<?php
/**
 * Dynamic XML Sitemap Generator for Life Balance
 * Generates SEO-optimized XML sitemap with hreflang, AI signals, and 2027 ranking factors
 * 
 * @version 1.0
 * @author Nikolay Maksimenko
 * @requirements: PHP 8.0+, PDO, MySQL/MariaDB
 * @compliance: Sitemaps.org protocol, Google AI indexing guidelines 2027
 */

declare(strict_types=1);
error_reporting(E_ALL & ~E_DEPRECATED & ~E_USER_DEPRECATED);
ini_set('display_errors', '0');

// =============================================================================
// CONFIGURATION
// =============================================================================
if (file_exists(__DIR__ . '/logs/init.php')) {
    require_once __DIR__ . '/logs/init.php';
}

define('SITE_URL', getenv('SITE_URL') ?: 'https://www.lifebalance.top/');
define('SITE_NAME', 'Life Balance');
define('DEFAULT_LANG', 'ru');
define('SUPPORTED_LANGUAGES', ['ru', 'en', 'de', 'fr', 'es', 'it']);
define('TARGET_COUNTRIES', ['US', 'DE', 'FR', 'ES', 'IT', 'PT', 'TR', 'GE', 'CN', 'RU']);

define('DB_DSN', getenv('DB_DSN') ?: null);
define('DB_USER', getenv('DB_USER') ?: null);
define('DB_PASS', getenv('DB_PASS') ?: null);

define('CACHE_PATH', __DIR__ . '/cache/sitemap.xml');
define('CACHE_TTL', (int)(getenv('SITEMAP_XML_TTL') ?: 7200));
define('LOG_PATH', __DIR__ . '/cache/sitemap_xml.log');
define('MAX_URLS_PER_SITEMAP', 49999);

// AI & 2027 Ranking Signals Configuration
define('AI_CONTENT_SIGNAL', getenv('AI_CONTENT_SIGNAL') === 'true');
define('EEAT_SIGNAL_ENABLED', true);
define('CORE_WEB_VITALS_PRIORITY', true);
define('SEMANTIC_RELEVANCE_WEIGHT', 1.0);

// =============================================================================
// CACHE & LOGGING UTILITIES
// =============================================================================
function initCacheDir(): void {
    if (!is_dir(__DIR__ . '/cache')) {
        @mkdir(__DIR__ . '/cache', 0755, true);
        @file_put_contents(__DIR__ . '/cache/.htaccess', "Options -Indexes\nDeny from all\n");
        @file_put_contents(__DIR__ . '/cache/index.html', '');
    }
}

function getCachedSitemap(string $path, int $ttl): ?string {
    if (!file_exists($path)) return null;
    if (time() - filemtime($path) > $ttl) return null;
    return file_get_contents($path);
}

function cacheSitemap(string $path, string $content): bool {
    return @file_put_contents($path, $content, LOCK_EX) !== false;
}

function logSitemapEvent(string $level, string $message, array $context = []): void {
    $entry = sprintf(
        "[%s] [%s] %s %s\n",
        date('Y-m-d H:i:s'),
        strtoupper($level),
        $message,
        empty($context) ? '' : json_encode($context, JSON_UNESCAPED_UNICODE)
    );
    @file_put_contents(LOG_PATH, $entry, FILE_APPEND | LOCK_EX);
}

// =============================================================================
// DATABASE INTEGRATION
// =============================================================================
function getDatabaseConnection(): ?PDO {
    if (!DB_DSN || !DB_USER) {
        return null;
    }
    
    try {
        return new PDO(DB_DSN, DB_USER, DB_PASS, [
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_EMULATE_PREPARES => false,
            PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8mb4",
            PDO::ATTR_PERSISTENT => false,
        ]);
    } catch (PDOException $e) {
        logSitemapEvent('ERROR', 'Database connection failed', [
            'message' => $e->getMessage(),
            'code' => $e->getCode()
        ]);
        return null;
    }
}

function fetchPagesForSitemap(PDO $pdo): array {
    $data = [
        'pages' => [],
        'posts' => [],
        'categories' => [],
        'products' => [],
    ];
    
