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.commons.internal.base;
  
  import java.util.Optional;
  
  import org.springframework.util.function.ThrowingSupplier;
  
  import org.apache.causeway.commons.internal.exceptions._Exceptions;
  
  import org.jspecify.annotations.NonNull;
  
  /**
   * package private implementation of _Lazy
   * @since 2.0
   */
  final class _Lazy_Simple<T> implements _Lazy<T> {
  
      private final ThrowingSupplier<? extends T> supplier;
      private T value;
      private boolean memoized;
      private boolean getting;
  
      _Lazy_Simple(final @NonNull ThrowingSupplier<? extends T> supplier) {
          this.supplier = supplier;
      }
  
      @Override
      public boolean isMemoized() {
          guardAgainstRecursiveCall();
          return memoized;
      }
  
      @Override
      public void clear() {
          guardAgainstRecursiveCall();
          this.memoized = false;
          this.value = null;
      }
  
      @Override
      public T get() {
          if(memoized) {
              return value;
          }
          guardAgainstRecursiveCall();
          getting = true; // prevent the supplier from doing a nested call
          try {
              value = supplier.get();
          } finally {
              getting = false;
              memoized = true; // post condition as per contract
          }
          return value;
      }
  
      @Override
      public Optional<T> getMemoized() {
          guardAgainstRecursiveCall();
          return Optional.ofNullable(value);
      }
  
      @Override
      public void set(final T value) {
          if(memoized) {
              throw _Exceptions.illegalState("cannot set value '%s' on Lazy that has already memoized a value", ""+value);
          }
          guardAgainstRecursiveCall();
          memoized = true;
          this.value = value;
      }
  
      // -- HELPER
  
      private final void guardAgainstRecursiveCall() {
          if(getting) {
              throw _Exceptions.illegalState("recursive call of lazy getter detected");
          }
      }
  
  }
  