<?php
declare(strict_types=1);

namespace Esun\FreeGift\Model;

use Magento\Framework\App\Config\ScopeConfigInterface;
use Magento\Framework\Serialize\Serializer\Json;
use Magento\Framework\Stdlib\DateTime\TimezoneInterface;
use Magento\Store\Model\ScopeInterface;

class Config
{
    private const XML_PATH_ENABLED = 'esun_free_gift/general/enabled';
    private const XML_PATH_GIFT_SKU = 'esun_free_gift/general/gift_sku';
    private const XML_PATH_START_DATE = 'esun_free_gift/general/start_date';
    private const XML_PATH_END_DATE = 'esun_free_gift/general/end_date';
    private const XML_PATH_TIER_ITEMS = 'esun_free_gift/tiers/items';
    private const XML_PATH_TIER_AMOUNT = 'esun_free_gift/tiers/tier_%d_amount';
    private const XML_PATH_TIER_QTY = 'esun_free_gift/tiers/tier_%d_qty';

    public function __construct(
        private readonly ScopeConfigInterface $scopeConfig,
        private readonly TimezoneInterface $timezone,
        private readonly Json $serializer
    ) {
    }

    public function isEnabled(?int $storeId = null): bool
    {
        return $this->scopeConfig->isSetFlag(
            self::XML_PATH_ENABLED,
            ScopeInterface::SCOPE_STORE,
            $storeId
        );
    }

    public function getGiftSku(?int $storeId = null): string
    {
        return trim((string)$this->scopeConfig->getValue(
            self::XML_PATH_GIFT_SKU,
            ScopeInterface::SCOPE_STORE,
            $storeId
        ));
    }

    public function isGiftSku(string $sku, ?int $storeId = null): bool
    {
        $giftSku = $this->getGiftSku($storeId);

        return $giftSku !== '' && strcasecmp($giftSku, trim($sku)) === 0;
    }

    public function isActive(?int $storeId = null): bool
    {
        if (!$this->isEnabled($storeId) || $this->getGiftSku($storeId) === '') {
            return false;
        }

        $today = $this->timezone->scopeDate($storeId)->format('Y-m-d');
        $startDate = $this->normalizeDate($this->getValue(self::XML_PATH_START_DATE, $storeId));
        $endDate = $this->normalizeDate($this->getValue(self::XML_PATH_END_DATE, $storeId));

        return ($startDate === '' || $today >= $startDate)
            && ($endDate === '' || $today <= $endDate);
    }

    public function getTargetQuantity(float $eligibleBaseSubtotal, ?int $storeId = null): int
    {
        if (!$this->isActive($storeId)) {
            return 0;
        }

        $targetQuantity = 0;
        $subtotal = round(max(0.0, $eligibleBaseSubtotal), 2);

        foreach ($this->getTiers($storeId) as $tier) {
            if ($subtotal + 0.0001 >= $tier['amount']) {
                $targetQuantity = $tier['qty'];
            }
        }

        return $targetQuantity;
    }

    /** @return array<int, array{amount: float, qty: int}> */
    public function getTiers(?int $storeId = null): array
    {
        $configuredTiers = $this->getConfiguredTiers($storeId);
        if ($configuredTiers !== []) {
            return $configuredTiers;
        }

        $tiers = [];

        for ($index = 1; $index <= 3; $index++) {
            $amount = max(0.0, (float)$this->getValue(sprintf(self::XML_PATH_TIER_AMOUNT, $index), $storeId));
            $quantity = max(0, (int)$this->getValue(sprintf(self::XML_PATH_TIER_QTY, $index), $storeId));

            if ($quantity > 0) {
                $tiers[] = ['amount' => $amount, 'qty' => $quantity];
            }
        }

        usort(
            $tiers,
            static fn (array $left, array $right): int => $left['amount'] <=> $right['amount']
        );

        return $tiers;
    }

    /** @return array<int, array{amount: float, qty: int}> */
    private function getConfiguredTiers(?int $storeId): array
    {
        $value = $this->scopeConfig->getValue(
            self::XML_PATH_TIER_ITEMS,
            ScopeInterface::SCOPE_STORE,
            $storeId
        );

        try {
            $items = is_array($value)
                ? $value
                : (trim((string)$value) === '' ? [] : $this->serializer->unserialize((string)$value));
        } catch (\InvalidArgumentException) {
            return [];
        }

        if (!is_array($items)) {
            return [];
        }

        $tiers = [];
        foreach ($items as $item) {
            if (!is_array($item)) {
                continue;
            }

            $quantity = max(0, (int)($item['qty'] ?? 0));
            if ($quantity <= 0) {
                continue;
            }

            $tiers[] = [
                'amount' => max(0.0, (float)($item['amount'] ?? 0)),
                'qty' => $quantity,
            ];
        }

        usort($tiers, static fn (array $left, array $right): int => $left['amount'] <=> $right['amount']);

        return $tiers;
    }

    private function getValue(string $path, ?int $storeId = null): string
    {
        return trim((string)$this->scopeConfig->getValue(
            $path,
            ScopeInterface::SCOPE_STORE,
            $storeId
        ));
    }

    private function normalizeDate(string $value): string
    {
        if ($value === '') {
            return '';
        }

        $timestamp = strtotime($value);

        return $timestamp === false ? '' : date('Y-m-d', $timestamp);
    }
}