/*
    * Copyright 2025 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 static java.lang.invoke.MethodType.methodType;
  
  /**
   * Provide a way to clean direct {@link ByteBuffer} instances on Java 24+,
   * where we don't have {@code Unsafe} available, but we have memory segments.
   */
  final class CleanerJava25 implements Cleaner {
      private static final InternalLogger logger;
  
      private static final MethodHandle INVOKE_ALLOCATOR;
  
      static {
          boolean suitableJavaVersion;
          if (System.getProperty("org.graalvm.nativeimage.imagecode") != null) {
              // native image supports this since 25, but we don't use PlatformDependent0 here, since
              // we need to initialize CleanerJava25 at build time.
              String v = System.getProperty("java.specification.version");
              try {
                  suitableJavaVersion = Integer.parseInt(v) >= 25;
              } catch (NumberFormatException e) {
                  suitableJavaVersion = false;
              }
              // also need to prevent initializing the logger at build time
              logger = null;
          } else {
              // Only attempt to use MemorySegments on Java 25 or greater, because of the following JDK bugs:
              // - https://bugs.openjdk.org/browse/JDK-8357145
              // - https://bugs.openjdk.org/browse/JDK-8357268
              suitableJavaVersion = PlatformDependent0.javaVersion() >= 25;
              logger = InternalLoggerFactory.getInstance(CleanerJava25.class);
          }
  
          MethodHandle method;
          Throwable error;
          if (suitableJavaVersion) {
              try {
                  // Here we compose and construct a MethodHandle that takes an 'int' capacity argument,
                  // and produces a 'CleanableDirectBufferImpl' instance.
                  // The method handle will create a new shared Arena instance, allocate a MemorySegment from it,
                  // convert the MemorySegment to a ByteBuffer and a memory address, and then pass both the Arena,
                  // the ByteBuffer, and the memory address to the CleanableDirectBufferImpl constructor,
                  // returning the resulting object.
                  //
                  // Effectively, we are recreating the following the Java code through MethodHandles alone:
                  //
                  //    Arena arena = Arena.ofShared();
                  //    MemorySegment segment = arena.allocate(size);
                  //    return new CleanableDirectBufferImpl(
                  //              (AutoCloseable) arena,
                  //              segment.asByteBuffer(),
                  //              segment.address());
                  //
                  // First, we need the types we'll use to set this all up.
                  Class<?> arenaCls = Class.forName("java.lang.foreign.Arena");
                  Class<?> memsegCls = Class.forName("java.lang.foreign.MemorySegment");
                  Class<CleanableDirectBufferImpl> bufCls = CleanableDirectBufferImpl.class;
                  // Acquire the private look up, so we can access the package-private 'CleanableDirectBufferImpl'
                  // constructor.
                  MethodHandles.Lookup lookup = MethodHandles.lookup();
  
