/*
    * Copyright 2018 the original author or authors.
    *
    *  Licensed under the Apache License, Version 2.0 (the "License");
    *  you may not use this file except in compliance with the License.
    *  You may obtain a copy of the License at
    *
    *         http://www.apache.org/licenses/LICENSE-2.0
    *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   */
  
  package org.openehealth.ipf.commons.ihe.fhir.support;
  
  import ca.uhn.fhir.context.FhirContext;
  import org.hl7.fhir.dstu3.hapi.validation.DefaultProfileValidationSupport;
  import org.hl7.fhir.dstu3.model.StructureDefinition;
  import org.hl7.fhir.instance.model.api.IBaseResource;
  
  import java.io.InputStream;
  import java.util.Optional;
  import java.util.Scanner;
  
  /**
   * Validation loader that first tries to load a custom structure definition before falling back to the
   * default.
   *
   * @author Christian Ohr
   * @since 3.4
   */
  public class CustomValidationSupport extends DefaultProfileValidationSupport {
  
      static final String HTTP_HL7_ORG_FHIR_STRUCTURE_DEFINITION = "http://hl7.org/fhir/StructureDefinition/";
      private String prefix = "profiles/";
  
      public CustomValidationSupport() {
      }
  
      public CustomValidationSupport(String prefix) {
          this.prefix = prefix;
      }
  
      @Override
      public <T extends IBaseResource> T fetchResource(FhirContext fhirContext, Class<T> clazz, String uri) {
          if (uri.startsWith(HTTP_HL7_ORG_FHIR_STRUCTURE_DEFINITION)) {
              return (T) findProfile(fhirContext, uri.substring(HTTP_HL7_ORG_FHIR_STRUCTURE_DEFINITION.length()))
                      .orElseGet(() -> super.fetchResource(fhirContext, clazz, uri));
          } else {
              return super.fetchResource(fhirContext, clazz, uri);
          }
      }
  
      private <T extends IBaseResource> Optional<T> findProfile(FhirContext fhirContext, String resourceName) {
          String path = prefix + resourceName + ".xml";
          InputStream is = getClass().getClassLoader().getResourceAsStream(path);
          if (is != null) {
              String profileText = new Scanner(getClass().getClassLoader().getResourceAsStream(path), "UTF-8").useDelimiter("\\A").next();
              T structureDefinition = (T) fhirContext.newXmlParser().parseResource(StructureDefinition.class, profileText);
              return Optional.of(structureDefinition);
          }
          return Optional.empty();
      }
  
      public void setPrefix(String prefix) {
          this.prefix = prefix;
      }
  }