<?php


namespace TinyFramework\core;


use Closure;
use Exception;
use ReflectionClass;

class ServiceContainer
{

    //singleton
    private static $container_instance = null;

    protected $instances = [];

    public static function init(){
        if(self::$container_instance === null){
            self::$container_instance = new self();
        }
        return self::$container_instance;
    }

    public function set($abstract, $concrete = NULL)
    {
        if ($concrete === NULL) {
            $concrete = $abstract;
        }
        $this->instances[$abstract] = $concrete;
    }

    public function get($abstract, $parameters = [])
    {
        // falls nicht vorhanden, registriere
        if (!isset($this->instances[$abstract])) {
            $this->set($abstract);
        }

        return $this->resolve($this->instances[$abstract], $parameters);
    }

    private function resolve($concrete, $parameters)
    {
        if ($concrete instanceof Closure) {
            return $concrete($this, $parameters);
        }

        $reflector = new ReflectionClass($concrete);

        // ist klasse instanziierbar?
        if (!$reflector->isInstantiable()) {
            throw new Exception("Klasse {$concrete} kann nicht instanziiert werden!");
        }

        // get Konstruktor
        $constructor = $reflector->getConstructor();
        if (is_null($constructor)) {
            // Klasseninstanz holen
            return $reflector->newInstance();
        }

        // get Konstruktor params
        $parameters = $constructor->getParameters();
        $dependencies = $this->getDependencies($parameters);

        //neue Instanz holen mit allen dependencies resolved
        return $reflector->newInstanceArgs($dependencies);
    }


    private function getDependencies($parameters)
    {
        $dependencies = [];
        foreach ($parameters as $parameter) {
            // get the type hinted class
            $dependency = $parameter->getClass();
            if ($dependency === NULL) {
                // default value für Parameter vorhanden?
                if ($parameter->isDefaultValueAvailable()) {
                    // get default value des Parameters
                    $dependencies[] = $parameter->getDefaultValue();
                } else {
                    throw new Exception("Parameter {$parameter->name} kann nicht resolved werden. Es wurde kein Standardwert gefunden.");
                }
            } else {
                // get dependency resolved
                $dependencies[] = $this->get($dependency->name);
            }
        }

        return $dependencies;
    }
}