Support for multiple FHIR profile extensions

bunsen/bunsen-avro/src/main/java/com/cerner/bunsen/avro/AvroConverter.java

@@ -7,15 +7,20 @@
 import com.cerner.bunsen.definitions.HapiConverter;
 import com.cerner.bunsen.definitions.HapiConverter.HapiObjectConverter;
 import com.cerner.bunsen.definitions.StructureDefinitions;
+import com.cerner.bunsen.exception.ProfileException;
+import com.google.common.base.Preconditions;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.stream.Collectors;
 import org.apache.avro.Schema;
 import org.apache.avro.Schema.Field;
 import org.apache.avro.generic.IndexedRecord;
+import org.apache.commons.collections.CollectionUtils;
 import org.hl7.fhir.instance.model.api.IBaseResource;
 
 /** Converter to change HAPI objects into Avro structures and vice versa. */
@@ -133,6 +138,28 @@ public static AvroConverter forResource(FhirContext context, String resourceType
     return forResource(context, resourceTypeUrl, Collections.emptyList());
   }
 
+  /**
+   * Similar to {@link #forResource(FhirContext, String)} this method returns an Avro converter, but
+   * the returned Avro converter is a union of all the converters for the given resourceTypeUrls,
+   * the union is formed by merging all the fields in each converter.
+   *
+   * @param context the FHIR context
+   * @param resourceTypeUrls the list of resource type profile urls. The resourceTypeUrl can either
+   *     be a relative URL for a base resource (e.g., "Condition" or "Observation"), or a URL
+   *     identifying the structure definition for a given profile, such as
+   *     "http://hl7.org/fhir/us/core/StructureDefinition/us-core-patient".
+   * @return the merged Avro converter
+   */
+  public static AvroConverter forResources(FhirContext context, List<String> resourceTypeUrls)
+      throws ProfileException {
+    List<AvroConverter> avroConverters = new ArrayList<>();
+    for (String resourceTypeUrl : resourceTypeUrls) {
+      AvroConverter avroConverter = forResource(context, resourceTypeUrl, Collections.emptyList());
+      avroConverters.add(avroConverter);
+    }
+    return mergeAvroConverters(avroConverters, context);
+  }
+
   /**
    * Returns an Avro converter for the given resource type. The resource type can either be a
    * relative URL for a base resource (e.g. "Condition" or "Observation"), or a URL identifying the
@@ -196,4 +223,29 @@ public Schema getSchema() {
   public String getResourceType() {
     return hapiToAvroConverter.getElementType();
   }
+
+  /**
+   * Merges all the given list of avroConverters to create a single AvroConverter which is a union
+   * of all the fields in the list of avroConverters
+   */
+  private static AvroConverter mergeAvroConverters(
+      List<AvroConverter> avroConverters, FhirContext context) throws ProfileException {
+    Preconditions.checkArgument(
+        !CollectionUtils.isEmpty(avroConverters), "AvroConverter list cannot be empty for merging");
+    Iterator<AvroConverter> iterator = avroConverters.iterator();
+    AvroConverter mergedConverter = iterator.next();
+    while (iterator.hasNext()) {
+      mergedConverter = mergeAvroConverters(mergedConverter, iterator.next(), context);
+    }
+    return mergedConverter;
+  }
+
+  private static AvroConverter mergeAvroConverters(
+      AvroConverter left, AvroConverter right, FhirContext context) throws ProfileException {
+    HapiConverter<Schema> mergedConverter =
+        left.hapiToAvroConverter.merge(right.hapiToAvroConverter);
+    RuntimeResourceDefinition[] resources = new RuntimeResourceDefinition[1];
+    resources[0] = context.getResourceDefinition(mergedConverter.getElementType());
+    return new AvroConverter(mergedConverter, resources);
+  }
 }