<?php
if ( ! defined( 'ABSPATH' ) ) exit;

/**
 * Serves AI-optimised Markdown copies of content for AEO/GEO:
 *   - Per page:  <permalink>.md
 *   - Whole site: /llms-full.txt   (every page's markdown concatenated)
 *
 * The markdown is built from the captured analysis (llm_context_block,
 * summaries, content_sections, approved entities with sameAs, FAQs) — a view
 * purpose-built for LLM retrieval, not a naive HTML→MD dump. Falls back to the
 * raw post content when a page hasn't been analysed.
 *
 * Also advertises each page's .md via <link rel="alternate" type="text/markdown">.
 */
class Semantic_Markdown {

    public static function init() {
        add_action( 'init',              [ __CLASS__, 'rewrite_rules' ] );
        add_filter( 'query_vars',        [ __CLASS__, 'query_vars' ] );
        add_action( 'template_redirect', [ __CLASS__, 'serve' ] );
        add_action( 'wp_head',           [ __CLASS__, 'alternate_link' ], 6 );
    }

    public static function rewrite_rules() {
        // <any-path>.md  → markdown for that page
        add_rewrite_rule( '^(.+)\.md$', 'index.php?semantic_md_path=$matches[1]', 'top' );
        // /llms-full.txt → full-corpus markdown
        add_rewrite_rule( '^llms-full\.txt$', 'index.php?semantic_llms_full=1', 'top' );
    }

    public static function query_vars( $vars ) {
        $vars[] = 'semantic_md_path';
        $vars[] = 'semantic_llms_full';
        return $vars;
    }

    public static function serve() {
        if ( ! Semantic_Settings::markdown_enabled() ) return;

        // Whole-site corpus
        if ( get_query_var( 'semantic_llms_full' ) ) {
            header( 'Content-Type: text/markdown; charset=utf-8' );
            header( 'X-Robots-Tag: noindex' );
            header( 'X-Content-Type-Options: nosniff' );
            // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Plain-text markdown response (Content-Type: text/markdown sent above); HTML escaping would corrupt the output.
            echo self::full_corpus();
            exit;
        }

        // Per-page markdown
        $path = get_query_var( 'semantic_md_path' );
        if ( $path === '' || $path === null ) return;

        $path    = trim( $path, '/' );
        $post_id = url_to_postid( home_url( '/' . $path . '/' ) );
        if ( ! $post_id ) $post_id = url_to_postid( home_url( '/' . $path ) );
        if ( ! $post_id ) {
            status_header( 404 );
            header( 'Content-Type: text/markdown; charset=utf-8' );
            echo "# Not found\n\nNo page matches this URL.\n";
            exit;
        }

        $post = get_post( $post_id );
        // Same public-content gate as every other public surface: published, public,
        // password-free, non-excluded, publicly-queryable type. Anything else 404s.
        if ( ! $post || ! Semantic_Settings::is_publicly_servable( $post ) ) {
            status_header( 404 );
            header( 'Content-Type: text/markdown; charset=utf-8' );
            echo "# Not found\n";
            exit;
        }

        header( 'Content-Type: text/markdown; charset=utf-8' );
        header( 'X-Robots-Tag: noindex' );
        header( 'X-Content-Type-Options: nosniff' );
        // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Plain-text markdown response (Content-Type: text/markdown sent above); HTML escaping would corrupt the output.
        echo self::render_post( $post );
        exit;
    }

    /** Advertise the .md alternate on singular pages so agents can discover it. */
    public static function alternate_link() {
        if ( ! Semantic_Settings::markdown_enabled() ) return;
        if ( ! is_singular() ) return;
        $post = get_queried_object();
        if ( ! $post instanceof WP_Post ) return;
        // Only advertise .md where we'd actually serve it (skips password-protected,
        // excluded and non-public posts, matching serve()).
        if ( ! Semantic_Settings::is_publicly_servable( $post ) ) return;
        $md = self::md_url( $post );
        if ( $md ) {
            echo '<link rel="alternate" type="text/markdown" href="' . esc_url( $md ) . '" />' . "\n";
        }
    }

    /** Build the .md URL for a post from its permalink. */
    public static function md_url( WP_Post $post ) {
        $url = get_permalink( $post );
        if ( ! $url ) return '';
        // Insert .md before any trailing slash / query.
        $parts = wp_parse_url( $url );
        $path  = isset( $parts['path'] ) ? rtrim( $parts['path'], '/' ) : '';
        if ( $path === '' ) return '';
        $base  = ( $parts['scheme'] ?? 'https' ) . '://' . ( $parts['host'] ?? '' );
        return $base . $path . '.md';
    }

    // -------------------------------------------------------------------------
    // Rendering
    // -------------------------------------------------------------------------

    /** Render one post as AI-optimised markdown. */
    public static function render_post( WP_Post $post ) {
        global $wpdb;

        $url = get_permalink( $post );
        $analysis = $wpdb->get_row( $wpdb->prepare(
            "SELECT * FROM {$wpdb->prefix}semantic_analyses
             WHERE post_id = %d AND status = 'completed'
             ORDER BY finished_at DESC LIMIT 1",
            $post->ID
        ), ARRAY_A );

        $lines = [];
        $lines[] = '# ' . wp_strip_all_tags( get_the_title( $post ) );
        $lines[] = '';

        $desc = $analysis['llm_description'] ?? '';
        if ( $desc ) { $lines[] = '> ' . $desc; $lines[] = ''; }

