Feat[Experiment]: Add AI-Powered Content Translation

includes/Abilities/Content_Translation/Content_Translation.php

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+<?php
+/**
+ * Content translation WordPress Ability implementation.
+ *
+ * @package WordPress\AI
+ */
+
+declare( strict_types=1 );
+
+namespace WordPress\AI\Abilities\Content_Translation;
+
+use WP_Error;
+use WordPress\AI\Abstracts\Abstract_Ability;
+use WordPress\AI\Experiments\Content_Translation\Content_Translation as Content_Translation_Experiment;
+
+use function WordPress\AI\count_words;
+
+/**
+ * Content Translation WordPress Ability.
+ *
+ * @since x.x.x
+ */
+class Content_Translation extends Abstract_Ability {
+
+	/**
+	 * The minimum word count for translation.
+	 *
+	 * @since x.x.x
+	 *
+	 * @var int
+	 */
+	protected const MIN_WORDS = 1;
+
+	/**
+	 * {@inheritDoc}
+	 *
+	 * @since x.x.x
+	 */
+	protected function input_schema(): array {
+		return array(
+			'type'       => 'object',
+			'properties' => array(
+				'post_id'         => array(
+					'type'        => 'integer',
+					'description' => esc_html__( 'The ID of the post to translate content for.', 'ai' ),
+				),
+				'content'         => array(
+					'type'        => 'string',
+					'description' => esc_html__( 'The block content to translate.', 'ai' ),
+				),
+				'target_language' => array(
+					'type'        => 'string',
+					'enum'        => Languages::get_codes(),
+					'default'     => Languages::get_default_target_language(),
+					'description' => esc_html__( 'The target language for translation.', 'ai' ),
+				),
+			),
+		);
+	}
+
+	/**
+	 * {@inheritDoc}
+	 *
+	 * @since x.x.x
+	 */
+	protected function output_schema(): array {
+		return array(
+			'type'        => 'string',
+			'description' => esc_html__( 'The translated content.', 'ai' ),
+		);
+	}
+
+	/**
+	 * {@inheritDoc}
+	 *
+	 * @since x.x.x
+	 */
+	protected function execute_callback( $input ) {
+		// Default arguments for the translation process.
+		$args = wp_parse_args(
+			$input,
+			array(
+				'post_id'         => null,
+				'content'         => null,
+				'target_language' => Languages::get_default_target_language(),
+			)
+		);
+
+		// Skip normalization of content to retain HTML tags.
+		$content = $args['content'] ?? '';
+
+		if ( empty( $content ) ) {
+			return new WP_Error(
+				'content_not_provided',
+				esc_html__( 'No content provided for translation.', 'ai' )
+			);
+		}
+
+		if ( count_words( wp_strip_all_tags( $content ) ) < self::MIN_WORDS ) {
+			return new WP_Error(
+				'content_too_short',
+				sprintf(
+					/* translators: %d: minimum number of words required for translation */
+					esc_html__( 'A minimum of %d words is required for translation.', 'ai' ),
+					self::MIN_WORDS
+				)
+			);
+		}
+
+		$prompt = sprintf( '<content>%s</content>', $content );
+
+		// Validate the target language.
+		$target_language = sanitize_key( (string) $args['target_language'] );
+		$language        = Languages::get_language_name( $target_language );
+		if ( null === $language ) {
+			return new WP_Error(
+				'invalid_target_language',
+				esc_html__( 'The specified target language is not supported for translation.', 'ai' )
+			);
+		}
+
+		$result = $this->generate_translated_content( $prompt, $language );
+
+		if ( is_wp_error( $result ) ) {
+			return $result;
+		}
+
+		if ( empty( $result ) ) {
+			return new WP_Error(
+				'no_results',
+				esc_html__( 'No translated content was generated.', 'ai' )
+			);
+		}
+
+		return wp_kses_post( $result );
+	}
+
+	/**
+	 * {@inheritDoc}
+	 *
+	 * @since x.x.x
+	 */
+	protected function permission_callback( $args ) {
+		// Ensure the user has permission to edit the post if a post ID is provided.
+		if ( isset( $args['post_id'] ) ) {
+			$post_id = absint( $args['post_id'] );
+			$post    = get_post( $post_id );
+
+			if ( ! $post ) {
+				return new WP_Error(
+					'post_not_found',
+					sprintf(
+					/* translators: %d: post ID */
+						esc_html__( 'Post with ID %d not found.', 'ai' ),
+						$post_id
+					)
+				);
+			}
+
+			if ( ! current_user_can( 'edit_post', $post_id ) ) {
+				return new WP_Error(
+					'insufficient_permissions',
+					esc_html__( 'You do not have permission to edit this post.', 'ai' )
+				);
+			}
+		} elseif ( ! current_user_can( 'edit_posts' ) ) {
+			return new WP_Error(
+				'insufficient_permissions',
+				esc_html__( 'You do not have permission to translate content.', 'ai' )
+			);
+		}
+
+		return true;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 *
+	 * @since x.x.x
+	 */
+	protected function meta(): array {
+		return array(
+			'show_in_rest' => true,
+		);
+	}
+
+	/**
+	 * Generates translated content using the AI Client.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $prompt The prompt to use for the content translation.
+	 * @param string $language The target language for the translation.
+	 * @return string|\WP_Error The translated content, or a WP_Error if there was an error.
+	 */
+	protected function generate_translated_content( string $prompt, string $language ) {
+		$builder = $this->get_prompt_builder( $prompt, $language );
+
+		if ( is_wp_error( $builder ) ) {
+			return $builder;
+		}
+
+		return $builder->generate_text();
+	}
+
+	/**
+	 * Returns a prompt builder for content translation.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $prompt The prompt to build.
+	 * @param string $language The target language.
+	 * @return \WP_AI_Client_Prompt_Builder|\WP_Error The prompt builder, or a WP_Error if there isn't a model that supports text generation.
+	 */
+	private function get_prompt_builder( string $prompt, string $language ) {
+		$prompt_builder = wp_ai_client_prompt( $prompt )
+			->using_system_instruction(
+				$this->get_system_instruction(
+					'system-instruction.php',
+					array(
+						'target_language' => $language,
+					)
+				)
+			)
+			->using_temperature( 0.7 );
+
+		$prompt_builder = $this->set_provider_model_preference(
+			$prompt_builder,
+			Content_Translation_Experiment::class
+		);
+
+		return $this->ensure_text_generation_supported(
+			$prompt_builder,
+			esc_html__( 'Content translation failed. Please ensure you have a connected provider that supports text generation.', 'ai' )
+		);
+	}
+}

