/**
 * 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.utils;

import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.InputStream;
import java.util.Map;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.atomic.AtomicBoolean;

import org.apache.storm.Config;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;



abstract public class ShellUtils {
    public static final Logger LOG = LoggerFactory.getLogger(ShellUtils.class);

    // OSType detection
    public enum OSType {
        OS_TYPE_LINUX,
        OS_TYPE_WIN,
        OS_TYPE_SOLARIS,
        OS_TYPE_MAC,
        OS_TYPE_FREEBSD,
        OS_TYPE_OTHER
    }

    public static final OSType osType = getOSType();

    static private OSType getOSType() {
        String osName = System.getProperty("os.name");
        if (osName.startsWith("Windows")) {
            return OSType.OS_TYPE_WIN;
        } else if (osName.contains("SunOS") || osName.contains("Solaris")) {
            return OSType.OS_TYPE_SOLARIS;
        } else if (osName.contains("Mac")) {
            return OSType.OS_TYPE_MAC;
        } else if (osName.contains("FreeBSD")) {
            return OSType.OS_TYPE_FREEBSD;
        } else if (osName.startsWith("Linux")) {
            return OSType.OS_TYPE_LINUX;
        } else {
            // Some other form of Unix
            return OSType.OS_TYPE_OTHER;
        }
    }

    // Helper static vars for each platform
    public static final boolean WINDOWS = (osType == OSType.OS_TYPE_WIN);
    public static final boolean SOLARIS = (osType == OSType.OS_TYPE_SOLARIS);
    public static final boolean MAC     = (osType == OSType.OS_TYPE_MAC);
    public static final boolean FREEBSD = (osType == OSType.OS_TYPE_FREEBSD);
    public static final boolean LINUX   = (osType == OSType.OS_TYPE_LINUX);
    public static final boolean OTHER   = (osType == OSType.OS_TYPE_OTHER);


    /** Token separator regex used to parse Shell tool outputs */
    public static final String TOKEN_SEPARATOR_REGEX
        = WINDOWS ? "[|\n\r]" : "[ \t\n\r\f]";

    private long    interval;   // refresh interval in msec
    private long    lastTime;   // last time the command was performed
    final private boolean redirectErrorStream; // merge stdout and stderr
    private Map<String, String> environment; // env for the command execution
    private File dir;
    private Process process; // sub process used to execute the command
    private int exitCode;
    /**Time after which the executing script would be timedout*/
    protected long timeOutInterval = 0L;
    /** If or not script timed out*/
    private AtomicBoolean timedOut;

    /**If or not script finished executing*/
    private volatile AtomicBoolean completed;

    public ShellUtils() {
        this(0L);
    }

    public ShellUtils(long interval) {
        this(interval, false);
    }

    /** get the exit code
     * @return the exit code of the process
     */
    public int getExitCode() {
      return exitCode;
    }

    /**
     * @param interval the minimum duration to wait before re-executing the
     *        command.
     */
    public ShellUtils(long interval, boolean redirectErrorStream) {
        this.interval = interval;
        this.lastTime = (interval<0) ? 0 : -interval;
        this.redirectErrorStream = redirectErrorStream;
    }

    /** set the environment for the command
     * @param env Mapping of environment variables
     */
    protected void setEnvironment(Map<String, String> env) {
        this.environment = env;
    }

    /** set the working directory
     * @param dir The directory where the command would be executed
     */
    protected void setWorkingDirectory(File dir) {
        this.dir = dir;
    }

    /** a Unix command to get the current user's groups list */
    public static String[] getGroupsCommand() {
        return (WINDOWS)? new String[]{"cmd", "/c", "groups"}
        : new String[]{"bash", "-c", "groups"};
    }

    /**
     * a Unix command to get a given user's groups list.
     * If the OS is not WINDOWS, the command will get the user's primary group
     * first and finally get the groups list which includes the primary group.
     * i.e. the user's primary group will be included twice.
     */
    public static String[] getGroupsForUserCommand(final String user) {
        //'groups username' command return is non-consistent across different unixes
        return new String [] {"bash", "-c", "id -gn " + user
                         + "&& id -Gn " + user};
    }


    /** check to see if a command needs to be executed and execute if needed */
    protected void run() throws IOException {
        if (lastTime + interval > System.currentTimeMillis())
            return;
        exitCode = 0; // reset for next run
        runCommand();
    }

