<?php
namespace PluginMagnet\AIStockPredictor\Api;

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

/**
 * AI Integration Class
 *
 * @package PluginMagnet\AIStockPredictor\Api
 */
class API {
	/**
	 * Constructor
	 *
	 * @since 1.0.0
	 * @return void
	 */
	public function __construct() {
		// Initialize any required properties
	}

	/**
	 * Generate prediction using AI
	 *
	 * @param array $data Product data for prediction.
	 *
	 * @since 1.0.0
	 * @return array|\WP_Error
	 */
	public function generate_prediction( $data ) {
		$settings = get_option( 'aistpr_api_settings', array() );
		$provider = isset( $settings['ai_provider'] ) ? $settings['ai_provider'] : 'openai';

		// Validate required data.
		if ( empty( $data['current_stock'] ) || ! isset( $data['sales_velocity'] ) ) {
			return new \WP_Error( 'invalid_data', __( 'Missing required product data', 'ai-stock-predictor' ) );
		}

		if ( 'openai' === $provider ) {
			return $this->predict_with_openai( $data );
		} else {
			return $this->predict_with_deepseek( $data );
		}
	}

	/**
	 * Generate prediction using OpenAI
	 *
	 * @param array $data Product data for prediction.
	 *
	 * @since 1.0.0
	 * @return array|\WP_Error
	 */
	private function predict_with_openai( $data ) {

		$settings = get_option( 'aistpr_api_settings', array() );
		$api_key  = isset( $settings['openai_api_key'] ) ? $settings['openai_api_key'] : '';

		if ( empty( $api_key ) ) {
			return new \WP_Error( 'missing_api_key', __( 'OpenAI API key is not configured', 'ai-stock-predictor' ) );
		}

		$prompt = $this->prepare_ai_prompt( $data );

		$request_body = array(
			'model'       => 'gpt-3.5-turbo',
			'messages'    => array(
				array(
					'role'    => 'system',
					'content' => 'You are a helpful assistant that predicts when products will go out of stock based on sales data and current inventory levels. Respond in JSON format only with "stockout_date" (YYYY-MM-DD) and "risk_level" (High/Medium/Low).',
				),
				array(
					'role'    => 'user',
					'content' => $prompt,
				),
			),
			'temperature' => 0.3,
			'max_tokens'  => 150,
		);

		$args = array(
			'headers' => array(
				'Content-Type'  => 'application/json',
				'Authorization' => 'Bearer ' . $api_key,
			),
			'body'    => wp_json_encode( $request_body ),
			'timeout' => 30,
		);

		$response = wp_remote_post( 'https://api.openai.com/v1/chat/completions', $args );

		return $this->process_ai_response( $response, 'openai' );
	}

	/**
	 * Generate prediction using DeepSeek
	 *
	 * @param array $data Product data for prediction.
	 *
	 * @since 1.0.0
	 * @return array|\WP_Error
	 */
	private function predict_with_deepseek( $data ) {
		$settings = get_option( 'aistpr_api_settings', array() );
		$api_key  = isset( $settings['deepseek_api_key'] ) ? $settings['deepseek_api_key'] : '';

		if ( empty( $api_key ) ) {
			return new \WP_Error( 'missing_api_key', __( 'DeepSeek API key is not configured', 'ai-stock-predictor' ) );
		}

		$prompt = $this->prepare_ai_prompt( $data );

		$args = array(
			'headers' => array(
				'Content-Type'  => 'application/json',
				'Authorization' => 'Bearer ' . $api_key,
			),
			'body'    => wp_json_encode(
				array(
					'model'       => 'deepseek-chat',
					'messages'    => array(
						array(
							'role'    => 'system',
							'content' => 'You are a helpful assistant that predicts when products will go out of stock based on sales data and current inventory levels. Respond in JSON format only with "stockout_date" (YYYY-MM-DD) and "risk_level" (High/Medium/Low).',
						),
						array(
							'role'    => 'user',
							'content' => $prompt,
						),
					),
					'temperature' => 0.3,
					'max_tokens'  => 150,
				)
			),
			'timeout' => 30,
		);

		$response = wp_remote_post( 'https://api.deepseek.com/v1/chat/completions', $args );

		return $this->process_ai_response( $response, 'deepseek' );
	}

	/**
	 * Prepare AI prompt with product data
	 *
	 * @param array $data Product data.
	 *
	 * @since 1.0.0
	 * @return string
	 */
	private function prepare_ai_prompt( $data ) {
		$today = gmdate( 'Y-m-d' );