    // Main pages with AI relevance signals
    $stmt = $pdo->prepare("
        SELECT 
            p.id, p.title, p.slug AS url, p.meta_description, p.main_image,
            p.priority, p.changefreq, p.language, p.target_countries,
            UNIX_TIMESTAMP(p.updated_at) AS lastmod,
            p.ai_relevance_score, p.eeat_signals, p.semantic_keywords
        FROM pages p
        WHERE p.status = 'published' 
            AND p.is_sitemap_visible = 1
            AND p.noindex != 1
        ORDER BY p.priority DESC, p.updated_at DESC
        LIMIT 5000
    ");
    $stmt->execute();
    $data['pages'] = $stmt->fetchAll();
    
    // Blog posts with publication dates
    $stmt = $pdo->prepare("
        SELECT 
            post.id, post.title, post.slug AS url, post.excerpt AS description,
            post.featured_image AS image, post.language, post.target_countries,
            UNIX_TIMESTAMP(post.published_at) AS lastmod,
            post.category_slug, post.reading_time, post.ai_summary
        FROM posts post
        WHERE post.status = 'published'
            AND post.is_sitemap_visible = 1
            AND post.noindex != 1
        ORDER BY post.published_at DESC
        LIMIT 10000
    ");
    $stmt->execute();
    $data['posts'] = $stmt->fetchAll();
    
    // Product pages with structured data signals
    $stmt = $pdo->prepare("
        SELECT 
            prod.id, prod.name AS title, prod.slug AS url, prod.short_description,
            prod.main_image, prod.price, prod.currency, prod.availability,
            prod.language, prod.target_markets,
            UNIX_TIMESTAMP(prod.updated_at) AS lastmod,
            prod.rating_value, prod.review_count, prod.sku
        FROM products prod
        WHERE prod.status = 'active'
            AND prod.is_visible = 1
        ORDER BY prod.priority DESC, prod.updated_at DESC
        LIMIT 2000
    ");
    $stmt->execute();
    $data['products'] = $stmt->fetchAll();
    
    // Category/taxonomy pages
    $stmt = $pdo->query("
        SELECT 
            cat.id, cat.name AS title, cat.slug AS url, cat.description,
            cat.language, cat.parent_id,
            UNIX_TIMESTAMP(cat.updated_at) AS lastmod,
            COUNT(rel.object_id) AS item_count
        FROM categories cat
        LEFT JOIN category_relations rel ON rel.category_id = cat.id
        WHERE cat.is_sitemap_visible = 1
        GROUP BY cat.id
        ORDER BY cat.priority DESC
        LIMIT 500
    ");
    $data['categories'] = $stmt->fetchAll();
    
    return $data;
}

// =============================================================================
// URL & HREFLANG UTILITIES
// =============================================================================
function buildAbsoluteUrl(string $path, string $lang = DEFAULT_LANG): string {
    $path = ltrim($path, '/');
    
    if ($lang !== DEFAULT_LANG) {
        return rtrim(SITE_URL, '/') . '/' . $lang . '/' . $path;
    }
    
    return rtrim(SITE_URL, '/') . '/' . $path;
}

function generateHreflangLinks(string $baseUrl, array $languages, string $defaultLang = DEFAULT_LANG): string {
    $output = '';
    
    foreach ($languages as $lang) {
        $href = ($lang === $defaultLang) 
            ? $baseUrl 
            : rtrim(SITE_URL, '/') . '/' . $lang . '/' . ltrim(parse_url($baseUrl, PHP_URL_PATH), '/');
        
        $output .= '    <xhtml:link rel="alternate" hreflang="' . htmlspecialchars($lang, ENT_XML1) . '" href="' . htmlspecialchars($href, ENT_XML1) . '"/>' . "\n";
    }
    
    $output .= '    <xhtml:link rel="alternate" hreflang="x-default" href="' . htmlspecialchars($baseUrl, ENT_XML1) . '"/>' . "\n";
    
    return $output;
}

function getChangefreq(string $contentType, ?int $updateInterval = null): string {
    $defaults = [
        'homepage' => 'daily',
        'product' => 'weekly',
        'blog' => 'weekly',
        'category' => 'monthly',
        'static' => 'monthly',
        'legal' => 'yearly',
    ];
    
    return $defaults[$contentType] ?? 'monthly';
}

function calculatePriority(array $signals): float {
    $base = 0.5;
    
    if (!empty($signals['is_homepage'])) $base = 1.0;
    elseif (!empty($signals['is_product'])) $base = 0.9;
    elseif (!empty($signals['is_blog_featured'])) $base = 0.8;
    elseif (!empty($signals['is_category'])) $base = 0.7;
    
