class ProxyBuilder

class ProxyBuilder {
    
    /**
     * Generates the used proxy class name from a given class name.
     *
     * @param string $class_name
     *   The class name of the actual service.
     *
     * @return string
     *   The class name of the proxy.
     */
    public static function buildProxyClassName($class_name) {
        $match = [];
        preg_match('/([a-zA-Z0-9_]+\\\\[a-zA-Z0-9_]+)\\\\(.+)/', $class_name, $match);
        $root_namespace = $match[1];
        $rest_fqcn = $match[2];
        $proxy_class_name = $root_namespace . '\\ProxyClass\\' . $rest_fqcn;
        return $proxy_class_name;
    }
    
    /**
     * Generates the used proxy namespace from a given class name.
     *
     * @param string $class_name
     *   The class name of the actual service.
     *
     * @return string
     *   The namespace name of the proxy.
     */
    public static function buildProxyNamespace($class_name) {
        $proxy_classname = static::buildProxyClassName($class_name);
        preg_match('/(.+)\\\\[a-zA-Z0-9]+/', $proxy_classname, $match);
        $proxy_namespace = $match[1];
        return $proxy_namespace;
    }
    
    /**
     * Builds a proxy class string.
     *
     * @param string $class_name
     *   The class name of the actual service.
     *
     * @return string
     *   The full string with namespace class and methods.
     */
    public function build($class_name) {
        $reflection = new \ReflectionClass($class_name);
        $proxy_class_name = $this->buildProxyClassName($class_name);
        $proxy_namespace = $this->buildProxyNamespace($class_name);
        $proxy_class_shortname = str_replace($proxy_namespace . '\\', '', $proxy_class_name);
        $output = '';
        $class_documentation = <<<'EOS'

namespace {{ namespace }}{

    /**
     * Provides a proxy class for \{{ class_name }}.
     *
     * @see \Drupal\Component\ProxyBuilder
     */

EOS;
        $class_start = '    class {{ proxy_class_shortname }}';
        // For cases in which the implemented interface is a child of another
        // interface, getInterfaceNames() also returns the parent. This causes a
        // PHP error.
        // In order to avoid that, check for each interface, whether one of its
        // parents is also in the list and exclude it.
        if ($interfaces = $reflection->getInterfaces()) {
            foreach ($interfaces as $interface) {
                // Exclude all parents from the list of implemented interfaces of the
                // class.
                if ($parent_interfaces = $interface->getInterfaceNames()) {
                    foreach ($parent_interfaces as $parent_interface) {
                        unset($interfaces[$parent_interface]);
                    }
                }
            }
            $interface_names = [];
            foreach ($interfaces as $interface) {
                $interface_names[] = '\\' . $interface->getName();
            }
            $class_start .= ' implements ' . implode(', ', $interface_names);
        }
        $output .= $this->buildUseStatements();
        // The actual class;
        $properties = <<<'EOS'
/**
 * The id of the original proxied service.
 *
 * @var string
 */
protected $drupalProxyOriginalServiceId;

/**
 * The real proxied service, after it was lazy loaded.
 *
 * @var \{{ class_name }}
 */
protected $service;

/**
 * The service container.
 *
 * @var \Symfony\Component\DependencyInjection\ContainerInterface
 */
protected $container;


EOS;
        $output .= $properties;
        // Add all the methods.
        $methods = [];
        $methods[] = $this->buildConstructorMethod();
        $methods[] = $this->buildLazyLoadItselfMethod();
        // Add all the methods of the proxied service.
        $reflection_methods = $reflection->getMethods();
        foreach ($reflection_methods as $method) {
            if ($method->getName() === '__construct') {
                continue;
            }
            if ($method->isPublic()) {
                $methods[] = $this->buildMethod($method) . "\n";
            }
        }
        $output .= implode("\n", $methods);
        // Indent the output.
        $output = implode("\n", array_map(function ($value) {
            if ($value === '') {
                return $value;
            }
            return "        {$value}";
        }, explode("\n", $output)));
        $final_output = $class_documentation . $class_start . "\n    {\n\n" . $output . "\n    }\n\n}\n";
        $final_output = str_replace('{{ class_name }}', $class_name, $final_output);
        $final_output = str_replace('{{ namespace }}', $proxy_namespace ? $proxy_namespace . ' ' : '', $final_output);
        $final_output = str_replace('{{ proxy_class_shortname }}', $proxy_class_shortname, $final_output);
        return $final_output;
    }
    
