/**
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The ASF licenses this file to you under the Apache License, Version
 * 2.0 (the "License"); you may not use this file except in compliance with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
 * and limitations under the License.
 */

package org.apache.storm.container.cgroup;

import java.io.IOException;
import java.nio.channels.ClosedByInterruptException;
import org.apache.storm.shade.org.apache.commons.io.IOUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A class that implements system operations for using cgroups.
 */
public class SystemOperation {

    private static final Logger LOG = LoggerFactory.getLogger(SystemOperation.class);

    public static boolean isRoot() throws IOException {
        String result = SystemOperation.exec("echo $EUID").substring(0, 1);
        return Integer.valueOf(result.substring(0, result.length())).intValue() == 0 ? true : false;
    }

    public static void mount(String name, String target, String type, String options) throws IOException {
        StringBuilder sb = new StringBuilder();
        sb.append("mount -t ")
                .append(type)
                .append(" -o ")
                .append(options)
                .append(" ")
                .append(name)
                .append(" ")
                .append(target);
        SystemOperation.exec(sb.toString());
    }

    public static void umount(String pathToDir) throws IOException {
        StringBuilder sb = new StringBuilder();
        sb.append("umount ").append(pathToDir);
        SystemOperation.exec(sb.toString());
    }

    public static String exec(String cmd) throws IOException {
        LOG.debug("Shell cmd: {}", cmd);
        Process process = new ProcessBuilder(new String[]{ "/bin/bash", "-c", cmd }).start();
        try {
            process.waitFor();
            String output = IOUtils.toString(process.getInputStream());
            String errorOutput = IOUtils.toString(process.getErrorStream());
            LOG.debug("Shell Output: {}", output);
            if (errorOutput.length() != 0) {
                LOG.error("Shell Error Output: {}", errorOutput);
                throw new IOException(errorOutput);
            }
            return output;
        } catch (InterruptedException | ClosedByInterruptException ie) {
            throw new IOException(ie);
        }
    }
}