                  // ofShared.type() = ()Arena
                  MethodHandle ofShared = lookup.findStatic(arenaCls, "ofShared", methodType(arenaCls));
                  // allocate.type() = (Arena,long)MemorySegment
                  MethodHandle allocate = lookup.findVirtual(arenaCls, "allocate", methodType(memsegCls, long.class));
                  // asByteBuffer.type() = (MemorySegment)ByteBuffer
                  MethodHandle asByteBuffer = lookup.findVirtual(memsegCls, "asByteBuffer", methodType(ByteBuffer.class));
                  // address.type() = (MemorySegment)long
                  MethodHandle address = lookup.findVirtual(memsegCls, "address", methodType(long.class));
                  // bufClsCtor.type() = (AutoCloseable,ByteBuffer,long)CleanableDirectBufferImpl
                  MethodHandle bufClsCtor = lookup.findConstructor(bufCls,
                          methodType(void.class, AutoCloseable.class, ByteBuffer.class, long.class));
                  // The 'allocate' method takes a 'long' capacity, but we'll be providing an 'int'.
                  // Explicitly cast the 'long' to 'int' so we can use 'invokeExact'.
                  // allocateInt.type() = (Arena,int)MemorySegment
                  MethodHandle allocateInt = MethodHandles.explicitCastArguments(allocate,
                         methodType(memsegCls, arenaCls, int.class));
                 // Use the 'asByteBuffer' and 'address' methods as a filter, to transform the constructor into a method
                 // that takes two MemorySegment arguments instead of a ByteBuffer and a long argument.
                 // ctorArenaMemsegMemseg.type() = (Arena,MemorySegment,MemorySegment)CleanableDirectBufferImpl
                 MethodHandle ctorArenaMemsegMemseg = MethodHandles.explicitCastArguments(
                         MethodHandles.filterArguments(bufClsCtor, 1, asByteBuffer, address),
                         methodType(bufCls, arenaCls, memsegCls, memsegCls));
                 // Our method now takes two MemorySegment arguments, but we actually only want to pass one.
                 // Specifically, we want to get both the ByteBuffer and the memory address from the same MemorySegment
                 // instance.
                 // We permute the argument array such that the first MemorySegment argument gest passed to both
                 // parameters, and then the second parameter value gets ignored.
                 // ctorArenaMemsegNull.type() = (Arena,MemorySegment,MemorySegment)CleanableDirectBufferImpl
                 MethodHandle ctorArenaMemsegNull = MethodHandles.permuteArguments(ctorArenaMemsegMemseg,
                         methodType(bufCls, arenaCls, memsegCls, memsegCls), 0, 1, 1);
                 // With the second MemorySegment argument ignored, we can statically bind it to 'null' to effectively
                 // drop it from our parameter list.
                 MethodHandle ctorArenaMemseg = MethodHandles.insertArguments(
                         ctorArenaMemsegNull, 2, new Object[]{null});
                 // Use the 'allocateInt' method to transform the last MemorySegment argument of the constructor,
                 // into an (Arena,int) argument pair.
                 // ctorArenaArenaInt.type() = (Arena,Arena,int)CleanableDirectBufferImpl
                 MethodHandle ctorArenaArenaInt = MethodHandles.collectArguments(ctorArenaMemseg, 1, allocateInt);
                 // Our method now takes two Arena arguments, but we actually only want to pass one. Specifically, it's
                 // very important that it's the same arena we use for both allocation and deallocation.
                 // We permute the argument array such that the first Arena argument gets passed to both parameters,
                 // and the second parameter value gets ignored.
                 // ctorArenaNullInt.type() = (Arena,Arena,int)CleanableDirectBufferImpl
                 MethodHandle ctorArenaNullInt = MethodHandles.permuteArguments(ctorArenaArenaInt,
                         methodType(bufCls, arenaCls, arenaCls, int.class), 0, 0, 2);
                 // With the second Arena parameter value ignored, we can statically bind it to 'null' to effectively
                 // drop it from our parameter list.
                 // ctorArenaInt.type() = (Arena,int)CleanableDirectBufferImpl
                 MethodHandle ctorArenaInt = MethodHandles.insertArguments(ctorArenaNullInt, 1, new Object[]{null});
                 // Now we just need to create our Arena instance. We fold the Arena parameter into the 'ofShared'
                 // static method, so we effectively bind the argument to the result of calling that method.
                 // Since 'ofShared' takes no further parameters, we effectively eliminate the first parameter.
                 // This creates our method handle that takes an 'int' and returns a 'CleanableDirectBufferImpl'.
                 // ctorInt.type() = (int)CleanableDirectBufferImpl
                 method = MethodHandles.foldArguments(ctorArenaInt, ofShared);
                 error = null;
             } catch (Throwable throwable) {
                 method = null;
                 error = throwable;
             }
         } else {
             method = null;
             error = new UnsupportedOperationException("java.lang.foreign.MemorySegment unavailable");
         }
         if (logger != null) {
             if (error == null) {
                 logger.debug("java.nio.ByteBuffer.cleaner(): available");
             } else {
                 logger.debug("java.nio.ByteBuffer.cleaner(): unavailable", error);
             }
         }
         INVOKE_ALLOCATOR = method;
     }
 
     static boolean isSupported() {
         return INVOKE_ALLOCATOR != null;
     }
 
     @SuppressWarnings("OverlyStrongTypeCast") // The cast is needed for 'invokeExact' semantics.
     @Override
     public CleanableDirectBuffer allocate(int capacity) {
         try {
             return (CleanableDirectBufferImpl) INVOKE_ALLOCATOR.invokeExact(capacity);
         } catch (RuntimeException e) {
             throw e; // Propagate the runtime exceptions that the Arena would normally throw.
         } catch (Throwable e) {
             throw new IllegalStateException("Unexpected allocation exception", e);
         }
     }
 
     @Override
     public void freeDirectBuffer(ByteBuffer buffer) {
         throw new UnsupportedOperationException("Cannot clean arbitrary ByteBuffer instances");
     }
 
     private static final class CleanableDirectBufferImpl implements CleanableDirectBuffer {
         private final AutoCloseable closeable;
         private final ByteBuffer buffer;
         private final long memoryAddress;
 
         // NOTE: must be at least package-protected to allow calls from the method handles!
         CleanableDirectBufferImpl(AutoCloseable closeable, ByteBuffer buffer, long memoryAddress) {
             this.closeable = closeable;
             this.buffer = buffer;
             this.memoryAddress = memoryAddress;
         }
 
         @Override
         public ByteBuffer buffer() {
             return buffer;
         }
 
         @Override
         public void clean() {
             try {
                 closeable.close();
             } catch (RuntimeException e) {
                 throw e; // Propagate the runtime exceptions that Arena would normally throw.
             } catch (Exception e) {
                 throw new IllegalStateException("Unexpected close exception", e);
             }
         }
 
         @Override
         public boolean hasMemoryAddress() {
             return true;
         }
 
         @Override
         public long memoryAddress() {
             return memoryAddress;
         }
     }
 }