class CompositeResolver

class CompositeResolver {
    
    /** @var list<ResolverInterface> */
    private array $resolvers = [];
    public static function instance() : self {
        static $instance;
        $instance ??= new self([
            new EnvironmentResolver(),
            new PhpIniResolver(),
        ]);
        return $instance;
    }
    public function __construct($resolvers) {
        foreach ($resolvers as $resolver) {
            $this->addResolver($resolver);
        }
    }
    public function addResolver(ResolverInterface $resolver) : void {
        $this->resolvers[] = $resolver;
    }
    public function getResolvers() : array {
        return $this->resolvers;
    }
    public function resolve(string $variableName, $default = '') {
        foreach ($this->resolvers as $resolver) {
            if ($resolver->hasVariable($variableName)) {
                return $resolver->retrieveValue($variableName);
            }
        }
        return Configuration::isEmpty($default) ? Configuration::getDefault($variableName) : $default;
    }
    public function hasVariable(string $variableName) : bool {
        foreach ($this->resolvers as $resolver) {
            if ($resolver->hasVariable($variableName)) {
                return true;
            }
        }
        return false;
    }

}