<?php
/**
 * Translation engine for the AI Translator plugin.
 *
 * Wraps the WordPress AI client (https://github.com/WordPress/ai) so the rest of the
 * plugin does not need to know which AI provider is configured.
 *
 * @package ROBOTSTXT\AI_Translator
 * @since   1.0.0
 */

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

if ( ! class_exists( 'AI_Translator_Translator' ) ) {

	/**
	 * Talks to the WordPress AI client to translate strings.
	 *
	 * @since 1.0.0
	 */
	class AI_Translator_Translator {

		/**
		 * Settings handler.
		 *
		 * @since 1.2.0
		 * @var AI_Translator_Settings
		 */
		private $settings;

		/**
		 * Timeout value (seconds) enforced during an active translate() call.
		 * Null when no call is in progress.
		 *
		 * @since 1.2.0
		 * @var int|null
		 */
		private $active_timeout = null;

		/**
		 * Constructor.
		 *
		 * @since 1.2.0
		 *
		 * @param AI_Translator_Settings $settings Settings handler.
		 */
		public function __construct( AI_Translator_Settings $settings ) {
			$this->settings = $settings;
		}

		/**
		 * Filters the http_request_timeout value while an AI translation call is
		 * in progress. Registered and de-registered by translate() around each call.
		 *
		 * @since 1.2.0
		 *
		 * @param mixed $timeout Current timeout value passed by WordPress.
		 *
		 * @return int
		 */
		public function filter_timeout( $timeout ) {
			if ( null !== $this->active_timeout ) {
				return $this->active_timeout;
			}

			return is_numeric( $timeout ) ? (int) $timeout : 30;
		}

		/**
		 * Indicates whether AI features are enabled for this WordPress installation.
		 *
		 * `wp_ai_client_prompt()` is a native WordPress 7.0 function — the API is always
		 * present. This method checks `wp_supports_ai()`, which returns false only when the
		 * `WP_AI_SUPPORT` constant is set to false or the `wp_supports_ai` filter disables it.
		 *
		 * @since 1.0.0
		 *
		 * @return bool True when WordPress AI is enabled for this installation.
		 */
		public function is_available() {
			return wp_supports_ai();
		}

		/**
		 * Indicates whether the WordPress AI client supports text generation right now.
		 *
		 * The check uses a tiny dummy prompt so the AI client can answer whether at
		 * least one configured provider can serve text generation requests.
		 *
		 * @since 1.0.0
		 *
		 * @return bool True if text generation is supported.
		 */
		public function is_supported() {
			if ( ! $this->is_available() ) {
				return false;
			}

			try {
				$builder = wp_ai_client_prompt( 'test' );

				return (bool) $builder->is_supported_for_text_generation();
			} catch ( Exception $e ) {
				return false;
			} catch ( Throwable $e ) {
				return false;
			}
		}

		/**
		 * Translates a single piece of text to the target locale.
		 *
		 * Applies the configured request_timeout via the http_request_timeout filter
		 * for the duration of the AI call, then restores the previous timeout.
		 *
		 * @since 1.0.0
		 *
		 * @param string $text          Source text. Plain text or HTML; preserved as-is.
		 * @param string $target_locale WordPress locale code (for example: es_ES, en_US, fr_FR).
		 *
		 * @return string|WP_Error Translated text, or WP_Error on failure.
		 */
		public function translate( $text, $target_locale ) {
			$text = (string) $text;

			if ( '' === trim( $text ) ) {
				return '';
			}

			if ( ! $this->is_available() ) {
				return new WP_Error(
					'ai_translator_disabled',
					__( 'AI features are disabled for this WordPress installation.', 'robotstxt-ai-translator' )
				);
			}

			if ( ! $this->is_supported() ) {
				return new WP_Error(
					'ai_translator_unsupported',
					__( 'No AI provider is configured for text generation. Open Settings → AI to set one up.', 'robotstxt-ai-translator' )
				);
			}

			$language_name = $this->locale_to_language_name( $target_locale );

			if ( '' === $language_name ) {
				return new WP_Error(
					'ai_translator_invalid_locale',
					__( 'The target language is not installed on this site.', 'robotstxt-ai-translator' )
				);
			}

			$system_instruction = sprintf(
				/* translators: %s: target language name. */
				__( 'You are a professional translator. Translate the user message into %s. Preserve any HTML, shortcodes, line breaks, and Markdown exactly as they appear. Return only the translated text, without explanations, prefaces, or quotation marks.', 'robotstxt-ai-translator' ),
				$language_name
			);

			// Apply the configured request timeout around the AI call.
			$site_settings        = $this->settings->get_settings();
			$this->active_timeout = max( 30, (int) $site_settings['request_timeout'] );
			add_filter( 'http_request_timeout', array( $this, 'filter_timeout' ), PHP_INT_MAX );

			try {
				$result = wp_ai_client_prompt( $text )
					->using_system_instruction( $system_instruction )
					->generate_text();
			} catch ( Exception $e ) {
				$result = new WP_Error( 'ai_translator_exception', $e->getMessage() );
			} catch ( Throwable $e ) {
				$result = new WP_Error( 'ai_translator_exception', $e->getMessage() );
			}

			remove_filter( 'http_request_timeout', array( $this, 'filter_timeout' ), PHP_INT_MAX );
			$this->active_timeout = null;

			if ( is_wp_error( $result ) ) {
				return $result;
			}

			if ( ! is_string( $result ) ) {
				return new WP_Error(
					'ai_translator_invalid_response',
					__( 'The AI service returned an unexpected response.', 'robotstxt-ai-translator' )
				);
			}

			return trim( $result );
		}

		/**
		 * Converts a WordPress locale code into a human-readable language name.
		 *
		 * Only locales installed on the site (en_US plus any installed .po files) are
		 * accepted, so the editor cannot request translations to languages that the
		 * site has not declared as available.
		 *
		 * @since 1.0.0
		 *
		 * @param string $locale WordPress locale code.
		 *
		 * @return string Native language name, or empty string when the locale is not installed.
		 */
		public function locale_to_language_name( $locale ) {
			$locale = (string) $locale;

			if ( '' === $locale ) {
				return '';
			}

			$installed = $this->get_installed_locales();

			if ( ! in_array( $locale, $installed, true ) ) {
				return '';
			}

			if ( 'en_US' === $locale ) {
				return 'English (United States)';
			}

			if ( ! function_exists( 'wp_get_available_translations' ) ) {
				require_once ABSPATH . 'wp-admin/includes/translation-install.php';
			}

			if ( function_exists( 'wp_get_available_translations' ) ) {
				$translations = wp_get_available_translations();
				if ( isset( $translations[ $locale ]['native_name'] ) && '' !== $translations[ $locale ]['native_name'] ) {
					return (string) $translations[ $locale ]['native_name'];
				}
				if ( isset( $translations[ $locale ]['english_name'] ) && '' !== $translations[ $locale ]['english_name'] ) {
					return (string) $translations[ $locale ]['english_name'];
				}
			}

			return $locale;
		}

		/**
		 * Returns the locales installed on the site, including en_US.
		 *
		 * @since 1.0.0
		 *
		 * @return array<int,string> List of locale codes.
		 */
		public function get_installed_locales() {
			$locales = array( 'en_US' );

			if ( function_exists( 'get_available_languages' ) ) {
				$installed = get_available_languages();
				if ( is_array( $installed ) ) {
					foreach ( $installed as $locale ) {
						$locales[] = (string) $locale;
					}
				}
			}

			return array_values( array_unique( $locales ) );
		}
	}
}