<?php
/**
 * AI Engine Class
 * Multi-provider AI integration with RAG support
 *
 * @package AI_Commerce_Assistant
 */

if ( !defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * AI Engine Class
 */
class AICA_AI_Engine {

	/**
	 * Single instance
	 *
	 * @var AICA_AI_Engine
	 */
	private static $instance = null;

	/**
	 * Settings
	 *
	 * @var array
	 */
	private $settings;

	/**
	 * Get instance
	 *
	 * @return AICA_AI_Engine
	 */
	public static function get_instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}
		return self::$instance;
	}

	/**
	 * Constructor
	 */
	private function __construct() {
		$this->settings = get_option( 'aica_settings', array() );
	}

	/**
	 * Generate AI response
	 *
	 * @param string $user_message User message
	 * @param string $session_id Session ID
	 * @param array  $context Additional context
	 * @return array Response with message, products, actions
	 */
	public function generate_response( $user_message, $session_id, $context = array() ) {
		try {
			// Get conversation history
			$history = $this->get_conversation_history( $session_id );

			// Retrieve relevant products using RAG
			$relevant_products = $this->retrieve_relevant_products( $user_message );

			// Build system prompt
			$system_prompt = $this->build_system_prompt( $relevant_products, $context );

			// Build messages array
			$messages = array_merge(
				array(
					array(
						'role'    => 'system',
						'content' => $system_prompt,
					),
				),
				$history,
				array(
					array(
						'role'    => 'user',
						'content' => $user_message,
					),
				)
			);

			// Call AI provider
			$provider = $this->settings['ai_provider'] ?? 'openai';

			switch ( $provider ) {
				case 'openai':
					$response = $this->call_openai( $messages );
					break;
				case 'anthropic':
					$response = $this->call_anthropic( $messages );
					break;
				case 'google':
					$response = $this->call_google( $messages );
					break;
				case 'openrouter':
					$response = $this->call_openrouter( $messages );
					break;
				default:
					throw new Exception( __( 'Invalid AI provider selected. Please check your settings.', 'aica-smart-ai-commerce-assistant' ) );
			}

			// Parse response for structured data (products, actions)
			return $this->parse_ai_response( $response, $relevant_products );

		} catch ( Exception $e ) {
			// Log the actual error for debugging
			error_log( 'AICA Error: ' . $e->getMessage() );

			// Return user-friendly error message
			$user_message = $this->get_user_friendly_error( $e->getMessage() );

			// Return error as a response instead of throwing
			return array(
				'message'  => $user_message,
				'products' => array(),
				'actions'  => array(),
				'error'    => true,
			);
		}
	}

	/**
	 * Convert technical error to user-friendly message
	 *
	 * @param string $error_message Technical error message
	 * @return string User-friendly error message
	 */
	private function get_user_friendly_error( $error_message ) {
		$error_lower = strtolower( $error_message );

		// API key errors
		if ( strpos( $error_lower, 'api key' ) !== false ||
			strpos( $error_lower, 'authentication' ) !== false ||
			strpos( $error_lower, 'unauthorized' ) !== false ) {
			return __( 'The AI service is not properly configured. Please contact the site administrator to set up the API key.', 'aica-smart-ai-commerce-assistant' );
		}

		// Rate limit errors
		if ( strpos( $error_lower, 'rate limit' ) !== false ||
			strpos( $error_lower, 'quota' ) !== false ||
			strpos( $error_lower, 'too many requests' ) !== false ) {
			return __( 'The AI service is temporarily busy. Please try again in a few minutes.', 'aica-smart-ai-commerce-assistant' );
		}

		// Network/timeout errors
		if ( strpos( $error_lower, 'timeout' ) !== false ||
			strpos( $error_lower, 'connection' ) !== false ||
			strpos( $error_lower, 'network' ) !== false ) {
			return __( 'Unable to connect to the AI service. Please check your internet connection and try again.', 'aica-smart-ai-commerce-assistant' );
		}