    /** Run a command */
    private void runCommand() throws IOException {
        ProcessBuilder builder = new ProcessBuilder(getExecString());
        Timer timeOutTimer = null;
        ShellTimeoutTimerTask timeoutTimerTask = null;
        timedOut = new AtomicBoolean(false);
        completed = new AtomicBoolean(false);

        if (environment != null) {
            builder.environment().putAll(this.environment);
        }
        if (dir != null) {
            builder.directory(this.dir);
        }

        builder.redirectErrorStream(redirectErrorStream);
        process = builder.start();

        if (timeOutInterval > 0) {
            timeOutTimer = new Timer("Shell command timeout");
            timeoutTimerTask = new ShellTimeoutTimerTask(this);
            //One time scheduling.
            timeOutTimer.schedule(timeoutTimerTask, timeOutInterval);
        }
        final BufferedReader errReader =
            new BufferedReader(new InputStreamReader(process
                                                     .getErrorStream()));
        BufferedReader inReader =
            new BufferedReader(new InputStreamReader(process
                                                     .getInputStream()));
        final StringBuffer errMsg = new StringBuffer();

        // read error and input streams as this would free up the buffers
        // free the error stream buffer
        Thread errThread = new Thread() {
                @Override
                public void run() {
                    try {
                        String line = errReader.readLine();
                        while((line != null) && !isInterrupted()) {
                            errMsg.append(line);
                            errMsg.append(System.getProperty("line.separator"));
                            line = errReader.readLine();
                        }
                    } catch(IOException ioe) {
                        LOG.warn("Error reading the error stream", ioe);
                    }
                }
            };
        try {
            errThread.start();
        } catch (IllegalStateException ise) { }
        try {
            parseExecResult(inReader); // parse the output
            // clear the input stream buffer
            String line = inReader.readLine();
            while(line != null) {
                line = inReader.readLine();
            }
            // wait for the process to finish and check the exit code
            exitCode  = process.waitFor();
            // make sure that the error thread exits
            joinThread(errThread);
            completed.set(true);
            //the timeout thread handling
            //taken care in finally block
            if (exitCode != 0) {
                throw new ExitCodeException(exitCode, errMsg.toString());
            }
        } catch (InterruptedException ie) {
            throw new IOException(ie.toString());
        } finally {
            if (timeOutTimer != null) {
                timeOutTimer.cancel();
            }
            // close the input stream
            try {
                // JDK 7 tries to automatically drain the input streams for us
                // when the process exits, but since close is not synchronized,
                // it creates a race if we close the stream first and the same
                // fd is recycled.  the stream draining thread will attempt to
                // drain that fd!!  it may block, OOM, or cause bizarre behavior
                // see: https://bugs.openjdk.java.net/browse/JDK-8024521
                //      issue is fixed in build 7u60
                InputStream stdout = process.getInputStream();
                synchronized (stdout) {
                    inReader.close();
                }
            } catch (IOException ioe) {
                LOG.warn("Error while closing the input stream", ioe);
            }
            if (!completed.get()) {
                errThread.interrupt();
                joinThread(errThread);
            }
            try {
                InputStream stderr = process.getErrorStream();
                synchronized (stderr) {
                    errReader.close();
                }
            } catch (IOException ioe) {
                LOG.warn("Error while closing the error stream", ioe);
            }
            process.destroy();
            lastTime = System.currentTimeMillis();
        }
    }

    private static void joinThread(Thread t) {
        while (t.isAlive()) {
            try {
                t.join();
            } catch (InterruptedException ie) {
                if (LOG.isWarnEnabled()) {
                    LOG.warn("Interrupted while joining on: " + t, ie);
                }
                t.interrupt(); // propagate interrupt
            }
        }
    }

    /** return an array containing the command name & its parameters */
    protected abstract String[] getExecString();

    /** Parse the execution result */
    protected abstract void parseExecResult(BufferedReader lines)
        throws IOException;

    /** get the current sub-process executing the given command
     * @return process executing the command
     */
    public Process getProcess() {
        return process;
    }

    /**
     * This is an IOException with exit code added.
     */
    public static class ExitCodeException extends IOException {
        int exitCode;

        public ExitCodeException(int exitCode, String message) {
            super(message);
            this.exitCode = exitCode;
        }

        public int getExitCode() {
            return exitCode;
        }
    }

    /**
     * A simple shell command executor.
     *
     * <code>ShellCommandExecutor</code>should be used in cases where the output
     * of the command needs no explicit parsing and where the command, working
     * directory and the environment remains unchanged. The output of the command
     * is stored as-is and is expected to be small.
     */
    public static class ShellCommandExecutor extends ShellUtils {

        private String[] command;
        private StringBuffer output;


        public ShellCommandExecutor(String[] execString) {
            this(execString, null);
        }

        public ShellCommandExecutor(String[] execString, File dir) {
            this(execString, dir, null);
        }

        public ShellCommandExecutor(String[] execString, File dir,
                                    Map<String, String> env) {
            this(execString, dir, env , 0L);
        }

