package fr.expdev.fromendreader;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;

public class FromEndReader {

	private final File file;

	private final RandomAccessFile raf;

	private int max;

	private long position;

	public FromEndReader(final String file, final int max) throws IOException {
		super();
		this.max = max;
		this.file = new File(file);
		raf = new RandomAccessFile(this.file, "r");
		position = raf.length();
	}

	public String readLine() throws IOException {
		StringBuilder line = new StringBuilder();
		byte code = 0;

		while (--position >= 0 & max != 0) {
			raf.seek(position);
			code = raf.readByte();

			if (code == 13 || code == 10) {
				raf.seek(position - 1);
				int nextCode = raf.readByte();
				max--;

				if ((code == 13 && nextCode == 10) || (code == 10 && nextCode == 13)) {
					position--;
				}

				break;
			}

			line.insert(0, (char) code);
			max--;
		}

		if (line.length() == 0) {
			return null;
		} else {
			return line.toString();
		}
	}

	public Byte readByte() throws IOException {
		Byte theByte = null;

		if (position > 0 && max != 0) {
			raf.seek(position - 1);
			theByte = raf.readByte();
			position--;
			max--;
		}

		return theByte;
	}

	public void close() throws IOException {
		raf.close();
	}

}