content: /*
   *  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.facets.object.viewmodel;
  
  import java.lang.reflect.Constructor;
  import java.net.URLDecoder;
  import java.net.URLEncoder;
  import java.util.Optional;
  import java.util.stream.Collectors;
  
  import org.jspecify.annotations.Nullable;
  
  import org.apache.causeway.applib.ViewModel;
  import org.apache.causeway.applib.services.bookmark.Bookmark;
  import org.apache.causeway.applib.services.registry.ServiceRegistry;
  import org.apache.causeway.commons.collections.Can;
  import org.apache.causeway.commons.functional.IndexedConsumer;
  import org.apache.causeway.commons.internal.assertions._Assert;
  import org.apache.causeway.commons.internal.reflection._GenericResolver.ResolvedConstructor;
  import org.apache.causeway.commons.io.UrlUtils;
  import org.apache.causeway.core.config.progmodel.ProgrammingModelConstants;
  import org.apache.causeway.core.metamodel.commons.ClassExtensions;
  import org.apache.causeway.core.metamodel.facetapi.FacetHolder;
  import org.apache.causeway.core.metamodel.object.ManagedObject;
  import org.apache.causeway.core.metamodel.spec.ObjectSpecification;
  import org.apache.causeway.core.metamodel.specloader.validator.ValidationFailure;
  
  import lombok.Getter;
  import org.jspecify.annotations.NonNull;
  import lombok.RequiredArgsConstructor;
  import lombok.SneakyThrows;
  import lombok.experimental.Accessors;
  
  /**
   * Corresponds to {@link ViewModel} interface.
   */
  public class ViewModelFacetForViewModelInterface
  extends ViewModelFacetAbstract {
  
      public static <T> Optional<ViewModelFacet> create(
              final Class<T> cls,
              final FacetHolder holder) {
  
          if(!ViewModel.class.isAssignableFrom(cls)) {
              return Optional.empty();
          }
  
          ResolvedConstructor pickedConstructor = null; // not used for abstract types
  
          if(!cls.isInterface()
                  && !ClassExtensions.isAbstract(cls)) {
  
              var explicitInjectConstructors = ProgrammingModelConstants.ViewmodelConstructor.PUBLIC_WITH_INJECT_SEMANTICS.getAll(cls);
              var publicConstructors = ProgrammingModelConstants.ViewmodelConstructor.PUBLIC_ANY.getAll(cls);
  
              var violation = explicitInjectConstructors.getCardinality().isMultiple()
                      ? ProgrammingModelConstants.MessageTemplate.VIEWMODEL_MULTIPLE_CONSTRUCTORS_WITH_INJECT_SEMANTICS
                      : explicitInjectConstructors.getCardinality().isZero()
                          && !publicConstructors.getCardinality().isOne()
                              // in absence of a constructor with inject semantics there must be exactly one public to pick instead
                              ? ProgrammingModelConstants.MessageTemplate.VIEWMODEL_MISSING_OR_MULTIPLE_PUBLIC_CONSTRUCTORS
                              : null;
  
              if(violation!=null) {
  
                  ValidationFailure.raiseFormatted(holder,
                          violation
                              .builder()
                              .addVariable("type", cls.getName())
                              .addVariable("found", explicitInjectConstructors.getCardinality().isMultiple()
                                      ? "{" + explicitInjectConstructors.stream()
                                              .map(ResolvedConstructor::constructor)
                                              .map(Constructor::toString)
                                              .collect(Collectors.joining(", ")) + "}"
                                      : "none")
                              .buildMessage());
  
                  return Optional.empty();
  
              }
  
              // -- else happy case
  
              pickedConstructor = explicitInjectConstructors.getCardinality().isOne()
                      ? explicitInjectConstructors.getSingletonOrFail()
                      : publicConstructors.getSingletonOrFail();
  
