/*
    *    Copyright 2009-2021 the original author or authors.
    *
    *    Licensed 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.ibatis.type;
  
  import java.lang.reflect.ParameterizedType;
  import java.lang.reflect.Type;
  
  /**
   * References a generic type.
   *
   * @param <T> the referenced type
   * @since 3.1.0
   * @author Simone Tripodi
   */
  public abstract class TypeReference<T> {
  
    private final Type rawType;
  
    protected TypeReference() {
      rawType = getSuperclassTypeParameter(getClass());
    }
  
    Type getSuperclassTypeParameter(Class<?> clazz) {
      Type genericSuperclass = clazz.getGenericSuperclass();
      if (genericSuperclass instanceof Class) {
        // try to climb up the hierarchy until meet something useful
        if (TypeReference.class != genericSuperclass) {
          return getSuperclassTypeParameter(clazz.getSuperclass());
        }
  
        throw new TypeException("'" + getClass() + "' extends TypeReference but misses the type parameter. "
          + "Remove the extension or add a type parameter to it.");
      }
  
      Type rawType = ((ParameterizedType) genericSuperclass).getActualTypeArguments()[0];
      // TODO remove this when Reflector is fixed to return Types
      if (rawType instanceof ParameterizedType) {
        rawType = ((ParameterizedType) rawType).getRawType();
      }
  
      return rawType;
    }
  
    public final Type getRawType() {
      return rawType;
    }
  
    @Override
    public String toString() {
      return rawType.toString();
    }
  
  }