		$prompt  = "Today's date: {$today}\n\n";
		$prompt .= "Product Data:\n";
		$prompt .= "- Sales velocity (30 days): {$data['sales_velocity']['30']} units per day\n";
		$prompt .= "- Sales velocity (60 days): {$data['sales_velocity']['60']} units per day\n";
		$prompt .= "- Sales velocity (90 days): {$data['sales_velocity']['90']} units per day\n";
		$prompt .= "- Current stock level: {$data['current_stock']} units\n";

		if ( ! empty( $data['lead_time'] ) ) {
			$prompt .= "- Lead time for restocking: {$data['lead_time']} days\n";
		}

		$prompt .= "\nBased on this data, predict:
1. When will this product go out of stock (provide date in YYYY-MM-DD format)?
2. What is the risk level of stockout (High/Medium/Low)?

For risk assessment use these guidelines:
- High: Will run out of stock within 14 days
- Medium: Will run out of stock within 15-30 days
- Low: Has stock for more than 30 days

Return your answer in JSON format only:
{
  \"stockout_date\": \"YYYY-MM-DD\",
  \"risk_level\": \"High/Medium/Low\"
}";

		return $prompt;
	}

	/**
	 * Process AI API response
	 *
	 * @param array|\WP_Error $response API response.
	 * @param string          $provider API provider (openai or deepseek).
	 *
	 * @since 1.0.0
	 * @return array|\WP_Error
	 */
	private function process_ai_response( $response, $provider ) {
		if ( is_wp_error( $response ) ) {
			return $response;
		}

		$response_code = wp_remote_retrieve_response_code( $response );
		if ( 200 !== $response_code ) {
			$body          = wp_remote_retrieve_body( $response );
			$error_message = ! empty( $body ) ? $body : "API error: HTTP {$response_code}";
			return new \WP_Error( 'api_error', $error_message );
		}

		$body = json_decode( wp_remote_retrieve_body( $response ), true );

		$content = '';
		if ( 'openai' === $provider ) {
			if ( isset( $body['choices'][0]['message']['content'] ) ) {
				$content = $body['choices'][0]['message']['content'];
			}
		} elseif ( isset( $body['choices'][0]['message']['content'] ) ) {
			$content = $body['choices'][0]['message']['content'];
		}

		if ( empty( $content ) ) {
			return new \WP_Error( 'invalid_response', __( 'Invalid response from AI service', 'ai-stock-predictor' ) );
		}

		$json_matches = array();
		preg_match( '/\{.*\}/s', $content, $json_matches );

		if ( empty( $json_matches ) ) {
			return new \WP_Error( 'invalid_format', __( 'Could not extract JSON from AI response', 'ai-stock-predictor' ) );
		}

		$prediction = json_decode( $json_matches[0], true );

		if ( ! isset( $prediction['stockout_date'] ) || ! isset( $prediction['risk_level'] ) ) {
			return new \WP_Error( 'missing_data', __( 'Required prediction data is missing', 'ai-stock-predictor' ) );
		}

		return array(
			'stockout_date' => sanitize_text_field( $prediction['stockout_date'] ),
			'risk_level'    => sanitize_text_field( $prediction['risk_level'] ),
		);
	}

	/**
	 * Calculate a simple prediction fallback without AI
	 * Used when AI fails or is not configured
	 *
	 * @param array $data Product data.
	 *
	 * @since 1.0.0
	 * @return array
	 */
	public function generate_fallback_prediction( $data ) {
		$daily_sales = $data['sales_velocity']['30'];

		if ( $daily_sales <= 0 ) {
			$daily_sales = $data['sales_velocity']['60'];
		}

		if ( $daily_sales <= 0 ) {
			$daily_sales = $data['sales_velocity']['90'];
		}

		if ( $daily_sales <= 0 ) {
			$daily_sales = 0.01;
		}

		$days_until_stockout = $data['current_stock'] / $daily_sales;

		$stockout_timestamp = strtotime( "+{$days_until_stockout} days" );
		$stockout_date      = gmdate( 'Y-m-d', $stockout_timestamp );

		$risk_level = 'Low';
		if ( $days_until_stockout <= 14 ) {
			$risk_level = 'High';
		} elseif ( $days_until_stockout <= 30 ) {
			$risk_level = 'Medium';
		}

		return array(
			'stockout_date' => $stockout_date,
			'risk_level'    => $risk_level,
		);
	}
}