#!/usr/bin/perl -w
  
  # In general, doing 
  #  slurm.pl some.log a b c 
  # is like running the command a b c as an interactive SLURM job, and putting the 
  # standard error and output into some.log.
  # It is a de-facto-mimicry of run.pl, with the difference, that it allocates the
  # jobs on a slurm cluster.  The calling script (e.g. decode.sh) should have the 
  # required allocation, e.g.
  #   $ sbatch -n 40 steps/decode.sh --nj 40 --cmd utils/slurm.pl ...
  # The benefit compared to qsub.pl is that there is no active wait involved, as
  # this script waits on all forked processes to finish.
  # To run parallel jobs (backgrounded on the host machine), you can do (e.g.)
  #  slurm.pl JOB=1:4 some.JOB.log a b c JOB is like running the command a b c JOB
  # and putting it in some.JOB.log, for each one. [Note: JOB can be any identifier].
  # If any of the jobs fails, this script will fail.
  
  # A typical example is:
  #  slurm.pl some.log my-prog "--opt=foo bar" foo \|  other-prog baz
  # and slurm.pl will run something like:
  # ( my-prog '--opt=foo bar' foo |  other-prog baz ) >& some.log
  # 
  # Basically it takes the command-line arguments, quotes them
  # as necessary to preserve spaces, and evaluates them with bash.
  # In addition it puts the command line at the top of the log, and
  # the start and end times of the command at the beginning and end.
  # The reason why this is useful is so that we can create a different
  # version of this program that uses a queueing system instead.
  
  @ARGV < 2 && die "usage: slurm.pl log-file command-line arguments...";
  
  $jobstart=1;
  $jobend=1;
  
  # First parse an option like JOB=1:4
  
  if (@ARGV > 0) {
    if ($ARGV[0] =~ m/^([\w_][\w\d_]*)+=(\d+):(\d+)$/) {
      $jobname = $1;
      $jobstart = $2;
      $jobend = $3;
      shift;
      if ($jobstart > $jobend) {
        die "slurm.pl: invalid job range $ARGV[0]";
      }
    } elsif ($ARGV[0] =~ m/^([\w_][\w\d_]*)+=(\d+)$/) { # e.g. JOB=1.
      $jobname = $1;
      $jobstart = $2;
      $jobend = $2;
      shift;
    } elsif ($ARGV[0] =~ m/.+\=.*\:.*$/) {
      print STDERR "Warning: suspicious first argument to slurm.pl: $ARGV[0]
  ";
    }
  }
  
  $logfile = shift @ARGV;
  
  if (defined $jobname && $logfile !~ m/$jobname/ &&
      $jobend > $jobstart) {
    print STDERR "slurm.pl: you are trying to run a parallel job but "
      . "you are putting the output into just one log file ($logfile)
  ";
    exit(1);
  }
  
  $cmd = "";
  
  foreach $x (@ARGV) { 
      if ($x =~ m/^\S+$/) { $cmd .=  $x . " "; }
      elsif ($x =~ m:\":) { $cmd .= "'$x' "; }
      else { $cmd .= "\"$x\" "; } 
  }
  
  
  for ($jobid = $jobstart; $jobid <= $jobend; $jobid++) {
    $childpid = fork();
    if (!defined $childpid) { die "Error forking in slurm.pl (writing to $logfile)"; }
    if ($childpid == 0) { # We're in the child... this branch
      # executes the job and returns (possibly with an error status).
      if (defined $jobname) { 
        $cmd =~ s/$jobname/$jobid/g;
        $logfile =~ s/$jobname/$jobid/g;
      }
      system("mkdir -p `dirname $logfile` 2>/dev/null");
      open(F, ">$logfile") || die "Error opening log file $logfile";
      print F "# " . $cmd . "
  ";
      print F "# Started at " . `date`;
      $starttime = `date +'%s'`;
      print F "#
  ";
      close(F);
  
      # Pipe into bash.. make sure we're not using any other shell.
  
      open(B, "|-", "srun -N 1 -n 1 bash") || die "Error opening shell command"; 
      print B "( " . $cmd . ") 2>>$logfile >> $logfile";
      close(B);                   # If there was an error, exit status is in $?
      $ret = $?;
  
      $endtime = `date +'%s'`;
      open(F, ">>$logfile") || die "Error opening log file $logfile (again)";
      $enddate = `date`;
      chop $enddate;
      print F "# Ended (code $ret) at " . $enddate . ", elapsed time " . ($endtime-$starttime) . " seconds
  ";
      close(F);
      exit($ret == 0 ? 0 : 1);
    }
  }
  
  $ret = 0;
  $numfail = 0;
  for ($jobid = $jobstart; $jobid <= $jobend; $jobid++) {
    $r = wait();
    if ($r == -1) { die "Error waiting for child process"; } # should never happen.
    if ($? != 0) { $numfail++; $ret = 1; } # The child process failed.
  }
  
  if ($ret != 0) {
    $njobs = $jobend - $jobstart + 1;
    if ($njobs == 1) { 
      print STDERR "slurm.pl: job failed, log is in $logfile
  ";
      if ($logfile =~ m/JOB/) {
        print STDERR "slurm.pl: probably you forgot to put JOB=1:\$nj in your script.
  ";
      }
    }
    else {
      $logfile =~ s/$jobname/*/g;
      print STDERR "slurm.pl: $numfail / $njobs failed, log is in $logfile
  ";
    }
  }
  
  
  exit ($ret);