<?php
/**
 * TDM Reservation Protocol.
 *
 * @package AIBlackout
 */

namespace AIBlackout\Declarations;

use AIBlackout\Core\Settings;

defined( 'ABSPATH' ) || exit;

/**
 * Publishes a machine-readable reservation of text-and-data-mining rights.
 *
 * @since 1.0.0
 */
class Tdmrep {

	/**
	 * Query variable used to serve the well-known file.
	 *
	 * @var string
	 */
	const QUERY_VAR = 'aiblackout_tdmrep';

	/**
	 * Path the well-known file is served from.
	 *
	 * @var string
	 */
	const PATH = '.well-known/tdmrep.json';

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

	/**
	 * 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_action( 'init', array( $this, 'add_rewrite_rule' ) );
		add_filter( 'query_vars', array( $this, 'add_query_var' ) );
		add_action( 'parse_request', array( $this, 'maybe_serve' ) );
		add_action( 'wp_head', array( $this, 'print_meta' ), 1 );
		add_filter( 'wp_headers', array( $this, 'add_headers' ) );
	}

	/**
	 * Whether the reservation is switched on.
	 *
	 * @return bool True when rights are reserved.
	 */
	public function is_enabled(): bool {
		return ! aiblackout_is_disabled() && (bool) $this->settings->get_declaration( 'tdm_reservation', false );
	}

	/**
	 * Returns the configured TDM policy URL.
	 *
	 * @return string Policy URL, or an empty string when none is set.
	 */
	public function get_policy_url(): string {
		$url = (string) $this->settings->get_declaration( 'tdm_policy_url', '' );

		return '' !== $url ? esc_url_raw( $url ) : '';
	}

	/**
	 * Adds the rewrite rule for the well-known file.
	 *
	 * @return void
	 */
	public function add_rewrite_rule(): void {
		add_rewrite_rule(
			'^\.well-known/tdmrep\.json$',
			'index.php?' . self::QUERY_VAR . '=1',
			'top'
		);
	}

	/**
	 * Registers the query variable.
	 *
	 * @param array $vars Registered query variables.
	 * @return array Filtered query variables.
	 */
	public function add_query_var( $vars ): array {
		$vars   = is_array( $vars ) ? $vars : array();
		$vars[] = self::QUERY_VAR;

		return $vars;
	}

	/**
	 * Serves the well-known file when it is requested.
	 *
	 * @param \WP $wp Current WordPress environment.
	 * @return void
	 */
	public function maybe_serve( $wp ): void {
		$requested = isset( $wp->query_vars[ self::QUERY_VAR ] );

		if ( ! $requested && ! $this->is_tdmrep_request() ) {
			return;
		}

		if ( ! $this->is_enabled() ) {
			status_header( 404 );
			nocache_headers();
			exit;
		}

		status_header( 200 );
		header( 'Content-Type: application/json; charset=utf-8' );
		header( 'X-Robots-Tag: noindex' );

		echo wp_json_encode( $this->build_document(), JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES );
		exit;
	}

	/**
	 * Whether the current request is for the well-known file.
	 *
	 * @return bool True when the path matches.
	 */
	private function is_tdmrep_request(): bool {
		if ( empty( $_SERVER['REQUEST_URI'] ) ) {
			return false;
		}

		$uri  = sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) );
		$path = (string) wp_parse_url( $uri, PHP_URL_PATH );

		if ( '' === $path ) {
			return false;
		}

		$expected = (string) wp_parse_url( $this->get_url(), PHP_URL_PATH );

		return '' !== $expected && untrailingslashit( $path ) === untrailingslashit( $expected );
	}

	/**
	 * Returns the URL the well-known file is published at.
	 *
	 * @return string Absolute URL.
	 */
	public function get_url(): string {
		return home_url( '/' . self::PATH );
	}

	/**
	 * Builds the tdmrep.json document.
	 *
	 * @return array The document, ready to encode.
	 */
	public function build_document(): array {
		$entry = array(
			'location'        => '/',

			'tdm-reservation' => 1,
		);

		$policy = $this->get_policy_url();

		if ( '' !== $policy ) {
			$entry['tdm-policy'] = $policy;
		}

		return array( $entry );
	}

	/**
	 * Returns the document as it would be served.
	 *
	 * @return string JSON, or an empty string when the reservation is off.
	 */
	public function preview(): string {
		if ( ! $this->is_enabled() ) {
			return '';
		}

		return (string) wp_json_encode( $this->build_document(), JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES );
	}

	/**
	 * Prints the meta tags on front-end pages.
	 *
	 * @return void
	 */
	public function print_meta(): void {
		if ( ! $this->is_enabled() || is_admin() ) {
			return;
		}

		echo '<meta name="tdm-reservation" content="1" />' . "\n";

		$policy = $this->get_policy_url();

		if ( '' !== $policy ) {
			printf( '<meta name="tdm-policy" content="%s" />' . "\n", esc_url( $policy ) );
		}
	}

	/**
	 * Adds the HTTP headers 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();

		if ( ! $this->is_enabled() || is_admin() ) {
			return $headers;
		}

		$headers['tdm-reservation'] = '1';

		$policy = $this->get_policy_url();

		if ( '' !== $policy ) {
			$headers['tdm-policy'] = $policy;
		}

		return $headers;
	}

	/**
	 * Records the current declaration in the history log.
	 *
	 * @return void
	 */
	public function record(): void {
		if ( ! $this->is_enabled() ) {
			$this->history->record(
				self::TYPE,
				__( 'Text and data mining reservation withdrawn.', 'ai-blackout' ),
				array( 'tdm-reservation' => 0 )
			);

			return;
		}

		$this->history->record(
			self::TYPE,
			__( 'Reserved text and data mining rights site-wide under EU Directive 2019/790 Article 4.', 'ai-blackout' ),
			$this->build_document()
		);
	}
}