<?php
/**
 * Automatic AI-friendly summary generator.
 *
 * Adds an LLM-optimized summary at the top of articles.
 *
 * @package Aidentity_GEO
 * @since 1.0.0
 */

// Block direct access.
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

/**
 * AI-friendly summary generation class.
 *
 * @since 1.0.0
 */
class Aidentity_GEO_AI_Summary {

    /**
     * Single class instance.
     *
     * @var Aidentity_GEO_AI_Summary|null
     */
    private static $instance = null;

    /**
     * Returns the single class instance.
     *
     * @since 1.0.0
     * @return Aidentity_GEO_AI_Summary
     */
    public static function get_instance() {
        if ( null === self::$instance ) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
     * Constructor.
     *
     * @since 1.0.0
     */
    private function __construct() {
        add_filter( 'the_content', array( $this, 'add_summary' ), 5 );
    }

    /**
     * Adds the summary to the content.
     *
     * @since 1.0.0
     * @param string $content Post content.
     * @return string Content with summary.
     */
    public function add_summary( $content ) {
        /**
         * Post types where the automatic summary is injected.
         *
         * By default the summary is only added to single blog posts:
         * injecting it into pages breaks page-builder layouts and
         * static front pages (e.g. corporate/showcase sites).
         *
         * @since 1.0.3
         * @param array $post_types Post types that receive the summary.
         */
        $summary_post_types = apply_filters( 'aidentity_geo_summary_post_types', array( 'post' ) );

        // Only on singular views of allowed post types, in the main loop,
        // and never on a static front page.
        if ( ! is_singular( $summary_post_types ) || ! in_the_loop() || ! is_main_query() || is_front_page() ) {
            return $content;
        }

        $settings = aidentity_geo_get_settings();

        if ( empty( $settings['auto_summary'] ) ) {
            return $content;
        }

        global $post;

        // Check whether the post is excluded.
        if ( get_post_meta( $post->ID, '_geo_exclude', true ) ) {
            return $content;
        }

        // Check if there is a custom summary already.
        $custom_summary = get_post_meta( $post->ID, '_geo_custom_summary', true );

        if ( ! empty( $custom_summary ) ) {
            $summary = $custom_summary;
        } else {
            $summary = $this->generate_summary( $post );
        }

        if ( empty( $summary ) ) {
            return $content;
        }

        // Build the summary block.
        $summary_html = $this->build_summary_html( $summary, $post );

        return $summary_html . $content;
    }

    /**
     * Generates the summary automatically.
     *
     * @since 1.0.0
     * @param WP_Post $post Post object.
     * @return string Generated summary.
     */
    private function generate_summary( $post ) {
        // First try: Yoast meta description.
        $yoast = get_post_meta( $post->ID, '_yoast_wpseo_metadesc', true );
        if ( ! empty( $yoast ) && strlen( $yoast ) > 50 ) {
            return $yoast;
        }

        // Second try: RankMath meta description.
        $rankmath = get_post_meta( $post->ID, 'rank_math_description', true );
        if ( ! empty( $rankmath ) && strlen( $rankmath ) > 50 ) {
            return $rankmath;
        }

        // Third try: excerpt.
        if ( ! empty( $post->post_excerpt ) && strlen( $post->post_excerpt ) > 50 ) {
            return $post->post_excerpt;
        }

        // Fallback: extract from content.
        return $this->extract_summary_from_content( $post->post_content );
    }

    /**
     * Extracts a summary from the content.
     *
     * @since 1.0.0
     * @param string $content Post content.
     * @return string Extracted summary.
     */
    private function extract_summary_from_content( $content ) {
        // Remove shortcodes and process blocks.
        $text = strip_shortcodes( $content );
        $text = do_blocks( $text );

        // Strip HTML.
        $text = wp_strip_all_tags( $text );

        // Clean whitespace.
        $text = preg_replace( '/\s+/', ' ', $text );
        $text = trim( $text );

        if ( strlen( $text ) < 50 ) {
            return '';
        }

        // Take the first 2-3 sentences.
        $sentences = preg_split( '/(?<=[.!?])\s+/', $text, 4 );

        $summary    = '';
        $max_length = 200;

        foreach ( $sentences as $sentence ) {
            if ( strlen( $summary ) + strlen( $sentence ) > $max_length ) {
                break;
            }
            $summary .= $sentence . ' ';
        }

        return trim( $summary );
    }

    /**
     * Builds the summary HTML.
     *
     * @since 1.0.0
     * @param string  $summary Summary text.
     * @param WP_Post $post Post object.
     * @return string Summary HTML.
     */
    private function build_summary_html( $summary, $post ) {
        $reading_time = $this->calculate_reading_time( $post->post_content );
        $date         = get_the_date( 'F j, Y', $post );

        $html  = '<div class="aidentity-geo-summary" style="';
        $html .= 'background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);';
        $html .= 'border-left: 4px solid #0066cc;';
        $html .= 'padding: 20px 24px;';
        $html .= 'margin-bottom: 32px;';
        $html .= 'border-radius: 0 8px 8px 0;';
        $html .= 'font-size: 1.05em;';
        $html .= 'line-height: 1.6;';
        $html .= '">';

        // Main summary.
        $html .= '<p style="margin: 0 0 12px 0; color: #333;"><strong>' . esc_html__( 'In short:', 'aidentity-generative-engine-optimizer' ) . '</strong> ';
        $html .= esc_html( $summary );
        $html .= '</p>';

        // Meta info.
        $html .= '<p style="margin: 0; font-size: 0.85em; color: #666;">';
        $html .= '<span>📅 ' . esc_html( $date ) . '</span>';
        $html .= ' &nbsp;•&nbsp; ';
        /* translators: %d: reading time in minutes */
        $html .= '<span>⏱️ ' . sprintf( esc_html__( '%d min read', 'aidentity-generative-engine-optimizer' ), $reading_time ) . '</span>';
        $html .= '</p>';

        $html .= '</div>';

        // Add an HTML comment for AI crawlers.
        $html .= "\n<!-- AI Summary: " . esc_html( $summary ) . " -->\n";

        return $html;
    }

    /**
     * Calculates the reading time.
     *
     * @since 1.0.0
     * @param string $content Post content.
     * @return int Reading time in minutes.
     */
    private function calculate_reading_time( $content ) {
        $text         = wp_strip_all_tags( strip_shortcodes( $content ) );
        $word_count   = str_word_count( $text );
        $reading_time = ceil( $word_count / 200 ); // 200 words per minute.

        return max( 1, $reading_time );
    }
}