package org.simantics.db.common;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ReadableByteChannel;

import org.simantics.db.common.utils.Logger;
import org.simantics.db.service.Bytes;

final public class ByteFileReader {

	public static int BUFFER = 65536;

	final private FileInputStream fs;
	final private ReadableByteChannel channel;
	final private ByteBuffer byteBuffer;
	
	final private byte[] bytes = new byte[BUFFER];
	private int size;

	protected int byteIndex = 0;

	final protected ReadableByteChannel getChannel() {
		return channel;
	}
	
	final protected ByteBuffer getByteBuffer() {
		return byteBuffer;
	}

	final protected byte[] getBytes() {
		return bytes;
	}

	final public byte[] readBytes(int amount) throws IOException {

		byte[] result = new byte[amount];
		
		int has = size-byteIndex;
		if(amount >= has) {
			ReadableByteChannel c = channel;
			System.arraycopy(bytes, byteIndex, result, 0, has);
			ByteBuffer bb2 = ByteBuffer.wrap(result);
			bb2.position(has);
			while(has < amount)
				has += c.read(bb2);
			getSome();
		} else {
			System.arraycopy(bytes, byteIndex, result, 0, amount);
			byteIndex += amount;
		}

		return result;
		
	}

	final public void getSome() throws IOException {

		ReadableByteChannel c = channel;
		ByteBuffer bb = byteBuffer;
		bb.position(0);
		bb.limit(BUFFER);
		size = c.read(bb);
		if(size == 0) {
			long start = System.nanoTime();
			while(size == 0) {
				if(System.nanoTime() - start > 10000000000L) throw new IOException("Timeout");
				size = c.read(bb);
			}
		}
		bb.position(0);
		byteIndex = 0;
		
	}
	
	final public int readShort() throws IOException {

		if(byteIndex >= (size-3)) {
			short result = 0;
			if(byteIndex == size) {
				getSome();
			}
			result |= ((short)(bytes[byteIndex++]&0xff)<<0);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((short)(bytes[byteIndex++]&0xff)<<8);
			if(byteIndex == size) {
				getSome();
			}
			return result;
		} else {
			int result = Bytes.readLE2(bytes, byteIndex);
			byteIndex += 2;
			return result;
		}
		
	}
	
	final public int readInt() throws IOException {

		if(byteIndex >= (size-5)) {
			int result = 0;
			if(byteIndex == size) {
				getSome();
			}
			result |= ((int)(bytes[byteIndex++]&0xff)<<0);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((int)(bytes[byteIndex++]&0xff)<<8);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((int)(bytes[byteIndex++]&0xff)<<16);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((int)(bytes[byteIndex++]&0xff)<<24);
			if(byteIndex == size) {
				getSome();
			}
			return result;
		} else {
			int result = Bytes.readLE4(bytes, byteIndex);
			byteIndex += 4;
			return result;
		}
		
	}
	
	final public long readLong() throws IOException {

		if(byteIndex >= (size-9)) {
			long result = 0;
			if(byteIndex == size) {
				getSome();
			}
			result |= ((long)(bytes[byteIndex++]&0xff)<<0);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((long)(bytes[byteIndex++]&0xff)<<8);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((long)(bytes[byteIndex++]&0xff)<<16);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((long)(bytes[byteIndex++]&0xff)<<24);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((long)(bytes[byteIndex++]&0xff)<<32);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((long)(bytes[byteIndex++]&0xff)<<40);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((long)(bytes[byteIndex++]&0xff)<<48);
			if(byteIndex == size) {
				getSome();
			}
			result |= ((long)(bytes[byteIndex++]&0xff)<<56);
			if(byteIndex == size) {
				getSome();
			}
			return result;
		} else {
			long result = Bytes.readLE8(bytes, byteIndex);
			byteIndex += 8;
			return result;
		}
		
	}

	public void close() {
		try {
			fs.close();
		} catch (IOException e) {
			Logger.defaultLogError(e);
		}
	}
	
	public ByteFileReader(File file) throws IOException {

		byteBuffer = ByteBuffer.wrap(bytes);

		fs = new FileInputStream(file);
		
		channel = fs.getChannel();
		
		this.size = channel.read(byteBuffer);
		
		byteBuffer.position(0);
		
	}
	
}