<?php
namespace Rafgrid;

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

/**
 * AI text generation.
 *
 * Primary path: the WordPress AI Client (WordPress 7.0+), using whichever
 * provider the site owner configured for the whole site. Fallback, only when
 * the AI Client is unavailable or has no provider: an OpenAI-compatible
 * endpoint that an administrator entered in Settings together with their own
 * key. Nothing is sent anywhere when neither is configured.
 */
class AI {

	/**
	 * Generate text for a task. Returns text or WP_Error.
	 *
	 * @param string $task    description|seo_title|seo_desc.
	 * @param int    $post_id Post ID.
	 * @return string|\WP_Error
	 */
	public static function generate( string $task, int $post_id ) {
		$post = get_post( $post_id );
		if ( ! $post ) {
			return new \WP_Error( 'rafgrid_not_found', __( 'Post not found.', 'rafgrid' ) );
		}
		$prompts = array(
			'description' => 'Write a short, clear product/content description (2-3 sentences, no fluff) for: ',
			'seo_title'   => 'Write one SEO title, max 55 chars, no quotes, for: ',
			'seo_desc'    => 'Write one meta description, max 155 chars, no quotes, for: ',
		);
		$prompt = ( $prompts[ $task ] ?? $prompts['description'] ) . $post->post_title . '. ' . wp_trim_words( wp_strip_all_tags( $post->post_content ), 60 );

		if ( self::core_available() ) {
			$text = wp_ai_client_prompt( $prompt )->generate_text();
			if ( ! is_wp_error( $text ) || ! self::fallback_configured() ) {
				return self::clean( $text );
			}
		}
		if ( self::fallback_configured() ) {
			return self::clean( self::fallback( $prompt ) );
		}
		return new \WP_Error( 'rafgrid_no_ai', __( 'No AI provider is configured. Set one up in the WordPress AI settings, or enter a fallback AI connection in Rafgrid settings.', 'rafgrid' ) );
	}

	/**
	 * Is the WordPress AI Client present, allowed and able to generate text?
	 *
	 * @return bool
	 */
	public static function core_available(): bool {
		if ( ! function_exists( 'wp_ai_client_prompt' ) || ( function_exists( 'wp_supports_ai' ) && ! wp_supports_ai() ) ) {
			return false;
		}
		return (bool) wp_ai_client_prompt( 'ping' )->is_supported_for_text_generation();
	}

	/**
	 * Did an administrator enter a fallback OpenAI-compatible connection?
	 *
	 * @return bool
	 */
	public static function fallback_configured(): bool {
		$settings = new Settings();
		return '' !== (string) $settings->get( 'ai_api_key', '' ) && '' !== (string) $settings->get( 'ai_base_url', '' ) && '' !== (string) $settings->get( 'ai_model', '' );
	}

	/**
	 * Fallback: chat completions on the administrator's own endpoint and key.
	 *
	 * @param string $prompt Prompt.
	 * @return string|\WP_Error
	 */
	private static function fallback( string $prompt ) {
		$settings = new Settings();
		$base     = untrailingslashit( (string) $settings->get( 'ai_base_url', '' ) );
		$valid    = Security::validate_outbound_url( $base );
		if ( is_wp_error( $valid ) ) {
			return $valid;
		}
		$res = wp_remote_post(
			$base . '/chat/completions',
			array(
				'timeout' => 45,
				'headers' => array(
					'Authorization' => 'Bearer ' . (string) $settings->get( 'ai_api_key', '' ),
					'Content-Type'  => 'application/json',
				),
				'body'    => wp_json_encode(
					array(
						'model'    => (string) $settings->get( 'ai_model', '' ),
						'messages' => array( array( 'role' => 'user', 'content' => $prompt ) ),
					)
				),
			)
		);
		if ( is_wp_error( $res ) ) {
			return $res;
		}
		$data = json_decode( (string) wp_remote_retrieve_body( $res ), true );
		return (string) ( $data['choices'][0]['message']['content'] ?? '' );
	}

	/**
	 * Normalize a generation result.
	 *
	 * @param string|\WP_Error $text Text.
	 * @return string|\WP_Error
	 */
	private static function clean( $text ) {
		if ( is_wp_error( $text ) ) {
			return $text;
		}
		if ( '' === trim( (string) $text ) ) {
			return new \WP_Error( 'rafgrid_ai_empty', __( 'AI returned an empty answer.', 'rafgrid' ) );
		}
		return trim( (string) $text );
	}
}