includes/Abilities/Content_Translation/Languages.php

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+<?php
+/**
+ * Supported languages for AI Content translation.
+ *
+ * @package WordPress\AI\Abilities\Content_Translation
+ */
+
+declare( strict_types=1 );
+
+namespace WordPress\AI\Abilities\Content_Translation;
+
+/**
+ * Class providing supported languages for AI content translation.
+ *
+ * @since x.x.x
+ */
+final class Languages {
+
+	/**
+	 * The default target language for translation.
+	 *
+	 * @since x.x.x
+	 *
+	 * @var string
+	 */
+	private const DEFAULT_TARGET_LANGUAGE = 'en-us';
+
+	/**
+	 * Returns the default target language for translation.
+	 *
+	 * @since x.x.x
+	 *
+	 * @return string The default target language code.
+	 */
+	public static function get_default_target_language(): string {
+		return self::DEFAULT_TARGET_LANGUAGE;
+	}
+
+	/**
+	 * Returns the supported languages for AI content translation.
+	 *
+	 * @since x.x.x
+	 *
+	 * @return array<string, string> Supported languages.
+	 */
+	public static function get_supported_languages(): array {
+		$languages = array(
+			'ar'    => __( 'Arabic', 'ai' ),
+			'zh-cn' => __( 'Chinese (Simplified)', 'ai' ),
+			'zh-tw' => __( 'Chinese (Traditional)', 'ai' ),
+			'nl-nl' => __( 'Dutch', 'ai' ),
+			'en-gb' => __( 'English (UK)', 'ai' ),
+			'en-us' => __( 'English (US)', 'ai' ),
+			'fr-fr' => __( 'French', 'ai' ),
+			'de-de' => __( 'German', 'ai' ),
+			'hi'    => __( 'Hindi', 'ai' ),
+			'it-it' => __( 'Italian', 'ai' ),
+			'ja'    => __( 'Japanese', 'ai' ),
+			'ko'    => __( 'Korean', 'ai' ),
+			'pt-br' => __( 'Portuguese (Brazil)', 'ai' ),
+			'es-es' => __( 'Spanish', 'ai' ),
+		);
+
+		/**
+		 * Filters supported target languages for AI content translation.
+		 *
+		 * @param array<string, string> $languages Supported languages.
+		 */
+		return (array) apply_filters( 'wpai_content_translation_languages', $languages );
+	}
+
+	/**
+	 * Returns the supported languages for AI content translation in a format suitable for JavaScript.
+	 *
+	 * @since x.x.x
+	 *
+	 * @return array<int, array{code: string, name: string}> Supported languages for JavaScript.
+	 */
+	public static function get_supported_languages_for_js(): array {
+		$languages = self::get_supported_languages();
+
+		return array_map(
+			static function ( string $code, string $name ): array {
+				return array(
+					'code' => $code,
+					'name' => $name,
+				);
+			},
+			array_keys( $languages ),
+			$languages
+		);
+	}
+
+	/**
+	 * Returns the name of a language given its code.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $language_code The language code.
+	 * @return string|null The name of the language, or null if not found.
+	 */
+	public static function get_language_name( string $language_code ): ?string {
+		$languages = self::get_supported_languages();
+
+		if ( array_key_exists( $language_code, $languages ) ) {
+			return $languages[ $language_code ];
+		}
+
+		return null;
+	}
+
+	/**
+	 * Returns the language codes of supported languages.
+	 *
+	 * @since x.x.x
+	 *
+	 * @return string[] Array of supported language codes.
+	 */
+	public static function get_codes(): array {
+		return array_keys( self::get_supported_languages() );
+	}
+
+	/**
+	 * Checks if a language is supported for translation.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param string $language_code The language code to check.
+	 * @return bool True if the language is supported, false otherwise.
+	 */
+	public static function is_supported( string $language_code ): bool {
+		return array_key_exists( $language_code, self::get_supported_languages() );
+	}
+}