/*
    *    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.binding;
  
  import java.io.Serializable;
  import java.lang.invoke.MethodHandle;
  import java.lang.invoke.MethodHandles;
  import java.lang.invoke.MethodHandles.Lookup;
  import java.lang.invoke.MethodType;
  import java.lang.reflect.Constructor;
  import java.lang.reflect.InvocationHandler;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.Map;
  
  import org.apache.ibatis.reflection.ExceptionUtil;
  import org.apache.ibatis.session.SqlSession;
  import org.apache.ibatis.util.MapUtil;
  
  /**
   * @author Clinton Begin
   * @author Eduardo Macarron
   */
  public class MapperProxy<T> implements InvocationHandler, Serializable {
  
    private static final long serialVersionUID = -4724728412955527868L;
    private static final int ALLOWED_MODES = MethodHandles.Lookup.PRIVATE | MethodHandles.Lookup.PROTECTED
        | MethodHandles.Lookup.PACKAGE | MethodHandles.Lookup.PUBLIC;
    private static final Constructor<Lookup> lookupConstructor;
    private static final Method privateLookupInMethod;
    private final SqlSession sqlSession;
    private final Class<T> mapperInterface;
    private final Map<Method, MapperMethodInvoker> methodCache;
  
    public MapperProxy(SqlSession sqlSession, Class<T> mapperInterface, Map<Method, MapperMethodInvoker> methodCache) {
      this.sqlSession = sqlSession;
      this.mapperInterface = mapperInterface;
      this.methodCache = methodCache;
    }
  
    static {
      Method privateLookupIn;
      try {
        privateLookupIn = MethodHandles.class.getMethod("privateLookupIn", Class.class, MethodHandles.Lookup.class);
      } catch (NoSuchMethodException e) {
        privateLookupIn = null;
      }
      privateLookupInMethod = privateLookupIn;
  
      Constructor<Lookup> lookup = null;
      if (privateLookupInMethod == null) {
        // JDK 1.8
        try {
          lookup = MethodHandles.Lookup.class.getDeclaredConstructor(Class.class, int.class);
          lookup.setAccessible(true);
        } catch (NoSuchMethodException e) {
          throw new IllegalStateException(
              "There is neither 'privateLookupIn(Class, Lookup)' nor 'Lookup(Class, int)' method in java.lang.invoke.MethodHandles.",
              e);
        } catch (Exception e) {
          lookup = null;
        }
      }
      lookupConstructor = lookup;
    }
  
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
      try {
        if (Object.class.equals(method.getDeclaringClass())) {
          return method.invoke(this, args);
        } else {
          return cachedInvoker(method).invoke(proxy, method, args, sqlSession);
        }
      } catch (Throwable t) {
        throw ExceptionUtil.unwrapThrowable(t);
      }
    }
  
    private MapperMethodInvoker cachedInvoker(Method method) throws Throwable {
      try {
        return MapUtil.computeIfAbsent(methodCache, method, m -> {
          if (m.isDefault()) {
            try {
              if (privateLookupInMethod == null) {
                return new DefaultMethodInvoker(getMethodHandleJava8(method));
             } else {
               return new DefaultMethodInvoker(getMethodHandleJava9(method));
             }
           } catch (IllegalAccessException | InstantiationException | InvocationTargetException
               | NoSuchMethodException e) {
             throw new RuntimeException(e);
           }
         } else {
           return new PlainMethodInvoker(new MapperMethod(mapperInterface, method, sqlSession.getConfiguration()));
         }
       });
     } catch (RuntimeException re) {
       Throwable cause = re.getCause();
       throw cause == null ? re : cause;
     }
   }
 
   private MethodHandle getMethodHandleJava9(Method method)
       throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
     final Class<?> declaringClass = method.getDeclaringClass();
     return ((Lookup) privateLookupInMethod.invoke(null, declaringClass, MethodHandles.lookup())).findSpecial(
         declaringClass, method.getName(), MethodType.methodType(method.getReturnType(), method.getParameterTypes()),
         declaringClass);
   }
 
   private MethodHandle getMethodHandleJava8(Method method)
       throws IllegalAccessException, InstantiationException, InvocationTargetException {
     final Class<?> declaringClass = method.getDeclaringClass();
     return lookupConstructor.newInstance(declaringClass, ALLOWED_MODES).unreflectSpecial(method, declaringClass);
   }
 
   interface MapperMethodInvoker {
     Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable;
   }
 
   private static class PlainMethodInvoker implements MapperMethodInvoker {
     private final MapperMethod mapperMethod;
 
     public PlainMethodInvoker(MapperMethod mapperMethod) {
       super();
       this.mapperMethod = mapperMethod;
     }
 
     @Override
     public Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable {
       return mapperMethod.execute(sqlSession, args);
     }
   }
 
   private static class DefaultMethodInvoker implements MapperMethodInvoker {
     private final MethodHandle methodHandle;
 
     public DefaultMethodInvoker(MethodHandle methodHandle) {
       super();
       this.methodHandle = methodHandle;
     }
 
     @Override
     public Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable {
       return methodHandle.bindTo(proxy).invokeWithArguments(args);
     }
   }
 }