<?php
/**
 * Storage factory for Prometheus metrics.
 *
 * @package WP_Prometheus
 */

namespace Magdev\WpPrometheus\Metrics;

use Prometheus\Storage\Adapter;
use Prometheus\Storage\InMemory;
use Prometheus\Storage\Redis;
use Prometheus\Storage\APC;
use Prometheus\Exception\StorageException;

// Prevent direct file access.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * StorageFactory class.
 *
 * Creates and configures storage adapters for Prometheus metrics.
 * Supports configuration via WordPress options or environment variables.
 */
class StorageFactory {

	/**
	 * Available storage adapters.
	 */
	public const ADAPTER_INMEMORY = 'inmemory';
	public const ADAPTER_REDIS    = 'redis';
	public const ADAPTER_APCU     = 'apcu';

	/**
	 * Environment variable names.
	 */
	private const ENV_STORAGE_ADAPTER  = 'WP_PROMETHEUS_STORAGE_ADAPTER';
	private const ENV_REDIS_HOST       = 'WP_PROMETHEUS_REDIS_HOST';
	private const ENV_REDIS_PORT       = 'WP_PROMETHEUS_REDIS_PORT';
	private const ENV_REDIS_PASSWORD   = 'WP_PROMETHEUS_REDIS_PASSWORD';
	private const ENV_REDIS_DATABASE   = 'WP_PROMETHEUS_REDIS_DATABASE';
	private const ENV_REDIS_PREFIX     = 'WP_PROMETHEUS_REDIS_PREFIX';
	private const ENV_APCU_PREFIX      = 'WP_PROMETHEUS_APCU_PREFIX';

	/**
	 * Default Redis prefix.
	 */
	private const DEFAULT_REDIS_PREFIX = 'WORDPRESS_PROMETHEUS_';

	/**
	 * Default APCu prefix.
	 */
	private const DEFAULT_APCU_PREFIX = 'wp_prom';

	/**
	 * Singleton instance of the storage adapter.
	 *
	 * @var Adapter|null
	 */
	private static ?Adapter $instance = null;

	/**
	 * Last error message.
	 *
	 * @var string
	 */
	private static string $last_error = '';

	/**
	 * Get the storage adapter instance.
	 *
	 * @return Adapter
	 */
	public static function get_adapter(): Adapter {
		if ( null === self::$instance ) {
			self::$instance = self::create_adapter();
		}
		return self::$instance;
	}

	/**
	 * Reset the singleton instance (useful for testing or config changes).
	 *
	 * @return void
	 */
	public static function reset(): void {
		self::$instance = null;
		self::$last_error = '';
	}

	/**
	 * Get the last error message.
	 *
	 * @return string
	 */
	public static function get_last_error(): string {
		return self::$last_error;
	}

	/**
	 * Get available storage adapters.
	 *
	 * @return array<string, string>
	 */
	public static function get_available_adapters(): array {
		return array(
			self::ADAPTER_INMEMORY => __( 'In-Memory (default, no persistence)', 'wp-prometheus' ),
			self::ADAPTER_REDIS    => __( 'Redis (requires PHP Redis extension)', 'wp-prometheus' ),
			self::ADAPTER_APCU     => __( 'APCu (requires APCu extension)', 'wp-prometheus' ),
		);
	}

	/**
	 * Check if a storage adapter is available on this system.
	 *
	 * @param string $adapter Adapter name.
	 * @return bool
	 */
	public static function is_adapter_available( string $adapter ): bool {
		switch ( $adapter ) {
			case self::ADAPTER_INMEMORY:
				return true;

			case self::ADAPTER_REDIS:
				return extension_loaded( 'redis' );

			case self::ADAPTER_APCU:
				return extension_loaded( 'apcu' ) && apcu_enabled();

			default:
				return false;
		}
	}

	/**
	 * Get the configured storage adapter name.
	 *
	 * @return string
	 */
	public static function get_configured_adapter(): string {
		// Check environment variable first.
		$env_adapter = getenv( self::ENV_STORAGE_ADAPTER );
		if ( false !== $env_adapter && ! empty( $env_adapter ) ) {
			return strtolower( $env_adapter );
		}

		// Fall back to WordPress option.
		return get_option( 'wp_prometheus_storage_adapter', self::ADAPTER_INMEMORY );
	}

	/**
	 * Get the active storage adapter name (may differ from configured if fallback occurred).
	 *
	 * @return string
	 */
	public static function get_active_adapter(): string {
		// Ensure adapter is created.
		self::get_adapter();

