<?php
/**
 * Conversation Manager
 *
 * Handles session-based chat history with MySQL table storage.
 * Supports both post-linked and standalone sessions.
 *
 * @package WP_Agentic_Writer
 */

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

class WP_Agentic_Writer_Conversation_Manager {

	/**
	 * Singleton instance
	 *
	 * @var WP_Agentic_Writer_Conversation_Manager
	 */
	private static $instance = null;

	/**
	 * Database table name
	 *
	 * @var string
	 */
	private $table_name;

	/**
	 * Current session ID
	 *
	 * @var string
	 */
	private $current_session_id = null;

	/**
	 * Get singleton instance
	 *
	 * @return WP_Agentic_Writer_Conversation_Manager
	 */
	public static function get_instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}
		return self::$instance;
	}

	/**
	 * Constructor
	 */
	private function __construct() {
		global $wpdb;
		$this->table_name = $wpdb->prefix . 'wpaw_conversations';
	}

	/**
	 * Generate a unique session ID
	 *
	 * @return string
	 */
	public function generate_session_id() {
		return substr( md5( uniqid( wp_rand(), true ) ), 0, 16 );
	}

	/**
	 * Create a new conversation session
	 *
	 * @param array $data Session data.
	 * @return string|WP_Error Session ID or error.
	 */
	public function create_session( $data = array() ) {
		global $wpdb;

		$session_id = $this->generate_session_id();
		$user_id    = get_current_user_id();

		$result = $wpdb->insert(
			$this->table_name,
			array(
				'session_id'    => $session_id,
				'user_id'       => $user_id,
				'post_id'       => isset( $data['post_id'] ) ? (int) $data['post_id'] : 0,
				'title'         => isset( $data['title'] ) ? sanitize_text_field( $data['title'] ) : '',
				'focus_keyword' => isset( $data['focus_keyword'] ) ? sanitize_text_field( $data['focus_keyword'] ) : '',
				'messages'     => isset( $data['messages'] ) ? json_encode( $data['messages'] ) : '[]',
				'context'       => isset( $data['context'] ) ? json_encode( $data['context'] ) : '{}',
				'status'        => 'active',
			),
			array( '%s', '%d', '%d', '%s', '%s', '%s', '%s', '%s' )
		);

		if ( false === $result ) {
			return new WP_Error(
				'db_error',
				__( 'Failed to create session.', 'wp-agentic-writer' ),
				array( 'status' => 500 )
			);
		}

		$this->current_session_id = $session_id;
		return $session_id;
	}

	/**
	 * Check if current user can access a session
	 *
	 * @param string $session_id Session ID.
	 * @return bool True if user can access.
	 */
	public function current_user_can_access( $session_id ) {
		$session = $this->get_session( $session_id );

		if ( ! $session ) {
			return false;
		}

		$current_user_id = get_current_user_id();

		// User owns this session
		if ( (int) $session['user_id'] === $current_user_id ) {
			return true;
		}

		// For post-linked sessions, check if user can edit the post
		if ( ! empty( $session['post_id'] ) ) {
			$post_id = (int) $session['post_id'];
			if ( $post_id > 0 && current_user_can( 'edit_post', $post_id ) ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Get a session by session ID (with authorization check)
	 *
	 * @param string $session_id Session ID.
	 * @return array|null Session data or null if not found/not authorized.
	 */
	public function get_session( $session_id ) {
		global $wpdb;

		$session = $wpdb->get_row(
			$wpdb->prepare(
				"SELECT * FROM {$this->table_name} WHERE session_id = %s",
				$session_id
			),
			ARRAY_A
		);

		if ( ! $session ) {
			return null;
		}

		// Decode JSON fields
		$session['messages'] = json_decode( $session['messages'], true ) ?: array();
		$session['context']   = json_decode( $session['context'], true ) ?: array();

		return $session;
	}

	/**
	 * Get a session by session ID (public - for internal use only)
	 * Use this only when authorization is handled separately
	 *
	 * @param string $session_id Session ID.
	 * @return array|null Session data or null if not found.
	 */
	public function get_session_unchecked( $session_id ) {
		global $wpdb;

