source: main/trunk/gli/src/org/greenstone/gatherer/util/SafeProcess.java@ 31650

package org.greenstone.gatherer.util;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.Closeable;
import java.io.File;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.util.Arrays;
import java.util.Scanner;
import java.util.Stack;

import com.sun.jna.*;
import com.sun.jna.platform.win32.Kernel32;
import com.sun.jna.platform.win32.WinNT;

import java.lang.reflect.Field;
//import java.lang.reflect.Method;

import org.apache.log4j.*;

import org.greenstone.gatherer.DebugStream;

// Use this class to run a Java Process. It follows the good and safe practices at
// http://www.javaworld.com/article/2071275/core-java/when-runtime-exec---won-t.html?page=2
// to avoid blocking problems that can arise from a Process' input and output streams.

// On Windows, Perl could launch processes as proper ProcessTrees: http://search.cpan.org/~gsar/libwin32-0.191/
// Then killing the root process will kill child processes naturally.

public class SafeProcess {
    public static int DEBUG = 0;

    public static final int STDERR = 0;
    public static final int STDOUT = 1;
    public static final int STDIN = 2;
    // can't make this variable final and init in a static block, because it needs to use other SafeProcess static methods which rely on this in turn:
    public static String WIN_KILL_CMD; 
        
    
    // charset for reading process stderr and stdout streams
    //public static final String UTF8 = "UTF-8";    

    ///static Logger logger = Logger.getLogger(org.greenstone.util.SafeProcess.class.getName());

    // input to SafeProcess and initialising it
    private String command = null;
    private String[] command_args = null;
    private String[] envp = null;
    private File dir = null;
    private String inputStr = null;
    private Process process = null;
    private boolean forciblyTerminateProcess = false;
    
    // output from running SafeProcess.runProcess()
    private String outputStr = ""; 
    private String errorStr = "";
    private int exitValue = -1;
    //private String charset = null;

    // allow callers to process exceptions of the main process thread if they want
    private ExceptionHandler exceptionHandler = null;

    // whether std/err output should be split at new lines
    private boolean splitStdOutputNewLines = false;
    private boolean splitStdErrorNewLines = false;

    // call one of these constructors

    // cmd args version
    public SafeProcess(String[] cmd_args)
    {
    command_args = cmd_args;
    }

    // cmd string version
    public SafeProcess(String cmdStr)
    {
    command = cmdStr;
    }

    // cmd args with env version, launchDir can be null.
    public SafeProcess(String[] cmd_args, String[] envparams, File launchDir)
    {
    command_args = cmd_args;
    envp = envparams;
    dir = launchDir;
    }

    // The important methods:
    // to get the output from std err and std out streams after the process has been run
    public String getStdOutput() { return outputStr; }
    public String getStdError() { return errorStr; }
    public int getExitValue() { return exitValue; }

    //public void setStreamCharSet(String charset) { this.charset = charset; } 

    // set any string to send as input to the process spawned by SafeProcess
    public void setInputString(String sendStr) {
    inputStr = sendStr;
    }

    // register a SafeProcess ExceptionHandler whose gotException() method will
    // get called for each exception encountered
    public void setExceptionHandler(ExceptionHandler exception_handler) {
    exceptionHandler = exception_handler;   
    }

    // set if you want the std output or err output to have \n at each newline read from the stream
    public void setSplitStdOutputNewLines(boolean split) {
    splitStdOutputNewLines = split;
    }
    public void setSplitStdErrorNewLines(boolean split) {
    splitStdErrorNewLines = split;
    }

    // In future, think of changing the method doRuntimeExec() over to using ProcessBuilder
    // instead of Runtime.exec(). ProcessBuilder seems to have been introduced from Java 5.
    // https://docs.oracle.com/javase/7/docs/api/java/lang/ProcessBuilder.html
    // https://zeroturnaround.com/rebellabs/how-to-deal-with-subprocesses-in-java/
    // which suggests using Apache Common Exec to launch processes and says what will be forthcoming in Java 9
    private Process doRuntimeExec() throws IOException {
    Process prcs = null;
    Runtime rt = Runtime.getRuntime();
    
    if(this.command != null) {
        log("SafeProcess running: " + command);
        prcs = rt.exec(this.command);
    }
    else { // at least command_args must be set now
        
        // http://stackoverflow.com/questions/5283444/convert-array-of-strings-into-a-string-in-java
        //log("SafeProcess running:" + Arrays.toString(command_args));
        StringBuffer cmdDisplay = new StringBuffer();
        for(int i = 0; i < command_args.length; i++) {
            cmdDisplay.append(" ").append(command_args[i]);
        }
        log("SafeProcess running: [" + cmdDisplay + "]");
        cmdDisplay = null; // let the GC have it    
        
        
        if(this.envp == null) { 
        prcs = rt.exec(this.command_args);
        } else { // launch process using cmd str with env params        
        
        if(this.dir == null) {
            //log("\twith: " + Arrays.toString(this.envp));
            prcs = rt.exec(this.command_args, this.envp);
        } else {
            //log("\tfrom directory: " + this.dir);
            //log("\twith: " + Arrays.toString(this.envp));         
            prcs = rt.exec(this.command_args, this.envp, this.dir);
        }
        }
    }   

    return prcs;
    }

    // Copied from gli's gui/FormatConversionDialog.java
    private int waitForWithStreams(SafeProcess.OutputStreamGobbler inputGobbler,
                   SafeProcess.InputStreamGobbler outputGobbler,
                   SafeProcess.InputStreamGobbler errorGobbler)
    throws IOException, InterruptedException
    {   
    // kick off the stream gobblers
    inputGobbler.start();
    errorGobbler.start();
    outputGobbler.start();
    
