/*
    * 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.maven.di;
  
  import java.lang.reflect.ParameterizedType;
  import java.lang.reflect.Type;
  import java.util.Objects;
  
  import org.apache.maven.api.annotations.Nullable;
  import org.apache.maven.di.impl.ReflectionUtils;
  import org.apache.maven.di.impl.Types;
  import org.apache.maven.di.impl.Utils;
  
  /**
   * The key defines an identity of a binding. In any DI, a key is usually a type of the object along
   * with some optional tag to distinguish between bindings which make objects of the same type.
   * <p>
   * In ActiveJ Inject, a key is also a type token - special abstract class that can store type information
   * with the shortest syntax possible in Java.
   * <p>
   * For example, to create a key of type Map&lt;String, List&lt;Integer&gt;&gt;, you can just use
   * this syntax: <code>new Key&lt;Map&lt;String, List&lt;Integer&gt;&gt;&gt;(){}</code>.
   * <p>
   * If your types are not known at compile time, you can use {@link Types#parameterizedType} to make a
   * parameterized type and give it to a {@link #ofType Key.ofType} constructor.
   *
   * @param <T> binding type
   */
  public abstract class Key<T> {
      private final Type type;
      private final @Nullable Object qualifier;
  
      private int hash;
  
      protected Key() {
          this(null);
      }
  
      protected Key(@Nullable Object qualifier) {
          this.type = Types.simplifyType(getTypeParameter());
          this.qualifier = qualifier;
      }
  
      protected Key(Type type, @Nullable Object qualifier) {
          this.type = Types.simplifyType(type);
          this.qualifier = qualifier;
      }
  
      static final class KeyImpl<T> extends Key<T> {
          KeyImpl(Type type, Object qualifier) {
              super(type, qualifier);
          }
      }
  
      public static <T> Key<T> of(Class<T> type) {
          return new KeyImpl<>(type, null);
      }
  
      public static <T> Key<T> of(Class<T> type, @Nullable Object qualifier) {
          return new KeyImpl<>(type, qualifier);
      }
  
      public static <T> Key<T> ofType(Type type) {
          return new KeyImpl<>(type, null);
      }
  
      public static <T> Key<T> ofType(Type type, @Nullable Object qualifier) {
          return new KeyImpl<>(type, qualifier);
      }
  
      private Type getTypeParameter() {
          // this cannot possibly fail so not even a check here
          Type typeArgument = ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0];
          Object outerInstance = ReflectionUtils.getOuterClassInstance(this);
          //		// the outer instance is null in static context
          return outerInstance != null
                  ? Types.bind(typeArgument, Types.getAllTypeBindings(outerInstance.getClass()))
                  : typeArgument;
      }
  
      public Type getType() {
          return type;
      }
 
     /**
      * A shortcut for <code>{@link Types#getRawType(Type)}(key.getType())</code>.
      * Also casts the result to a properly parameterized class.
      */
     @SuppressWarnings("unchecked")
     public Class<T> getRawType() {
         return (Class<T>) Types.getRawType(type);
     }
 
     /**
      * Returns a type parameter of the underlying type wrapped as a key with no qualifier.
      *
      * @throws IllegalStateException when underlying type is not a parameterized one.
      */
     public <U> Key<U> getTypeParameter(int index) {
         if (type instanceof ParameterizedType) {
             return new KeyImpl<>(((ParameterizedType) type).getActualTypeArguments()[index], null);
         }
         throw new IllegalStateException("Expected type from key " + getDisplayString() + " to be parameterized");
     }
 
     public @Nullable Object getQualifier() {
         return qualifier;
     }
 
     /**
      * Returns an underlying type with display string formatting (package names stripped)
      * and prepended qualifier display string if this key has a qualifier.
      */
     public String getDisplayString() {
         return (qualifier != null ? Utils.getDisplayString(qualifier) + " " : "")
                 + ReflectionUtils.getDisplayName(type);
     }
 
     @Override
     public boolean equals(Object o) {
         if (this == o) {
             return true;
         }
         if (!(o instanceof Key<?>)) {
             return false;
         }
         Key<?> that = (Key<?>) o;
         return type.equals(that.type) && Objects.equals(qualifier, that.qualifier);
     }
 
     @Override
     public int hashCode() {
         int hashCode = hash;
         if (hashCode == 0) {
             hash = 31 * type.hashCode() + (qualifier == null ? 0 : qualifier.hashCode());
         }
         return hash;
     }
 
     @Override
     public String toString() {
         return (qualifier != null ? qualifier + " " : "") + type.getTypeName();
     }
 }