/*
 * The MIT License (MIT)
 *
 * Copyright (C) 2014 Aaron Weiss
 *
 * 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 provider.pkgnx;

import provider.pkgnx.internal.LazyNXTables;
import provider.pkgnx.internal.NXHeader;
import provider.pkgnx.util.NodeParser;
import provider.pkgnx.util.SeekableLittleEndianAccessor;

import java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.Paths;

/**
 * A lazy-loaded memory-mapped file for reading specification-compliant NX files.
 *
 * @author Aaron Weiss
 * @version 1.0.0
 * @since 1/21/14
 */
public class LazyNXFile extends NXFile {
	private final SeekableLittleEndianAccessor slea;
	private NXNode[] nodes;

	/**
	 * Creates a new {@code EagerNXFile} from the specified {@code path}.
	 *
	 * @param path the absolute or relative path to the file
	 * @throws java.io.IOException if something goes wrong in reading the file
	 */
	public LazyNXFile(String path) throws IOException {
		this(Paths.get(path));
	}

	/**
	 * Creates a new {@code EagerNXFile} from the specified {@code path}.
	 *
	 * @param path the absolute or relative path to the file
	 * @throws IOException if something goes wrong in reading the file
	 */
	public LazyNXFile(Path path) throws IOException {
		super(path.toString());
		FileChannel channel = FileChannel.open(path);
		slea = new SeekableLittleEndianAccessor(channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size()));
		header = new NXHeader(this, slea);
		nodes = new NXNode[(int) header.getNodeCount()];
		tables = new LazyNXTables(header, slea);
	}

	@Override
	public NXNode getNode(int index) {
		NXNode ret = nodes[index];
		if (ret != null)
			return ret;
		slea.seek(header.getNodeOffset() + index * NXNode.NODE_SIZE);
		return (nodes[index] = NodeParser.parseNode(this, slea));
	}
}