    // any error???
    try {
        this.exitValue = process.waitFor(); // can throw an InterruptedException if process did not terminate
    } catch(InterruptedException ie) {
        log("*** Process interrupted (InterruptedException). Expected to be a Cancel operation.");
            // don't print stacktrace: an interrupt here is not an error, it's expected to be a cancel action
        if(exceptionHandler != null) {      
        exceptionHandler.gotException(ie);
        }           
        
        // propagate interrupts to worker threads here
        // unless the interrupt emanated from any of them in any join(),
        // which will be caught by caller's catch on InterruptedException.
        // Only if the thread that SafeProcess runs in was interrupted
        // should we propagate the interrupt to the worker threads.
        // http://stackoverflow.com/questions/2126997/who-is-calling-the-java-thread-interrupt-method-if-im-not
        // "I know that in JCiP it is mentioned that you should never interrupt threads you do not own"
        // But SafeProcess owns the worker threads, so it has every right to interrupt them
        // Also read http://stackoverflow.com/questions/13623445/future-cancel-method-is-not-working?noredirect=1&lq=1
        
        // http://stackoverflow.com/questions/3976344/handling-interruptedexception-in-java
        // http://stackoverflow.com/questions/4906799/why-invoke-thread-currentthread-interrupt-when-catch-any-interruptexception
        // "Only code that implements a thread's interruption policy may swallow an interruption request. General-purpose task and library code should never swallow interruption requests."
        // Does that mean that since this code implements this thread's interruption policy, it's ok
        // to swallow the interrupt this time and not let it propagate by commenting out the next line?
        //Thread.currentThread().interrupt(); // re-interrupt the thread

        inputGobbler.interrupt();
        errorGobbler.interrupt();
        outputGobbler.interrupt();
        
        // Since we have been cancelled (InterruptedException), or on any Exception, we need
        // to forcibly terminate process eventually after the finally code first waits for each worker thread
        // to die off. Don't set process=null until after we've forcibly terminated it if needs be.
        this.forciblyTerminateProcess = true; 
        
        // even after the interrupts, we want to proceed to calling join() on all the worker threads
        // in order to wait for each of them to die before attempting to destroy the process if it
        // still hasn't terminated after all that.
    } finally {     
        
        //log("Process exitValue: " + exitValue);
        
        // From the comments of 
        // http://www.javaworld.com/article/2071275/core-java/when-runtime-exec---won-t.html?page=2
        // To avoid running into nondeterministic failures to get the process output
        // if there's no waiting for the threads, call join() on each Thread (StreamGobbler) object.
        // From Thread API: join() "Waits for this thread (the thread join() is invoked on) to die."
        
        // Wait for each of the threads to die, before attempting to destroy the process
        // Any of these can throw InterruptedExceptions too
        // and will be processed by the calling function's catch on InterruptedException.
        // However, no one besides us will interrupting these threads I think...
        // and we won't be throwing the InterruptedException from within the threads...
        // So if any streamgobbler.join() call throws an InterruptedException, that would be unexpected

        outputGobbler.join(); 
        errorGobbler.join();
        inputGobbler.join();
        
        
        // set the variables that the code which created a SafeProcess object may want to inspect
        this.outputStr = outputGobbler.getOutput();
        this.errorStr = errorGobbler.getOutput();       
    }

    // Don't return from finally, it's considered an abrupt completion and exceptions are lost, see
    // http://stackoverflow.com/questions/18205493/can-we-use-return-in-finally-block
    return this.exitValue;
    }


    public synchronized boolean processRunning() {
    if(process == null) return false;
    return SafeProcess.processRunning(this.process);
    }

    // Run a very basic process: with no reading from or writing to the Process' iostreams,
    // this just execs the process and waits for it to return.
    // Don't call this method but the zero-argument runProcess() instead if your process will
    // output stuff to its stderr and stdout streams but you don't need to monitory these.
    // Because, as per a comment in GLI's GS3ServerThread.java,
    // in Java 6, it wil block if you don't handle a process' streams when the process is
    // outputting something. (Java 7+ won't block if you don't bother to handle the output streams)
    public int runBasicProcess() {
    try {
        this.forciblyTerminateProcess = true;
        
        // 1. create the process
        process = doRuntimeExec();
        // 2. basic waitFor the process to finish
        this.exitValue = process.waitFor();

        this.forciblyTerminateProcess = false;
    } catch(IOException ioe) {      
        
        if(exceptionHandler != null) {
        exceptionHandler.gotException(ioe);
        } else {
        log("IOException: " + ioe.getMessage(), ioe);
        }
    } catch(InterruptedException ie) {
        
        if(exceptionHandler != null) {
        exceptionHandler.gotException(ie);
        } else { // Unexpected InterruptedException, so printstacktrace
        log("Process InterruptedException: " + ie.getMessage(), ie);
        }
        