    if (!empty($signals['ai_relevance_score']) && $signals['ai_relevance_score'] > 0.8) {
        $base = min(1.0, $base + 0.1);
    }
    
    if (!empty($signals['eeat_strength']) && $signals['eeat_strength'] === 'high') {
        $base = min(1.0, $base + 0.05);
    }
    
    return round($base, 1);
}

// =============================================================================
// AI & 2027 RANKING SIGNALS
// =============================================================================
function generateAIRelevanceMetadata(array $page): array {
    $metadata = [];
    
    if (!empty($page['ai_relevance_score'])) {
        $metadata['ai:relevance'] = number_format((float)$page['ai_relevance_score'], 2);
    }
    
    if (!empty($page['semantic_keywords'])) {
        $keywords = is_string($page['semantic_keywords']) 
            ? json_decode($page['semantic_keywords'], true) 
            : $page['semantic_keywords'];
        
        if (is_array($keywords) && !empty($keywords)) {
            $metadata['ai:keywords'] = implode(', ', array_slice($keywords, 0, 10));
        }
    }
    
    if (!empty($page['eeat_signals'])) {
        $eeat = is_string($page['eeat_signals']) 
            ? json_decode($page['eeat_signals'], true) 
            : $page['eeat_signals'];
        
        if (is_array($eeat)) {
            if (!empty($eeat['expertise'])) $metadata['eeat:expertise'] = $eeat['expertise'];
            if (!empty($eeat['authoritativeness'])) $metadata['eeat:authority'] = $eeat['authoritativeness'];
            if (!empty($eeat['trustworthiness'])) $metadata['eeat:trust'] = $eeat['trustworthiness'];
        }
    }
    
    if (!empty($page['reading_time'])) {
        $metadata['content:readingTime'] = (int)$page['reading_time'] . 'min';
    }
    
    return $metadata;
}

function generateCoreWebVitalsHints(array $page): string {
    $hints = [];
    
    if (!empty($page['lcp_element'])) {
        $hints[] = 'data-lcp="' . htmlspecialchars($page['lcp_element'], ENT_XML1) . '"';
    }
    
    if (!empty($page['cls_score']) && (float)$page['cls_score'] < 0.1) {
        $hints[] = 'data-cls="good"';
    }
    
    if (!empty($page['fid_ms']) && (int)$page['fid_ms'] < 100) {
        $hints[] = 'data-fid="good"';
    }
    
    return empty($hints) ? '' : ' ' . implode(' ', $hints);
}

// =============================================================================
// XML GENERATION FUNCTIONS
// =============================================================================
function generateSitemapHeader(): string {
    return '<?xml version="1.0" encoding="UTF-8"?>' . "\n" .
        '<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"' . "\n" .
        '        xmlns:xhtml="http://www.w3.org/1999/xhtml"' . "\n" .
        '        xmlns:image="http://www.google.com/schemas/sitemap-image/1.1"' . "\n" .
        '        xmlns:video="http://www.google.com/schemas/sitemap-video/1.1"' . "\n" .
        '        xmlns:news="http://www.google.com/schemas/sitemap-news/0.9"' . "\n" .
        '        xmlns:ai="https://www.lifebalance.top/schemas/ai-signals/1.0"' . "\n" .
        '        xmlns:eeat="https://www.lifebalance.top/schemas/eeat/1.0"' . "\n" .
        '        xmlns:content="http://purl.org/rss/1.0/modules/content/">' . "\n";
}

function generateUrlEntry(array $page, string $contentType = 'page'): string {
    $loc = buildAbsoluteUrl($page['url'], $page['language'] ?? DEFAULT_LANG);
    $lastmod = !empty($page['lastmod']) ? gmdate('Y-m-d\TH:i:s+00:00', (int)$page['lastmod']) : gmdate('Y-m-d\TH:i:s+00:00');
    $changefreq = $page['changefreq'] ?? getChangefreq($contentType);
    $priority = $page['priority'] ?? calculatePriority($page);
    
    $xml = '  <url>' . "\n";
    $xml .= '    <loc>' . htmlspecialchars($loc, ENT_XML1) . '</loc>' . "\n";
    $xml .= '    <lastmod>' . $lastmod . '</lastmod>' . "\n";
    $xml .= '    <changefreq>' . $changefreq . '</changefreq>' . "\n";
    $xml .= '    <priority>' . $priority . '</priority>' . "\n";
    
    if (!empty($page['language'])) {
        $languages = !empty($page['target_countries']) && is_string($page['target_countries'])
            ? array_merge([DEFAULT_LANG], array_diff(SUPPORTED_LANGUAGES, [$page['language']]))
            : SUPPORTED_LANGUAGES;
        
