package org.simantics.acorn.lru;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.file.Path;
import java.util.ArrayList;

import org.simantics.acorn.ClusterManager;
import org.simantics.acorn.Persistable;
import org.simantics.acorn.exception.AcornAccessVerificationException;
import org.simantics.acorn.exception.IllegalAcornStateException;
import org.simantics.acorn.internal.ClusterChange;
import org.simantics.acorn.internal.UndoClusterUpdateProcessor;
import org.simantics.compressions.CompressionCodec;
import org.simantics.compressions.Compressions;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.service.Bytes;
import org.simantics.utils.datastructures.Pair;

import gnu.trove.list.array.TByteArrayList;

public class ClusterStreamChunk extends LRUObject<String, ClusterStreamChunk> implements Persistable {

	// 500KB is a fine chunk
	private static int MAX_CHUNK_SIZE = 500*1024;

	int size = 0;
	final private ClusterManager manager;
	private boolean committed = false;
	
	public int nextToProcess = 0;
	
	public ArrayList<ClusterUpdateOperation> operations = new ArrayList<ClusterUpdateOperation>();
	
	// Stub
	public ClusterStreamChunk(ClusterManager manager, LRU<String, ClusterStreamChunk> LRU, Path readDir, String id, int offset, int length) throws AcornAccessVerificationException {
		super(LRU, id, readDir, "clusterStream", offset, length, false, false);
		this.manager = manager;
		LRU.map(this);
	}
	
	// Creation
	public ClusterStreamChunk(ClusterManager manager, LRU<String, ClusterStreamChunk> LRU, String id) throws AcornAccessVerificationException {
		super(LRU, id, LRU.getDirectory(), "clusterStream", true, true);
		this.manager = manager;
		LRU.insert(this, accessTime);
	}
	
	public UndoClusterUpdateProcessor getUndoProcessor(ClusterManager clusters, int chunkOffset, String ccsId) throws DatabaseException {
		
		if(VERIFY) verifyAccess();
		
		makeResident(true);

		ClusterUpdateOperation op = operations.get(chunkOffset);
		if(op == null) throw new IllegalAcornStateException("Cluster Update Operation " + ccsId + " was not found.");
		if(op.ccs == null) throw new IllegalAcornStateException("Cluster ChangeSet " + ccsId + " was not found.");

		UndoClusterUpdateProcessor proc = new UndoClusterUpdateProcessor(clusters, this, op.ccs);
		if(proc.version != ClusterChange.VERSION)
			return null;

		// This cluster and CCS can still be under preparation => wait
		clusters.clusterLRU.ensureUpdates(proc.getClusterUID());

		proc.process();

		cancelForceResident();
		
		return proc;
		
	}
	
	public void addOperation(ClusterUpdateOperation op) throws IllegalAcornStateException {
		if(committed)
			throw new IllegalAcornStateException("Cannot add operation " + op + " to " + this + " if commited == true");
		operations.add(op);
		size += op.data.length;
//		if(isCommitted()) {
//			LRU.refresh(this);
//		}
	}
	
	public byte[] getOperation(int index) {
		return operations.get(index).data;
	}
	
	public void commit() {
		committed = true;
	}
	
	public boolean isCommitted() {
		if(size > MAX_CHUNK_SIZE) committed = true;
		return committed;
	}
	
	@Override
	public boolean canBePersisted() throws AcornAccessVerificationException {
		if(!super.canBePersisted()) return false;
		if(!isCommitted()) return false;
		for(ClusterUpdateOperation op : operations) {
			if(!op.finished) return false;
		}
		return true;
	}

	private static void writeLE(TByteArrayList bytes, int value) {
		
		bytes.add( (byte) (value & 0xFF));
		bytes.add((byte) ((value >>> 8) & 0xFF));
		bytes.add((byte) ((value >>> 16) & 0xFF));
		bytes.add((byte) ((value >>> 24) & 0xFF));

	}

	final public static void writeLE8(TByteArrayList bytes, long value) {
		
		bytes.add( (byte) (value & 0xFF));
		bytes.add((byte) ((value >>> 8) & 0xFF));
		bytes.add((byte) ((value >>> 16) & 0xFF));
		bytes.add((byte) ((value >>> 24) & 0xFF));
		bytes.add((byte) ((value >>> 32) & 0xFF));
		bytes.add((byte) ((value >>> 40) & 0xFF));
		bytes.add((byte) ((value >>> 48) & 0xFF));
		bytes.add((byte) ((value >>> 56) & 0xFF));
		
	}
	
	@Override
	protected Pair<byte[], Integer> toBytes() {
		
		assert(isCommitted());
		
