<?php
/**
 * REST API Controller.
 *
 * @package AISupportAssistant\REST
 */

// phpcs:disable WordPress.DB.DirectDatabaseQuery

namespace AISupportAssistant\REST;

use AISupportAssistant\Admin\Settings;
use AISupportAssistant\Documents\DocumentManager;
use AISupportAssistant\Chat\ChatService;
use AISupportAssistant\Chat\ChatHistory;
use AISupportAssistant\Database\DatabaseManager;
use AISupportAssistant\Helpers\Logger;
use WP_REST_Controller;
use WP_REST_Server;
use WP_REST_Request;
use WP_REST_Response;
use WP_Error;

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

/**
 * Class RestController
 */
class RestController extends WP_REST_Controller {

	/**
	 * Single instance of the class.
	 *
	 * @var RestController|null
	 */
	private static ?RestController $instance = null;

	/**
	 * Get active instance of the class.
	 *
	 * @return RestController
	 */
	public static function get_instance(): RestController {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}
		return self::$instance;
	}

	/**
	 * Constructor.
	 */
	private function __construct() {
		$this->namespace = 'ai-support-assistant/v1';
		add_action( 'rest_api_init', array( $this, 'register_routes' ) );
	}

	/**
	 * Register API routes.
	 *
	 * @return void
	 */
	public function register_routes(): void {
		// Admin: Index Media Attachment.
		register_rest_route(
			$this->namespace,
			'/admin/documents/upload-attachment',
			array(
				array(
					'methods'             => WP_REST_Server::CREATABLE,
					'callback'            => array( $this, 'upload_attachment' ),
					'permission_callback' => array( $this, 'check_admin_permission' ),
					'args'                => array(
						'attachment_id' => array(
							'required'          => true,
							'sanitize_callback' => 'absint',
						),
					),
				),
			)
		);

		// Admin: Crawl and Index Webpage URL.
		register_rest_route(
			$this->namespace,
			'/admin/documents/crawl-url',
			array(
				array(
					'methods'             => WP_REST_Server::CREATABLE,
					'callback'            => array( $this, 'crawl_url' ),
					'permission_callback' => array( $this, 'check_admin_permission' ),
					'args'                => array(
						'url' => array(
							'required'          => true,
							'sanitize_callback' => 'esc_url_raw',
						),
					),
				),
			)
		);

		// Admin: Reindex Document.
		register_rest_route(
			$this->namespace,
			'/admin/documents/(?P<id>\d+)/reindex',
			array(
				array(
					'methods'             => WP_REST_Server::CREATABLE,
					'callback'            => array( $this, 'reindex_document' ),
					'permission_callback' => array( $this, 'check_admin_permission' ),
				),
			)
		);

		// Admin: Delete Document.
		register_rest_route(
			$this->namespace,
			'/admin/documents/(?P<id>\d+)',
			array(
				array(
					'methods'             => WP_REST_Server::DELETABLE,
					'callback'            => array( $this, 'delete_document' ),
					'permission_callback' => array( $this, 'check_admin_permission' ),
				),
			)
		);

		// Admin: Get Document Chunks Preview.
		register_rest_route(
			$this->namespace,
			'/admin/documents/(?P<id>\d+)/chunks',
			array(
				array(
					'methods'             => WP_REST_Server::READABLE,
					'callback'            => array( $this, 'get_document_chunks' ),
					'permission_callback' => array( $this, 'check_admin_permission' ),
				),
			)
		);

		// Admin: Export Logs.
		register_rest_route(
			$this->namespace,
			'/history/export',
			array(
				array(
					'methods'             => WP_REST_Server::READABLE,
					'callback'            => array( $this, 'export_history' ),
					'permission_callback' => array( $this, 'check_admin_permission' ),
				),
			)
		);

		// Admin: Get & Delete Chat History Log — both methods on same URI in a single registration.
		register_rest_route(
			$this->namespace,
			'/admin/history/(?P<id>\d+)',
			array(
				array(
					'methods'             => WP_REST_Server::READABLE,
					'callback'            => array( $this, 'get_history_log' ),
					'permission_callback' => array( $this, 'check_admin_permission' ),
				),
				array(
					'methods'             => WP_REST_Server::DELETABLE,
					'callback'            => array( $this, 'delete_history_log' ),
					'permission_callback' => array( $this, 'check_admin_permission' ),
				),
			)
		);

