/**************************************************************************
    *
    * Copyright (c) 2016-2020 Yawg project contributors.
    *
    **************************************************************************/
   
   package com.varmateo.yawg.core;
   
   import java.util.Optional;
  import java.util.function.Function;
  
  import io.vavr.collection.Seq;
  import io.vavr.control.Option;
  
  import com.varmateo.yawg.api.YawgException;
  import com.varmateo.yawg.spi.Template;
  import com.varmateo.yawg.spi.TemplateService;
  
  
  /**
   * 
   */
  /* default */ final class CollectiveTemplateService
          implements TemplateService {
  
  
      private final Function<String, Optional<Template>> _templateFetcher;
  
  
      private CollectiveTemplateService(final Seq<TemplateService> services) {
  
          if ( services.isEmpty() ) {
              _templateFetcher = name -> Optional.empty();
          } else {
              _templateFetcher = name -> prepareTemplateFromServices(services, name);
          }
      }
  
  
      /**
       *
       */
      public static TemplateService create(final Seq<TemplateService> services) {
          return new CollectiveTemplateService(services);
      }
  
  
      /**
       * {@inheritDoc}
       */
      @Override
      public Optional<Template> prepareTemplate(final String name) {
  
          return _templateFetcher.apply(name);
      }
  
  
      /**
       *
       */
      private static Optional<Template> prepareTemplateFromServices(
              final Seq<TemplateService> services,
              final String name) {
  
          final Option<Template> result = services
                  .map(service -> service.prepareTemplate(name))
                  .map(Option::ofOptional)
                  .filter(Option::isDefined)
                  .map(Option::get)
                  .headOption();
  
          if ( !result.isDefined() ) {
              throw CollectiveTemplateServiceException.unsupportedTemplateFormat(name);
          }
  
          return result.toJavaOptional();
      }
  
  
  }