<?php
/**
 * The noai and noimageai directives.
 *
 * @package AIBlackout
 */

namespace AIBlackout\Declarations;

use AIBlackout\Core\Settings;

defined( 'ABSPATH' ) || exit;

/**
 * Emits the `noai` and `noimageai` directives.
 *
 * @since 1.0.0
 */
class MetaTags {

	/**
	 * Declaration type recorded in history.
	 *
	 * @var string
	 */
	const TYPE = 'noai';

	/**
	 * Plugin settings.
	 *
	 * @var Settings
	 */
	private $settings;

	/**
	 * Declaration history.
	 *
	 * @var History
	 */
	private $history;

	/**
	 * Constructor.
	 *
	 * @param Settings $settings Plugin settings.
	 * @param History  $history  Declaration history.
	 */
	public function __construct( Settings $settings, History $history ) {
		$this->settings = $settings;
		$this->history  = $history;
	}

	/**
	 * Registers hooks.
	 *
	 * @return void
	 */
	public function register(): void {
		add_filter( 'wp_robots', array( $this, 'add_robots' ), PHP_INT_MAX );
		add_filter( 'wp_headers', array( $this, 'add_headers' ) );
	}

	/**
	 * Returns the directives that are switched on.
	 *
	 * @return string[] Directive tokens.
	 */
	public function get_directives(): array {
		if ( aiblackout_is_disabled() ) {
			return array();
		}

		$directives = array();

		if ( $this->settings->get_declaration( 'noai', false ) ) {
			$directives[] = 'noai';
		}

		if ( $this->settings->get_declaration( 'noimageai', false ) ) {
			$directives[] = 'noimageai';
		}

		return $directives;
	}

	/**
	 * Whether anything is being declared.
	 *
	 * @return bool True when at least one directive is on.
	 */
	public function is_enabled(): bool {
		return ! empty( $this->get_directives() );
	}

	/**
	 * Adds the directives to the page's robots meta tag.
	 *
	 * @param array $robots Directives assembled so far, keyed by directive.
	 * @return array Filtered directives.
	 */
	public function add_robots( $robots ): array {
		$robots     = is_array( $robots ) ? $robots : array();
		$directives = $this->get_directives();

		if ( empty( $directives ) || is_admin() ) {
			return $robots;
		}

		foreach ( $directives as $directive ) {
			$robots[ $directive ] = true;
		}

		return $robots;
	}

	/**
	 * Adds the X-Robots-Tag header to front-end responses.
	 *
	 * @param array $headers Response headers.
	 * @return array Filtered headers.
	 */
	public function add_headers( $headers ): array {
		$headers    = is_array( $headers ) ? $headers : array();
		$directives = $this->get_directives();

		if ( empty( $directives ) || is_admin() ) {
			return $headers;
		}

		$existing = isset( $headers['X-Robots-Tag'] ) ? trim( (string) $headers['X-Robots-Tag'] ) : '';

		if ( '' !== $existing ) {
			$directives = array_merge( array( $existing ), $directives );
		}

		$headers['X-Robots-Tag'] = implode( ', ', $directives );

		return $headers;
	}

	/**
	 * Records the current declaration in the history log.
	 *
	 * @return void
	 */
	public function record(): void {
		$directives = $this->get_directives();

		$this->history->record(
			self::TYPE,
			empty( $directives )
				? __( 'noai and noimageai directives withdrawn.', 'ai-blackout' )
				: sprintf(
					/* translators: %s: Comma-separated directive names. */
					__( 'Publishing the %s directive(s) in page markup and HTTP headers.', 'ai-blackout' ),
					implode( ', ', $directives )
				),
			$directives
		);
	}
}