/*
    * 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.buildcache.hash;
  
  import java.io.IOException;
  import java.lang.reflect.Method;
  import java.nio.ByteBuffer;
  import java.nio.channels.FileChannel;
  import java.nio.channels.FileChannel.MapMode;
  
  import static org.apache.maven.buildcache.hash.ReflectionUtils.getField;
  import static org.apache.maven.buildcache.hash.ReflectionUtils.getMethod;
  
  /**
   * CloseableBuffer https://stackoverflow.com/a/54046774
   */
  public class CloseableBuffer implements AutoCloseable {
  
      private static final Cleaner CLEANER = getJVMDependentCleaner();
  
      private static Cleaner getJVMDependentCleaner() {
          final String jsv = System.getProperty("java.specification.version", "9");
          if (jsv.startsWith("1.")) {
              return DirectCleaner.isSupported() ? new DirectCleaner() : new NoopCleaner();
          } else {
              return UnsafeCleaner.isSupported() ? new UnsafeCleaner() : new NoopCleaner();
          }
      }
  
      public static CloseableBuffer directBuffer(int capacity) {
          return new CloseableBuffer(ByteBuffer.allocateDirect(capacity));
      }
  
      public static CloseableBuffer mappedBuffer(FileChannel channel, MapMode mode) throws IOException {
          return new CloseableBuffer(channel.map(mode, 0, channel.size()));
      }
  
      private ByteBuffer buffer;
  
      /**
       * Unmap only DirectByteBuffer and MappedByteBuffer
       */
      private CloseableBuffer(ByteBuffer buffer) {
          // Java 8: buffer.isDirect()
          this.buffer = buffer;
      }
  
      /**
       * Do not use buffer after close
       */
      public ByteBuffer getBuffer() {
          return buffer;
      }
  
      @Override
      public void close() {
          boolean done = CLEANER.clean(buffer);
          if (done) {
              buffer = null;
          }
      }
  
      // Java 8: @FunctionalInterface
      private interface Cleaner {
  
          boolean clean(ByteBuffer buffer);
      }
  
      private static class NoopCleaner implements Cleaner {
  
          @Override
          public boolean clean(ByteBuffer buffer) {
              return false;
          }
      }
  
      private static class DirectCleaner implements Cleaner {
  
          private static final Method ATTACHMENT = getMethod("sun.nio.ch.DirectBuffer", "attachment");
          private static final Method CLEANER = getMethod("sun.nio.ch.DirectBuffer", "cleaner");
          private static final Method CLEAN = getMethod("sun.misc.Cleaner", "clean");
  
          public static boolean isSupported() {
             return ATTACHMENT != null && CLEAN != null && CLEANER != null;
         }
 
         /**
          * Make sure duplicates and slices are not cleaned, since this can result in duplicate attempts to clean the
          * same buffer, which trigger a crash with: "A fatal error has been detected by the Java Runtime Environment:
          * EXCEPTION_ACCESS_VIOLATION" See: https://stackoverflow.com/a/31592947/3950982
          */
         @Override
         public boolean clean(ByteBuffer buffer) {
             try {
                 if (ATTACHMENT.invoke(buffer) == null) {
                     CLEAN.invoke(CLEANER.invoke(buffer));
                     return true;
                 }
             } catch (Exception ignore) {
             }
             return false;
         }
     }
 
     private static class UnsafeCleaner implements Cleaner {
 
         // Java 9: getMethod("jdk.internal.misc.Unsafe", "invokeCleaner", ByteBuffer.class);
         private static final Method INVOKE_CLEANER = getMethod("sun.misc.Unsafe", "invokeCleaner", ByteBuffer.class);
         private static final Object UNSAFE = getField("sun.misc.Unsafe", "theUnsafe");
 
         public static boolean isSupported() {
             return UNSAFE != null && INVOKE_CLEANER != null;
         }
 
         /**
          * Calling the above code in JDK9+ gives a reflection warning on stderr,
          * Unsafe.theUnsafe.invokeCleaner(byteBuffer)
          * makes the same call, but does not print the reflection warning
          */
         @Override
         public boolean clean(ByteBuffer buffer) {
             try {
                 // throws IllegalArgumentException if buffer is a duplicate or slice
                 INVOKE_CLEANER.invoke(UNSAFE, buffer);
                 return true;
             } catch (Exception ignore) {
             }
             return false;
         }
     }
 }