        $xml .= generateHreflangLinks($loc, $languages, $page['language']);
    }
    
    if (!empty($page['image']) || !empty($page['main_image'])) {
        $imageUrl = !empty($page['image']) ? $page['image'] : $page['main_image'];
        if (!str_starts_with($imageUrl, 'http')) {
            $imageUrl = SITE_URL . ltrim($imageUrl, '/');
        }
        
        $xml .= '    <image:image>' . "\n";
        $xml .= '      <image:loc>' . htmlspecialchars($imageUrl, ENT_XML1) . '</image:loc>' . "\n";
        $xml .= '      <image:title>' . htmlspecialchars($page['title'] ?? '', ENT_XML1) . '</image:title>' . "\n";
        if (!empty($page['description']) || !empty($page['meta_description']) || !empty($page['short_description'])) {
            $desc = $page['description'] ?? $page['meta_description'] ?? $page['short_description'] ?? '';
            $xml .= '      <image:caption>' . htmlspecialchars(mb_substr($desc, 0, 255), ENT_XML1) . '</image:caption>' . "\n";
        }
        $xml .= '    </image:image>' . "\n";
    }
    
    if ($contentType === 'blog' || $contentType === 'news') {
        $xml .= '    <news:news>' . "\n";
        $xml .= '      <news:publication>' . "\n";
        $xml .= '        <news:name>' . SITE_NAME . '</news:name>' . "\n";
        $xml .= '        <news:language>' . ($page['language'] ?? DEFAULT_LANG) . '</news:language>' . "\n";
        $xml .= '      </news:publication>' . "\n";
        $xml .= '      <news:publication_date>' . $lastmod . '</news:publication_date>' . "\n";
        $xml .= '      <news:title>' . htmlspecialchars($page['title'], ENT_XML1) . '</news:title>' . "\n";
        $xml .= '    </news:news>' . "\n";
    }
    
    if (AI_CONTENT_SIGNAL && !empty($page['ai_relevance_score'])) {
        $aiMeta = generateAIRelevanceMetadata($page);
        foreach ($aiMeta as $attr => $value) {
            $xml .= '    <' . $attr . '>' . htmlspecialchars($value, ENT_XML1) . '</' . $attr . '>' . "\n";
        }
    }
    
    $cwhints = generateCoreWebVitalsHints($page);
    if ($cwhints) {
        $xml .= '    <url:attributes' . $cwhints . '/>' . "\n";
    }
    
    $xml .= '  </url>' . "\n";
    
    return $xml;
}

function generateSitemapIndex(array $sitemaps): string {
    $xml = '<?xml version="1.0" encoding="UTF-8"?>' . "\n";
    $xml .= '<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"' . "\n";
    $xml .= '              xmlns:xhtml="http://www.w3.org/1999/xhtml">' . "\n";
    
    foreach ($sitemaps as $sitemap) {
        $xml .= '  <sitemap>' . "\n";
        $xml .= '    <loc>' . htmlspecialchars($sitemap['loc'], ENT_XML1) . '</loc>' . "\n";
        $xml .= '    <lastmod>' . $sitemap['lastmod'] . '</lastmod>' . "\n";
        $xml .= '  </sitemap>' . "\n";
    }
    
    $xml .= '</sitemapindex>' . "\n";
    return $xml;
}

// =============================================================================
// MAIN GENERATION LOGIC
// =============================================================================
function generateXMLSitemap(array $data): string {
    $xml = generateSitemapHeader();
    $urlCount = 0;
    
    $xml .= '  <url>' . "\n";
    $xml .= '    <loc>' . htmlspecialchars(SITE_URL, ENT_XML1) . '</loc>' . "\n";
    $xml .= '    <lastmod>' . gmdate('Y-m-d\TH:i:s+00:00') . '</lastmod>' . "\n";
    $xml .= '    <changefreq>daily</changefreq>' . "\n";
    $xml .= '    <priority>1.0</priority>' . "\n";
    $xml .= generateHreflangLinks(SITE_URL, SUPPORTED_LANGUAGES);
    $xml .= '  </url>' . "\n";
    $urlCount++;
    
    foreach ($data['pages'] as $page) {
        $xml .= generateUrlEntry($page, 'page');
        $urlCount++;
    }
    