		$session = $wpdb->get_row(
			$wpdb->prepare(
				"SELECT * FROM {$this->table_name} WHERE session_id = %s",
				$session_id
			),
			ARRAY_A
		);

		if ( ! $session ) {
			return null;
		}

		// Decode JSON fields
		$session['messages'] = json_decode( $session['messages'], true ) ?: array();
		$session['context']   = json_decode( $session['context'], true ) ?: array();

		return $session;
	}

	/**
	 * Get session by post ID
	 *
	 * @param int $post_id Post ID.
	 * @return array|null Session data or null.
	 */
	public function get_session_by_post_id( $post_id ) {
		global $wpdb;

		$session = $wpdb->get_row(
			$wpdb->prepare(
				"SELECT * FROM {$this->table_name} WHERE post_id = %d AND status != 'archived' ORDER BY updated_at DESC LIMIT 1",
				$post_id
			),
			ARRAY_A
		);

		if ( ! $session ) {
			return null;
		}

		$session['messages'] = json_decode( $session['messages'], true ) ?: array();
		$session['context']   = json_decode( $session['context'], true ) ?: array();

		return $session;
	}

	/**
	 * Get all active sessions for current user
	 *
	 * @param string $status Status filter (active, completed, archived).
	 * @param int    $limit   Number of results.
	 * @return array Sessions list.
	 */
	public function get_user_sessions( $status = 'active', $limit = 20 ) {
		global $wpdb;
		$user_id = get_current_user_id();
		$posts_table = $wpdb->posts;

		$sessions = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT c.id, c.session_id, c.post_id, c.title, c.focus_keyword, c.status, c.created_at, c.updated_at,
					JSON_LENGTH(c.messages) as message_count,
					COALESCE(p.post_status, '') as post_status
				FROM {$this->table_name} c
				LEFT JOIN {$posts_table} p ON p.ID = c.post_id
				WHERE c.user_id = %d AND c.status = %s
				ORDER BY updated_at DESC
				LIMIT %d",
				$user_id,
				$status,
				$limit
			),
			ARRAY_A
		);

		return $sessions ?: array();
	}

	/**
	 * Get all uncompleted sessions (post_id = 0) for current user
	 *
	 * @param int $limit Number of results.
	 * @return array Sessions list.
	 */
	public function get_uncompleted_sessions( $limit = 20 ) {
		global $wpdb;
		$user_id = get_current_user_id();

		$sessions = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT id, session_id, post_id, title, focus_keyword, status, created_at, updated_at,
					JSON_LENGTH(messages) as message_count
				FROM {$this->table_name}
				WHERE user_id = %d AND post_id = 0 AND status = 'active'
				ORDER BY updated_at DESC
				LIMIT %d",
				$user_id,
				$limit
			),
			ARRAY_A
		);

		return $sessions ?: array();
	}

	/**
	 * Update session messages
	 *
	 * @param string $session_id Session ID.
	 * @param array  $messages    Messages array.
	 * @return bool True on success.
	 */
	public function update_messages( $session_id, $messages ) {
		global $wpdb;

		$result = $wpdb->update(
			$this->table_name,
			array(
				'messages'   => json_encode( $messages ),
				'updated_at'  => current_time( 'mysql' ),
			),
			array( 'session_id' => $session_id ),
			array( '%s', '%s' ),
			array( '%s' )
		);

		return false !== $result;
	}

	/**
	 * Update session context
	 *
	 * @param string $session_id Session ID.
	 * @param array  $context    Context data.
	 * @return bool True on success.
	 */
	public function update_context( $session_id, $context ) {
		global $wpdb;

		$result = $wpdb->update(
			$this->table_name,
			array(
				'context'     => json_encode( $context ),
				'updated_at'  => current_time( 'mysql' ),
			),
			array( 'session_id' => $session_id ),
			array( '%s', '%s' ),
			array( '%s' )
		);

		return false !== $result;
	}

	/**
	 * Link session to a post
	 *
	 * @param string $session_id Session ID.
	 * @param int    $post_id    Post ID.
	 * @return bool True on success.
	 */
	public function link_to_post( $session_id, $post_id ) {
		global $wpdb;

		$result = $wpdb->update(
			$this->table_name,
			array(
				'post_id'     => (int) $post_id,
				'updated_at'  => current_time( 'mysql' ),
			),
			array( 'session_id' => $session_id ),
			array( '%d', '%s' ),
			array( '%s' )
		);

		return false !== $result;
	}

	/**
	 * Update session title
	 *
	 * @param string $session_id Session ID.
	 * @param string $title      New title.
	 * @return bool True on success.
	 */
	public function update_title( $session_id, $title ) {
		global $wpdb;