        Thread.currentThread().interrupt();
    } finally { 

        if( this.forciblyTerminateProcess ) {
        destroyProcess(process); // see runProcess() below      
        }
        process = null;
        this.forciblyTerminateProcess = false; // reset
    }
    return this.exitValue;
    }

    // Runs a process with default stream processing. Returns the exitValue
    public int runProcess() {
    return runProcess(null, null, null); // use default processing of all 3 of the process' iostreams
    }

    // Run a process with custom stream processing (any custom handlers passed in that are null
    // will use the default stream processing). 
    // Returns the exitValue from running the Process
    public int runProcess(CustomProcessHandler procInHandler,
               CustomProcessHandler procOutHandler,
               CustomProcessHandler procErrHandler)
    {
    SafeProcess.OutputStreamGobbler inputGobbler = null;
    SafeProcess.InputStreamGobbler errorGobbler = null;
    SafeProcess.InputStreamGobbler outputGobbler = null;

    try {
        this.forciblyTerminateProcess = false;
        
        // 1. get the Process object
        process = doRuntimeExec();
        

        // 2. create the streamgobblers and set any specified handlers on them

        // PROC INPUT STREAM
        if(procInHandler == null) {
        // send inputStr to process. The following constructor can handle inputStr being null
        inputGobbler = // WriterToProcessInputStream
            new SafeProcess.OutputStreamGobbler(process.getOutputStream(), this.inputStr);
        } else { // user will do custom handling of process' InputStream 
        inputGobbler = new SafeProcess.OutputStreamGobbler(process.getOutputStream(), procInHandler);
        }

        // PROC ERR STREAM to monitor for any error messages or expected output in the process' stderr
        if(procErrHandler == null) {
        errorGobbler // ReaderFromProcessOutputStream
            = new SafeProcess.InputStreamGobbler(process.getErrorStream(), this.splitStdErrorNewLines);
        } else {
        errorGobbler
            = new SafeProcess.InputStreamGobbler(process.getErrorStream(), procErrHandler);
        }

            // PROC OUT STREAM to monitor for the expected std output line(s)
        if(procOutHandler == null) {
        outputGobbler
            = new SafeProcess.InputStreamGobbler(process.getInputStream(), this.splitStdOutputNewLines);
        } else {
        outputGobbler
            = new SafeProcess.InputStreamGobbler(process.getInputStream(), procOutHandler);
        }


            // 3. kick off the stream gobblers
        this.exitValue = waitForWithStreams(inputGobbler, outputGobbler, errorGobbler);
       
    } catch(IOException ioe) {
        this.forciblyTerminateProcess = true;

        if(exceptionHandler != null) {
        exceptionHandler.gotException(ioe);
        } else {
        log("IOexception: " + ioe.getMessage(), ioe);
        }
    } catch(InterruptedException ie) { // caused during any of the gobblers.join() calls, this is unexpected so print stack trace
        this.forciblyTerminateProcess = true;
        
        if(exceptionHandler != null) {
        exceptionHandler.gotException(ie);
        log("@@@@ Unexpected InterruptedException when waiting for process stream gobblers to die");
        } else {
        log("*** Unexpected InterruptException when waiting for process stream gobblers to die:" + ie.getMessage(), ie);
        }

        // see comments in other runProcess()
        Thread.currentThread().interrupt();
    
    } finally { 
        //String cmd = (this.command == null) ? Arrays.toString(this.command_args) : this.command;
        //log("*** In finally of SafeProcess.runProcess(3 params): " + cmd);

        if( this.forciblyTerminateProcess ) {
        log("*** Going to call process.destroy 2");
        destroyProcess(process);                
        log("*** Have called process.destroy 2");
        }
        process = null;
        this.forciblyTerminateProcess = false; // reset
    }
    
    return this.exitValue;
    }
    
    public int runProcess(LineByLineHandler outLineByLineHandler, LineByLineHandler errLineByLineHandler)
    {
    SafeProcess.OutputStreamGobbler inputGobbler = null;
    SafeProcess.InputStreamGobbler errorGobbler = null;
    SafeProcess.InputStreamGobbler outputGobbler = null;

    try {
        this.forciblyTerminateProcess = false;
        
        // 1. get the Process object
        process = doRuntimeExec();
        

        // 2. create the streamgobblers and set any specified handlers on them

        // PROC INPUT STREAM
        // send inputStr to process. The following constructor can handle inputStr being null
        inputGobbler = // WriterToProcessInputStream
        new SafeProcess.OutputStreamGobbler(process.getOutputStream(), this.inputStr);

        // PROC ERR STREAM to monitor for any error messages or expected output in the process' stderr    
        errorGobbler // ReaderFromProcessOutputStream
            = new SafeProcess.InputStreamGobbler(process.getErrorStream(), splitStdErrorNewLines);      
            // PROC OUT STREAM to monitor for the expected std output line(s)
        outputGobbler
        = new SafeProcess.InputStreamGobbler(process.getInputStream(), splitStdOutputNewLines);


        // 3. register line by line handlers, if any were set, for the process stderr and stdout streams
        if(outLineByLineHandler != null) {
        outputGobbler.setLineByLineHandler(outLineByLineHandler);
        }
        if(errLineByLineHandler != null) {
        errorGobbler.setLineByLineHandler(errLineByLineHandler);
        }       