    /**
     * Generates the string for the method which loads the actual service.
     *
     * @return string
     */
    protected function buildLazyLoadItselfMethod() {
        $output = <<<'EOS'
/**
 * Lazy loads the real service from the container.
 *
 * @return object
 *   Returns the constructed real service.
 */
protected function lazyLoadItself()
{
    if (!isset($this->service)) {
        $this->service = $this->container->get($this->drupalProxyOriginalServiceId);
    }

    return $this->service;
}

EOS;
        return $output;
    }
    
    /**
     * Generates the string representation of a single method: signature, body.
     *
     * @param \ReflectionMethod $reflection_method
     *   A reflection method for the method.
     *
     * @return string
     */
    protected function buildMethod(\ReflectionMethod $reflection_method) {
        $parameters = [];
        foreach ($reflection_method->getParameters() as $parameter) {
            $parameters[] = $this->buildParameter($parameter);
        }
        $function_name = $reflection_method->getName();
        $reference = '';
        if ($reflection_method->returnsReference()) {
            $reference = '&';
        }
        $signature_line = <<<'EOS'
/**
 * {@inheritdoc}
 */

EOS;
        if ($reflection_method->isStatic()) {
            $signature_line .= 'public static function ' . $reference . $function_name . '(';
        }
        else {
            $signature_line .= 'public function ' . $reference . $function_name . '(';
        }
        $signature_line .= implode(', ', $parameters);
        $signature_line .= ')';
        if ($reflection_method->hasReturnType()) {
            $signature_line .= ': ';
            $return_type = $reflection_method->getReturnType();
            if ($return_type->allowsNull()) {
                $signature_line .= '?';
            }
            if (!$return_type->isBuiltin()) {
                // The parameter is a class or interface.
                $signature_line .= '\\';
            }
            $return_type_name = $return_type->getName();
            if ($return_type_name === 'self') {
                $return_type_name = $reflection_method->getDeclaringClass()
                    ->getName();
            }
            $signature_line .= $return_type_name;
        }
        $output = $signature_line . "\n{\n";
        $output .= $this->buildMethodBody($reflection_method);
        $output .= "\n" . '}';
        return $output;
    }
    
    /**
     * Builds a string for a single parameter of a method.
     *
     * @param \ReflectionParameter $parameter
     *   A reflection object of the parameter.
     *
     * @return string
     */
    protected function buildParameter(\ReflectionParameter $parameter) {
        $parameter_string = '';
        if ($parameter->hasType()) {
            $type = $parameter->getType();
            if ($type->allowsNull()) {
                $parameter_string .= '?';
            }
            if (!$type->isBuiltin()) {
                // The parameter is a class or interface.
                $parameter_string .= '\\';
            }
            $type_name = $type->getName();
            if ($type_name === 'self') {
                $type_name = $parameter->getDeclaringClass()
                    ->getName();
            }
            $parameter_string .= $type_name . ' ';
        }
        if ($parameter->isPassedByReference()) {
            $parameter_string .= '&';
        }
        $parameter_string .= '$' . $parameter->getName();
        if ($parameter->isDefaultValueAvailable()) {
            $parameter_string .= ' = ';
            $parameter_string .= var_export($parameter->getDefaultValue(), TRUE);
        }
        return $parameter_string;
    }
    
    /**
     * Builds the body of a wrapped method.
     *
     * @param \ReflectionMethod $reflection_method
     *   A reflection method for the method.
     *
     * @return string
     */
    protected function buildMethodBody(\ReflectionMethod $reflection_method) {
        $output = '';
        $function_name = $reflection_method->getName();
        if (!$reflection_method->isStatic()) {
            if ($reflection_method->getReturnType() && $reflection_method->getReturnType()
                ->getName() === 'void') {
                $output .= '    $this->lazyLoadItself()->' . $function_name . '(';
            }
            else {
                $output .= '    return $this->lazyLoadItself()->' . $function_name . '(';
            }
        }
        else {
            $class_name = $reflection_method->getDeclaringClass()
                ->getName();
            $output .= "    \\{$class_name}::{$function_name}(";
        }
        // Add parameters;
        $parameters = [];
        foreach ($reflection_method->getParameters() as $parameter) {
            $parameters[] = '$' . $parameter->getName();
        }
        $output .= implode(', ', $parameters) . ');';
        return $output;
    }
    
    /**
     * Builds the constructor used to inject the actual service ID.
     *
     * @return string
     */
    protected function buildConstructorMethod() {
        $output = <<<'EOS'
/**
 * Constructs a ProxyClass Drupal proxy object.
 *
 * @param \Symfony\Component\DependencyInjection\ContainerInterface $container
 *   The container.
 * @param string $drupal_proxy_original_service_id
 *   The service ID of the original service.
 */
public function __construct(\Symfony\Component\DependencyInjection\ContainerInterface $container, $drupal_proxy_original_service_id)
{
    $this->container = $container;
    $this->drupalProxyOriginalServiceId = $drupal_proxy_original_service_id;
}

EOS;
        return $output;
    }
    
    /**
     * Build the required use statements of the proxy class.
     *
     * @return string
     */
    protected function buildUseStatements() {
        $output = '';
        return $output;
    }

}