		$result = $wpdb->update(
			$this->table_name,
			array(
				'title'      => sanitize_text_field( $title ),
				'updated_at' => current_time( 'mysql' ),
			),
			array( 'session_id' => $session_id ),
			array( '%s', '%s' ),
			array( '%s' )
		);

		return false !== $result;
	}

	/**
	 * Update focus keyword
	 *
	 * @param string $session_id   Session ID.
	 * @param string $focus_keyword Focus keyword.
	 * @return bool True on success.
	 */
	public function update_focus_keyword( $session_id, $focus_keyword ) {
		global $wpdb;

		$result = $wpdb->update(
			$this->table_name,
			array(
				'focus_keyword' => sanitize_text_field( $focus_keyword ),
				'updated_at'    => current_time( 'mysql' ),
			),
			array( 'session_id' => $session_id ),
			array( '%s', '%s' ),
			array( '%s' )
		);

		return false !== $result;
	}

	/**
	 * Mark session as completed
	 *
	 * @param string $session_id Session ID.
	 * @return bool True on success.
	 */
	public function mark_completed( $session_id ) {
		global $wpdb;

		$result = $wpdb->update(
			$this->table_name,
			array(
				'status'     => 'completed',
				'updated_at' => current_time( 'mysql' ),
			),
			array( 'session_id' => $session_id ),
			array( '%s', '%s' ),
			array( '%s' )
		);

		return false !== $result;
	}

	/**
	 * Delete a session
	 *
	 * @param string $session_id Session ID.
	 * @return bool True on success.
	 */
	public function delete_session( $session_id ) {
		global $wpdb;

		$result = $wpdb->delete(
			$this->table_name,
			array( 'session_id' => $session_id ),
			array( '%s' )
		);

		return false !== $result;
	}

	/**
	 * Get or create session for post
	 *
	 * @param int $post_id Post ID (can be 0 for new posts).
	 * @return array Session data with session_id.
	 */
	public function get_or_create_session_for_post( $post_id = 0 ) {
		// Try to find existing session for this post
		if ( $post_id > 0 ) {
			$session = $this->get_session_by_post_id( $post_id );
			if ( $session ) {
				return $session;
			}
		}

		// Create new session
		$session_id = $this->create_session( array( 'post_id' => $post_id ) );

		if ( is_wp_error( $session_id ) ) {
			return null;
		}

		return $this->get_session( $session_id );
	}

	/**
	 * Set current session ID
	 *
	 * @param string $session_id Session ID.
	 */
	public function set_current_session( $session_id ) {
		$this->current_session_id = $session_id;
	}

	/**
	 * Get current session ID
	 *
	 * @return string|null
	 */
	public function get_current_session_id() {
		return $this->current_session_id;
	}

	/**
	 * Get current session data
	 *
	 * @return array|null
	 */
	public function get_current_session() {
		if ( ! $this->current_session_id ) {
			return null;
		}
		return $this->get_session( $this->current_session_id );
	}

	/**
	 * Check if current session has post ID
	 *
	 * @return bool
	 */
	public function current_session_has_post() {
		$session = $this->get_current_session();
		return $session && $session['post_id'] > 0;
	}

	/**
	 * Check if editor has content (for auto-save decision)
	 *
	 * @param int $post_id Post ID.
	 * @return bool True if post has content blocks.
	 */
	public function post_has_content( $post_id ) {
		if ( $post_id <= 0 ) {
			return false;
		}

		$post = get_post( $post_id );
		if ( ! $post ) {
			return false;
		}

		// Check if post has any blocks or content
		$blocks = parse_blocks( $post->post_content );
		return ! empty( $blocks );
	}

	/**
	 * Get all sessions for a specific post.
	 *
	 * @param int $post_id Post ID.
	 * @return array Sessions array.
	 */
	public function get_sessions_for_post( $post_id ) {
		global $wpdb;

		if ( $post_id <= 0 ) {
			return array();
		}

		$sessions = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT *, JSON_LENGTH(messages) as message_count FROM {$this->table_name} WHERE post_id = %d ORDER BY updated_at DESC",
				$post_id
			),
			ARRAY_A
		);

		// Decode JSON fields for each session
		foreach ( $sessions as &$session ) {
			$session['messages'] = json_decode( $session['messages'], true ) ?: array();
			$session['context']  = json_decode( $session['context'], true ) ?: array();
		}

		return $sessions ?: array();
	}
}