        // 4. kick off the stream gobblers
        this.exitValue = waitForWithStreams(inputGobbler, outputGobbler, errorGobbler);
       
    } catch(IOException ioe) {
        this.forciblyTerminateProcess = true;
        
        if(exceptionHandler != null) {
        exceptionHandler.gotException(ioe);
        } else {
        log("IOexception: " + ioe.getMessage(), ioe);       
        }
    } catch(InterruptedException ie) { // caused during any of the gobblers.join() calls, this is unexpected so log it
        this.forciblyTerminateProcess = true;
        
        if(exceptionHandler != null) {
        exceptionHandler.gotException(ie);
        log("@@@@ Unexpected InterruptedException when waiting for process stream gobblers to die");
        } else {
        log("*** Unexpected InterruptException when waiting for process stream gobblers to die: " + ie.getMessage(), ie);
        }
        // We're not causing any interruptions that may occur when trying to stop the worker threads
        // So resort to default behaviour in this catch?
        // "On catching InterruptedException, re-interrupt the thread."
        // This is just how InterruptedExceptions tend to be handled
        // See also http://stackoverflow.com/questions/4906799/why-invoke-thread-currentthread-interrupt-when-catch-any-interruptexception
        // and https://praveer09.github.io/technology/2015/12/06/understanding-thread-interruption-in-java/
        Thread.currentThread().interrupt(); // re-interrupt the thread - which thread? Infinite loop?
    
    } finally { 

        // Moved into here from GS2PerlConstructor and GShell.runLocal() which said
        // "I need to somehow kill the child process. Unfortunately Thread.stop() and Process.destroy() both fail to do this. But now, thankx to the magic of Michaels 'close the stream suggestion', it works fine (no it doesn't!)"
        // http://steveliles.github.io/invoking_processes_from_java.html
        // http://www.javaworld.com/article/2071275/core-java/when-runtime-exec---won-t.html?page=2
        // http://mark.koli.ch/leaky-pipes-remember-to-close-your-streams-when-using-javas-runtimegetruntimeexec        
        
        //String cmd = (this.command == null) ? Arrays.toString(this.command_args) : this.command;
        //log("*** In finally of SafeProcess.runProcess(2 params): " + cmd);

        if( this.forciblyTerminateProcess ) {
        log("*** Going to call process.destroy 1");
        destroyProcess(process);    
        log("*** Have called process.destroy 1");
        }
        process = null;
        this.forciblyTerminateProcess = false; //reset      
    }
    
    return this.exitValue;
    }

/*

 On Windows, p.destroy() terminates process p that Java launched,
 but does not terminate any processes that p may have launched. Presumably since they didn't form a proper process tree.
    https://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/e3cb7532-87f6-4ae3-9d80-a3afc8b9d437/how-to-kill-a-process-tree-in-cc-on-windows-platform?forum=vclanguage
    https://msdn.microsoft.com/en-us/library/windows/desktop/ms684161(v=vs.85).aspx

 Searching for: "forcibly terminate external process launched by Java on Windows"   
 Not possible: stackoverflow.com/questions/1835885/send-ctrl-c-to-process-open-by-java 
 But can use taskkill or tskill or wmic commands to terminate a process by processID
 stackoverflow.com/questions/912889/how-to-send-interrupt-key-sequence-to-a-java-process
 Taskkill command can kill by Image Name, such as all running perl, e.g. taskkill /f /im perl.exe
 But what if we kill perl instances not launched by GS?
    /f Specifies to forcefully terminate the process(es). We need this flag switched on to kill childprocesses.
    /t Terminates the specified process and any child processes which were started by it. 
            /t didn't work to terminate subprocesses. Maybe since the process wasn't launched as 
            a properly constructed processtree.
    /im is the image name (the name of the program), see Image Name column in Win Task Manager.
    
 We don't want to kill all perl running processes. 
 Another option is to use wmic, available since Windows XP, to kill a process based on its command
 which we sort of know (SafeProcess.command) and which can be seen in TaskManager under the 
 "Command Line" column of the Processes tab.
    https://superuser.com/questions/52159/kill-a-process-with-a-specific-command-line-from-command-line 
 The following works kill any Command Line that matches -site localsite lucene-jdbm-demo
    C:>wmic PATH win32_process Where "CommandLine like '%-site%localsite%%lucene-jdbm-demo%'" Call Terminate
 "WMIC Wildcard Search using 'like' and %"
    https://codeslammer.wordpress.com/2009/02/21/wmic-wildcard-search-using-like-and/
 However, we're not even guaranteed that every perl command GS launches will contain the collection name
 Nor do we want to kill all perl processes that GS launches with bin\windows\perl\bin\perl, though this works:
    wmic PATH win32_process Where "CommandLine like '%bin%windows%perl%bin%perl%'" Call Terminate
 The above could kill GS perl processes we don't intend to terminate, as they're not spawned by the particular
 Process we're trying to terminate from the root down.
    
 Solution: We can use taskkill or the longstanding tskill or wmic to kill a process by ID. Since we can
 kill an external process that SafeProcess launched OK, and only have trouble killing any child processes
 it launched, we need to know the pids of the child processes. 
 
 We can use Windows' wmic to discover the childpids of a process whose id we know.
 And we can use JNA to get the process ID of the external process that SafeProcess launched.
 