		// Invalid model errors
		if ( strpos( $error_lower, 'model' ) !== false &&
			strpos( $error_lower, 'not found' ) !== false ) {
			return __( 'The selected AI model is not available. Please contact the site administrator.', 'aica-smart-ai-commerce-assistant' );
		}

		// Insufficient credits/billing errors
		if ( strpos( $error_lower, 'insufficient' ) !== false ||
			strpos( $error_lower, 'billing' ) !== false ||
			strpos( $error_lower, 'payment' ) !== false ) {
			return __( 'The AI service account needs attention. Please contact the site administrator.', 'aica-smart-ai-commerce-assistant' );
		}

		// Content policy violations
		if ( strpos( $error_lower, 'content policy' ) !== false ||
			strpos( $error_lower, 'safety' ) !== false ) {
			return __( 'Your message could not be processed. Please rephrase your question and try again.', 'aica-smart-ai-commerce-assistant' );
		}

		// Generic fallback
		return __( 'Sorry, I encountered an error while processing your request. Please try again or contact support if the problem persists.', 'aica-smart-ai-commerce-assistant' );
	}

	/**
	 * Retrieve relevant products using RAG
	 *
	 * @param string $query User query
	 * @return array Products array
	 */
	private function retrieve_relevant_products( $query ) {
		global $wpdb;

		$table        = $wpdb->prefix . 'aica_indexed_products';
		$max_products = intval( $this->settings['max_products_per_response'] ?? 5 );

		// Check if embeddings are enabled
		if ( isset( $this->settings['enable_embeddings'] ) && $this->settings['enable_embeddings'] === 'yes' ) {
			// Use embedding-based search (we'll implement this)
			return $this->embedding_based_search( $query, $max_products );
		}

		// Fallback to full-text search
		$cache_key = 'aica_relevant_products_' . md5( $query );
		$products  = wp_cache_get( $cache_key, 'aica_ai_engine' );
		if ( false !== $products ) {
			return $products;
		}

		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		$results = $wpdb->get_results(
			$wpdb->prepare(
				"SELECT product_id, content, price, stock_quantity, metadata
            FROM {$wpdb->prefix}aica_indexed_products
            WHERE MATCH(content) AGAINST(%s IN NATURAL LANGUAGE MODE)
            AND stock_quantity > 0
            LIMIT %d",
				$query,
				$max_products
			)
		);

		$products = array();
		foreach ( $results as $row ) {
			$product = wc_get_product( $row->product_id );
			if ( $product ) {
				$products[] = array(
					'id'                => $product->get_id(),
					'name'              => $product->get_name(),
					'price'             => $product->get_price(),
					'regular_price'     => $product->get_regular_price(),
					'sale_price'        => $product->get_sale_price(),
					'description'       => wp_trim_words( $product->get_description(), 50 ),
					'short_description' => wp_trim_words( $product->get_short_description(), 30 ),
					'image'             => wp_get_attachment_url( $product->get_image_id() ),
					'url'               => $product->get_permalink(),
					'in_stock'          => $product->is_in_stock(),
					'stock_quantity'    => $product->get_stock_quantity(),
					'categories'        => wp_get_post_terms( $product->get_id(), 'product_cat', array( 'fields' => 'names' ) ),
				);
			}
		}

		wp_cache_set( $cache_key, $products, 'aica_ai_engine', HOUR_IN_SECONDS );

		return $products;
	}

	/**
	 * Embedding-based search (advanced RAG)
	 *
	 * @param string $query Search query
	 * @param int    $limit Max results
	 * @return array Products
	 */
	private function embedding_based_search( $query, $limit ) {
		// Generate embedding for query
		$query_embedding = $this->generate_embedding( $query );

		if ( !$query_embedding ) {
			// Fallback to regular search
			return $this->retrieve_relevant_products( $query );
		}

		global $wpdb;
		$table = $wpdb->prefix . 'aica_indexed_products';

		// Get all products with embeddings with caching
		$rows = wp_cache_get( 'aica_all_indexed_embeddings', 'aica_ai_engine' );
		if ( false === $rows ) {
			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
			$rows = $wpdb->get_results( "SELECT * FROM {$wpdb->prefix}aica_indexed_products WHERE embedding IS NOT NULL AND stock_quantity > 0" );
			wp_cache_set( 'aica_all_indexed_embeddings', $rows, 'aica_ai_engine', HOUR_IN_SECONDS );
		}