        /**
         * Create a new instance of the ShellCommandExecutor to execute a command.
         *
         * @param execString The command to execute with arguments
         * @param dir If not-null, specifies the directory which should be set
         *            as the current working directory for the command.
         *            If null, the current working directory is not modified.
         * @param env If not-null, environment of the command will include the
         *            key-value pairs specified in the map. If null, the current
         *            environment is not modified.
         * @param timeout Specifies the time in milliseconds, after which the
         *                command will be killed and the status marked as timedout.
         *                If 0, the command will not be timed out.
         */
        public ShellCommandExecutor(String[] execString, File dir,
                                    Map<String, String> env, long timeout) {
            command = execString.clone();
            if (dir != null) {
                setWorkingDirectory(dir);
            }
            if (env != null) {
                setEnvironment(env);
            }
            timeOutInterval = timeout;
        }


        /** Execute the shell command. */
        public void execute() throws IOException {
            this.run();
        }

        @Override
        public String[] getExecString() {
            return command;
        }

        @Override
        protected void parseExecResult(BufferedReader lines) throws IOException {
            output = new StringBuffer();
            char[] buf = new char[512];
            int nRead;
            while ( (nRead = lines.read(buf, 0, buf.length)) > 0 ) {
                output.append(buf, 0, nRead);
            }
        }

        /** Get the output of the shell command.*/
        public String getOutput() {
            return (output == null) ? "" : output.toString();
        }

        /**
         * Returns the commands of this instance.
         * Arguments with spaces in are presented with quotes round; other
         * arguments are presented raw
         *
         * @return a string representation of the object.
         */
        @Override
        public String toString() {
            StringBuilder builder = new StringBuilder();
            String[] args = getExecString();
            for (String s : args) {
                if (s.indexOf(' ') >= 0) {
                    builder.append('"').append(s).append('"');
                } else {
                    builder.append(s);
                }
                builder.append(' ');
            }
            return builder.toString();
        }
    }

    /**
     * To check if the passed script to shell command executor timed out or
     * not.
     *
     * @return if the script timed out.
     */
    public boolean isTimedOut() {
        return timedOut.get();
    }

    /**
     * Set if the command has timed out.
     *
     */
    private void setTimedOut() {
        this.timedOut.set(true);
    }


    /**
     * Static method to execute a shell command.
     * Covers most of the simple cases without requiring the user to implement
     * the <code>Shell</code> interface.
     * @param cmd shell command to execute.
     * @return the output of the executed command.
     */
    public static String execCommand(String ... cmd) throws IOException {
        return execCommand(null, cmd, 0L);
    }

    /**
     * Static method to execute a shell command.
     * Covers most of the simple cases without requiring the user to implement
     * the <code>Shell</code> interface.
     * @param env the map of environment key=value
     * @param cmd shell command to execute.
     * @param timeout time in milliseconds after which script should be marked timeout
     * @return the output of the executed command.o
     */

    public static String execCommand(Map<String, String> env, String[] cmd,
                                     long timeout) throws IOException {
        ShellCommandExecutor exec = new ShellCommandExecutor(cmd, null, env,
                                                             timeout);
        exec.execute();
        return exec.getOutput();
    }

    /**
     * Static method to execute a shell command.
     * Covers most of the simple cases without requiring the user to implement
     * the <code>Shell</code> interface.
     * @param env the map of environment key=value
     * @param cmd shell command to execute.
     * @return the output of the executed command.
     */
    public static String execCommand(Map<String,String> env, String ... cmd)
        throws IOException {
        return execCommand(env, cmd, 0L);
    }

    /**
     * Timer which is used to timeout scripts spawned off by shell.
     */
    private static class ShellTimeoutTimerTask extends TimerTask {

        private ShellUtils shell;

        public ShellTimeoutTimerTask(ShellUtils shell) {
            this.shell = shell;
        }

        @Override
        public void run() {
            Process p = shell.getProcess();
            try {
                p.exitValue();
            } catch (Exception e) {
                //Process has not terminated.
                //So check if it has completed
                //if not just destroy it.
                if (p != null && !shell.completed.get()) {
                    shell.setTimedOut();
                    p.destroy();
                }
            }
        }
    }

    public static ShellLogHandler getLogHandler(Map stormConf) {
        if (stormConf == null) {
            throw new IllegalArgumentException("Config is required");
        }

        String logHandlerClassName = null;
        if (stormConf.containsKey(Config.TOPOLOGY_MULTILANG_LOG_HANDLER)) {
            try {
                logHandlerClassName = stormConf.get(Config.TOPOLOGY_MULTILANG_LOG_HANDLER).toString();
                return (ShellLogHandler) Class.forName(logHandlerClassName).newInstance();
            } catch (ClassCastException | InstantiationException | IllegalAccessException | ClassNotFoundException e) {
                throw new RuntimeException("Error loading ShellLogHandler " + logHandlerClassName, e);
            }
        }
        return new DefaultShellLogHandler();
    }
}