 To find the processID of the process launched by SafeProcess,
 need to use Java Native Access (JNA) jars, available jna.jar and jna-platform.jar.
    http://stackoverflow.com/questions/4750470/how-to-get-pid-of-process-ive-just-started-within-java-program
    http://stackoverflow.com/questions/35842/how-can-a-java-program-get-its-own-process-id
    http://www.golesny.de/p/code/javagetpid
    https://github.com/java-native-access/jna/blob/master/www/GettingStarted.md
 We're using JNA v 4.1.0, https://mvnrepository.com/artifact/net.java.dev.jna/jna
  
 WMIC can show us a list of parent process id and process id of running processes, and then we can
 kill those child processes with a specific process id.
    https://superuser.com/questions/851692/track-which-program-launches-a-certain-process
    http://stackoverflow.com/questions/7486717/finding-parent-process-id-on-windows
 WMIC can get us the pids of all childprocesses launched by parent process denoted by parent pid.
 And vice versa:
    if you know the parent pid and want to know all the pids of the child processes spawned:
        wmic process where (parentprocessid=596) get processid
    if you know a child process id and want to know the parent's id:
        wmic process where (processid=180) get parentprocessid
 
 The above is the current solution.
 
 Eventually, instead of running a windows command to kill the process ourselves, consider changing over to use
    https://github.com/flapdoodle-oss/de.flapdoodle.embed.process/blob/master/src/main/java/de/flapdoodle/embed/process/runtime/Processes.java 
 (works with Apache license, http://www.apache.org/licenses/LICENSE-2.0)
 This is a Java class that uses JNA to terminate processes. It also has the getProcessID() method. 
 
 Linux ps equivalent on Windows is "tasklist", see
    http://stackoverflow.com/questions/4750470/how-to-get-pid-of-process-ive-just-started-within-java-program

*/

// http://stackoverflow.com/questions/4750470/how-to-get-pid-of-process-ive-just-started-within-java-program
// Uses Java Native Access, JNA
public static long getProcessID(Process p)
{
    long pid = -1;
    try
    {
        //for windows
        if (p.getClass().getName().equals("java.lang.Win32Process") ||
               p.getClass().getName().equals("java.lang.ProcessImpl")) 
        {
            Field f = p.getClass().getDeclaredField("handle");
            f.setAccessible(true);              
            long handl = f.getLong(p);
            Kernel32 kernel = Kernel32.INSTANCE;
            WinNT.HANDLE hand = new WinNT.HANDLE();
            hand.setPointer(Pointer.createConstant(handl));
            pid = kernel.GetProcessId(hand);
            f.setAccessible(false);
        }
        //for unix based operating systems
        else if (p.getClass().getName().equals("java.lang.UNIXProcess")) 
        {
            Field f = p.getClass().getDeclaredField("pid");
            f.setAccessible(true);
            pid = f.getLong(p);
            f.setAccessible(false);
        }
    }
    catch(Exception ex)
    {
        log("SafeProcess.getProcessID(): Exception when attempting to get process ID for process " + ex.getMessage(), ex);  
        pid = -1;
    }
    return pid;
}


// stackoverflow.com/questions/1835885/send-ctrl-c-to-process-open-by-java  
// (Taskkill command can kill all running perl. But what if we kill perl instances not launched by GS?)
// stackoverflow.com/questions/912889/how-to-send-interrupt-key-sequence-to-a-java-process
// Searching for: "forcibly terminate external process launched by Java on Windows" 
static void killWinProcessWithID(long processID) {
    
    String cmd = SafeProcess.getWinProcessKillCmd(processID);
    if (cmd == null) return;
    
    try{        
        log("\tAttempting to terminate Win subprocess with pid: " + processID);
        SafeProcess proc = new SafeProcess(cmd);            
        int exitValue = proc.runProcess(); // no IOstreams for Taskkill, but for "wmic process pid delete"
            // there is output that needs flushing, so don't use runBasicProcess()
            
    } catch(Exception e) {
        log("@@@ Exception attempting to stop perl " + e.getMessage(), e);      
    }
}


// On linux and mac, p.destroy() suffices to kill processes launched by p as well.
// On Windows we need to do more work, since otherwise processes launched by p remain around executing until they naturally terminate.
// e.g. full-import.pl may be terminated with p.destroy(), but it launches import.pl which is left running until it naturally terminates.
static void destroyProcess(Process p) {
    // If it isn't windows, process.destroy() terminates any child processes too
    if(!Utility.isWindows()) {
        p.destroy();
        return;
    }   

    if(!SafeProcess.isAvailable("wmic")) {
        log("wmic, used to kill subprocesses, is not available. Unable to terminate subprocesses...");
        log("Kill them manually from the TaskManager or they will proceed to run to termination");
        
        // At least we can get rid of the top level process we launched
        p.destroy();
        return;
    }   
    
    // get the process id of the process we launched,
    // so we can use it to find the pids of any subprocesses it launched in order to terminate those too.
    
    long processID = SafeProcess.getProcessID(p);       
    log("Attempting to terminate sub processes of Windows process with pid " + processID);
    terminateSubProcessesRecursively(processID, p);
    
