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   *  Licensed to the Apache Software Foundation (ASF) under one
   *  or more contributor license agreements.  See the NOTICE file
   *  distributed with this work for additional information
   *  regarding copyright ownership.  The ASF licenses this file
   *  to you 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.apache.causeway.core.metamodel.valuesemantics;
  
  import java.util.Optional;
  import java.util.function.UnaryOperator;
  import java.util.stream.Stream;
  
  import org.jspecify.annotations.Nullable;
  
  import org.apache.causeway.applib.exceptions.recoverable.TextEntryParseException;
  import org.apache.causeway.applib.services.i18n.TranslationContext;
  import org.apache.causeway.applib.services.i18n.TranslationService;
  import org.apache.causeway.applib.util.Enums;
  import org.apache.causeway.applib.value.semantics.DefaultsProvider;
  import org.apache.causeway.applib.value.semantics.OrderRelation;
  import org.apache.causeway.applib.value.semantics.Parser;
  import org.apache.causeway.applib.value.semantics.Renderer;
  import org.apache.causeway.applib.value.semantics.ValueDecomposition;
  import org.apache.causeway.applib.value.semantics.ValueSemanticsAbstract;
  import org.apache.causeway.applib.value.semantics.ValueSemanticsProvider;
  import org.apache.causeway.commons.collections.Can;
  import org.apache.causeway.commons.functional.Try;
  import org.apache.causeway.commons.internal.base._Lazy;
  import org.apache.causeway.commons.internal.base._Strings;
  import org.apache.causeway.commons.internal.exceptions._Exceptions;
  import org.apache.causeway.commons.internal.primitives._Ints;
  import org.apache.causeway.core.metamodel.context.MetaModelContext;
  import org.apache.causeway.core.metamodel.object.ManagedObject;
  import org.apache.causeway.core.metamodel.object.MmTitleUtils;
  import org.apache.causeway.core.metamodel.spec.ObjectSpecification;
  import org.apache.causeway.schema.common.v2.EnumDto;
  import org.apache.causeway.schema.common.v2.ValueType;
  import org.apache.causeway.schema.common.v2.ValueWithTypeDto;
  
  import lombok.Getter;
  import lombok.experimental.Accessors;
  
  public class EnumValueSemantics<T extends Enum<T>>
  extends ValueSemanticsAbstract<T>
  implements
      DefaultsProvider<T>,
      Parser<T>,
      Renderer<T>,
      OrderRelation<T, Void>{
  
      @Getter(onMethod_ = {@Override}) private final Class<T> correspondingClass;
      @Getter(onMethod_ = {@Override}) @Accessors(fluent = true) private final int maxLength;
  
      private final _Lazy<ObjectSpecification> enumSpecLazy;
  
      @Override
      public ValueType getSchemaValueType() {
          return ValueType.ENUM;
      }
  
      public static <T extends Enum<T>> EnumValueSemantics<T> create(
              final TranslationService translationService,
              final Class<T> correspondingClass) {
          return new EnumValueSemantics<>(
                  translationService,
                  correspondingClass);
      }
  
      // -- CONSTRUCTION
  
      protected EnumValueSemantics(
              final TranslationService translationService,
              final Class<T> enumClass) {
          super();
          this.translationService = translationService;
          this.correspondingClass = enumClass;
          this.maxLength = maxLengthFor(enumClass);
          this.enumSpecLazy = _Lazy.threadSafe(()->loadEnumSpec(enumClass));
      }
  
      // -- DEFAULTS PROVIDER
  
      @Override
      public T getDefaultValue() {
          return correspondingClass.getEnumConstants()[0];
      }
  
      // -- COMPOSER
  
      @Override
      public ValueDecomposition decompose(final T value) {
          return decomposeAsNullable(value, UnaryOperator.identity(), ()->null);
      }
  
      @Override
      public T compose(final ValueDecomposition decomposition) {
          return composeFromNullable(
                  decomposition, ValueWithTypeDto::getEnum, this::fromEnumName, ()->null);
      }
  
      private T fromEnumName(final EnumDto enumDto) {
          var enumName = enumDto.getEnumName();
  
          return enumName!=null
                  ? Stream.of(correspondingClass.getEnumConstants())
                          .filter(e->e.name().equals(enumName))
                          .findFirst()
                          .orElseThrow(()->_Exceptions
                                  .noSuchElement("enum %s has no matching %s",
                                          correspondingClass.getName(),
                                          enumName))
                  : null;
      }
  
      // -- RENDERER
  
      @Override
      public String titlePresentation(final Context context, final T value) {
          return renderTitle(value, v->friendlyName(context, v));
      }
  
      @Override
      public String htmlPresentation(final Context context, final T value) {
          return renderHtml(value, v->friendlyName(context, v));
      }
  
      // -- PARSER
  
      @Override
      public String parseableTextRepresentation(final Context context, final T enumValue) {
          if(enumValue==null) {
              return null;
          }
          return Enums.getFriendlyNameOf(enumValue);
      }
  
      @Override
      public T parseTextRepresentation(
              final ValueSemanticsProvider.Context context,
              final String text) {
          var input = _Strings.blankToNullOrTrim(text);
          if(input==null) {
              return null;
          }
          return Enums.parseFriendlyName(correspondingClass, input)
                  .orElseThrow(()->new TextEntryParseException("Unknown enum constant '" + input + "'"));
      }
  
      // -- ORDER RELATION
  
      @Override public Void epsilon() { return null; }
      @Override public int compare(final T a, final T b, final Void epsilon) {
          if(a==null) {
              return b==null ? 0 : -1; // null first semantic
          }
          if(b==null) return 1; // null first semantic
          return _Ints.compare(a.ordinal(), b.ordinal()); // strictly returning -1, 0, or 1
      }
      @Override public boolean equals(final T a, final T b, final Void epsilon) {
          return a == b; // ordinal is only ever equal if object-ids are same (null-safe)
      }
  
      // --
  
      @Override
      public final int typicalLength() {
          return maxLength();
      }
  
      @Override
      public Can<T> getExamples() {
          return Stream.of(correspondingClass.getEnumConstants())
                  .limit(2)
                  .collect(Can.toCan());
      }
  
      // -- HELPER
  
      private String friendlyName(final Context context, final T objectAsEnum) {
          var friendlyNameOfEnum = Optional.ofNullable(enumSpecLazy.get())
              .map(enumSpec->ManagedObject.value(enumSpec, objectAsEnum))
              .map(MmTitleUtils::titleOf)
              .orElseGet(()->Enums.getFriendlyNameOf(objectAsEnum.name()));
  
          return Optional.ofNullable(translationService)
                  .map(ts->ts.translate(TranslationContext.forEnum(objectAsEnum), friendlyNameOfEnum))
                  .orElse(friendlyNameOfEnum);
      }
  
      private static <T extends Enum<T>> int maxLengthFor(final Class<T> enumClass) {
          int max = Integer.MIN_VALUE;
          for(T e: enumClass.getEnumConstants()) {
              final int nameLength = e.name().length();
              final int toStringLength = e.toString().length();
              max = Math.max(max, Math.max(nameLength, toStringLength));
          }
          return max;
      }
  
      @Nullable
      private static ObjectSpecification loadEnumSpec(
          final Class<?> enumClass) {
          var enumSpec = Try.call(()->
                  MetaModelContext.instance()
                  .map(MetaModelContext::getSpecificationLoader)
                  .flatMap(specLoader->specLoader.specForType(enumClass))
                  .orElse(null))
              .valueAsNullableElseFail();
          return enumSpec;
      }
  
  }
  