<?php

if (!defined('ABSPATH')) {
    exit;
}

class ShadowSync_SEO_Scanner {

    public function __construct() {
        add_action('wp_ajax_shadowsync_seo_run_scan', [$this, 'run_scan']);
    }

    public function run_scan() {

        check_ajax_referer( 'shadowsync_seo_scan_nonce', 'nonce' );
        ShadowSync_SEO_Security::require_admin();

        $posts = get_posts([
            'numberposts' => -1,
            'post_status' => 'publish',
            'post_type'   => ['post', 'page'],
        ]);

        $summary = [
            'posts_scanned' => 0,
            'issues_found'  => 0,
            'avg_score'     => 0,
            'results'       => [],
        ];

        $total_score = 0;

        foreach ($posts as $post) {

            $result = $this->audit_post($post);

            // Defensive guard: never trust $result blindly
            if (!is_array($result) || !isset($result['score'], $result['issues'])) {
                $result = ['score' => 0, 'issues' => [], 'word_count' => 0];
            }

            if (!is_array($result['issues'])) {
                $result['issues'] = [];
            }

            $score = isset($result['score']) ? intval($result['score']) : 0;

            // Save results to postmeta
            update_post_meta($post->ID, '_shadowsync_seo_audit_result', $result);
            update_post_meta($post->ID, '_shadowsync_seo_score', $score);

            $total_score += $score;
            $summary['issues_found'] += count($result['issues']);
            $summary['results'][] = [
                'id'     => $post->ID,
                'title'  => get_the_title($post->ID),
                'url'    => get_permalink($post->ID),
                'score'  => $score,
                'issues' => $result['issues'],
            ];

            $summary['posts_scanned']++;
        }

        if ($summary['posts_scanned'] > 0) {
            $summary['avg_score'] = round($total_score / $summary['posts_scanned']);
        }

        // Save summary
        update_option('_shadowsync_seo_last_scan_summary', $summary);
        update_option('_shadowsync_seo_last_scan_time', current_time('mysql'));

        wp_send_json_success($summary);
    }

    private function audit_post($post) {

        // Guard against unexpected input
        if (!is_object($post) || !isset($post->ID)) {
            return ['score' => 0, 'issues' => [], 'word_count' => 0];
        }

        $issues  = [];
        $score   = 100;
        $content = isset($post->post_content) ? (string) $post->post_content : '';

        // The title search engines show: the SEO title when one is set,
        // otherwise the post title, as the front end prints it.
        $title = (string) get_post_meta($post->ID, '_shadowsync_seo_meta_title', true);
        if ('' === trim($title)) {
            $title = (string) get_the_title($post->ID);
        }

        // --- CHECK 1: Title length ---
        $title_len = strlen($title);
        if ($title_len < 30) {
            $issues[] = ['type' => 'title_short', 'message' => 'Title is too short (' . $title_len . ' chars). Aim for 30–60.'];
            $score -= 15;
        } elseif ($title_len > 60) {
            $issues[] = ['type' => 'title_long', 'message' => 'Title is too long (' . $title_len . ' chars). Keep under 60.'];
            $score -= 10;
        }

        // --- CHECK 2: Meta description ---
        $meta_desc = get_post_meta($post->ID, '_shadowsync_seo_meta_description', true);
        if (empty($meta_desc)) {
            $issues[] = ['type' => 'missing_meta_desc', 'message' => 'Meta description is missing.'];
            $score -= 15;
        } elseif (strlen($meta_desc) < 50) {
            $issues[] = ['type' => 'meta_desc_short', 'message' => 'Meta description is too short. Aim for 50–160 chars.'];
            $score -= 8;
        } elseif (strlen($meta_desc) > 160) {
            $issues[] = ['type' => 'meta_desc_long', 'message' => 'Meta description is too long. Keep under 160 chars.'];
            $score -= 5;
        }

        // --- CHECK 3: H1 headings in content ---
        // Themes print the post title as the page's H1, so content without an
        // H1 is correct, matching the editor's SEO Analysis tab. Only more
        // than one is a problem.
        $h1_count = preg_match_all('/<h1[^>]*>.*?<\/h1>/is', $content);
        $h1_count = ($h1_count === false) ? 0 : $h1_count;
        if ($h1_count > 1) {
            $issues[] = ['type' => 'multiple_h1', 'message' => 'Multiple H1 headings found. Use only one.'];
            $score -= 8;
        }

        // --- CHECK 4: Images missing alt tags ---
        $img_matches = [];
        $img_count   = preg_match_all('/<img[^>]+>/i', $content, $img_matches);
        $img_count   = ($img_count === false) ? 0 : $img_count;
        $missing_alt = 0;
        if ($img_count > 0 && !empty($img_matches[0])) {
            foreach ($img_matches[0] as $img) {
                if (!preg_match('/alt=["\'][^"\']+["\']/i', $img)) {
                    $missing_alt++;
                }
            }
            if ($missing_alt > 0) {
                $issues[] = ['type' => 'missing_alt', 'message' => $missing_alt . ' image(s) missing alt tags.'];
                $score -= min(10, $missing_alt * 3);
            }
        }

        // --- CHECK 5: Content length ---
        $word_count = str_word_count(wp_strip_all_tags($content));
        if ($word_count < 300) {
            $issues[] = ['type' => 'thin_content', 'message' => 'Content is too short (' . $word_count . ' words). Aim for 300+.'];
            $score -= 15;
        }

        // --- CHECK 6: Internal links ---
        $site_url   = home_url();
        $link_count = preg_match_all('/<a[^>]+href=["\']' . preg_quote($site_url, '/') . '[^"\']*["\']/i', $content);
        $link_count = ($link_count === false) ? 0 : $link_count;
        if ($link_count === 0) {
            $issues[] = ['type' => 'no_internal_links', 'message' => 'No internal links found. Add links to other pages.'];
            $score -= 10;
        }

        // Floor at 0
        $score = max(0, $score);

        return [
            'score'      => $score,
            'issues'     => $issues,
            'word_count' => $word_count,
        ];
    }
}