<?php

class Registry {

    private function __construct() {}
    private function __clone() {}

    public static function clear() {
        $self = self::getInstance();
        $self->storage = array();
        return $self;
    }

    public static function add($name, $instance) {
        $self = self::getInstance();
        $self->ensureIsFree($name);
        if (!is_object($instance)) {
            throw new \ InvalidArgumentException('Instance is not an object');
        }
        $self->storage[$name] = $instance;
        return $self;
    }

    public static function addLazy($name, $class_name, array $constructor_arguments = array()) {
        $self = self::getInstance();
        $self->ensureIsFree($name);
        $self->storage[$name] = array((string)$class_name, $constructor_arguments);
        return $self;
    }

    public static function __callStatic($name, $arguments_ignored) {
        $self = self::getInstance();
        if (!isset($self->storage[$name])) {
            throw new \ LogicException("No instance for name '$name' is registered");
        }
        $instance = $self->storage[$name];
        if (is_array($instance)) {
            list($class_name, $constructor_arguments) = $instance;
            $instance = call_user_func_array(
                array(new \ ReflectionClass($class_name), 'newInstance'),
                $constructor_arguments
            );
            $self->storage[$name] = $instance;
        }
        return $instance;
    }

    protected function ensureIsFree($name) {
        if (isset($this->storage[$name])) {
            throw new \ LogicException("An instance named '$name' is already registered");
        }
    }

    protected function getInstance() {
        if (null === self::$instance) {
            self::$instance = new self;
        }
        return self::$instance;
    }

    public static function setInstance($instance) {
        self::$instance = $instance;
    }

    private $storage = array();
    private static $instance = null;

}