		// Calculate cosine similarity
		$similarities = array();
		foreach ( $rows as $row ) {
			$product_embedding = json_decode( $row->embedding, true );
			if ( $product_embedding ) {
				$similarity     = $this->cosine_similarity( $query_embedding, $product_embedding );
				$similarities[] = array(
					'product_id' => $row->product_id,
					'similarity' => $similarity,
				);
			}
		}

		// Sort by similarity
		usort(
			$similarities,
			function ( $a, $b ) {
				return $b['similarity'] <=> $a['similarity'];
			}
		);

		// Get top products
		$top_products = array_slice( $similarities, 0, $limit );

		$products = array();
		foreach ( $top_products as $item ) {
			$product = wc_get_product( $item['product_id'] );
			if ( $product ) {
				$products[] = array(
					'id'                => $product->get_id(),
					'name'              => $product->get_name(),
					'price'             => $product->get_price(),
					'regular_price'     => $product->get_regular_price(),
					'sale_price'        => $product->get_sale_price(),
					'description'       => wp_trim_words( $product->get_description(), 50 ),
					'short_description' => wp_trim_words( $product->get_short_description(), 30 ),
					'image'             => wp_get_attachment_url( $product->get_image_id() ),
					'url'               => $product->get_permalink(),
					'in_stock'          => $product->is_in_stock(),
					'stock_quantity'    => $product->get_stock_quantity(),
					'categories'        => wp_get_post_terms( $product->get_id(), 'product_cat', array( 'fields' => 'names' ) ),
					'relevance_score'   => round( $item['similarity'], 2 ),
				);
			}
		}

		return $products;
	}

	/**
	 * Generate embedding using OpenAI
	 *
	 * @param string $text Text to embed
	 * @return array|false Embedding vector or false on failure
	 */
	public function generate_embedding( $text ) {
		$api_key = $this->settings['openai_api_key'] ?? '';
		if ( empty( $api_key ) ) {
			return false;
		}

		$model = $this->settings['embedding_model'] ?? 'text-embedding-3-small';

		$response = wp_remote_post(
			'https://api.openai.com/v1/embeddings',
			array(
				'headers' => array(
					'Authorization' => 'Bearer ' . $api_key,
					'Content-Type'  => 'application/json',
				),
				'body'    => wp_json_encode(
					array(
						'model' => $model,
						'input' => $text,
					)
				),
				'timeout' => 30,
			)
		);

		if ( is_wp_error( $response ) ) {
			return false;
		}

		$body = json_decode( wp_remote_retrieve_body( $response ), true );

		if ( isset( $body['data'][0]['embedding'] ) ) {
			return $body['data'][0]['embedding'];
		}

		return false;
	}

	/**
	 * Calculate cosine similarity
	 *
	 * @param array $vec1 Vector 1
	 * @param array $vec2 Vector 2
	 * @return float Similarity score
	 */
	private function cosine_similarity( $vec1, $vec2 ) {
		$dot_product = 0;
		$magnitude1  = 0;
		$magnitude2  = 0;

		for ( $i = 0; $i < count( $vec1 ); $i++ ) {
			$dot_product += $vec1[ $i ] * $vec2[ $i ];
			$magnitude1  += $vec1[ $i ] * $vec1[ $i ];
			$magnitude2  += $vec2[ $i ] * $vec2[ $i ];
		}

		$magnitude1 = sqrt( $magnitude1 );
		$magnitude2 = sqrt( $magnitude2 );

		if ( $magnitude1 == 0 || $magnitude2 == 0 ) {
			return 0;
		}

		return $dot_product / ( $magnitude1 * $magnitude2 );
	}

	/**
	 * Build system prompt
	 *
	 * @param array $products Products context
	 * @param array $context Additional context
	 * @return string System prompt
	 */
	private function build_system_prompt( $products, $context ) {
		$store_name = get_bloginfo( 'name' );

