<?php
/**
 * The scan's eyes in the browser.
 *
 * @package WorkMoreCookieCrumb
 */

namespace WorkMore\CookieCrumb\Scan;

/**
 * Prints the probe (src/public/probe.js) at the very start of `<head>` of a
 * page opened for a scan — through WordPress' script API, like the guard.
 * The probe watches what the page loads and stores, and tells the screen
 * that opened it; it is never part of a page a visitor gets.
 */
final class Probe {

	public const HANDLE = 'workmore-cookie-crumb-scan';

	/**
	 * One of Request::MODES.
	 *
	 * @var string
	 */
	private $mode;

	/**
	 * The page's place in the scan.
	 *
	 * @var int
	 */
	private $index;

	/**
	 * Absolute path to the plugin root, trailing slash.
	 *
	 * @var string
	 */
	private $base_dir;

	/**
	 * Constructor.
	 *
	 * @param string $mode     One of Request::MODES.
	 * @param int    $index    The page's place in the scan.
	 * @param string $base_dir Absolute plugin directory path.
	 */
	public function __construct( string $mode, int $index, string $base_dir = WMCC_PLUGIN_DIR ) {
		$this->mode     = $mode;
		$this->index    = $index;
		$this->base_dir = trailingslashit( $base_dir );
	}

	/**
	 * Attach hooks.
	 *
	 * @return void
	 */
	public function register(): void {
		add_action( 'wp_enqueue_scripts', array( $this, 'enqueue' ), 0 );
		// wp_enqueue_scripts runs at wp_head 1; right after it, and — being
		// registered first — before the guard.
		add_action( 'wp_head', array( $this, 'printNow' ), 2 );
	}

	/**
	 * Register the probe with what it has to know.
	 *
	 * @return void
	 */
	public function enqueue(): void {
		$probe = $this->base_dir . 'assets/probe.js';

		// A development checkout before `npm run build`: nothing to print.
		if ( ! is_readable( $probe ) ) {
			return;
		}

		$config = array(
			'mode'  => $this->mode,
			'index' => $this->index,
			// The arguments of the scan, for the probe to take out of the address.
			'strip' => array( Request::QUERY, Request::TOKEN, Request::INDEX, '_wpnonce' ),
		);

		wp_register_script( self::HANDLE, false, array(), WMCC_VERSION, false );
		wp_add_inline_script( self::HANDLE, 'window.wmccScanPage=' . (string) wp_json_encode( $config, JSON_HEX_TAG | JSON_HEX_AMP | JSON_HEX_APOS | JSON_HEX_QUOT ) . ';' . (string) file_get_contents( $probe ) ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents -- A local file of this plugin, read to print it inline.
	}

	/**
	 * Print the probe now, ahead of the head's other scripts.
	 *
	 * @return void
	 */
	public function printNow(): void {
		if ( wp_script_is( self::HANDLE, 'registered' ) ) {
			wp_scripts()->do_items( array( self::HANDLE ) );
		}
	}
}