<?php

declare(strict_types=1);

namespace App\Blog\Support;

use Illuminate\Http\Request;
use Illuminate\Support\Facades\Cache;
use Symfony\Component\HttpFoundation\Response;

/**
 * 前台页面响应缓存：
 * - 仅缓存匿名 GET 请求的 HTML 页面（首页/列表/文章/归档/标签等）
 * - 登录用户、后台、API、动态端点不缓存
 * - 浏览量走独立的 /track-view 端点，不受整页缓存影响
 */
class PageCacheMiddleware
{
    public const TAG = 'pages';

    public function handle(Request $request, \Closure $next): Response
    {
        if (! $this->shouldCache($request)) {
            return $next($request);
        }

        $key = $this->key($request);
        $ttl = (int) config('blog.page_cache_ttl', 300);

        if ($cached = Cache::get($key)) {
            self::increment('hits');

            return response($cached['body'], 200, [
                'Content-Type' => $cached['type'],
                'Cache-Control' => 'public, max-age='.$ttl,
            ]);
        }

        self::increment('misses');

        $response = $next($request);

        if ($response->getStatusCode() === 200) {
            $body = $response->getContent();
            Cache::put($key, [
                'body' => $body,
                'type' => $response->headers->get('Content-Type') ?: 'text/html; charset=utf-8',
            ], $ttl);
            self::rememberKey($key, $request->fullUrl(), strlen($body), $ttl);
        }

        return $response;
    }

    public static function flush(): void
    {
        foreach (array_keys((array) Cache::get(self::TAG.'_keys', [])) as $key) {
            Cache::forget((string) $key);
        }

        Cache::forget(self::TAG.'_keys');
    }

    public static function count(): int
    {
        return count((array) Cache::get(self::TAG.'_keys', []));
    }

    /**
     * 命中/未命中统计（按日滚动），用于判断前台缓存效果。
     */
    public static function stats(): array
    {
        $hits = (int) Cache::get(self::TAG.'_hits', 0);
        $misses = (int) Cache::get(self::TAG.'_misses', 0);
        $total = $hits + $misses;

        return [
            'hits' => $hits,
            'misses' => $misses,
            'count' => self::count(),
            'rate' => $total > 0 ? round($hits / $total * 100, 1) : 0.0,
        ];
    }

    public static function resetStats(): void
    {
        Cache::forget(self::TAG.'_hits');
        Cache::forget(self::TAG.'_misses');
    }

    /**
     * @return list<array{key: string, url: string, cached_at: string, size: int, expires_at: string}>
     */
    public static function entries(): array
    {
        $entries = [];

        foreach ((array) Cache::get(self::TAG.'_keys', []) as $key => $meta) {
            $entries[] = [
                'key' => (string) $key,
                'url' => is_array($meta) ? (string) ($meta['url'] ?? $key) : (string) $key,
                'cached_at' => is_array($meta) ? (string) ($meta['cached_at'] ?? '') : '',
                'size' => is_array($meta) ? (int) ($meta['size'] ?? 0) : 0,
                'expires_at' => is_array($meta) ? (string) ($meta['expires_at'] ?? '') : '',
            ];
        }

        usort($entries, fn (array $left, array $right): int => strcmp($right['cached_at'], $left['cached_at']));

        return $entries;
    }

    public static function forget(string $key): void
    {
        Cache::forget($key);
        $keys = (array) Cache::get(self::TAG.'_keys', []);
        unset($keys[$key]);
        Cache::put(self::TAG.'_keys', $keys, now()->addDay());
    }

    private static function increment(string $metric): void
    {
        $key = self::TAG.'_'.$metric;
        Cache::put($key, (int) Cache::get($key, 0) + 1, now()->addDay());
    }

    private static function rememberKey(string $key, ?string $url = null, int $size = 0, int $ttl = 0): void
    {
        $keys = (array) Cache::get(self::TAG.'_keys', []);
        $previous = $keys[$key] ?? [];

        $keys[$key] = [
            'url' => $url ?: (is_array($previous) ? (string) ($previous['url'] ?? '') : ''),
            'cached_at' => now()->toDateTimeString(),
            'size' => $size,
            'expires_at' => $ttl > 0 ? now()->addSeconds($ttl)->toDateTimeString() : '',
        ];

        Cache::put(self::TAG.'_keys', $keys, now()->addDay());
    }

    private function shouldCache(Request $request): bool
    {
        if (! $request->isMethod('GET')) {
            return false;
        }

        if (auth()->check()) {
            return false;
        }

        $path = $request->path();

        if (str_starts_with($path, 'admin') || str_starts_with($path, 'api') || str_starts_with($path, 'themes')) {
            return false;
        }

        // 动态端点、订阅和 agent 索引不进整页缓存，新文章要马上能看到
        if (str_starts_with($path, 'track-view')) {
            return false;
        }

        if (in_array($path, ['rss.xml', 'rss.php', 'sitemap.xml', 'robots.txt', 'llms.txt'], true)) {
            return false;
        }

        if (str_ends_with($path, '.md')) {
            return false;
        }

        return true;
    }

    private function key(Request $request): string
    {
        return self::TAG.':'.md5($request->fullUrl().'|view:'.HomeViewMode::resolve($request));
    }
}