		$prompt  = "You are a helpful AI shopping assistant for {$store_name}. ";
		$prompt .= 'Your role is to help customers find products, answer questions, and assist with purchases. ';
		$currency_symbol = html_entity_decode( get_woocommerce_currency_symbol(), ENT_QUOTES, 'UTF-8' );
		$price_example   = html_entity_decode( strip_tags( wc_price( 1234.56 ) ), ENT_QUOTES, 'UTF-8' );
		$prompt .= "Be friendly, concise, and helpful.\n";
		$prompt .= "Prices are in " . get_woocommerce_currency() . " ({$currency_symbol}). Always format prices exactly like this: {$price_example}\n\n";

		if ( !empty( $products ) ) {
			$prompt .= "Here are some relevant products from our catalog:\n\n";
			foreach ( $products as $product ) {
				$prompt .= "- {$product['name']} (ID: {$product['id']})\n";
				$prompt .= '  Price: ' . html_entity_decode( strip_tags( wc_price( $product['price'] ) ), ENT_QUOTES, 'UTF-8' ) . "\n";
				if ( !empty( $product['short_description'] ) ) {
					$prompt .= "  Description: {$product['short_description']}\n";
				}
				$prompt .= '  Stock: ' . ( $product['in_stock'] ? 'In stock' : 'Out of stock' ) . "\n\n";
			}
		}

		$prompt .= "\nWhen recommending products, mention their ID so the system can display them properly.";
		$prompt .= "\nIf asked to add a product to cart, respond with: ADD_TO_CART:product_id";

		return $prompt;
	}

	/**
	 * Get conversation history
	 *
	 * @param string $session_id Session ID
	 * @param int    $limit Max messages
	 * @return array Messages array
	 */
	private function get_conversation_history( $session_id, $limit = 10 ) {
		global $wpdb;

		$table = $wpdb->prefix . 'aica_conversations';

		$cache_key = 'aica_conversation_history_' . $session_id;
		$results   = wp_cache_get( $cache_key, 'aica_ai_engine' );
		
		if ( false === $results ) {
			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
			$results = $wpdb->get_results(
				$wpdb->prepare(
					"SELECT message, role FROM {$wpdb->prefix}aica_conversations 
                WHERE session_id = %s 
                ORDER BY created_at DESC 
                LIMIT %d",
					$session_id,
					$limit
				)
			);
			wp_cache_set( $cache_key, $results, 'aica_ai_engine', 300 ); // Cache for 5 minutes
		}

		$messages = array();
		foreach ( array_reverse( $results ) as $row ) {
			$messages[] = array(
				'role'    => $row->role === 'user' ? 'user' : 'assistant',
				'content' => $row->message,
			);
		}

		return $messages;
	}

	/**
	 * Call OpenAI API
	 *
	 * @param array $messages Messages array
	 * @return string Response text
	 * @throws Exception
	 */
	private function call_openai( $messages ) {
		$api_key = $this->settings['openai_api_key'] ?? '';
		if ( empty( $api_key ) ) {
			throw new Exception( esc_html__( 'OpenAI API key not configured', 'aica-smart-ai-commerce-assistant' ) );
		}

		$model       = $this->settings['openai_model'] ?? 'gpt-4o-mini';
		$temperature = floatval( $this->settings['temperature'] ?? 0.7 );
		$max_tokens  = intval( $this->settings['max_tokens'] ?? 500 );

		$response = wp_remote_post(
			'https://api.openai.com/v1/chat/completions',
			array(
				'headers' => array(
					'Authorization' => 'Bearer ' . $api_key,
					'Content-Type'  => 'application/json',
				),
				'body'    => wp_json_encode(
					array(
						'model'       => $model,
						'messages'    => $messages,
						'temperature' => $temperature,
						'max_tokens'  => $max_tokens,
					)
				),
				'timeout' => 30,
			)
		);

		if ( is_wp_error( $response ) ) {
			throw new Exception( esc_html( $response->get_error_message() ) );
		}

