package once

// Singleton contains a pointer to T that must be set once.
// Until the value is set all Get() calls will block.
type Singleton[T any] struct {
	v   *T
	set chan struct{}
}

// NewSingleton creates a new unset singleton.
func NewSingleton[T any]() *Singleton[T] {
	return &Singleton[T]{set: make(chan struct{}), v: nil}
}

// Get will return the singleton value.
func (s *Singleton[T]) Get() *T {
	<-s.set
	return s.v

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;

import static java.lang.annotation.RetentionPolicy.RUNTIME;

@Scope
@Documented
@Retention(RUNTIME)

        container.singleton("archiveStreamFactory", ArchiveStreamFactory.class)
                .singleton("compressorStreamFactory", CompressorStreamFactory.class).singleton("mimeTypeHelper", MimeTypeHelperImpl.class)
                .singleton("tikaExtractor", TikaExtractor.class).singleton("tarExtractor", TarExtractor.class)
                .<ExtractorFactory> singleton("extractorFactory", ExtractorFactory.class, factory -> {

import jcifs.config.PropertyConfiguration;


/**
 * Global singleton context
 * 
 * @author mbechler
 *
 */
public class SingletonContext extends BaseContext implements CIFSContext {

    private static final Logger log = LoggerFactory.getLogger(SingletonContext.class);
    private static SingletonContext INSTANCE;


    /**
     * Initialize singleton context using custom properties
     * 

        StandardCrawlerContainer container = new StandardCrawlerContainer().singleton("dataHelper", MemoryDataHelper.class)//
                .singleton("urlFilterService", UrlFilterServiceImpl.class)//
                .singleton("includeFilter", UrlFilterImpl.class)//
                .singleton("excludeFilter", UrlFilterImpl.class)//
                .singleton("domainFilter", UrlFilterImpl.class)//
        ;

		<property name="name">"htmlTransformer"</property>
		<property name="featureMap">defaultFeatureMap</property>
		<property name="propertyMap">defaultPropertyMap</property>
		<property name="childUrlRuleMap">htmlUrlRuleMap</property>
	</component>

	<component name="textTransformer"
		class="org.codelibs.fess.crawler.transformer.impl.TextTransformer" instance="singleton">

                .singleton("pdfExtractor", PdfExtractor.class)//
                .singleton("lhaExtractor", LhaExtractor.class)//
                .singleton("mimeTypeHelper", MimeTypeHelperImpl.class)//
                .singleton("contentLengthHelper", ContentLengthHelper.class)//
                .singleton("extractorFactory", ExtractorFactory.class);

                .singleton("httpClient", FaultTolerantClient.class)//
                .singleton("fsClient", FileSystemClient.class)//
                .singleton("smbClient", SmbClient.class)//
                .singleton("smb1Client", org.codelibs.fess.crawler.client.smb1.SmbClient.class)//
                .singleton("ftpClient", FtpClient.class)//

                .singleton("urlConvertHelper", UrlConvertHelper.class).singleton("intervalController", DefaultIntervalController.class)
                .singleton("sitemapsHelper", SitemapsHelper.class).singleton("logHelper", LogHelperImpl.class)
                .singleton("encodingHelper", EncodingHelper.class).singleton("contentLengthHelper", ContentLengthHelper.class)
                .singleton("mimeTypeHelper", MimeTypeHelperImpl.class)

        return this;
    }

    public <T> StandardCrawlerContainer singleton(final String name, final Class<T> cls, final Consumer<T> initializer) {
        return singleton(name, cls, initializer, (Consumer<T>) null);
    }

    public <T> StandardCrawlerContainer singleton(final String name, final Class<T> cls) {
        return singleton(name, cls, (Consumer<T>) null, (Consumer<T>) null);
    }