/*  _____ _
 * |_   _| |_  _ _ ___ ___ _ __  __ _
 *   | | | ' \| '_/ -_) -_) '  \/ _` |_
 *   |_| |_||_|_| \___\___|_|_|_\__,_(_)
 *
 * Threema for Android
 * Copyright (c) 2013-2020 Threema GmbH
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <https://www.gnu.org/licenses/>.
 */

package ch.threema.app.utils;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

public class SecureDeleteUtil {
	private static final Logger logger = LoggerFactory.getLogger(SecureDeleteUtil.class);

    public static void secureDelete(File file) throws IOException {
        if (file != null && file.exists()) {
			if (file.isDirectory()) {
				File[] children = file.listFiles();
				if (children != null) {
					for (int i = 0; i < children.length; i++) {
						SecureDeleteUtil.secureDelete(children[i]);
					}
				}
				//remove directory
				FileUtil.deleteFileOrWarn(file, "secureDelete", logger);
				return;
			}

            long length = file.length();
            try (RandomAccessFile raf = new RandomAccessFile(file, "rw")) {
	            raf.seek(0);
	            byte[] zero = new byte[16384];
	            long pos = 0;
	            while (pos < length) {
		            int nwrite = (int) Math.min((long) zero.length, length - pos);
		            raf.write(zero, 0, nwrite);
		            pos += nwrite;
	            }
            }
	        FileUtil.deleteFileOrWarn(file, "secureDelete", logger);
        }
    }
}
