<?php
defined( 'ABSPATH' ) || exit;

class ADCT_LLMS_Generator {

	public static function build( $file = 'llms' ) {
		$settings = ADCT_LLMS_Settings::get();
		$file     = ( 'full' === $file ) ? 'full' : 'llms';
		$sections = $settings[ $file ] ?? array();

		$lines   = array();
		$lines[] = '# ' . ADCT_LLMS_Settings::get_site_title();
		$lines[] = '';
		$lines[] = '> ' . self::escape_blockquote( $settings['site_summary'] ?? '' );
		$lines[] = '';
		$lines[] = 'Generated by ADCT LLM Index v' . ADCT_LLMS_VERSION . '. Curated index for AI assistants and LLM crawlers.';
		$lines[] = '';

		$primary = self::build_primary_pages( $settings );
		if ( ! empty( $primary ) ) {
			$lines[] = '## Primary pages';
			$lines[] = '';
			$lines   = array_merge( $lines, self::items_to_lines( $primary ) );
			$lines[] = '';
		}

		$order = array( 'brands', 'pages', 'products', 'posts' );
		foreach ( $order as $section_key ) {
			$section = $sections[ $section_key ] ?? array();
			if ( empty( $section['enabled'] ) ) {
				continue;
			}

			$items = ADCT_LLMS_Scanner::collect_section( $section_key, $section, $settings, $file );
			$items = self::dedupe_items( $items, $primary );

			if ( empty( $items ) ) {
				continue;
			}

			$title = trim( (string) ( $section['title'] ?? ucfirst( $section_key ) ) );
			$lines[] = '## ' . $title;
			$lines[] = '';
			$lines   = array_merge( $lines, self::items_to_lines( $items ) );
			$lines[] = '';
		}

		$cpts = $sections['cpts'] ?? array();
		foreach ( $cpts as $post_type => $section ) {
			if ( empty( $section['enabled'] ) ) {
				continue;
			}

			$items = ADCT_LLMS_Scanner::collect_section( $post_type, $section, $settings, $file );
			if ( empty( $items ) ) {
				continue;
			}

			$title = trim( (string) ( $section['title'] ?? ucfirst( $post_type ) ) );
			$lines[] = '## ' . $title;
			$lines[] = '';
			$lines   = array_merge( $lines, self::items_to_lines( $items ) );
			$lines[] = '';
		}

		$lines[] = '## Optional';
		$lines[] = '';

		if ( 'llms' === $file ) {
			$lines[] = '- [Full index (llms-full.txt)](' . esc_url( home_url( '/llms-full.txt' ) ) . '): Expanded site index with more pages, products, and posts.';
		}

		if ( function_exists( 'wp_sitemaps_get_server' ) || class_exists( 'WPSEO_Sitemaps' ) ) {
			$lines[] = '- [XML sitemap](' . esc_url( home_url( '/sitemap_index.xml' ) ) . '): Complete sitemap for deep crawling.';
		}

		$lines[] = '';

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

	private static function build_primary_pages( array $settings ) {
		$ids = array();

		if ( ! empty( $settings['shop_page_id'] ) ) {
			$ids[] = absint( $settings['shop_page_id'] );
		}

		$ids = array_merge( $ids, array_map( 'absint', (array) ( $settings['pinned_page_ids'] ?? array() ) ) );
		$ids = array_values( array_unique( array_filter( $ids ) ) );

		if ( empty( $ids ) ) {
			return array();
		}

		$query = new WP_Query(
			array(
				'post_type'      => 'page',
				'post_status'    => 'publish',
				'post__in'       => $ids,
				'orderby'        => 'post__in',
				'posts_per_page' => count( $ids ),
				'no_found_rows'  => true,
			)
		);

		$items = array();
		foreach ( $query->posts as $post ) {
			$items[] = array(
				'title'       => get_the_title( $post ),
				'url'         => get_permalink( $post ),
				'description' => self::primary_page_description( $post, $settings ),
			);
		}

		return $items;
	}

	private static function primary_page_description( WP_Post $post, array $settings ) {
		if ( absint( $settings['shop_page_id'] ?? 0 ) === (int) $post->ID ) {
			return 'Main inventory and shop page.';
		}

		$text = wp_strip_all_tags( has_excerpt( $post ) ? $post->post_excerpt : $post->post_content );
		$text = preg_replace( '/\s+/', ' ', trim( $text ) );

		if ( strlen( $text ) > 160 ) {
			$text = substr( $text, 0, 157 ) . '...';
		}

		return $text;
	}

	private static function items_to_lines( array $items ) {
		$lines = array();

		foreach ( $items as $item ) {
			$title = self::escape_markdown_text( $item['title'] ?? '' );
			$url   = esc_url( $item['url'] ?? '' );
			$line  = '- [' . $title . '](' . $url . ')';

			if ( ! empty( $item['description'] ) ) {
				$line .= ': ' . self::escape_markdown_text( $item['description'] );
			}

			$lines[] = $line;
		}

		return $lines;
	}

	private static function dedupe_items( array $items, array $primary ) {
		if ( empty( $primary ) ) {
			return $items;
		}

		$seen = array();
		foreach ( $primary as $row ) {
			if ( ! empty( $row['url'] ) ) {
				$seen[ $row['url'] ] = true;
			}
		}

		$clean = array();
		foreach ( $items as $item ) {
			$url = $item['url'] ?? '';
			if ( $url && isset( $seen[ $url ] ) ) {
				continue;
			}
			$clean[] = $item;
		}

		return $clean;
	}

	private static function escape_blockquote( $text ) {
		$text = wp_strip_all_tags( (string) $text );
		$text = preg_replace( '/\s+/', ' ', trim( $text ) );
		return str_replace( array( "\r", "\n" ), ' ', $text );
	}

	private static function escape_markdown_text( $text ) {
		$text = wp_strip_all_tags( (string) $text );
		$text = preg_replace( '/\s+/', ' ', trim( $text ) );
		return str_replace( array( '[', ']', '(', ')', '\\' ), array( '\\[', '\\]', '\\(', '\\)', '\\\\' ), $text );
	}
}