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/**
 *
 *  Copyright © 2013 Nayuki Minase
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a copy of
 *  this software and associated documentation files (the "Software"), to deal in
 *  the Software without restriction, including without limitation the rights to
 *  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 *  the Software, and to permit persons to whom the Software is furnished to do so,
 *  subject to the following conditions:
 *
 *  * The above copyright notice and this permission notice shall be included in
 *    all copies or substantial portions of the Software.
 *
 *  * The Software is provided "as is", without warranty of any kind, express or
 *    implied, including but not limited to the warranties of merchantability,
 *    fitness for a particular purpose and noninfringement. In no event shall the
 *    authors or copyright holders be liable for any claim, damages or other
 *    liability, whether in an action of contract, tort or otherwise, arising from,
 *    out of or in connection with the Software or the use or other dealings in the
 *    Software.
 */

package nayuki.huffmancoding;

import java.io.IOException;


public final class HuffmanDecoder {
	
	private BitInputStream input;
	
	// Must be initialized before calling read().
	// The code tree can be changed after each symbol decoded, as long as the encoder and decoder have the same code tree at the same time.
	public CodeTree codeTree;
	
	
	
	public HuffmanDecoder(BitInputStream in) {
		if (in == null)
			throw new NullPointerException("Argument is null");
		input = in;
	}
	
	
	
	public int read() throws IOException {
		if (codeTree == null)
			throw new NullPointerException("Code tree is null");
		
		InternalNode currentNode = codeTree.root;
		while (true) {
			int temp = input.readNoEof();
			Node nextNode;
			if      (temp == 0) nextNode = currentNode.leftChild;
			else if (temp == 1) nextNode = currentNode.rightChild;
			else throw new AssertionError();
			
			if (nextNode instanceof Leaf)
				return ((Leaf)nextNode).symbol;
			else if (nextNode instanceof InternalNode)
				currentNode = (InternalNode)nextNode;
			else
				throw new AssertionError();
		}
	}
	
}