<?php
/**
 * Lightweight dependency injection container.
 *
 * @package AICommerce
 */

declare(strict_types=1);

namespace AICommerce\Core;

use InvalidArgumentException;

/**
 * ServiceContainer provides a simple PSR-11-inspired DI container
 * without requiring the full PSR-11 interface package.
 */
class ServiceContainer {

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

	/**
	 * Resolved singleton instances.
	 *
	 * @var array<string, object>
	 */
	private array $instances = array();

	/**
	 * Register a service factory.
	 *
	 * The factory receives the container as its only argument, enabling
	 * constructor injection of other services.
	 *
	 * @param string   $id      Service identifier (typically FQCN).
	 * @param callable $factory Factory closure: fn(ServiceContainer): object.
	 *
	 * @return void
	 */
	public function register( string $id, callable $factory ): void {
		$this->factories[ $id ] = $factory;

		// Clear any previously resolved instance so the new factory takes effect.
		unset( $this->instances[ $id ] );
	}

	/**
	 * Resolve a service by its identifier.
	 *
	 * Services are lazily instantiated and cached as singletons for the
	 * lifetime of the container.
	 *
	 * @param string $id Service identifier.
	 *
	 * @return object
	 *
	 * @throws InvalidArgumentException If the service is not registered.
	 */
	public function get( string $id ): object {
		if ( isset( $this->instances[ $id ] ) ) {
			return $this->instances[ $id ];
		}

		if ( ! isset( $this->factories[ $id ] ) ) {
			throw new InvalidArgumentException(
				esc_html(
					sprintf(
						'Service "%s" is not registered in the container.',
						$id
					)
				)
			);
		}

		$this->instances[ $id ] = ( $this->factories[ $id ] )( $this );

		return $this->instances[ $id ];
	}

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

	/**
	 * Set an already-constructed instance directly.
	 *
	 * Useful for binding values that don't need a factory (e.g., config arrays
	 * wrapped in an object, or test doubles).
	 *
	 * @param string $id       Service identifier.
	 * @param object $instance The pre-built instance.
	 *
	 * @return void
	 */
	public function set( string $id, object $instance ): void {
		$this->instances[ $id ] = $instance;
		// Remove factory if one existed — the explicit instance takes precedence.
		unset( $this->factories[ $id ] );
	}
}