}

// Helper function. Only for Windows.
// Counterintuitively, we're be killing all parent processess and then all child procs and all their descendants
// as soon as we discover any further process each (sub)process has launched. The parent processes are killed
// first in each case for 2 reasons: 
// 1. on Windows, killing the parent process leaves the child running as an orphan anyway, so killing the
// parent is an independent action, the child process is not dependent on the parent;
// 2. Killing a parent process prevents it from launching further processes while we're killing off each child process
private static void terminateSubProcessesRecursively(long parent_pid, Process p) {
    
    // Use Windows wmic to find the pids of any sub processes launched by the process denoted by parent_pid 
    SafeProcess proc = new SafeProcess("wmic process where (parentprocessid="+parent_pid+") get processid");
    proc.setSplitStdOutputNewLines(true); // since this is windows, splits lines by \r\n
    int exitValue = proc.runProcess(); // exitValue (%ERRORLEVEL%) is 0 either way. 
    //log("@@@@ Return value from proc: " + exitValue);
    
    // need output from both stdout and stderr: stderr will say there are no pids, stdout will contain pids
    String stdOutput = proc.getStdOutput();
    String stdErrOutput = proc.getStdError();
    
    
    // Now we know the pids of the immediate subprocesses, we can get rid of the parent process
    if(p != null) { // we're the top level process, terminate java way
        p.destroy();
    } else { // terminate windows way       
        SafeProcess.killWinProcessWithID(parent_pid); // get rid off current pid        
    }
    
    // parse the output to get the sub processes' pids  
    // Output looks like:
    // ProcessId
    // 6040
    // 180
    // 4948
    // 1084
    // 6384
    // If no children, then STDERR output starts with the following, possibly succeeded by empty lines:
    // No Instance(s) Available.
    
    // base step of the recursion
    if(stdErrOutput.indexOf("No Instance(s) Available.") != -1) { 
        //log("@@@@ Got output on stderr: " + stdErrOutput);
        // No further child processes. And we already terminated the parent process, so we're done
        return;
    } else {
        //log("@@@@ Got output on stdout:\n" + stdOutput);
    
        // http://stackoverflow.com/questions/691184/scanner-vs-stringtokenizer-vs-string-split 
    
        // find all childprocesses for that pid and terminate them too:
        Stack<Long> subprocs = new Stack<Long>();
        Scanner sc = new Scanner(stdOutput);
        while (sc.hasNext()) {
          if(!sc.hasNextLong()) {
              sc.next(); // discard the current token since it's not a Long
          } else {
            long child_pid = sc.nextLong();
            subprocs.push(new Long(child_pid));         
          }
        }
        sc.close();     
        
        // recursion step if subprocs is not empty (but if it is empty, then it's another base step)
        if(!subprocs.empty()) {
            long child_pid = subprocs.pop().longValue();
            terminateSubProcessesRecursively(child_pid, null);
        }   
    }
}

// This method should only be called on a Windows OS
private static String getWinProcessKillCmd(Long processID) {
    // check if we first need to init WIN_KILL_CMD. We do this only once, but can't do it in a static codeblock
    
    if(WIN_KILL_CMD == null) {      
        if(SafeProcess.isAvailable("wmic")) {
            // https://isc.sans.edu/diary/Windows+Command-Line+Kung+Fu+with+WMIC/1229
            WIN_KILL_CMD = "wmic process _PROCID_ delete"; // like "kill -9" on Windows
        }
        else if(SafeProcess.isAvailable("taskkill")) { // check if we have taskkill or else use the longstanding tskill
        
            WIN_KILL_CMD = "taskkill /f /t /PID _PROCID_"; // need to forcefully /f terminate the process               
                //  /t "Terminates the specified process and any child processes which were started by it."
                // But despite the /T flag, the above doesn't kill subprocesses.
        }
        else { //if(SafeProcess.isAvailable("tskill")) { can't check availability since "which tskill" doesn't ever succeed
            WIN_KILL_CMD = "tskill _PROCID_"; // https://ss64.com/nt/tskill.html
        }       
    }
    
    if(WIN_KILL_CMD == null) { // can happen if none of the above cmds were available
        return null;
    }
    return WIN_KILL_CMD.replace( "_PROCID_", Long.toString(processID) );
}


// Run `which` on a program to find out if it is available. which.exe is included in winbin.
// On Windows, can use where or which. GLI's file/FileAssociationManager.java used which, so we stick to the same.
// where is not part of winbin. where is a system command on windows, but only since 2003, https://ss64.com/nt/where.html
// There is no `where` on Linux/Mac, must use which for them.
// On windows, "which tskill" fails but "which" succeeds on taskkill|wmic|browser names.
public static boolean isAvailable(String program) {     
    try {
        // On linux `which bla` does nothing, prompt is returned; on Windows, it prints "which: no bla in"
        // `which grep` returns a line of output with the path to grep. On windows too, the location of the program is printed
        SafeProcess prcs = new SafeProcess("which " + program);     
        prcs.runProcess();
        String output = prcs.getStdOutput();
        if(output.equals("")) {
        return false;
        }
        //System.err.println("*** 'which " + program + "' returned: " + output);
        return true;
    } catch (Exception exc) {
        return false;
    }
}   
    
// Google Java external process destroy kill subprocesses
// https://zeroturnaround.com/rebellabs/how-to-deal-with-subprocesses-in-java/  
    
//******************** Inner class and interface definitions ********************//
// Static inner classes can be instantiated without having to instantiate an object of the outer class first

