package org.kne.cloud.network;

import java.lang.foreign.Arena;
import java.lang.foreign.MemorySegment;
import java.lang.foreign.MemorySegment.Scope;
import java.lang.ref.PhantomReference;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.nio.ByteBuffer;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.ReentrantLock;

public class BufferedArena implements Arena{
	private static long blockSize=10*1024L*1024L;
	private volatile PreAlloc buffer;
	private static ReferenceQueue<MemorySegment> refq=new ReferenceQueue<>();
	private static MemorySegmentPool msp=new MemorySegmentPool(1000, blockSize,true);
	
	public static long getBlockSize() {
		return blockSize;
	}



	public static void setBlockSize(long blockSizex) {
		blockSize = blockSizex;
	}



	private ReentrantLock lock=new ReentrantLock();
	
	private class PreAlloc{
		private MemorySegment segment;
		private AtomicLong pos=new AtomicLong(0);
		private AtomicLong refs=new AtomicLong(0);
		public MemorySegment getSegment() {
			return segment;
		}
		public AtomicLong getPos() {
			return pos;
		}
		public PreAlloc(MemorySegment segment) {
			super();
			this.segment = segment;
		}
		public long byteSize() {
			return segment.byteSize();
		}
		public AtomicLong getRefs() {
			return refs;
		}
		
	}
	
	private void allocateNew(long blockSize2) {
		lock.lock();
		try {
		//buffer=Arena.ofAuto().allocate(blockSize);
		MemorySegment raw=msp.borrow();
		buffer=new PreAlloc(raw);
			
		}finally {
			lock.unlock();
		}
	}



	static {
		Thread t= new Thread(()->{
			while(true) {
			try {
			Reference<? extends MemorySegment> ref;
				ref = refq.remove();
			if(ref!=null) {
				ref.clear();
			}
			} catch (InterruptedException e) {
				// TODO 自动生成的 catch 块
				e.printStackTrace();
			}
			}
		});
		t.setDaemon(true);
		t.setPriority(Thread.MAX_PRIORITY-1);
		t.start();
	}



	public BufferedArena() {
		super();
		allocateNew(blockSize);
	}

	@Override
	public MemorySegment allocate(long byteSize, long byteAlignment) {
		if(byteSize>blockSize)
			throw new IndexOutOfBoundsException("byteSize can't large than buffer block");
		long pos;
		PreAlloc bufferx;
		 do{
			 bufferx=this.buffer;
		 pos=bufferx.getPos().getAndAdd(byteSize);
		if(pos+byteSize>bufferx.byteSize()) {
			allocateNew(blockSize);
		}else {
			break;
		}
		}while(true);
		 bufferx.getRefs().incrementAndGet();
		MemorySegment sliced=bufferx.getSegment().asSlice(pos, byteSize);
		new MemorySegmentPhantomReference(sliced, refq, bufferx, msp);
			return sliced;
		
	}

	@Override
	public Scope scope() {
		return Arena.ofAuto().scope();
	}

	@Override
	public void close() {
		Arena.ofAuto().close();
	}
	public static BufferedArena ofBuffered() {
		return new BufferedArena();
	}
	
private class MemorySegmentPhantomReference extends PhantomReference<MemorySegment>{
		
		private static AtomicReference<MemorySegmentPhantomReference> first=new AtomicReference<>(null);
		
		private AtomicReference<MemorySegmentPhantomReference> next=new AtomicReference<>(null);
		private AtomicReference<MemorySegmentPhantomReference> prev=new AtomicReference<>(null);
		
		private PreAlloc father;
		private MemorySegmentPool pool;

		public MemorySegmentPhantomReference(MemorySegment referent, ReferenceQueue<? super MemorySegment> q,PreAlloc bufferx,MemorySegmentPool pool) {
			super(referent, q);
			this.father=bufferx;
			this.pool=pool;
			insert();
		}
		
		private void insert() {
			MemorySegmentPhantomReference refn= first.getAndSet(this);
			if(refn!=null) {
			next.set(refn);
			refn.prev.set(this);
			}
		}

		private void remove() {
			MemorySegmentPhantomReference prevn= prev.getAndSet(null);
			MemorySegmentPhantomReference nextn=next.getAndSet(null);
			if(prevn!=null) 
			prevn.next.set(nextn);
			if(nextn!=null) 
			nextn.prev.set(prevn);
		}
		
		@Override
		public void clear() {
			if(father.getRefs().decrementAndGet()<=0) {
				if(buffer!=father)
			pool.back(father.getSegment());	
			}
			remove();
			super.clear();
		}
	}
}