		// Public: Chat Query Endpoint.
		register_rest_route(
			$this->namespace,
			'/chat',
			array(
				array(
					'methods'             => WP_REST_Server::CREATABLE,
					'callback'            => array( $this, 'handle_chat' ),
					'permission_callback' => '__return_true', // Nonce checked in callback for fine-grained visitor filtering.
					'args'                => array(
						'question'   => array(
							'required'          => true,
							'sanitize_callback' => 'sanitize_text_field',
						),
						'session_id' => array(
							'required'          => false,
							'sanitize_callback' => 'sanitize_text_field',
						),
						'nonce'      => array(
							'required'          => false,
							'sanitize_callback' => 'sanitize_text_field',
						),
					),
				),
			)
		);
	}

	/**
	 * Check if current user is admin.
	 *
	 * @return bool
	 */
	public function check_admin_permission(): bool {
		return current_user_can( 'manage_options' );
	}

	/**
	 * REST Callback: Index a WP Media Attachment.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function upload_attachment( WP_REST_Request $request ) {
		$attachment_id = $request->get_param( 'attachment_id' );

		try {
			$doc_id = DocumentManager::upload_attachment( $attachment_id );
			if ( $doc_id > 0 ) {
				return new WP_REST_Response(
					array(
						'success'     => true,
						'document_id' => $doc_id,
						'message'     => __( 'Document indexed successfully.', 'ai-support-assistant' ),
					),
					200
				);
			}
			return new WP_Error( 'ai_support_assistant_upload_failed', __( 'Unable to process and index the document.', 'ai-support-assistant' ), array( 'status' => 500 ) );
		} catch ( \Exception $e ) {
			return new WP_Error( 'ai_support_assistant_upload_failed', $e->getMessage(), array( 'status' => 500 ) );
		}
	}

	/**
	 * REST Callback: Crawl and index URL.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function crawl_url( WP_REST_Request $request ) {
		$url = $request->get_param( 'url' );

		try {
			$doc_id = DocumentManager::crawl_and_index_url( $url );
			if ( $doc_id > 0 ) {
				return new WP_REST_Response(
					array(
						'success'     => true,
						'document_id' => $doc_id,
						'message'     => __( 'URL crawled and indexed successfully.', 'ai-support-assistant' ),
					),
					200
				);
			}
			return new WP_Error( 'ai_support_assistant_crawl_failed', __( 'Unable to process and index the URL.', 'ai-support-assistant' ), array( 'status' => 500 ) );
		} catch ( \Exception $e ) {
			return new WP_Error( 'ai_support_assistant_crawl_failed', $e->getMessage(), array( 'status' => 500 ) );
		}
	}

	/**
	 * REST Callback: Reindex document.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function reindex_document( WP_REST_Request $request ) {
		$id = $request->get_param( 'id' );

		try {
			$success = DocumentManager::index_document( $id );
			if ( $success ) {
				return new WP_REST_Response(
					array(
						'success' => true,
						'message' => __( 'Document re-indexed successfully.', 'ai-support-assistant' ),
					),
					200
				);
			}
			return new WP_Error( 'ai_support_assistant_reindex_failed', __( 'Re-indexing process failed.', 'ai-support-assistant' ), array( 'status' => 500 ) );
		} catch ( \Exception $e ) {
			return new WP_Error( 'ai_support_assistant_reindex_failed', $e->getMessage(), array( 'status' => 500 ) );
		}
	}

	/**
	 * REST Callback: Delete document.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function delete_document( WP_REST_Request $request ) {
		$id = $request->get_param( 'id' );

		$success = DocumentManager::delete_document( $id );
		if ( $success ) {
			return new WP_REST_Response(
				array(
					'success' => true,
					'message' => __( 'Document and vector embeddings deleted.', 'ai-support-assistant' ),
				),
				200
			);
		}

		return new WP_Error( 'ai_support_assistant_delete_failed', __( 'Delete document operation failed.', 'ai-support-assistant' ), array( 'status' => 500 ) );
	}

	/**
	 * REST Callback: Retrieve document chunks for admin preview list.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function get_document_chunks( WP_REST_Request $request ) {
		global $wpdb;
		$id           = $request->get_param( 'id' );
		$chunks_table = DatabaseManager::get_chunks_table();

		$chunks = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT chunk_number, page_number, chunk_text, token_count FROM %i WHERE document_id = %d ORDER BY chunk_number ASC",
				$chunks_table,
				$id
			),
			ARRAY_A
		);

		return new WP_REST_Response( array( 'chunks' => $chunks ), 200 );
	}

	/**
	 * REST Callback: Export logs CSV.
	 *
	 * Streams a CSV file download directly. ChatHistory::export_csv() will
	 * send HTTP headers and call exit(), so the return below is unreachable
	 * in practice but satisfies the REST API return-type contract.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function export_history( WP_REST_Request $request ) {
		ChatHistory::export_csv();
		// Unreachable — export_csv() always calls exit() after streaming.
		return new WP_REST_Response( array( 'success' => true ), 200 ); // phpcs:ignore Generic.CodeAnalysis.UnreachableCode.Found
	}

