class Factory

final class Factory {
    private static ?Factory $instance = null;
    
    /**
     * @psalm-var list<Comparator>
     */
    private array $customComparators = [];
    
    /**
     * @psalm-var list<Comparator>
     */
    private array $defaultComparators = [];
    public static function getInstance() : self {
        if (self::$instance === null) {
            self::$instance = new self();
            // @codeCoverageIgnore
        }
        return self::$instance;
    }
    public function __construct() {
        $this->registerDefaultComparators();
    }
    public function getComparatorFor(mixed $expected, mixed $actual) : Comparator {
        foreach ($this->customComparators as $comparator) {
            if ($comparator->accepts($expected, $actual)) {
                return $comparator;
            }
        }
        foreach ($this->defaultComparators as $comparator) {
            if ($comparator->accepts($expected, $actual)) {
                return $comparator;
            }
        }
        throw new RuntimeException('No suitable Comparator implementation found');
    }
    
    /**
     * Registers a new comparator.
     *
     * This comparator will be returned by getComparatorFor() if its accept() method
     * returns TRUE for the compared values. It has higher priority than the
     * existing comparators, meaning that its accept() method will be invoked
     * before those of the other comparators.
     */
    public function register(Comparator $comparator) : void {
        array_unshift($this->customComparators, $comparator);
        $comparator->setFactory($this);
    }
    
    /**
     * Unregisters a comparator.
     *
     * This comparator will no longer be considered by getComparatorFor().
     */
    public function unregister(Comparator $comparator) : void {
        foreach ($this->customComparators as $key => $_comparator) {
            if ($comparator === $_comparator) {
                unset($this->customComparators[$key]);
            }
        }
    }
    public function reset() : void {
        $this->customComparators = [];
    }
    private function registerDefaultComparators() : void {
        $this->registerDefaultComparator(new MockObjectComparator());
        $this->registerDefaultComparator(new DateTimeComparator());
        $this->registerDefaultComparator(new DOMNodeComparator());
        $this->registerDefaultComparator(new SplObjectStorageComparator());
        $this->registerDefaultComparator(new ExceptionComparator());
        $this->registerDefaultComparator(new ObjectComparator());
        $this->registerDefaultComparator(new ResourceComparator());
        $this->registerDefaultComparator(new ArrayComparator());
        $this->registerDefaultComparator(new NumericComparator());
        $this->registerDefaultComparator(new ScalarComparator());
        $this->registerDefaultComparator(new TypeComparator());
    }
    private function registerDefaultComparator(Comparator $comparator) : void {
        $this->defaultComparators[] = $comparator;
        $comparator->setFactory($this);
    }

}