/**
 * @author Aleksey Terzi
 *
 */

package com.encrox.instancedregions.chunkmap;

import java.io.IOException;

public class ChunkWriter {
	private byte[] data;
	private int bitsPerBlock;
	private int byteIndex;
	private int bitIndex;
	private long buffer;
	
	public ChunkWriter(byte[] data) {
		this.data = data;
	}
	
	public int getByteIndex() {
		return this.byteIndex;
	}
	
	public void init() {
		this.byteIndex = 0;
		this.bitIndex = 0;
		this.buffer = 0;
	}
	
	public void setBitsPerBlock(int bitsPerBlock) {
		this.bitsPerBlock = bitsPerBlock;
	}
	
	public void save() throws IOException {
		writeLong();
	}
	
	public void skip(int count) {
		this.byteIndex += count;
		this.bitIndex = 0;
	}
	
	public void writeBytes(byte[] source, int index, int length) throws IOException {
		if(this.byteIndex + length > this.data.length) {
			throw new IOException("No space to write.");
		}
		
		System.arraycopy(source, index, this.data, this.byteIndex, length);
		
		this.byteIndex += length;
	}
	
	public void writeBlockBits(long bits) throws IOException {
		if(this.bitIndex >= 64) {
			writeLong();
			this.bitIndex = 0;
		}
		
		int leftBits = 64 - this.bitIndex;
		
		this.buffer |= bits << this.bitIndex; 
		
		if(leftBits >= this.bitsPerBlock) {
			this.bitIndex += this.bitsPerBlock;
		} else {
			writeLong();
			
			this.buffer = bits >>> leftBits;
			
			this.bitIndex = this.bitsPerBlock - leftBits;
		}
	}
	
	private void writeLong() throws IOException {
		if(this.byteIndex + 7 >= this.data.length) {
			throw new IOException("No space to write.");
		}
		
		this.data[this.byteIndex++] = (byte)(this.buffer >> 56);
		this.data[this.byteIndex++] = (byte)(this.buffer >> 48);
		this.data[this.byteIndex++] = (byte)(this.buffer >> 40);
		this.data[this.byteIndex++] = (byte)(this.buffer >> 32);
		this.data[this.byteIndex++] = (byte)(this.buffer >> 24);
		this.data[this.byteIndex++] = (byte)(this.buffer >> 16);
		this.data[this.byteIndex++] = (byte)(this.buffer >> 8);
		this.data[this.byteIndex++] = (byte)this.buffer;
		
		this.buffer = 0;
	}
	
	public void writeVarInt(int value) throws IOException {
		while((value & ~0x7F) != 0) {
            writeByte((value & 0x7F) | 0x80);
            value >>>= 7;
        }

        writeByte(value);
    }
	
	public void writeByte(int value) throws IOException {
		if(this.byteIndex >= this.data.length) {
			throw new IOException("No space to write.");
		}
		
		this.data[this.byteIndex++] = (byte)value;
	}
}