          }
  
          return Optional.of(new ViewModelFacetForViewModelInterface(holder, pickedConstructor));
      }
  
      private ResolvedConstructor constructorAnyArgs;
  
      protected ViewModelFacetForViewModelInterface(
              final FacetHolder holder,
              final @Nullable ResolvedConstructor constructorAnyArgs) {
          super(holder, Precedence.HIGH);
          this.constructorAnyArgs = constructorAnyArgs;
      }
  
      @Override
      protected ManagedObject createViewmodel(
              final @NonNull ObjectSpecification viewmodelSpec) {
          return ManagedObject.viewmodel(
                  viewmodelSpec,
                  deserialize(viewmodelSpec, null),
                  Optional.empty());
      }
  
      @SneakyThrows
      @Override
      protected ManagedObject createViewmodel(
              final @NonNull ObjectSpecification viewmodelSpec,
              final @NonNull Bookmark bookmark) {
          return ManagedObject.bookmarked(
                          viewmodelSpec,
                          deserialize(viewmodelSpec, bookmark.identifier()),
                          bookmark);
      }
  
      @Override
      public String serialize(final ManagedObject viewModel) {
          final ViewModel viewModelPojo = (ViewModel) viewModel.getPojo();
          return SpecialMemento.encode(viewModelPojo.viewModelMemento());
      }
  
      // -- HELPER
  
      /**
       * In support of (stateless) {@link ViewModel}s that don't use a memento,
       * or if an empty memento String is actually considered a valid use-case.
       * (e.g. a Viewmodel that simply holds a String value for a search say)
       * @apiNote introduced so we can create valid bookmarks,
       *      that must have a non-empty identifier part
       * @implNote the pipe character '|' is regarded unsafe,
       *      hence gets processed by {@link URLEncoder} and {@link URLDecoder},
       *      which makes it safe for us to use with special meaning
       */
      @Getter @Accessors(fluent=true)
      @RequiredArgsConstructor
      enum SpecialMemento {
          EMPTY("||"),
          NULL("|");
          static String encode(final @Nullable String memento) {
              return memento==null
                      ? NULL.representationInUrl()
                      : memento.isEmpty()
                              ? EMPTY.representationInUrl()
                              : UrlUtils.urlEncodeUtf8(memento);
          }
          static String decode(final @Nullable String memento) {
              return NULL.matches(memento)
                      ? null
                      : EMPTY.matches(memento)
                              ? ""
                              : UrlUtils.urlDecodeUtf8(memento);
          }
          final String representationInUrl;
          boolean matches(final String other) {
              return representationInUrl.equals(other);
          }
      }
  
      @SneakyThrows
      private Object deserialize(
              final @NonNull ObjectSpecification viewmodelSpec,
              final @Nullable String mementoEncoded) {
  
          _Assert.assertNotNull(constructorAnyArgs, ()->"framework bug: required non-null, "
                  + "this can only happen, if we try to deserialize an abstract type");
  
          var memento = SpecialMemento.decode(mementoEncoded);
          var resolvedArgs = resolveArgsForConstructor(constructorAnyArgs, getServiceRegistry(), memento);
          var viewmodelPojo = constructorAnyArgs.constructor().newInstance(resolvedArgs);
          return viewmodelPojo;
      }
  
      private static Object[] resolveArgsForConstructor(
              final ResolvedConstructor constructor,
              final ServiceRegistry serviceRegistry,
              final String memento) {
  
          var paramTypes = Can.ofArray(constructor.paramTypes());
          var args = new Object[constructor.paramCount()];
          paramTypes.forEach(IndexedConsumer.zeroBased((final int i, final Class<?> paramType)->{
              if(paramType.equals(String.class)) {
                  args[i] = memento; // its ok to do this never, once, or more than once per constructor, see ViewModel java-doc
                  return;
              }
              args[i] = serviceRegistry.lookupServiceElseFail(paramType);
          }));
          return args;
      }
  
  }
  