    foreach ($data['products'] as $product) {
        $product['language'] = $product['language'] ?? DEFAULT_LANG;
        $xml .= generateUrlEntry($product, 'product');
        $urlCount++;
    }
    
    foreach ($data['posts'] as $post) {
        $post['language'] = $post['language'] ?? DEFAULT_LANG;
        $xml .= generateUrlEntry($post, 'blog');
        $urlCount++;
    }
    
    foreach ($data['categories'] as $category) {
        $category['language'] = $category['language'] ?? DEFAULT_LANG;
        $category['priority'] = 0.7;
        $category['changefreq'] = 'monthly';
        $xml .= generateUrlEntry($category, 'category');
        $urlCount++;
    }
    
    $xml .= '</urlset>' . "\n";
    
    logSitemapEvent('INFO', 'Sitemap generated', [
        'url_count' => $urlCount,
        'languages' => count(SUPPORTED_LANGUAGES),
        'ai_signals' => AI_CONTENT_SIGNAL ? 'enabled' : 'disabled'
    ]);
    
    return $xml;
}

function handleSitemapRequest(): void {
    initCacheDir();
    
    $forceRegenerate = isset($_GET['force']) && $_GET['force'] === 'true';
    
    if (!$forceRegenerate) {
        $cached = getCachedSitemap(CACHE_PATH, CACHE_TTL);
        if ($cached) {
            header('Content-Type: application/xml; charset=UTF-8');
            header('Cache-Control: public, max-age=' . CACHE_TTL);
            header('Last-Modified: ' . gmdate('D, d M Y H:i:s', filemtime(CACHE_PATH)) . ' GMT');
            header('X-Sitemap-Type: xml');
            header('X-Sitemap-Source: cache');
            header('X-URL-Count: ' . substr_count($cached, '<url>'));
            echo $cached;
            return;
        }
    }
    
    $pdo = getDatabaseConnection();
    if (!$pdo) {
        http_response_code(503);
        header('Content-Type: application/xml; charset=UTF-8');
        echo '<?xml version="1.0" encoding="UTF-8"?>' . "\n";
        echo '<error xmlns="https://www.lifebalance.top/schemas/errors/1.0">' . "\n";
        echo '  <code>DB_UNAVAILABLE</code>' . "\n";
        echo '  <message>Database connection failed</message>' . "\n";
        echo '  <retry-after>' . CACHE_TTL . '</retry-after>' . "\n";
        echo '</error>' . "\n";
        return;
    }
    
    try {
        $startTime = microtime(true);
        $data = fetchPagesForSitemap($pdo);
        $xml = generateXMLSitemap($data);
        
        if (cacheSitemap(CACHE_PATH, $xml)) {
            logSitemapEvent('INFO', 'Sitemap cached', [
                'size_bytes' => strlen($xml),
                'generation_time_ms' => round((microtime(true) - $startTime) * 1000, 2)
            ]);
        }
        
        header('Content-Type: application/xml; charset=UTF-8');
        header('Cache-Control: public, max-age=' . CACHE_TTL);
        header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT');
        header('X-Sitemap-Type: xml');
        header('X-Sitemap-Source: generated');
        header('X-Generation-Time: ' . round((microtime(true) - $startTime) * 1000, 2) . 'ms');
        header('X-URL-Count: ' . substr_count($xml, '<url>'));
        
        echo $xml;
        
    } catch (Throwable $e) {
        logSitemapEvent('CRITICAL', 'Sitemap generation failed', [
            'exception' => get_class($e),
            'message' => $e->getMessage(),
            'file' => $e->getFile(),
            'line' => $e->getLine()
        ]);
        
        http_response_code(500);
        header('Content-Type: application/xml; charset=UTF-8');
        echo '<?xml version="1.0" encoding="UTF-8"?>' . "\n";
        echo '<error xmlns="https://www.lifebalance.top/schemas/errors/1.0">' . "\n";
        echo '  <code>GENERATION_FAILED</code>' . "\n";
        echo '  <message>' . htmlspecialchars($e->getMessage(), ENT_XML1) . '</message>' . "\n";
        echo '</error>' . "\n";
    }
}

// =============================================================================
// EXECUTION
// =============================================================================
if (php_sapi_name() === 'cli') {
    parse_str(implode('&', array_slice($argv, 1)), $_GET);
}

handleSitemapRequest();
exit;