<?php
/**
 * Makes the files on disk match the settings.
 *
 * @package AIBlackout
 */

namespace AIBlackout\Enforcement;

use AIBlackout\Crawlers\Policy;

defined( 'ABSPATH' ) || exit;

/**
 * Writes every enforcement layer this server can take, from one call.
 *
 * @since 2.0.0
 */
class Publisher {

	/**
	 * Policy resolver.
	 *
	 * @var Policy
	 */
	private $policy;

	/**
	 * The .htaccess layer.
	 *
	 * @var Htaccess
	 */
	private $htaccess;

	/**
	 * The robots.txt layer.
	 *
	 * @var RobotsTxt
	 */
	private $robots;

	/**
	 * Constructor.
	 *
	 * @param Policy    $policy   Policy resolver.
	 * @param Htaccess  $htaccess The .htaccess layer.
	 * @param RobotsTxt $robots   The robots.txt layer.
	 */
	public function __construct( Policy $policy, Htaccess $htaccess, RobotsTxt $robots ) {
		$this->policy   = $policy;
		$this->htaccess = $htaccess;
		$this->robots   = $robots;
	}

	/**
	 * Publishes only when the files have fallen out of step with the settings.
	 *
	 * @return string[] Messages for anything that could not be written.
	 */
	public function sync(): array {
		return $this->is_in_step() ? array() : $this->publish();
	}

	/**
	 * Whether both files already say what the settings say.
	 *
	 * @return bool True when there is nothing to write.
	 */
	private function is_in_step(): bool {
		if ( $this->htaccess->is_available() && $this->htaccess->knows_site_root() ) {
			$wanted = ! empty( $this->policy->agents_to_enforce() );

			if ( $wanted !== $this->htaccess->is_applied() || $this->htaccess->is_stale() ) {
				return false;
			}
		}

		if ( $this->robots->has_physical_file() ) {
			if ( ( '' !== $this->robots->build_block() ) !== $this->robots->physical_file_has_block() ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * Brings both files into line with the current policy.
	 *
	 * @return string[] Messages for anything that could not be written.
	 */
	public function publish(): array {
		$errors = array();

		$this->publish_htaccess( $errors );
		$this->publish_robots( $errors );

		return $errors;
	}

	/**
	 * Writes, updates or removes the .htaccess block.
	 *
	 * @param string[] $errors Collected failures, appended to.
	 * @return void
	 */
	private function publish_htaccess( array &$errors ): void {
		if ( ! $this->htaccess->is_available() || ! $this->htaccess->knows_site_root() ) {
			return;
		}

		if ( empty( $this->policy->agents_to_enforce() ) ) {
			if ( $this->htaccess->is_applied() ) {
				$this->collect( $this->htaccess->revert(), $errors );
			}

			return;
		}

		$this->collect( $this->htaccess->apply(), $errors );
	}

	/**
	 * Keeps a robots.txt file on disk in step with the rules.
	 *
	 * @param string[] $errors Collected failures, appended to.
	 * @return void
	 */
	private function publish_robots( array &$errors ): void {
		if ( ! $this->robots->has_physical_file() ) {
			return;
		}

		if ( '' === $this->robots->build_block() ) {
			if ( $this->robots->physical_file_has_block() ) {
				$this->collect( $this->robots->revert_physical_file(), $errors );
			}

			return;
		}

		$this->collect( $this->robots->merge_into_physical_file(), $errors );
	}

	/**
	 * Records a layer's failure message, if it failed.
	 *
	 * @param mixed    $result Return value from an apply or revert.
	 * @param string[] $errors Collected failures, appended to.
	 * @return void
	 */
	private function collect( $result, array &$errors ): void {
		if ( is_wp_error( $result ) ) {
			$errors[] = $result->get_error_message();
		}
	}
}