/**
 * Gangwan Zhunong - SEO Enhancement Module
 * 港湾助农平台 SEO 增强模块
 * Open Graph + Twitter Card + 面包屑导航
 */

// ============================================
// 1. Open Graph Meta Tags（微信/微博/朋友圈）
// ============================================

function gw_add_open_graph_tags() {
    // 仅在非管理员页面输出
    if ( is_admin() ) {
        return;
    }
    
    $site_name   = get_bloginfo( 'name' );
    $title       = '';
    $description = '';
    $image       = '';
    $url         = get_permalink();
    $type        = 'website';
    
    if ( is_front_page() ) {
        $title       = $site_name . ' - 乡村振兴大宗采购平台';
        $description = '港湾助农响应乡村振兴，源头直供野生蜂蜜、手工红糖、时令农产品，专注政企福利采购。';
        $image       = get_theme_file_uri( '/assets/images/og-home.jpg' );
        $url         = home_url( '/' );
        
    } elseif ( is_singular( 'product' ) ) {
        $title       = get_the_title() . ' - ' . $site_name;
        $description = wp_trim_words( get_the_excerpt(), 30, '...' );
        $image       = get_the_post_thumbnail_url( get_the_ID(), 'large' );
        $type        = 'product';
        
    } elseif ( is_post_type_archive( 'product' ) ) {
        $title       = '助农产品中心 - ' . $site_name;
        $description = '浏览所有源头直供助农产品，野生蜂蜜、手工红糖、时令农产品，政企大宗福利采购首选。';
        $image       = get_theme_file_uri( '/assets/images/og-products.jpg' );
        
    } elseif ( is_author() ) {
        $author_id   = get_queried_object_id();
        $author_name = get_the_author_meta( 'display_name', $author_id );
        $title       = $author_name . ' 的助农产品 - ' . $site_name;
        $description = '查看 ' . $author_name . ' 发布的所有助农产品，源头直供，品质保障。';
        $image       = get_avatar_url( $author_id, array( 'size' => 400 ) );
        $type        = 'profile';
        
    } else {
        $title       = wp_get_document_title();
        $description = get_bloginfo( 'description' );
        $image       = get_theme_file_uri( '/assets/images/og-default.jpg' );
    }
    
    // 输出 Open Graph 标签
    echo "\n<!-- Open Graph / 微信 / 微博 -->\n";
    echo '<meta property="og:type" content="' . esc_attr( $type ) . '">' . "\n";
    echo '<meta property="og:site_name" content="' . esc_attr( $site_name ) . '">' . "\n";
    echo '<meta property="og:title" content="' . esc_attr( $title ) . '">' . "\n";
    echo '<meta property="og:description" content="' . esc_attr( $description ) . '">' . "\n";
    echo '<meta property="og:url" content="' . esc_url( $url ) . '">' . "\n";
    
    if ( $image ) {
        echo '<meta property="og:image" content="' . esc_url( $image ) . '">' . "\n";
    }
    
    // 产品页额外信息
    if ( is_singular( 'product' ) ) {
        $price = get_post_meta( get_the_ID(), '_price', true );
        if ( $price ) {
            $unit = get_post_meta( get_the_ID(), '_unit', true );
            echo '<meta property="product:price:amount" content="' . esc_attr( $price ) . '">' . "\n";
            echo '<meta property="product:price:currency" content="CNY">' . "\n";
        }
    }
}
add_action( 'wp_head', 'gw_add_open_graph_tags', 5 );

// ============================================
// 2. Twitter Card Meta Tags
// ============================================

function gw_add_twitter_card_tags() {
    if ( is_admin() ) {
        return;
    }
    
    $title       = wp_get_document_title();
    $description = get_bloginfo( 'description' );
    $image       = get_theme_file_uri( '/assets/images/twitter-card.jpg' );
    
    if ( is_singular( 'product' ) ) {
        $image = get_the_post_thumbnail_url( get_the_ID(), 'large' );
        $description = wp_trim_words( get_the_excerpt(), 30, '...' );
    }
    
    echo "\n<!-- Twitter Card -->\n";
    echo '<meta name="twitter:card" content="summary_large_image">' . "\n";
    echo '<meta name="twitter:title" content="' . esc_attr( $title ) . '">' . "\n";
    echo '<meta name="twitter:description" content="' . esc_attr( $description ) . '">' . "\n";
    
    if ( $image ) {
        echo '<meta name="twitter:image" content="' . esc_url( $image ) . '">' . "\n";
    }
}
add_action( 'wp_head', 'gw_add_twitter_card_tags', 6 );

// ============================================
// 3. 面包屑导航函数
// ============================================

function gw_breadcrumb( $echo = true ) {
    $breadcrumb = array();
    
