<?php

declare(strict_types=1);

namespace Mironsoft\Loyalty\Model\Service;

use Magento\Framework\Serialize\Serializer\Json;

/**
 * Pure business logic for calculating earned points and loyalty tiers.
 * Deliberately free of database or HTTP dependencies so it stays trivially
 * unit-testable (see block 11, chapters 91-92).
 */
class PointsCalculator
{
    /**
     * @var string
     */
    public const TIER_BRONZE = 'bronze';

    /**
     * @var string
     */
    public const TIER_SILVER = 'silver';

    /**
     * @var string
     */
    public const TIER_GOLD = 'gold';

    /**
     * @param Json $serializer Decodes the JSON-encoded tier thresholds configuration value.
     */
    public function __construct(
        private readonly Json $serializer,
    ) {
    }

    /**
     * Calculates how many points an order line item earns.
     *
     * @param float $lineTotal Line total excl. tax, in store currency.
     * @param float $pointsPerEuro Points-per-euro conversion rate from configuration.
     * @param float $productMultiplier Product-level multiplier (loyalty_points_multiplier attribute), 1.0 = no change.
     * @param float $categoryBonus Additional category-level bonus rate, 0.0 = no bonus.
     * @return int
     */
    public function calculatePoints(
        float $lineTotal,
        float $pointsPerEuro,
        float $productMultiplier = 1.0,
        float $categoryBonus = 0.0
    ): int {
        $rawPoints = $lineTotal * $pointsPerEuro * $productMultiplier;
        $rawPoints += $lineTotal * $categoryBonus;

        return (int) floor(max(0.0, $rawPoints));
    }

    /**
     * Determines the loyalty tier for a given total of earned points.
     *
     * @param int $totalPointsEarned Sum of all "earn" ledger entries for the customer.
     * @param string $tierThresholdsJson JSON-encoded thresholds, e.g. {"silver":500,"gold":2000}.
     * @return string
     */
    public function determineTier(int $totalPointsEarned, string $tierThresholdsJson): string
    {
        /** @var array{silver?: int, gold?: int} $thresholds */
        $thresholds = $this->serializer->unserialize($tierThresholdsJson);

        if ($totalPointsEarned >= ($thresholds['gold'] ?? PHP_INT_MAX)) {
            return self::TIER_GOLD;
        }

        if ($totalPointsEarned >= ($thresholds['silver'] ?? PHP_INT_MAX)) {
            return self::TIER_SILVER;
        }

        return self::TIER_BRONZE;
    }
}