	/**
	 * REST Callback: Handle public chat request.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function handle_chat( WP_REST_Request $request ) {
		$nonce    = $request->get_param( 'nonce' );
		$wp_nonce = $request->get_header( 'x_wp_nonce' );

		$authorized = false;
		if ( ! empty( $nonce ) && wp_verify_nonce( $nonce, 'ai_support_assistant_action' ) ) {
			$authorized = true;
		} elseif ( ! empty( $wp_nonce ) && wp_verify_nonce( $wp_nonce, 'wp_rest' ) ) {
			$authorized = true;
		} elseif ( current_user_can( 'manage_options' ) ) {
			$authorized = true;
		}

		if ( ! $authorized ) {
			return new WP_Error( 'ai_support_assistant_unauthorized', __( 'Invalid security nonce.', 'ai-support-assistant' ), array( 'status' => 403 ) );
		}

		$question   = $request->get_param( 'question' );
		$session_id = $request->get_param( 'session_id' );

		// If no session ID provided, generate a unique random hash.
		if ( empty( $session_id ) ) {
			$session_id = md5( uniqid( (string) wp_rand(), true ) );
		}

		try {
			$result = ChatService::answer_question( $session_id, $question );

			return new WP_REST_Response(
				array(
					'answer'           => $result['answer'],
					'citations'        => $result['citations'],
					'session_id'       => $session_id,
					'enable_streaming' => ! empty( Settings::get_instance()->get( 'enable_streaming', 1 ) ) ? 1 : 0,
				),
				200
			);
		} catch ( \Throwable $e ) {
			Logger::error( 'Chat request error: ' . $e->getMessage() );
			return new WP_REST_Response(
				array(
					'answer'           => __( 'Sorry, an unexpected error occurred while processing your query. Please try again.', 'ai-support-assistant' ),
					'citations'        => array(),
					'session_id'       => $session_id,
					'enable_streaming' => 0,
				),
				200
			);
		}
	}

	/**
	 * REST Callback: Delete a single history log entry.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function delete_history_log( WP_REST_Request $request ) {
		global $wpdb;
		$id          = $request->get_param( 'id' );
		$chat_table  = DatabaseManager::get_chat_history_table();

		$deleted = $wpdb->delete( $chat_table, array( 'id' => $id ), array( '%d' ) );
		if ( false !== $deleted ) {
			return new WP_REST_Response(
				array(
					'success' => true,
					'message' => __( 'Log entry deleted successfully.', 'ai-support-assistant' ),
				),
				200
			);
		}

		return new WP_Error( 'ai_support_assistant_delete_failed', __( 'Delete log operation failed.', 'ai-support-assistant' ), array( 'status' => 500 ) );
	}

	/**
	 * REST Callback: Get details of a single log entry.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response|WP_Error
	 */
	public function get_history_log( WP_REST_Request $request ) {
		global $wpdb;
		$id          = $request->get_param( 'id' );
		$chat_table  = DatabaseManager::get_chat_history_table();

		$log = $wpdb->get_row(
			$wpdb->prepare( "SELECT * FROM %i WHERE id = %d", $chat_table, $id )
		);

		if ( $log ) {
			$messages = array();
			if ( ! empty( $log->messages ) ) {
				$decoded = json_decode( $log->messages, true );
				if ( is_array( $decoded ) ) {
					$messages = $decoded;
				}
			}

			if ( empty( $messages ) ) {
				if ( ! empty( $log->question ) ) {
					$messages[] = array(
						'role'    => 'user',
						'content' => $log->question,
						'time'    => $log->created_at,
					);
				}
				if ( ! empty( $log->answer ) ) {
					$messages[] = array(
						'role'    => 'assistant',
						'content' => $log->answer,
						'time'    => $log->created_at,
					);
				}
			}

			return new WP_REST_Response(
				array(
					'success' => true,
					'log'     => array(
						'id'         => (int) $log->id,
						'session_id' => $log->session_id,
						'question'   => $log->question,
						'answer'     => $log->answer,
						'messages'   => $messages,
						'provider'   => $log->provider,
						'model'      => $log->model,
						'asked_at'   => mysql2date( get_option( 'date_format' ) . ' ' . get_option( 'time_format' ), $log->created_at ),
						'updated_at' => ! empty( $log->updated_at ) ? mysql2date( get_option( 'date_format' ) . ' ' . get_option( 'time_format' ), $log->updated_at ) : mysql2date( get_option( 'date_format' ) . ' ' . get_option( 'time_format' ), $log->created_at ),
					),
				),
				200
			);
		}

		return new WP_Error( 'ai_support_assistant_not_found', __( 'Log entry not found.', 'ai-support-assistant' ), array( 'status' => 404 ) );
	}
}