    // 首页链接
    $breadcrumb[] = '<a href="' . esc_url( home_url( '/' ) ) . '">🌾 首页</a>';
    
    if ( is_singular( 'product' ) ) {
        // 产品归档
        $breadcrumb[] = '<a href="' . esc_url( get_post_type_archive_link( 'product' ) ) . '">助农产品</a>';
        
        // 产品分类
        $terms = get_the_terms( get_the_ID(), 'product_cat' );
        if ( $terms && ! is_wp_error( $terms ) ) {
            $term = array_shift( $terms );
            $breadcrumb[] = '<a href="' . esc_url( get_term_link( $term ) ) . '">' . esc_html( $term->name ) . '</a>';
        }
        
        // 当前产品
        $breadcrumb[] = '<span>' . get_the_title() . '</span>';
        
    } elseif ( is_post_type_archive( 'product' ) ) {
        $breadcrumb[] = '<span>助农产品</span>';
        
    } elseif ( is_tax( 'product_cat' ) ) {
        $breadcrumb[] = '<a href="' . esc_url( get_post_type_archive_link( 'product' ) ) . '">助农产品</a>';
        $breadcrumb[] = '<span>' . single_term_title( '', false ) . '</span>';
        
    } elseif ( is_author() ) {
        $breadcrumb[] = '<a href="' . esc_url( get_post_type_archive_link( 'product' ) ) . '">助农产品</a>';
        $breadcrumb[] = '<span>' . get_the_author() . ' 的产品</span>';
        
    } elseif ( is_404() ) {
        $breadcrumb[] = '<span>页面未找到</span>';
        
    } elseif ( is_search() ) {
        $breadcrumb[] = '<span>搜索: ' . get_search_query() . '</span>';
    }
    
    // 拼接 HTML
    $html = '<nav class="gw-breadcrumb">';
    foreach ( $breadcrumb as $index => $item ) {
        if ( $index < count( $breadcrumb ) - 1 ) {
            $html .= '<span>' . $item . '</span><span class="sep"> › </span>';
        } else {
            $html .= '<span class="current">' . $item . '</span>';
        }
    }
    $html .= '</nav>';
    
    if ( $echo ) {
        echo $html;
    }
    
    return $html;
}

// ============================================
// 4. 面包屑 JSON-LD（SEO 结构化数据）
// ============================================

function gw_breadcrumb_json_ld() {
    if ( is_admin() ) {
        return;
    }
    
    $items = array();
    $position = 1;
    
    // 首页
    $items[] = array(
        '@type'    => 'ListItem',
        'position' => $position,
        'name'     => '首页',
        'item'     => home_url( '/' )
    );
    $position++;
    
    if ( is_singular( 'product' ) ) {
        // 产品归档
        $items[] = array(
            '@type'    => 'ListItem',
            'position' => $position,
            'name'     => '助农产品',
            'item'     => get_post_type_archive_link( 'product' )
        );
        $position++;
        
        // 产品分类
        $terms = get_the_terms( get_the_ID(), 'product_cat' );
        if ( $terms && ! is_wp_error( $terms ) ) {
            $term = array_shift( $terms );
            $items[] = array(
                '@type'    => 'ListItem',
                'position' => $position,
                'name'     => $term->name,
                'item'     => get_term_link( $term )
            );
            $position++;
        }
        
        // 当前产品
        $items[] = array(
            '@type'    => 'ListItem',
            'position' => $position,
            'name'     => get_the_title(),
            'item'     => get_permalink()
        );
    }
    
    if ( count( $items ) > 1 ) {
        $json_ld = array(
            '@context'        => 'https://schema.org',
            '@type'           => 'BreadcrumbList',
            'itemListElement' => $items
        );
        
        echo "\n<script type=\"application/ld+json\">\n";
        echo wp_json_encode( $json_ld, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT );
        echo "\n</script>\n";
    }
}
add_action( 'wp_head', 'gw_breadcrumb_json_ld', 7 );

// ============================================
// 5. Canonical URL（避免重复内容）
// ============================================

function gw_add_canonical_url() {
    if ( is_singular( 'product' ) ) {
        echo '<link rel="canonical" href="' . esc_url( get_permalink() ) . '">' . "\n";
    } elseif ( is_post_type_archive( 'product' ) ) {
        echo '<link rel="canonical" href="' . esc_url( get_post_type_archive_link( 'product' ) ) . '">' . "\n";
    }
}
add_action( 'wp_head', 'gw_add_canonical_url', 1 );

