<?php
/**
 * Core AI Summary functionality.
 *
 * @package AI_Summary_Generator
 */

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * AI Summary Generator Core Class.
 *
 * Handles core functionality including AI API communication,
 * summary generation, storage, and retrieval.
 */
class AI_Summary_Generator_Core {

	/**
	 * Generate AI summary for a post
	 *
	 * @param int $post_id Post ID.
	 * @param int $max_retries Maximum number of retry attempts.
	 * @return bool Success status
	 */
	public static function generate_summary( $post_id, $max_retries = 3 ) {
		$post = get_post( $post_id );
		if ( ! $post ) {
			return false;
		}

		$api_url    = get_option( 'ai_summary_generator_api_url' );
		$api_token  = get_option( 'ai_summary_generator_api_token' );
		$model_name = get_option( 'ai_summary_generator_model_name' );
		$prompt     = get_option( 'ai_summary_generator_prompt' );

		if ( ! $api_url || ! $api_token || ! $model_name ) {
			return false;
		}

		$request_body = array(
			'messages'    => array(
				array(
					'role'    => 'system',
					'content' => $prompt,
				),
				array(
					'role'    => 'user',
					'content' => 'Title: ' . $post->post_title . "\n\nContent: " . $post->post_content,
				),
			),
			'temperature' => 1.0,
			'top_p'       => 1.0,
			'model'       => $model_name,
		);

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

		// Retry logic.
		for ( $attempt = 1; $attempt <= $max_retries; $attempt++ ) {
			$response = wp_remote_post( $api_url, $request_args );

			if ( ! is_wp_error( $response ) ) {
				$response_code = wp_remote_retrieve_response_code( $response );

				// Success response codes.
				if ( $response_code >= 200 && $response_code < 300 ) {
					$body    = wp_remote_retrieve_body( $response );
					$data    = json_decode( $body, true );
					$summary = $data['choices'][0]['message']['content'] ?? '';

					if ( ! empty( $summary ) ) {
						update_post_meta( $post_id, '_ai_summary_generator_summary', $summary );
						update_post_meta( $post_id, '_ai_summary_generator_last_modified', $post->post_modified );
						return true;
					}
				}

				// Rate limit or server error - retry with backoff.
				if ( 429 === $response_code || ( $response_code >= 500 && $response_code < 600 ) ) {
					if ( $attempt < $max_retries ) {
						// Exponential backoff: 1s, 2s, 4s.
						$delay = pow( 2, $attempt - 1 );
						sleep( $delay );
						continue;
					}
				}

				// Client error (4xx) - don't retry.
				if ( $response_code >= 400 && $response_code < 500 && 429 !== $response_code ) {
					break;
				}
			} else {
				// Network error - retry with backoff.
				if ( $attempt < $max_retries ) {
					$delay = pow( 2, $attempt - 1 );
					sleep( $delay );
					continue;
				}
			}
		}

		return false;
	}

	/**
	 * Clear AI summary for a post
	 *
	 * @param int $post_id Post ID.
	 * @return bool Success status
	 */
	public static function clear_summary( $post_id ) {
		delete_post_meta( $post_id, '_ai_summary_generator_summary' );
		delete_post_meta( $post_id, '_ai_summary_generator_last_modified' );
		return true;
	}

	/**
	 * Get AI summary for a post
	 *
	 * @param int $post_id Post ID.
	 * @return string|false Summary content or false if not found
	 */
	public static function get_summary( $post_id ) {
		return get_post_meta( $post_id, '_ai_summary_generator_summary', true );
	}

	/**
	 * Check if post has AI summary
	 *
	 * @param int $post_id Post ID.
	 * @return bool
	 */
	public static function has_summary( $post_id ) {
		$summary = self::get_summary( $post_id );
		return ! empty( $summary );
	}

	/**
	 * Check if summary needs regeneration based on post modification date
	 *
	 * @param int $post_id Post ID.
	 * @return bool True if summary needs regeneration
	 */
	public static function needs_regeneration( $post_id ) {
		$post = get_post( $post_id );
		if ( ! $post ) {
			return false;
		}

		$summary_last_modified = get_post_meta( $post_id, '_ai_summary_generator_last_modified', true );

		// If no last modified timestamp, summary needs regeneration.
		if ( empty( $summary_last_modified ) ) {
			return true;
		}

		// Compare post modification time with summary last modified time.
		return $post->post_modified !== $summary_last_modified;
	}
}