		$configured = self::get_configured_adapter();
		if ( self::is_adapter_available( $configured ) && empty( self::$last_error ) ) {
			return $configured;
		}

		return self::ADAPTER_INMEMORY;
	}

	/**
	 * Create the storage adapter based on configuration.
	 *
	 * @return Adapter
	 */
	private static function create_adapter(): Adapter {
		$adapter = self::get_configured_adapter();
		self::$last_error = '';

		switch ( $adapter ) {
			case self::ADAPTER_REDIS:
				return self::create_redis_adapter();

			case self::ADAPTER_APCU:
				return self::create_apcu_adapter();

			case self::ADAPTER_INMEMORY:
			default:
				return new InMemory();
		}
	}

	/**
	 * Create Redis storage adapter.
	 *
	 * @return Adapter
	 */
	private static function create_redis_adapter(): Adapter {
		if ( ! extension_loaded( 'redis' ) ) {
			self::$last_error = __( 'PHP Redis extension is not installed.', 'wp-prometheus' );
			return new InMemory();
		}

		$config = self::get_redis_config();

		try {
			Redis::setPrefix( $config['prefix'] );

			$redis = new Redis( array(
				'host'                   => $config['host'],
				'port'                   => $config['port'],
				'password'               => $config['password'] ?: null,
				'timeout'                => 0.5,
				'read_timeout'           => 10,
				'persistent_connections' => true,
			) );

			// Test connection by triggering initialization.
			// The Redis adapter connects lazily, so we need to check it works.
			return $redis;
		} catch ( StorageException $e ) {
			self::$last_error = sprintf(
				/* translators: %s: Error message */
				__( 'Redis connection failed: %s', 'wp-prometheus' ),
				$e->getMessage()
			);
			return new InMemory();
		} catch ( \RedisException $e ) {
			self::$last_error = sprintf(
				/* translators: %s: Error message */
				__( 'Redis error: %s', 'wp-prometheus' ),
				$e->getMessage()
			);
			return new InMemory();
		} catch ( \Exception $e ) {
			self::$last_error = sprintf(
				/* translators: %s: Error message */
				__( 'Storage error: %s', 'wp-prometheus' ),
				$e->getMessage()
			);
			return new InMemory();
		}
	}

	/**
	 * Create APCu storage adapter.
	 *
	 * @return Adapter
	 */
	private static function create_apcu_adapter(): Adapter {
		if ( ! extension_loaded( 'apcu' ) ) {
			self::$last_error = __( 'APCu extension is not installed.', 'wp-prometheus' );
			return new InMemory();
		}

		if ( ! apcu_enabled() ) {
			self::$last_error = __( 'APCu is installed but not enabled.', 'wp-prometheus' );
			return new InMemory();
		}

		$prefix = self::get_apcu_prefix();

		try {
			return new APC( $prefix );
		} catch ( StorageException $e ) {
			self::$last_error = sprintf(
				/* translators: %s: Error message */
				__( 'APCu error: %s', 'wp-prometheus' ),
				$e->getMessage()
			);
			return new InMemory();
		}
	}

	/**
	 * Get Redis configuration.
	 *
	 * @return array{host: string, port: int, password: string, database: int, prefix: string}
	 */
	public static function get_redis_config(): array {
		// Check environment variables first.
		$env_host = getenv( self::ENV_REDIS_HOST );
		$env_port = getenv( self::ENV_REDIS_PORT );
		$env_password = getenv( self::ENV_REDIS_PASSWORD );
		$env_database = getenv( self::ENV_REDIS_DATABASE );
		$env_prefix = getenv( self::ENV_REDIS_PREFIX );

		// Get WordPress options as fallback.
		$options = get_option( 'wp_prometheus_redis_config', array() );

		return array(
			'host'     => ( false !== $env_host && ! empty( $env_host ) ) ? $env_host : ( $options['host'] ?? '127.0.0.1' ),
			'port'     => ( false !== $env_port && ! empty( $env_port ) ) ? (int) $env_port : ( (int) ( $options['port'] ?? 6379 ) ),
			'password' => ( false !== $env_password ) ? $env_password : ( $options['password'] ?? '' ),
			'database' => ( false !== $env_database && ! empty( $env_database ) ) ? (int) $env_database : ( (int) ( $options['database'] ?? 0 ) ),
			'prefix'   => ( false !== $env_prefix && ! empty( $env_prefix ) ) ? $env_prefix : ( $options['prefix'] ?? self::DEFAULT_REDIS_PREFIX ),
		);
	}

	/**
	 * Get APCu prefix.
	 *
	 * @return string
	 */
	public static function get_apcu_prefix(): string {
		$env_prefix = getenv( self::ENV_APCU_PREFIX );
		if ( false !== $env_prefix && ! empty( $env_prefix ) ) {
			return $env_prefix;
		}

		return get_option( 'wp_prometheus_apcu_prefix', self::DEFAULT_APCU_PREFIX );
	}

	/**
	 * Save storage configuration.
	 *
	 * @param array $config Configuration array.
	 * @return void
	 */
	public static function save_config( array $config ): void {
		if ( isset( $config['adapter'] ) ) {
			update_option( 'wp_prometheus_storage_adapter', sanitize_key( $config['adapter'] ) );
		}

		if ( isset( $config['redis'] ) && is_array( $config['redis'] ) ) {
			$redis_config = array(
				'host'     => sanitize_text_field( $config['redis']['host'] ?? '127.0.0.1' ),
				'port'     => absint( $config['redis']['port'] ?? 6379 ),
				'password' => sanitize_text_field( $config['redis']['password'] ?? '' ),
				'database' => absint( $config['redis']['database'] ?? 0 ),
				'prefix'   => sanitize_key( $config['redis']['prefix'] ?? self::DEFAULT_REDIS_PREFIX ),
			);
			update_option( 'wp_prometheus_redis_config', $redis_config );
		}

		if ( isset( $config['apcu_prefix'] ) ) {
			update_option( 'wp_prometheus_apcu_prefix', sanitize_key( $config['apcu_prefix'] ) );
		}