// ============================================
// 6. 禁止搜索引擎索引敏感页面
// ============================================

function gw_noindex_sensitive_pages() {
    if ( is_author() || is_search() || is_404() ) {
        echo '<meta name="robots" content="noindex, nofollow">' . "\n";
    }
}
add_action( 'wp_head', 'gw_noindex_sensitive_pages', 0 );

// ============================================
// 7. 农户认证等级徽章
// ============================================

function gw_get_farmer_badge( $user_id = null ) {
    if ( ! $user_id ) {
        $user_id = get_the_author_meta( 'ID' );
    }
    
    $status = get_user_meta( $user_id, 'farmer_status', true );
    $level  = get_user_meta( $user_id, 'farmer_level', true ); // bronze/silver/gold
    
    if ( $status !== 'approved' ) {
        return '';
    }
    
    $badges = array(
        'bronze' => array(
            'icon'  => '🥉',
            'label' => '签约农户',
            'color' => '#cd7f32'
        ),
        'silver' => array(
            'icon'  => '🥈',
            'label' => '优质农户',
            'color' => '#c0c0c0'
        ),
        'gold' => array(
            'icon'  => '🥇',
            'label' => '金牌农户',
            'color' => '#ffd700'
        )
    );
    
    $badge = $badges[ $level ] ?? $badges['bronze'];
    
    return sprintf(
        '<span class="gw-farmer-badge" style="display: inline-flex; align-items: center; gap: 5px; background: %s; color: #fff; padding: 4px 12px; border-radius: 20px; font-size: 0.85rem; font-weight: 600;">%s %s</span>',
        esc_attr( $badge['color'] ),
        $badge['icon'],
        esc_html( $badge['label'] )
    );
}

// ============================================
// 8. 产品评分聚合（预留接口）
// ============================================

function gw_get_product_rating( $post_id = null ) {
    if ( ! $post_id ) {
        $post_id = get_the_ID();
    }
    
    // 预留：从评论系统计算评分
    $rating_value = get_post_meta( $post_id, '_avg_rating', true );
    $rating_count = get_post_meta( $post_id, '_rating_count', true );
    
    if ( ! $rating_value || ! $rating_count ) {
        return false;
    }
    
    return array(
        'value' => floatval( $rating_value ),
        'count' => intval( $rating_count )
    );
}

// ============================================
// 9. 产品评分 JSON-LD 注入
// ============================================

function gw_product_rating_json_ld() {
    if ( ! is_singular( 'product' ) ) {
        return;
    }
    
    $rating = gw_get_product_rating();
    
    if ( ! $rating ) {
        return;
    }
    
    $json_ld = array(
        '@context'    => 'https://schema.org',
        '@type'       => 'Product',
        'name'        => get_the_title(),
        'aggregateRating' => array(
            '@type'       => 'AggregateRating',
            'ratingValue' => $rating['value'],
            'reviewCount' => $rating['count'],
            'bestRating'  => 5,
            'worstRating' => 1
        )
    );
    
    echo "\n<script type=\"application/ld+json\">\n";
    echo wp_json_encode( $json_ld, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT );
    echo "\n</script>\n";
}
add_action( 'wp_head', 'gw_product_rating_json_ld', 8 );
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at C:\wwwroot\gangwan\wp-content\themes\zhunong\inc\seo-enhancements.php:1) in <b>C:\wwwroot\gangwan\wp-content\themes\zhunong\functions.php</b> on line <b>14</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at C:\wwwroot\gangwan\wp-content\themes\zhunong\inc\seo-enhancements.php:1) in <b>C:\wwwroot\gangwan\wp-content\themes\zhunong\functions.php</b> on line <b>16</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at C:\wwwroot\gangwan\wp-content\themes\zhunong\inc\seo-enhancements.php:1) in <b>C:\wwwroot\gangwan\wp-content\themes\zhunong\functions.php</b> on line <b>18</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at C:\wwwroot\gangwan\wp-content\themes\zhunong\inc\seo-enhancements.php:1) in <b>C:\wwwroot\gangwan\wp-content\themes\zhunong\functions.php</b> on line <b>20</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at C:\wwwroot\gangwan\wp-content\themes\zhunong\inc\seo-enhancements.php:1) in <b>C:\wwwroot\gangwan\wp-content\themes\zhunong\functions.php</b> on line <b>22</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at C:\wwwroot\gangwan\wp-content\themes\zhunong\inc\seo-enhancements.php:1) in <b>C:\wwwroot\gangwan\wp-includes\pluggable.php</b> on line <b>1535</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at C:\wwwroot\gangwan\wp-content\themes\zhunong\inc\seo-enhancements.php:1) in <b>C:\wwwroot\gangwan\wp-includes\pluggable.php</b> on line <b>1538</b><br />