        $lines[] = '**Source:** ' . $url;
        $lines[] = '**Updated:** ' . get_post_modified_time( 'Y-m-d', true, $post );
        $lines[] = '';

        // No analysis yet → fall back to a clean text rendering of the content.
        if ( ! $analysis ) {
            $lines[] = self::content_to_markdown( $post );
            return implode( "\n", $lines ) . "\n";
        }

        // Summary
        $summary = $analysis['summary'] ?: '';
        if ( $summary ) {
            $lines[] = '## Summary';
            $lines[] = '';
            $lines[] = $summary;
            $lines[] = '';
        }

        // LLM context block — the self-contained retrieval paragraph.
        if ( ! empty( $analysis['llm_context_block'] ) ) {
            $lines[] = '## Overview';
            $lines[] = '';
            $lines[] = $analysis['llm_context_block'];
            $lines[] = '';
        }

        // Key entities (approved, with grounding links)
        $entities = $wpdb->get_results( $wpdb->prepare(
            "SELECT name, type, definition, canonical_entity_id, wikidata_qid, same_as
             FROM {$wpdb->prefix}semantic_suggested_entities
             WHERE analysis_id = %d AND approval_status = 'approved'
             ORDER BY relevance_score DESC LIMIT 25",
            $analysis['id']
        ), ARRAY_A );
        if ( $entities ) {
            $lines[] = '## Key entities';
            $lines[] = '';
            foreach ( $entities as $e ) {
                $same = json_decode( $e['same_as'] ?? '[]', true ) ?: [];
                $link = $same[0] ?? ( $e['canonical_entity_id'] ? home_url( '/entities/' . $e['canonical_entity_id'] ) : '' );
                $name = $link ? '[' . $e['name'] . '](' . $link . ')' : $e['name'];
                $row  = '- ' . $name;
                if ( ! empty( $e['type'] ) )         $row .= ' _(' . str_replace( '_', ' ', $e['type'] ) . ')_';
                if ( ! empty( $e['definition'] ) )   $row .= ' — ' . $e['definition'];
                if ( ! empty( $e['wikidata_qid'] ) ) $row .= ' (Wikidata: ' . $e['wikidata_qid'] . ')';
                $lines[] = $row;
            }
            $lines[] = '';
        }

        // Section outline
        $sections = json_decode( $analysis['content_sections'] ?? '[]', true ) ?: [];
        if ( $sections ) {
            $lines[] = '## Contents';
            $lines[] = '';
            foreach ( $sections as $sec ) {
                if ( empty( $sec['heading'] ) ) continue;
                $lines[] = '### ' . wp_strip_all_tags( $sec['heading'] );
                if ( ! empty( $sec['summary'] ) ) { $lines[] = ''; $lines[] = $sec['summary']; }
                $lines[] = '';
            }
        }

        // FAQs
        $faqs = $wpdb->get_results( $wpdb->prepare(
            "SELECT question, answer FROM {$wpdb->prefix}semantic_suggested_faqs
             WHERE analysis_id = %d AND approval_status = 'approved'
             ORDER BY ai_confidence DESC",
            $analysis['id']
        ), ARRAY_A );
        if ( $faqs ) {
            $lines[] = '## FAQ';
            $lines[] = '';
            foreach ( $faqs as $f ) {
                $lines[] = '**' . wp_strip_all_tags( $f['question'] ) . '**';
                $lines[] = '';
                $lines[] = wp_strip_all_tags( $f['answer'] );
                $lines[] = '';
            }
        }

        // Citable snippet
        if ( ! empty( $analysis['citable_snippet'] ) ) {
            $lines[] = '---';
            $lines[] = '';
            $lines[] = $analysis['citable_snippet'];
            $lines[] = '';
        }

        return implode( "\n", $lines ) . "\n";
    }

    /** Whole-site corpus: every published page's markdown, concatenated. */
    public static function full_corpus() {
        $name = Semantic_Settings::org_name();
        $out  = [ '# ' . $name . ' — Full Content Corpus', '' ];
        $desc = Semantic_Settings::org_description();
        if ( $desc ) { $out[] = '> ' . $desc; $out[] = ''; }

        $types = Semantic_Settings::public_post_types();
        $posts = empty( $types ) ? [] : get_posts( [
            'post_type'      => $types,
            'post_status'    => 'publish',
            'has_password'   => false,
            'posts_per_page' => 500,
            'orderby'        => 'menu_order title',
            'order'          => 'ASC',
            'meta_query'     => [ [ 'key' => Semantic_Settings::EXCLUDE_META, 'compare' => 'NOT EXISTS' ] ],
        ] );

        foreach ( $posts as $post ) {
            $out[] = self::render_post( $post );
            $out[] = "\n---\n";
        }

        return implode( "\n", $out ) . "\n";
    }

    /** Lightweight HTML→Markdown for un-analysed pages (headings, links, lists). */
    private static function content_to_markdown( WP_Post $post ) {
        $html = apply_filters( 'the_content', $post->post_content );
        $html = preg_replace( '/<h([1-6])[^>]*>(.*?)<\/h\1>/is', "\n" . '### $2' . "\n", $html );
        $html = preg_replace( '/<li[^>]*>(.*?)<\/li>/is', '- $1' . "\n", $html );
        $html = preg_replace( '/<a[^>]*href="([^"]*)"[^>]*>(.*?)<\/a>/is', '[$2]($1)', $html );
        $text = wp_strip_all_tags( $html );
        $text = preg_replace( "/\n{3,}/", "\n\n", $text );
        return trim( $text );
    }
}