<?php
/**
 * Minimal dependency-injection container.
 *
 * @package HandyMCP
 */

namespace HandyMCP;

defined( 'ABSPATH' ) || exit;

/**
 * Lazily builds and caches shared services.
 */
final class Container {

	/** @var array<string, callable> */
	private $factories = array();

	/** @var array<string, mixed> */
	private $instances = array();

	/**
	 * Register a shared service factory.
	 *
	 * @param string   $id      Service id.
	 * @param callable $factory Factory receiving the container.
	 */
	public function set( string $id, callable $factory ): void {
		$this->factories[ $id ] = $factory;
		unset( $this->instances[ $id ] );
	}

	/**
	 * Resolve a service.
	 *
	 * @param string $id Service id.
	 * @return mixed
	 * @throws \RuntimeException When the service is unknown.
	 */
	public function get( string $id ) {
		if ( array_key_exists( $id, $this->instances ) ) {
			return $this->instances[ $id ];
		}
		if ( ! isset( $this->factories[ $id ] ) ) {
			throw new \RuntimeException( 'Unknown service: ' . esc_html( $id ) );
		}
		$this->instances[ $id ] = call_user_func( $this->factories[ $id ], $this );
		return $this->instances[ $id ];
	}

	/**
	 * Whether a service is registered.
	 *
	 * @param string $id Service id.
	 */
	public function has( string $id ): bool {
		return isset( $this->factories[ $id ] );
	}
}