<?php
/**
 * Service container.
 *
 * @package HostKhata
 */

namespace HostKhata;

defined( 'ABSPATH' ) || exit;

use RuntimeException;

/**
 * Minimal dependency injection container.
 *
 * Services are registered as factories and resolved lazily. A factory receives
 * the container so it can pull in its own dependencies.
 *
 * @since 0.1.0
 */
final class Container {

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

	/**
	 * Ids that must resolve to a single shared instance.
	 *
	 * @var array<string, bool>
	 */
	private $shared = array();

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

	/**
	 * Registers a service that is built once and then reused.
	 *
	 * @since 0.1.0
	 *
	 * @param string   $id      Service id, normally the class name.
	 * @param callable $factory Receives the container, returns the service.
	 * @return void
	 */
	public function singleton( string $id, callable $factory ): void {
		$this->factories[ $id ] = $factory;
		$this->shared[ $id ]    = true;

		unset( $this->instances[ $id ] );
	}

	/**
	 * Registers a service that is built again on every request for it.
	 *
	 * @since 0.1.0
	 *
	 * @param string   $id      Service id.
	 * @param callable $factory Receives the container, returns the service.
	 * @return void
	 */
	public function bind( string $id, callable $factory ): void {
		$this->factories[ $id ] = $factory;
		$this->shared[ $id ]    = false;

		unset( $this->instances[ $id ] );
	}

	/**
	 * Tells whether a service id is registered.
	 *
	 * @since 0.1.0
	 *
	 * @param string $id Service id.
	 * @return bool
	 */
	public function has( string $id ): bool {
		return isset( $this->factories[ $id ] );
	}

	/**
	 * Resolves a service.
	 *
	 * @since 0.1.0
	 *
	 * @param string $id Service id.
	 * @return mixed
	 *
	 * @throws RuntimeException When the id is not registered.
	 */
	public function get( string $id ) {
		if ( ! $this->has( $id ) ) {
			// The id is a developer-supplied class name, never user input, and this class stays WordPress-free for unit testing.
			throw new RuntimeException( sprintf( 'HostKhata service "%s" is not registered.', $id ) ); // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped
		}

		if ( ! $this->shared[ $id ] ) {
			return call_user_func( $this->factories[ $id ], $this );
		}

		if ( ! array_key_exists( $id, $this->instances ) ) {
			$this->instances[ $id ] = call_user_func( $this->factories[ $id ], $this );
		}

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