/*
 * Copyright (c) 2014 tabletoptool.com team.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Public License v3.0
 * which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/gpl.html
 * 
 * Contributors:
 *     rptools.com team - initial implementation
 *     tabletoptool.com team - further development
 */
package com.t3.transfer;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.Serializable;

/**
 * Creates data chunks for transferring binary data.  Assumes large datasets (otherwise
 * it would be a direct transfer) so expects the data to be streamed from a file
 * 
 * @author trevor
 */
public class AssetProducer {
	private Serializable id;
	private String name;
	private File assetFile;
	private long length;
	private long currentPosition = 0;
	
	public AssetProducer(Serializable id, String name, File assetFile) {
		if (!assetFile.exists() || assetFile.isDirectory()) {
			throw new IllegalArgumentException(assetFile + " is an invalid asset path");
		}
		this.id = id;
		this.name = name;
		this.assetFile = assetFile;
		length = assetFile.length();
	}
	
	/**
	 * Get the header needed to create the corresponding AssetConsumer
	 * @throws IOException
	 */
	public AssetHeader getHeader() throws IOException {
		return new AssetHeader(id, name, assetFile.length());
	}

	/**
	 * Get the next chunk of data
	 * @param size how many bytes to grab, may end up being less if there isn't enough data
	 * @throws IOException
	 */
	public AssetChunk nextChunk(int size) throws IOException {
		if (currentPosition + size > length) {
			size = (int)(length - currentPosition);
		}
		byte[] data = new byte[size];
		try(FileInputStream in = new FileInputStream(assetFile)) {
			in.skip(currentPosition);
			in.read(data, 0, size);
		}
		
		currentPosition += size;
		return new AssetChunk(id, data);
	}

	/**
	 * Whether all the data has been transferred
	 */
	public boolean isComplete() {
		return currentPosition >= length;
	}
}