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package com.firefly.net.buffer;

import java.io.Closeable;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;

import com.firefly.utils.concurrent.Callback;
import com.firefly.utils.io.BufferReaderHandler;
import com.firefly.utils.io.FileUtils;

public class FileRegion implements Closeable {

	private final File file;
	private final long position;
	private final long length;
	private final boolean randomAccess;
	private FileChannel fileChannel;

	public FileRegion(File file) throws FileNotFoundException {
		this.file = file;
		position = 0;
		length = file.length();
		randomAccess = false;
	}

	public FileRegion(File file, long position, long length) throws FileNotFoundException {
		long fileLen = file.length();
		if (position < 0 || position >= fileLen) {
			throw new IndexOutOfBoundsException("the position range is illegal");
		}

		this.file = file;
		this.position = position;
		this.length = length;
		if (position > 0) {
			randomAccess = true;
		} else {
			randomAccess = (length < fileLen);
		}
	}

	public long getPosition() {
		return position;
	}

	public long getLength() {
		return length;
	}

	public FileChannel getFileChannel() throws IOException {
		if (fileChannel != null) {
			return fileChannel;
		} else {
			fileChannel = FileChannel.open(Paths.get(file.toURI()), StandardOpenOption.READ);
			return fileChannel;
		}
	}

	public boolean isRandomAccess() {
		return randomAccess;
	}

	public File getFile() {
		return file;
	}

	public long transferTo(Callback callback, BufferReaderHandler handler) throws IOException {
		long ret;
		if (isRandomAccess()) {
			ret = FileUtils.transferTo(getFileChannel(), getPosition(), getLength(), callback, handler);
		} else {
			ret = FileUtils.transferTo(getFileChannel(), getLength(), callback, handler);
		}
		return ret;
	}

	@Override
	public void close() throws IOException {
		if (fileChannel != null)
			fileChannel.close();
	}

}