		$body = json_decode( wp_remote_retrieve_body( $response ), true );

		if ( isset( $body['error'] ) ) {
			throw new Exception( esc_html( $body['error']['message'] ) );
		}

		return $body['choices'][0]['message']['content'] ?? '';
	}

	/**
	 * Call Anthropic Claude API
	 *
	 * @param array $messages Messages array
	 * @return string Response text
	 * @throws Exception
	 */
	private function call_anthropic( $messages ) {
		$api_key = $this->settings['anthropic_api_key'] ?? '';
		if ( empty( $api_key ) ) {
			throw new Exception( esc_html__( 'Anthropic API key not configured', 'aica-smart-ai-commerce-assistant' ) );
		}

		$model       = $this->settings['anthropic_model'] ?? 'claude-3-5-sonnet-20241022';
		$temperature = floatval( $this->settings['temperature'] ?? 0.7 );
		$max_tokens  = intval( $this->settings['max_tokens'] ?? 500 );

		// Extract system message
		$system       = '';
		$conversation = array();
		foreach ( $messages as $msg ) {
			if ( $msg['role'] === 'system' ) {
				$system = $msg['content'];
			} else {
				$conversation[] = $msg;
			}
		}

		$response = wp_remote_post(
			'https://api.anthropic.com/v1/messages',
			array(
				'headers' => array(
					'x-api-key'         => $api_key,
					'anthropic-version' => '2023-06-01',
					'Content-Type'      => 'application/json',
				),
				'body'    => wp_json_encode(
					array(
						'model'       => $model,
						'max_tokens'  => $max_tokens,
						'temperature' => $temperature,
						'system'      => $system,
						'messages'    => $conversation,
					)
				),
				'timeout' => 30,
			)
		);

		if ( is_wp_error( $response ) ) {
			throw new Exception( esc_html( $response->get_error_message() ) );
		}

		$body = json_decode( wp_remote_retrieve_body( $response ), true );

		if ( isset( $body['error'] ) ) {
			throw new Exception( esc_html( $body['error']['message'] ) );
		}

		return $body['content'][0]['text'] ?? '';
	}

	/**
	 * Call Google Gemini API
	 *
	 * @param array $messages Messages array
	 * @return string Response text
	 * @throws Exception
	 */
	private function call_google( $messages ) {
		$api_key = $this->settings['google_api_key'] ?? '';
		if ( empty( $api_key ) ) {
			throw new Exception( esc_html__( 'Google API key not configured', 'aica-smart-ai-commerce-assistant' ) );
		}

		$model       = $this->settings['google_model'] ?? 'gemini-2.5-flash';
		$temperature = floatval( $this->settings['temperature'] ?? 0.7 );
		$debug_mode  = defined( 'WP_DEBUG' ) && WP_DEBUG;

		// Convert messages to Gemini format
		$contents           = array();
		$system_instruction = '';

		foreach ( $messages as $msg ) {
			if ( $msg['role'] === 'system' ) {
				$system_instruction = $msg['content'];
			} else {
				$contents[] = array(
					'role'  => $msg['role'] === 'user' ? 'user' : 'model',
					'parts' => array( array( 'text' => $msg['content'] ) ),
				);
			}
		}

		// If we have system instruction, prepend it to first user message
		if ( !empty( $system_instruction ) && !empty( $contents ) ) {
			foreach ( $contents as $key => $content ) {
				if ( $content['role'] === 'user' ) {
					$contents[ $key ]['parts'][0]['text'] = $system_instruction . "\n\n" . $contents[ $key ]['parts'][0]['text'];
					break;
				}
			}
		}

		// Build request body matching your Angular code structure
		$body = array(
			'contents'         => $contents,
			'generationConfig' => array(
				'temperature'     => $temperature,
				'maxOutputTokens' => intval( $this->settings['max_tokens'] ?? 500 ),
			),
		);

		// Use correct URL format (no 'models/' prefix in URL path)
		$url = "https://generativelanguage.googleapis.com/v1beta/models/{$model}:generateContent";

		if ( $debug_mode ) {
			error_log( 'AICA: Calling Gemini API with model: ' . $model );
		}