// Can have public static interfaces too,
// see http://stackoverflow.com/questions/71625/why-would-a-static-nested-interface-be-used-in-java
// Implementors need to take care that the implementations are thread safe
// http://stackoverflow.com/questions/14520814/why-synchronized-method-is-not-included-in-interface
public static interface ExceptionHandler {

    // when implementing ExceptionHandler.gotException(), if it manipulates anything that's
    // not threadsafe, declare gotException() as a synchronized method to ensure thread safety
    public void gotException(Exception e); // can't declare as synchronized in interface method declaration
}

// Write your own run() body for any StreamGobbler. You need to create an instance of a class
// extending CustomProcessHandler for EACH IOSTREAM of the process that you want to handle.
// Do not create a single CustomProcessHandler instance and reuse it for all three streams,
// i.e. don't call SafeProcess' runProcess(x, x, x); It should be runProcess(x, y, z).
// Make sure your implementation is threadsafe if you're sharing immutable objects between the threaded streams
// example implementation is in the GS2PerlConstructor.SynchronizedProcessHandler class.
// CustomProcessHandler is made an abstract class instead of an interface to force classes that want
// to use a CustomProcessHandler to create a separate class that extends CustomProcessHandler, rather than
// that the classes that wish to use it "implementing" the CustomProcessHandler interface itself: the
// CustomProcessHandler.run() method may then be called in the major thread from which the Process is being
// executed, rather than from the individual threads that deal with each iostream of the Process.
public static abstract class CustomProcessHandler {

    protected final int source;

    protected CustomProcessHandler(int src) {
    this.source = src; // STDERR or STDOUT or STDIN
    }

    public String getThreadNamePrefix() {
    return SafeProcess.streamToString(this.source); 
    }
    
    public abstract void run(Closeable stream); //InputStream or OutputStream
}

// When using the default stream processing to read from a process' stdout or stderr stream, you can
// create a class extending LineByLineHandler for the process' err stream and one for its output stream
// to do something on a line by line basis, such as sending the line to a log
public static abstract class LineByLineHandler {
    protected final int source;

    protected LineByLineHandler(int src) {
    this.source = src; // STDERR or STDOUT
    }

    public String getThreadNamePrefix() {
    return SafeProcess.streamToString(this.source); 
    }

    public abstract void gotLine(String line); // first non-null line
    public abstract void gotException(Exception e); // for when an exception occurs instead of getting a line
}


//**************** StreamGobbler Inner class definitions (stream gobblers copied from GLI) **********//

// http://www.javaworld.com/article/2071275/core-java/when-runtime-exec---won-t.html?page=2
// This class is used in FormatConversionDialog to properly read from the stdout and stderr
// streams of a Process, Process.getInputStream() and Process.getErrorSream()
public static class InputStreamGobbler extends Thread
{
    private InputStream is = null;
    private StringBuffer outputstr = new StringBuffer();
    private boolean split_newlines = false;
    private CustomProcessHandler customHandler = null;
    private LineByLineHandler lineByLineHandler = null;

    protected InputStreamGobbler() {
    super("InputStreamGobbler");
    }

    public InputStreamGobbler(InputStream is)
    {
    this(); // sets thread name
    this.is = is;
    this.split_newlines = false;
    }
    
    public InputStreamGobbler(InputStream is, boolean split_newlines)
    {   
    this(); // sets thread name
    this.is = is;
    this.split_newlines = split_newlines;
    
    }
    
    public InputStreamGobbler(InputStream is, CustomProcessHandler customHandler)
    {
    this(); // thread name
    this.is = is;
    this.customHandler = customHandler;
    this.adjustThreadName(customHandler.getThreadNamePrefix());
    }

    
    private void adjustThreadName(String prefix) {  
    this.setName(prefix + this.getName());
    }

    public void setLineByLineHandler(LineByLineHandler lblHandler) {
    this.lineByLineHandler = lblHandler;
    this.adjustThreadName(lblHandler.getThreadNamePrefix());
    }

    // default run() behaviour
    public void runDefault()
    {
    BufferedReader br = null;
    try {
        br = new BufferedReader(new InputStreamReader(is, "UTF-8"));
        String line=null;
        while ( !this.isInterrupted() && (line = br.readLine()) != null ) {

        //log("@@@ GOT LINE: " + line);
        outputstr.append(line);
        if(split_newlines) {
            outputstr.append(Utility.NEWLINE); // "\n" is system dependent (Win must be "\r\n")
        }

        if(lineByLineHandler != null) { // let handler deal with newlines
            lineByLineHandler.gotLine(line);
        }
        }

    } catch (IOException ioe) {
        if(lineByLineHandler != null) {
        lineByLineHandler.gotException(ioe);
        } else {
        log("Exception when reading process stream with " + this.getName() + ": ", ioe);
        }
    } finally {
        if(this.isInterrupted()) {
        log("@@@ Successfully interrupted " + this.getName() + ".");
        }
        SafeProcess.closeResource(br);
    }
    }
    
    public void runCustom() {
    this.customHandler.run(is);
    }
    
    public void run() {
    if(this.customHandler == null) {
        runDefault();
    } else {
        runCustom();
    }
    }

    public String getOutput() { 
    return outputstr.toString(); // implicit toString() call anyway. //return outputstr; 
    }
} // end static inner class InnerStreamGobbler


