG;
        }

        return $this->roundWeightKg($totalWeightGrams / 1000);
    }

    public function getMaxWeightKgForProduct(?string $productCode): float
    {
        $productCode = strtoupper(trim((string) $productCode));

        return self::PRODUCT_MAX_WEIGHTS_KG[$productCode] ?? self::DEFAULT_MAX_WEIGHT_KG;
    }

    public function assertWithinProductLimit(float $weightKg, ?string $productCode): void
    {
        $maxWeightKg = $this->getMaxWeightKgForProduct($productCode);

        if ($weightKg > $maxWeightKg) {
            throw new InvalidArgumentException(sprintf(
                'Gewicht %.3f kg ueberschreitet das DHL-Maximalgewicht fuer %s (%.1f kg).',
                $weightKg,
                $productCode ?: 'das gewaehlte Produkt',
                $maxWeightKg
            ));
        }
    }

    private function calculateCompensationWeightGrams(ShoppingOrder $order): int
    {
        $items = $order->shopping_order_items ?? collect();
        $weightGrams = 0;

        foreach ($items as $item) {
            if ((int) ($item->comp ?? 0) <= 0) {
                continue;
            }

            $productWeight = (int) ($item->product?->weight ?? 0);
            if ($productWeight <= 0) {
                continue;
            }

            $quantity = max((int) ($item->qty ?? 1), 1);
            $weightGrams += $productWeight * $quantity;
        }

        return $weightGrams;
    }

    private function roundWeightKg(float $weightKg): float
    {
        return round(max($weightKg, 0.1), 3);
    }

    private function loadOrderItems(ShoppingOrder $order): void
    {
        if ($order->exists && ! $order->relationLoaded('shopping_order_items')) {
            $order->loadMissing('shopping_order_items.product');
        }
    }
}