		$response = wp_remote_post(
			$url,
			array(
				'headers' => array(
					'Content-Type'   => 'application/json',
					'x-goog-api-key' => $api_key,
				),
				'body'    => wp_json_encode( $body ),
				'timeout' => 30,
			)
		);

		if ( is_wp_error( $response ) ) {
			if ( $debug_mode ) {
				error_log( 'AICA: Gemini WP_Error: ' . $response->get_error_message() );
			}
			throw new Exception( esc_html( $response->get_error_message() ) );
		}

		$response_code = wp_remote_retrieve_response_code( $response );
		$body_response = json_decode( wp_remote_retrieve_body( $response ), true );

		if ( $response_code !== 200 ) {
			if ( $debug_mode ) {
				error_log( 'AICA: Gemini API HTTP ' . $response_code );
				error_log( 'AICA: Response: ' . print_r( $body_response, true ) );
			}
		}

		if ( isset( $body_response['error'] ) ) {
			$error_message = $body_response['error']['message'] ?? 'Unknown error';
			throw new Exception( esc_html( $error_message ) );
		}

		if ( !isset( $body_response['candidates'][0]['content']['parts'][0]['text'] ) ) {
			if ( $debug_mode ) {
				error_log( 'AICA: Unexpected response: ' . print_r( $body_response, true ) );
			}
			throw new Exception( 'Unexpected response format from Gemini API' );
		}

		$response_text = $body_response['candidates'][0]['content']['parts'][0]['text'];

		return $response_text;
	}

	/**
	 * Call OpenRouter API
	 *
	 * @param array $messages Messages array
	 * @return string Response text
	 * @throws Exception
	 */
	private function call_openrouter( $messages ) {
		$api_key = $this->settings['openrouter_api_key'] ?? '';
		if ( empty( $api_key ) ) {
			throw new Exception( esc_html__( 'OpenRouter API key not configured', 'aica-smart-ai-commerce-assistant' ) );
		}

		$model       = $this->settings['openrouter_model'] ?? 'anthropic/claude-3.5-sonnet';
		$temperature = floatval( $this->settings['temperature'] ?? 0.7 );
		$max_tokens  = intval( $this->settings['max_tokens'] ?? 500 );

		$response = wp_remote_post(
			'https://openrouter.ai/api/v1/chat/completions',
			array(
				'headers' => array(
					'Authorization' => 'Bearer ' . $api_key,
					'Content-Type'  => 'application/json',
					'HTTP-Referer'  => home_url(),
				),
				'body'    => wp_json_encode(
					array(
						'model'       => $model,
						'messages'    => $messages,
						'temperature' => $temperature,
						'max_tokens'  => $max_tokens,
					)
				),
				'timeout' => 30,
			)
		);

		if ( is_wp_error( $response ) ) {
			throw new Exception( esc_html( $response->get_error_message() ) );
		}

		$body = json_decode( wp_remote_retrieve_body( $response ), true );

		if ( isset( $body['error'] ) ) {
			throw new Exception( esc_html( $body['error']['message'] ) );
		}

		return $body['choices'][0]['message']['content'] ?? '';
	}

	/**
	 * Parse AI response for structured data
	 *
	 * @param string $response AI response text
	 * @param array  $available_products Available products
	 * @return array Parsed response
	 */
	private function parse_ai_response( $response, $available_products ) {
		$result = array(
			'message'  => $response,
			'products' => array(),
			'actions'  => array(),
		);

		// Check for ADD_TO_CART command
		if ( preg_match( '/ADD_TO_CART:(\d+)/', $response, $matches ) ) {
			$result['actions'][] = array(
				'type'       => 'add_to_cart',
				'product_id' => intval( $matches[1] ),
			);
			// Remove command from message
			$result['message'] = trim( str_replace( $matches[0], '', $response ) );
		}

		// Check if products are mentioned
		foreach ( $available_products as $product ) {
			if ( stripos( $response, (string) $product['id'] ) !== false ||
				stripos( $response, $product['name'] ) !== false ) {
				$result['products'][] = $product;
			}
		}

		return $result;
	}
}