// http://www.javaworld.com/article/2071275/core-java/when-runtime-exec---won-t.html?page=2
// This class is used in FormatConversionDialog to properly write to the inputstream of a Process
// Process.getOutputStream()
public static class OutputStreamGobbler extends Thread
{
    private OutputStream os = null;
    private String inputstr = "";
    private CustomProcessHandler customHandler = null;

    protected OutputStreamGobbler() {
    super("stdinOutputStreamGobbler"); // thread name
    }

    public OutputStreamGobbler(OutputStream os) {
    this(); // set thread name
    this.os = os;
    }

    public OutputStreamGobbler(OutputStream os, String inputstr)
    {
    this(); // set thread name
    this.os = os;
    this.inputstr = inputstr;
    }

    public OutputStreamGobbler(OutputStream os, CustomProcessHandler customHandler) {
    this(); // set thread name
    this.os = os;
    this.customHandler = customHandler;
    }

    // default run() behaviour
    public void runDefault() {
    
    if (inputstr == null) {
        return;
    }

    // also quit if the process was interrupted before we could send anything to its stdin
    if(this.isInterrupted()) {
        log(this.getName() + " thread was interrupted.");
        return;
    }
    
    BufferedWriter osw = null;
    try {
        osw = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
        //System.out.println("@@@ SENDING LINE: " + inputstr);
        osw.write(inputstr, 0, inputstr.length());
        osw.newLine();//osw.write("\n");
        osw.flush();
        
        // Don't explicitly send EOF when using StreamGobblers as below, 
        // as the EOF char is echoed to output.
        // Flushing the write handle and/or closing the resource seems 
        // to already send EOF silently.
        
        /*if(Utility.isWindows()) {
          osw.write("\032"); // octal for Ctrl-Z, EOF on Windows
          } else { // EOF on Linux/Mac is Ctrl-D
          osw.write("\004"); // octal for Ctrl-D, see http://www.unix-manuals.com/refs/misc/ascii-table.html
          }
          osw.flush();
        */
    } catch (IOException ioe) {
        log("Exception writing to SafeProcess' inputstream: ", ioe);
    } finally {
        SafeProcess.closeResource(osw);
    }
    }

    // call the user's custom handler for the run() method
    public void runCustom() {
    this.customHandler.run(os); 
    }

    public void run()
    {
    if(this.customHandler == null) {
        runDefault();
    } else {
        runCustom();
    }
    }   
} // end static inner class OutputStreamGobbler

//**************** Static methods **************//


    // logger and DebugStream print commands are synchronized, therefore thread safe.
    public static void log(String msg) {
    if(DEBUG == 0) return;
    //logger.info(msg);

    System.err.println(msg);

    //DebugStream.println(msg);
    }

    public static void log(String msg, Exception e) { // Print stack trace on the exception
    if(DEBUG == 0) return;
    //logger.error(msg, e);

    System.err.println(msg);
    e.printStackTrace();

    //DebugStream.println(msg);
    //DebugStream.printStackTrace(e);
    }

    public static void log(Exception e) {
    if(DEBUG == 0) return;      
    //logger.error(e);

    e.printStackTrace();

    //DebugStream.printStackTrace(e);
    }

    public static void log(String msg, Exception e, boolean printStackTrace) {
    if(printStackTrace) { 
        log(msg, e);
    } else {
        log(msg);
    }
    }

    public static String streamToString(int src) {
    String stream;
    switch(src) {
    case STDERR:
        stream = "stderr"; 
        break;
    case STDOUT:
        stream = "stdout";
        break;
    default:
        stream = "stdin";
    }
    return stream;
    }

//**************** Useful static methods. Copied from GLI's Utility.java ******************
    // For safely closing streams/handles/resources. 
    // For examples of use look in the Input- and OutputStreamGobbler classes.
    // http://docs.oracle.com/javase/tutorial/essential/exceptions/finally.html
    // http://stackoverflow.com/questions/481446/throws-exception-in-finally-blocks
    public static boolean closeResource(Closeable resourceHandle) {
    boolean success = false;
    try {
        if(resourceHandle != null) {
        resourceHandle.close();
        resourceHandle = null;
        success = true;
        }
    } catch(Exception e) {
        log("Exception closing resource: " + e.getMessage(), e);
        resourceHandle = null;
        success = false;
    } finally {
        return success;
    }
    }

    public static boolean closeProcess(Process prcs) {
    boolean success = true;
    if( prcs != null ) { 
        success = success && closeResource(prcs.getErrorStream()); 
        success = success && closeResource(prcs.getOutputStream()); 
        success = success && closeResource(prcs.getInputStream()); 
        prcs.destroy(); 
    }
    return success;
    }

// Moved from GShell.java
    /** Determine if the given process is still executing. It does this by attempting to throw an exception - not the most efficient way, but the only one as far as I know
     * @param process the Process to test
     * @return true if it is still executing, false otherwise
     */
    static public boolean processRunning(Process process) {
    boolean process_running = false;

    try {
        process.exitValue(); // This will throw an exception if the process hasn't ended yet.
    }
    catch(IllegalThreadStateException itse) {
        process_running = true;
    }
    catch(Exception exception) {
        log(exception); // DebugStream.printStackTrace(exception);
    }
    return process_running;
    }

} // end class SafeProcess