<?php
/**
 * AI Support Assistant Chatbot pipeline orchestrator.
 *
 * @package AISupportAssistant\Chat
 */

namespace AISupportAssistant\Chat;

use AISupportAssistant\Admin\Settings;
use AISupportAssistant\Providers\ChatProviderInterface;
use AISupportAssistant\Providers\WordPressAIProvider;
use AISupportAssistant\Providers\OpenAIProvider;
use AISupportAssistant\Providers\GeminiProvider;
use AISupportAssistant\Helpers\Logger;
use AISupportAssistant\Helpers\ConnectorHelper;

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

/**
 * Class ChatService
 */
class ChatService {

	/**
	 * Instantiate active chat provider.
	 *
	 * @return ChatProviderInterface
	 */
	public static function get_provider( string $override = '' ): ChatProviderInterface {
		$settings = Settings::get_instance();
		$provider = $override ?: $settings->get( 'ai_provider', 'wp_native_ai' );

		switch ( $provider ) {
			case 'wp_native_ai':
				return new WordPressAIProvider();
			case 'wp_connector_openai':
			case 'openai':
				return new OpenAIProvider();
			case 'wp_connector_gemini':
			case 'wp_connector_google':
			case 'wp_connector_google-gemini':
			case 'gemini':
				return new GeminiProvider();
			default:
				if ( WordPressAIProvider::is_available() ) {
					return new WordPressAIProvider();
				}
				return new GeminiProvider();
		}
	}

	/**
	 * Run AI Support Assistant retrieval, construct prompt context, call LLM, and log result.
	 *
	 * @param string $session_id User session ID.
	 * @param string $question   User query.
	 * @return array Answer and citation sources.
	 */
	public static function answer_question( string $session_id, string $question, string $override = '', ?callable $on_delta = null ): array {
		return SessionLock::run( $session_id, static function () use ( $session_id, $question, $override, $on_delta ) {
			return self::generate_answer( $session_id, $question, $override, $on_delta );
		} );
	}

	private static function generate_answer( string $session_id, string $question, string $override, ?callable $on_delta ): array {
		$settings = Settings::get_instance();
		$provider = $override ?: $settings->get( 'ai_provider', 'wp_native_ai' );

		$model   = 'default';
		$api_key = '';

		if ( 'wp_native_ai' === $provider ) {
			$model              = 'wp-native-ai';
			$has_native_or_keys = WordPressAIProvider::is_available() ||
								! empty( $settings->get_secret( 'openai_api_key' ) ) ||
								! empty( $settings->get_secret( 'gemini_api_key' ) ) ||
									! empty( ConnectorHelper::get_connector_api_key( 'google' ) ) ||
									! empty( ConnectorHelper::get_connector_api_key( 'openai' ) );

			if ( ! $has_native_or_keys ) {
				throw new \RuntimeException( 'No active AI provider credentials found.' );
			}
		} elseif ( 'openai' === $provider || 'wp_connector_openai' === $provider ) {
			$model   = $settings->get( 'openai_chat_model', '' ) ?: 'gpt-4o-mini';
			$api_key = $settings->get_secret( 'openai_api_key' );
			if ( empty( $api_key ) ) {
				$api_key = ConnectorHelper::get_connector_api_key( 'openai' );
			}
			if ( empty( $api_key ) ) {
				throw new \RuntimeException( 'OpenAI API key is missing.' );
			}
		} else {
			$model   = $settings->get( 'gemini_chat_model', '' ) ?: 'gemini-3.1-flash-lite';
			$api_key = $settings->get_secret( 'gemini_api_key' );
			if ( empty( $api_key ) ) {
				$api_key = ConnectorHelper::get_connector_api_key( 'google' );
				if ( empty( $api_key ) ) {
					$api_key = ConnectorHelper::get_connector_api_key( 'gemini' );
				}
			}
			if ( empty( $api_key ) ) {
				throw new \RuntimeException( 'Google Gemini API key is missing.' );
			}
		}

		$history = array();
		if ( $settings->get( 'enable_chat_history', 1 ) ) {
			$history = ChatHistory::get_history( $session_id, 5 );
		}

		Logger::debug( 'AI Support Assistant requested.' );

		// 1. Retrieve most relevant chunks.
		$chunks = RetrievalService::retrieve( $question );

		// If no context documents are available, respond with the fallback directly.
		$fallback_msg = $settings->get( 'chat_fallback_message', __( "I couldn't find that information in the uploaded documentation.", 'ai-support-assistant' ) );

		if ( empty( $chunks ) ) {
			ChatHistory::log( $session_id, $question, $fallback_msg, $provider, (string) $model, 'fallback' );
			if ( $on_delta ) { $on_delta( $fallback_msg ); }
			return array(
				'answer'    => $fallback_msg,
				'citations' => array(),
			);
		}

		// 2. Generate response via LLM provider.
		$active_provider = self::get_provider( $override );
		$answer          = $active_provider->generate_response( $chunks, $question, $history, $on_delta );

		// 3. Log query to database.
		$outcome = trim( $answer ) === trim( $fallback_msg ) ? 'fallback' : 'completed';
		ChatHistory::log( $session_id, $question, $answer, $provider, (string) $model, $outcome );

		// 4. Format citations (deduplicated by document).
		$citations = array();
		if ( 'fallback' !== $outcome && $settings->get( 'enable_citations', 1 ) ) {
			$seen_docs = array();
			foreach ( $chunks as $chunk ) {
				$doc_key = 'doc_' . ( $chunk['document_id'] ?? '0' );

				if ( ! isset( $seen_docs[ $doc_key ] ) ) {
					$seen_docs[ $doc_key ] = array(
						'document_id'  => $chunk['document_id'] ?? 0,
						'title'        => $chunk['title'] ?? '',
						'filename'     => $chunk['filename'] ?? '',
						'chunk_number' => $chunk['chunk_number'] ?? 1,
						'page_numbers' => array(),
						'similarity'   => round( $chunk['score'] ?? 0, 3 ),
					);
				}

				if ( ! empty( $chunk['page_number'] ) && ! in_array( $chunk['page_number'], $seen_docs[ $doc_key ]['page_numbers'], true ) ) {
					$seen_docs[ $doc_key ]['page_numbers'][] = $chunk['page_number'];
				}
			}

			foreach ( $seen_docs as $doc_data ) {
				if ( ! empty( $doc_data['page_numbers'] ) ) {
					sort( $doc_data['page_numbers'], SORT_NUMERIC );
					$doc_data['page_number'] = implode( ', ', $doc_data['page_numbers'] );
				} else {
					$doc_data['page_number'] = null;
				}
				unset( $doc_data['page_numbers'] );
				$citations[] = $doc_data;
			}
		}

		return array(
			'answer'    => $answer,
			'citations' => $citations,
		);
	}
}