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
   *
   *    https://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.cayenne.di.spi;
  
  import java.util.LinkedList;
  import java.util.List;
  
  import org.apache.cayenne.di.DIRuntimeException;
  import org.apache.cayenne.di.Key;
  
  /**
   * A helper object that tracks the injection stack to prevent circular dependencies.
   * 
   * @since 3.1
   */
  class InjectionStack {
  
      private ThreadLocal<LinkedList<Key<?>>> stack;
  
      InjectionStack() {
          this.stack = new ThreadLocal<LinkedList<Key<?>>>();
      }
  
      void reset() {
          List<Key<?>> localStack = stack.get();
          if (localStack != null) {
              localStack.clear();
          }
      }
  
      void push(Key<?> bindingKey) throws DIRuntimeException {
          LinkedList<Key<?>> localStack = stack.get();
          if (localStack == null) {
              localStack = new LinkedList<Key<?>>();
              stack.set(localStack);
          }
  
          if (localStack.contains(bindingKey)) {
              throw new DIRuntimeException(
                      "Circular dependency detected when binding a key \"%s\". Nested keys: %s"
                              + ". To resolve it, you should inject a Provider instead of an object.",
                      bindingKey,
                      localStack);
          }
  
          localStack.add(bindingKey);
      }
  
      void pop() {
          LinkedList<Key<?>> localStack = stack.get();
          if (localStack != null) {
              localStack.removeLast();
          }
          else {
              throw new IndexOutOfBoundsException("0");
          }
      }
  
      @Override
      public String toString() {
          List<Key<?>> localStack = stack.get();
          if (localStack != null) {
              return String.valueOf(localStack);
          }
          else {
              return "[]";
          }
      }
  }
  