<?php

/**
 * Title Generator Utility
 *
 * @package Aisentic\Api\Util
 */

namespace Aisentic\Util;

use Aisentic\Api\Repositories\Message_Repository;
use Aisentic\Api\Repositories\Conversation_Repository;

/**
 * Generates conversation titles from the first user message (no AI/LLM call).
 */
class Title_Generator {

	/**
	 * Generate a title for a conversation from its first user message.
	 *
	 * No AI/LLM call is involved — the title is derived directly from the text
	 * of the opening user message, so it is instant and free of token cost.
	 *
	 * @param string $conversationUuid Conversation UUID.
	 * @param int    $limit            How many opening messages to scan for the first user message.
	 * @return string|null Generated title or null if there is no usable user message.
	 */
	public static function generateTitle( string $conversationUuid, int $limit = 2 ): ?string {
		try {
			$messageRepo = new Message_Repository();

			// Fetch the opening messages (ordered oldest-first by the repository).
			$firstMessages = $messageRepo->getByConversation( $conversationUuid, $limit );

			if ( empty( $firstMessages ) ) {
				return null;
			}

			// Use the first user message as the basis for the title.
			$first_user_message = '';
			foreach ( $firstMessages as $msg ) {
				if ( 'user' === $msg->role && '' !== trim( (string) $msg->content ) ) {
					$first_user_message = (string) $msg->content;
					break;
				}
			}

			if ( '' === $first_user_message ) {
				return null;
			}

			$title = self::title_from_text( $first_user_message );

			return '' !== $title ? $title : null;
		} catch ( \Throwable $e ) {
			Log::error(
				'Title generation failed',
				[
					'conversation_uuid' => $conversationUuid,
					'error'             => $e->getMessage(),
					'error_class'       => get_class( $e ),
				]
			);
			return null;
		}
	}

	/**
	 * Build a short, clean conversation title from raw message text.
	 *
	 * Strips markup, collapses whitespace, and truncates to a sensible length
	 * on a word boundary. No AI is involved.
	 *
	 * @param string $text Raw user message content.
	 * @return string Title, or an empty string if the text has no usable content.
	 */
	private static function title_from_text( string $text ): string {
		$text = trim( wp_strip_all_tags( $text ) );

		if ( '' === $text ) {
			return '';
		}

		// Keep titles short: at most 8 words, hard-capped at 70 characters.
		$title = wp_trim_words( $text, 8, '…' );

		if ( mb_strlen( $title ) > 70 ) {
			$title = rtrim( mb_substr( $title, 0, 70 ) ) . '…';
		}

		return $title;
	}

	/**
	 * Process pending title generations
	 * This should be called by a cron job or hook
	 *
	 * Note: Only processes conversations WITHOUT titles (title IS NULL)
	 * to avoid regenerating existing titles
	 *
	 * @return void
	 */
	public static function processPending(): void {
		global $wpdb;

		$conversations_table = $wpdb->prefix . 'aisentic_conversations';
		$messages_table      = $wpdb->prefix . 'aisentic_messages';

		// Find conversations without titles that have at least 2 messages
		// Only processes NULL titles, never regenerates existing ones
		// Table names are safe - $wpdb->prefix is controlled by WordPress core
		$conversations_table = $wpdb->prefix . 'aisentic_conversations'; // phpcs:ignore PluginCheck.Security.DirectDB.UnescapedDBParameter -- $wpdb->prefix is trusted
		$messages_table      = $wpdb->prefix . 'aisentic_messages'; // phpcs:ignore PluginCheck.Security.DirectDB.UnescapedDBParameter -- $wpdb->prefix is trusted
		$sql                 = "SELECT c.uuid, c.id FROM `{$conversations_table}` c WHERE c.title IS NULL AND (SELECT COUNT(*) FROM `{$messages_table}` m WHERE m.conversation_uuid = c.uuid) >= %d AND (SELECT MAX(m.created_at) FROM `{$messages_table}` m WHERE m.conversation_uuid = c.uuid) <= (NOW() - INTERVAL 30 MINUTE) LIMIT %d";
		$query               = $wpdb->prepare( $sql, 2, 5 ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared, PluginCheck.Security.DirectDB.UnescapedDBParameter

		$conversations = $wpdb->get_results( $query ); // phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared, WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, PluginCheck.Security.DirectDB.UnescapedDBParameter -- $query is built via $wpdb->prepare() above.

		if ( empty( $conversations ) ) {
			return;
		}

		$conversationRepo = new Conversation_Repository();

		foreach ( $conversations as $conv ) {
			$title = self::generateTitle( $conv->uuid );

			if ( $title ) {
				$conversationRepo->update( $conv->uuid, [ 'title' => $title ] );
			}
		}
	}
}