		TByteArrayList raw = new TByteArrayList();
		
		writeLE(raw, operations.size());
		
		for(ClusterUpdateOperation op : operations) {
			
			writeLE(raw, op.data.length);
			raw.add(op.data);
			op.data = null;
			
			writeLE(raw, op.ccs.statementMask.size());
			raw.add(op.ccs.statementMask.toArray());
			writeLE(raw, op.ccs.oldValueEx.size());
			raw.add(op.ccs.oldValueEx.toArray());
			writeLE(raw, op.ccs.oldValues.size());
			
			for(byte[] oldValue : op.ccs.oldValues) {
				int len = (oldValue != null ? oldValue.length : -1);
				writeLE(raw, len);
				if(oldValue != null) {
					raw.add(oldValue);
				}
			}
			
		}
		
		byte[] raw_ = raw.toArray();
		CompressionCodec codec = Compressions.get(Compressions.LZ4);
		ByteBuffer input = ByteBuffer.wrap(raw_);
		ByteBuffer output = ByteBuffer.allocate(raw_.length + raw_.length/8);
		int compressedSize = codec.compressBuffer(input, 0, raw_.length, output, 0);

		// We append inflated size - cannot prepend since decompression cannot handle offsets in input
		final byte[] rawOutput = new byte[compressedSize+4];
		output.get(rawOutput,0,compressedSize);
		Bytes.writeLE(rawOutput, compressedSize, raw_.length);

		release();
		
		return Pair.make(rawOutput, rawOutput.length);
		
	}
	
	@Override
	void release() {
		
		for(ClusterUpdateOperation op : operations) {
			op.data = null;
			op.ccs = null;
		}

	}

	static class StreamDecompressor {
		
//		byte[] decompressBuffer = new byte[1024*1024];

		public synchronized byte[] decompressBuffer(byte[] compressed) throws IOException {
			
			int deflatedSize = Bytes.readLE4(compressed, compressed.length-4);
			
			byte[] result = new byte[deflatedSize];
			
//			if(decompressBuffer.length < deflatedSize)
//				decompressBuffer = new byte[Math.max(3*decompressBuffer.length / 2, deflatedSize)];
			
			CompressionCodec codec = Compressions.get(Compressions.LZ4);
			
			ByteBuffer input = ByteBuffer.wrap(compressed);
			ByteBuffer output = ByteBuffer.wrap(result);

			int decompressedSize = codec.decompressBuffer(input, 0, compressed.length-4, output, 0, result.length);
			assert(decompressedSize  == deflatedSize);
			
			return result;
			
		}

		
	}
	
	private static StreamDecompressor decompressor = new StreamDecompressor();
	
	@Override
	public void fromFile(byte[] data_) throws IllegalAcornStateException, AcornAccessVerificationException {

		try {
			
			byte[] data = decompressor.decompressBuffer(data_);
			
			operations = new ArrayList<ClusterUpdateOperation>();
			
			int offset = 0;
			int opLen = Bytes.readLE4(data, offset);
			offset += 4;
			
			for(int i=0;i<opLen;i++) {
				
				int len = Bytes.readLE4(data, offset);
				offset += 4;
				byte[] bytes  = new byte[len];
				System.arraycopy(data, offset, bytes, 0, len);
				offset += len;
				
				ClusterUpdateOperation op = new ClusterUpdateOperation(manager, bytes);
				
				String ccsKey = getKey() + "." + i;
				
				op.ccs = new ClusterChangeSet(ccsKey, op.uid);
				op.chunk = this;
				
				int statementMaskLen = Bytes.readLE4(data, offset);
				offset += 4;
				op.ccs.statementMask = new TByteArrayList(statementMaskLen);
				for(int j=0;j<statementMaskLen;j++)
					op.ccs.statementMask.add(data[offset++]);
				
				int oldValueExLen = Bytes.readLE4(data, offset);
				offset += 4;
				op.ccs.oldValueEx = new TByteArrayList(oldValueExLen);
				for(int j=0;j<oldValueExLen;j++)
					op.ccs.oldValueEx.add(data[offset++]);
				
				int oldValuesSize = Bytes.readLE4(data, offset);
				offset += 4;
				
				op.ccs.oldValues = new ArrayList<>(oldValuesSize);
				for(int j=0;j<oldValuesSize;j++) {

					int oldValueSize = Bytes.readLE4(data, offset);
					offset += 4;

					if(oldValueSize == -1) {
						op.ccs.oldValues.add(null);
					} else {
						byte[] oldValue = new byte[oldValueSize];
						System.arraycopy(data, offset, oldValue, 0, oldValueSize);
						offset += oldValueSize;
						op.ccs.oldValues.add(oldValue);
					}

				}
				operations.add(op);
			}
		} catch (IOException e) {
			throw new IllegalAcornStateException(e);
		} catch (IllegalAcornStateException | AcornAccessVerificationException e) {
            throw e;
        }
	}

	@Override
	String getExtension() {
		return "stream";
	}
	
	@Override
	public String toString() {
		return  "ClusterUpdateOperationChunk " + getKey();
	}
	
	@Override
	protected boolean overwrite() {
		return false;
	}
	
}