<?php

namespace OCA\SideMenu\Service;

use OC\App\AppStore\Fetcher\CategoryFetcher;
use OCA\SideMenu\AppInfo\Application;
use OCP\AppFramework\Utility\ITimeFactory;
use OCP\IAppConfig;
use OCP\ICache;
use OCP\ICacheFactory;
use OCP\IConfig;
use OCP\IUserSession;
use OCP\L10N\IFactory;

/**
 * class CategoryRepository.
 *
 * @author Simon Vieille <simon@deblan.fr>
 */
class CategoryRepository
{
    public const CACHE_KEY = 'cache-categories';

    /**
     * The app store categories rarely change, refresh them once a week.
     */
    protected const CACHE_TTL = 604800;

    public function __construct(
        protected CategoryFetcher $categoryFetcher,
        protected ConfigProxy $config,
        protected IConfig $iConfig,
        protected IFactory $l10nFactory,
        protected IUserSession $userSession,
        protected IAppConfig $appConfig,
        protected ITimeFactory $timeFactory,
        protected LangRepository $langRepository,
        protected ICacheFactory $cacheFactory,
    ) {
    }

    /**
     * Retrieves categories.
     */
    public function getOrderedCategories(): array
    {
        $currentLanguage = substr($this->l10nFactory->findLanguage(), 0, 2);
        $type = $this->config->getAppValue('categories-order-type', 'default');
        $order = $this->config->getAppValueArray('categories-order', '[]');
        $categoriesLabels = $this->getCategories();
        $customCategories = $this->config->getAppValueArray('categories-custom', '[]');

        foreach ($categoriesLabels as $k => $category) {
            $categoriesLabels[$category['id']] = $category['translations'][$currentLanguage]['name'] ??
                $category['translations']['en']['name'];

            unset($categoriesLabels[$k]);
        }

        $categoriesLabels['external_links'] = $this->l10nFactory->get('external')->t('External sites');
        $categoriesLabels['other'] = '';

        $user = $this->userSession->getUser();

        if ($user) {
            $lang = $this->iConfig->getUserValue($user->getUid(), 'core', 'lang');
        } else {
            $lang = 'en';
        }

        foreach ($customCategories as $category) {
            $categoriesLabels[$category['id']] = $category[$lang] ?? $category['en'];
        }

        asort($categoriesLabels);

        if ('custom' === $type) {
            $ordered = [];

            foreach ($order as $id) {
                if (isset($categoriesLabels[$id])) {
                    $ordered[$id] = $categoriesLabels[$id];
                }
            }

            foreach ($categoriesLabels as $id => $value) {
                if (!isset($ordered[$id])) {
                    $ordered[$id] = $value;
                }
            }

            $categoriesLabels = $ordered;
        }

        return $categoriesLabels;
    }

    public function clearCache(): void
    {
        $this->getDistributedCache()?->remove(self::CACHE_KEY);
        $this->appConfig->deleteKey(Application::APP_ID, self::CACHE_KEY);
    }

    /**
     * The languages to keep in the cache: English as fallback, the
     * default language and the languages of the users, as two-letter
     * codes like getOrderedCategories() looks them up. A user who picks
     * a new language sees English names until the cache is refreshed,
     * which saving the settings does right away.
     */
    protected function getCachedLangs(): array
    {
        $langs = $this->langRepository->getUsedLangs();
        $langs[] = (string) $this->iConfig->getSystemValue('default_language', 'en');
        $langs[] = (string) $this->iConfig->getSystemValue('force_language', 'en');

        return array_values(array_unique(array_filter(array_map(
            static fn (string $lang) => strtolower(substr($lang, 0, 2)),
            array_merge(['en'], $langs)
        ))));
    }

    /**
     * Returns the app store categories with only their names. They are
     * cached in the distributed cache (e.g. Redis) when one is configured,
     * otherwise in a lazy app config value, so they are not loaded on
     * every request with the other settings.
     */
    protected function getCategories(): array
    {
        $cache = $this->getDistributedCache();

        if ($cache !== null) {
            $categories = $cache->get(self::CACHE_KEY);

            if (is_array($categories)) {
                return $categories;
            }
        } else {
            $stored = $this->appConfig->getValueArray(Application::APP_ID, self::CACHE_KEY, [], lazy: true);

            if (isset($stored['expires'], $stored['categories']) && $stored['expires'] > $this->timeFactory->getTime()) {
                return $stored['categories'];
            }
        }

        $categories = $this->fetchCategories();

        // Don't cache an empty list, e.g. when the app store is unreachable
        if (empty($categories)) {
            return $categories;
        }

        $this->clearCache();

        if ($cache !== null) {
            $cache->set(self::CACHE_KEY, $categories, self::CACHE_TTL);
        } else {
            $this->appConfig->setValueArray(Application::APP_ID, self::CACHE_KEY, [
                'expires' => $this->timeFactory->getTime() + self::CACHE_TTL,
                'categories' => $categories,
            ], lazy: true);
        }

        return $categories;
    }

    protected function fetchCategories(): array
    {
        $langs = $this->getCachedLangs();
        $categories = [];

        foreach ($this->categoryFetcher->get() as $category) {
            $names = [];

            foreach ($category['translations'] ?? [] as $lang => $translation) {
                if (in_array($lang, $langs, true)) {
                    $names[$lang] = ['name' => $translation['name'] ?? ''];
                }
            }

            $categories[] = [
                'id' => $category['id'],
                'translations' => $names,
            ];
        }

        return $categories;
    }

    protected function getDistributedCache(): ?ICache
    {
        return $this->cacheFactory->isAvailable()
            ? $this->cacheFactory->createDistributed(Application::APP_ID)
            : null;
    }
}