/*
   * Copyright 2014 The Netty Project
   *
   * The Netty Project 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 io.netty.util.internal;
  
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.lang.invoke.MethodHandle;
  import java.lang.invoke.MethodHandles;
  import java.nio.ByteBuffer;
  import java.security.AccessController;
  import java.security.PrivilegedAction;
  import java.util.Objects;
  
  import static java.lang.invoke.MethodType.methodType;
  
  /**
   * Allows to free direct {@link ByteBuffer} by using Cleaner. This is encapsulated in an extra class to be able
   * to use {@link PlatformDependent0} on Android without problems.
   * <p>
   * For more details see <a href="https://github.com/netty/netty/issues/2604">#2604</a>.
   */
  final class CleanerJava6 implements Cleaner {
      private static final MethodHandle CLEAN_METHOD;
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(CleanerJava6.class);
  
      static {
          MethodHandle clean;
          Throwable error = null;
          final ByteBuffer direct = ByteBuffer.allocateDirect(1);
          try {
              Object mayBeCleanerField = AccessController.doPrivileged(new PrivilegedAction<Object>() {
                  @Override
                  public Object run() {
                      try {
                          Class<?> cleanerClass = Class.forName("sun.misc.Cleaner");
                          Class<?> directBufClass = Class.forName("sun.nio.ch.DirectBuffer");
                          MethodHandles.Lookup lookup = MethodHandles.lookup();
  
                          // Call clean() on the cleaner
                          MethodHandle clean = lookup.findVirtual(
                                  cleanerClass, "clean", methodType(void.class));
                          // But only if the cleaner is non-null
                          MethodHandle nullTest = lookup.findStatic(
                                  Objects.class, "nonNull", methodType(boolean.class, Object.class));
                          clean = MethodHandles.guardWithTest(
                                  nullTest.asType(methodType(boolean.class, cleanerClass)),
                                  clean,
                                  nullTest.asType(methodType(void.class, cleanerClass)));
                          // Change receiver to DirectBuffer, convert DirectBuffer to Cleaner by calling cleaner()
                          clean = MethodHandles.filterArguments(clean, 0, lookup.findVirtual(
                                  directBufClass,
                                  "cleaner",
                                  methodType(cleanerClass)));
                          // Change receiver to ByteBuffer, convert using explicit cast to DirectBuffer
                          clean = MethodHandles.explicitCastArguments(clean,
                                  methodType(void.class, ByteBuffer.class));
                          return clean;
                      } catch (Throwable cause) {
                          return cause;
                      }
                  }
              });
              if (mayBeCleanerField instanceof Throwable) {
                  throw (Throwable) mayBeCleanerField;
              }
  
              clean = (MethodHandle) mayBeCleanerField;
              clean.invokeExact(direct);
          } catch (Throwable t) {
              // We don't have ByteBuffer.cleaner().
              clean = null;
              error = t;
          }
  
          if (error == null) {
              logger.debug("java.nio.ByteBuffer.cleaner(): available");
          } else {
              logger.debug("java.nio.ByteBuffer.cleaner(): unavailable", error);
          }
          CLEAN_METHOD = clean;
      }
  
      static boolean isSupported() {
          return CLEAN_METHOD != null;
     }
 
     @Override
     public CleanableDirectBuffer allocate(int capacity) {
         return new CleanableDirectBufferImpl(ByteBuffer.allocateDirect(capacity));
     }
 
     @Deprecated
     @Override
     public void freeDirectBuffer(ByteBuffer buffer) {
         freeDirectBufferStatic(buffer);
     }
 
     private static void freeDirectBufferStatic(ByteBuffer buffer) {
         if (!buffer.isDirect()) {
             return;
         }
         if (System.getSecurityManager() == null) {
             try {
                 freeDirectBuffer0(buffer);
             } catch (Throwable cause) {
                 PlatformDependent0.throwException(cause);
             }
         } else {
             freeDirectBufferPrivileged(buffer);
         }
     }
 
     private static void freeDirectBufferPrivileged(final ByteBuffer buffer) {
         Throwable cause = AccessController.doPrivileged(new PrivilegedAction<Throwable>() {
             @Override
             public Throwable run() {
                 try {
                     freeDirectBuffer0(buffer);
                     return null;
                 } catch (Throwable cause) {
                     return cause;
                 }
             }
         });
         if (cause != null) {
             PlatformDependent0.throwException(cause);
         }
     }
 
     private static void freeDirectBuffer0(ByteBuffer buffer) throws Throwable {
         CLEAN_METHOD.invokeExact(buffer);
     }
 
     private static final class CleanableDirectBufferImpl implements CleanableDirectBuffer {
         private final ByteBuffer buffer;
 
         private CleanableDirectBufferImpl(ByteBuffer buffer) {
             this.buffer = buffer;
         }
 
         @Override
         public ByteBuffer buffer() {
             return buffer;
         }
 
         @Override
         public void clean() {
             freeDirectBufferStatic(buffer);
         }
     }
 }