		// Reset the singleton to apply new configuration.
		self::reset();
	}

	/**
	 * Test storage adapter connection.
	 *
	 * @param string $adapter Adapter name.
	 * @param array  $config  Optional configuration to test.
	 * @return array{success: bool, message: string}
	 */
	public static function test_connection( string $adapter, array $config = array() ): array {
		switch ( $adapter ) {
			case self::ADAPTER_REDIS:
				return self::test_redis_connection( $config );

			case self::ADAPTER_APCU:
				return self::test_apcu_connection( $config );

			case self::ADAPTER_INMEMORY:
				return array(
					'success' => true,
					'message' => __( 'In-Memory storage is always available.', 'wp-prometheus' ),
				);

			default:
				return array(
					'success' => false,
					'message' => __( 'Unknown storage adapter.', 'wp-prometheus' ),
				);
		}
	}

	/**
	 * Test Redis connection.
	 *
	 * @param array $config Redis configuration.
	 * @return array{success: bool, message: string}
	 */
	private static function test_redis_connection( array $config ): array {
		if ( ! extension_loaded( 'redis' ) ) {
			return array(
				'success' => false,
				'message' => __( 'PHP Redis extension is not installed.', 'wp-prometheus' ),
			);
		}

		$redis_config = ! empty( $config ) ? $config : self::get_redis_config();

		try {
			$redis = new \Redis();

			$connected = $redis->connect(
				$redis_config['host'],
				$redis_config['port'],
				0.5 // timeout
			);

			if ( ! $connected ) {
				return array(
					'success' => false,
					'message' => __( 'Could not connect to Redis server.', 'wp-prometheus' ),
				);
			}

			if ( ! empty( $redis_config['password'] ) ) {
				$authenticated = $redis->auth( $redis_config['password'] );
				if ( ! $authenticated ) {
					return array(
						'success' => false,
						'message' => __( 'Redis authentication failed.', 'wp-prometheus' ),
					);
				}
			}

			if ( $redis_config['database'] > 0 ) {
				$redis->select( $redis_config['database'] );
			}

			// Test with a ping.
			$pong = $redis->ping();
			$redis->close();

			if ( $pong ) {
				return array(
					'success' => true,
					'message' => sprintf(
						/* translators: %s: Redis host:port */
						__( 'Successfully connected to Redis at %s.', 'wp-prometheus' ),
						$redis_config['host'] . ':' . $redis_config['port']
					),
				);
			}

			return array(
				'success' => false,
				'message' => __( 'Redis ping failed.', 'wp-prometheus' ),
			);
		} catch ( \RedisException $e ) {
			return array(
				'success' => false,
				'message' => sprintf(
					/* translators: %s: Error message */
					__( 'Redis error: %s', 'wp-prometheus' ),
					$e->getMessage()
				),
			);
		}
	}

	/**
	 * Test APCu connection.
	 *
	 * @param array $config APCu configuration.
	 * @return array{success: bool, message: string}
	 */
	private static function test_apcu_connection( array $config ): array {
		if ( ! extension_loaded( 'apcu' ) ) {
			return array(
				'success' => false,
				'message' => __( 'APCu extension is not installed.', 'wp-prometheus' ),
			);
		}

		if ( ! apcu_enabled() ) {
			return array(
				'success' => false,
				'message' => __( 'APCu is installed but not enabled. Check your php.ini settings.', 'wp-prometheus' ),
			);
		}

		// Test with a simple store/fetch.
		$test_key = 'wp_prometheus_test_' . time();
		$test_value = 'test_' . wp_rand();

		$stored = apcu_store( $test_key, $test_value, 5 );
		if ( ! $stored ) {
			return array(
				'success' => false,
				'message' => __( 'APCu store operation failed.', 'wp-prometheus' ),
			);
		}

		$fetched = apcu_fetch( $test_key );
		apcu_delete( $test_key );

		if ( $fetched === $test_value ) {
			$info = apcu_cache_info( true );
			return array(
				'success' => true,
				'message' => sprintf(
					/* translators: %s: Memory info */
					__( 'APCu is working. Memory: %s used.', 'wp-prometheus' ),
					size_format( $info['mem_size'] ?? 0 )
				),
			);
		}

		return array(
			'success' => false,
			'message' => __( 'APCu fetch operation returned unexpected value.', 'wp-prometheus' ),
		);
	}
}