<?php
/**
 * Keeps the object-cache.php drop-in in line with Redis settings.
 *
 * @package Akantio\Cache
 */

declare(strict_types=1);

namespace Akantio\Cache\Application\Environment;

use Akantio\Cache\Application\ObjectCache\RedisProbe;
use Akantio\Cache\Domain\Settings\Settings;

/**
 * The drop-in is only installed after a successful connection check, and data is flushed
 * when caching (re)starts so WordPress never reads values that went stale while it was off.
 */
final class ObjectCacheEnvironment implements EnvironmentSync {

	/**
	 * @var \Closure(Settings): array<string, mixed>
	 */
	private readonly \Closure $redis_config;

	/**
	 * @param DropinInstaller                          $dropin        object-cache.php.
	 * @param RedisProbe                               $probe         Connection check.
	 * @param string                                   $dropin_source Drop-in source.
	 * @param callable(Settings): array<string, mixed> $redis_config Compiles the runtime "redis" section.
	 */
	public function __construct(
		private readonly DropinInstaller $dropin,
		private readonly RedisProbe $probe,
		private readonly string $dropin_source,
		callable $redis_config,
	) {
		$this->redis_config = \Closure::fromCallable( $redis_config );
	}

	/**
	 * {@inheritDoc}
	 *
	 * @param Settings $settings        Settings.
	 * @param bool     $replace_foreign Replace a foreign drop-in.
	 */
	public function apply( Settings $settings, bool $replace_foreign = false ): array {
		if ( ! $settings->get( 'redis_enabled' ) ) {
			return $this->remove();
		}

		$config = ( $this->redis_config )( $settings );
		$result = $this->probe->check( $config );
		if ( ! $result->ok ) {
			$this->remove();
			return [ new Problem( 'redis_unavailable', 'Object cache is off because Redis is unreachable: ' . $result->message ) ];
		}

		$was_ours = DropinStatus::Ours === $this->dropin->status();
		try {
			$this->dropin->install( $this->dropin_source, $replace_foreign );
		} catch ( ForeignDropinException ) {
			return [ new Problem( 'object_cache_foreign', 'Another plugin owns wp-content/object-cache.php. Replace it to use the AKantio object cache.' ) ];
		} catch ( \Throwable ) {
			return [ new Problem( 'object_cache_unwritable', 'wp-content/object-cache.php could not be written. Check file permissions.' ) ];
		}

		if ( ! $was_ours ) {
			try {
				$this->probe->flush( $config );
			} catch ( \Throwable ) {
				return [ new Problem( 'redis_unavailable', 'The object cache was enabled but stale data could not be flushed. Flush it from the Redis screen.' ) ];
			}
		}

		return [];
	}

	/**
	 * {@inheritDoc}
	 */
	public function remove(): array {
		try {
			$this->dropin->uninstall();
		} catch ( \Throwable ) {
			return [ new Problem( 'object_cache_unwritable', 'wp-content/object-cache.php could not be removed.' ) ];
		}

		return [];
	}
}