#!/bin/sh
#
# usage: casa-script <script.py> [script arguments...]
#
# Credit: https://github.com/pkgw/pwpy - intfbin/casa-script
# License: GPLv3+
#
# This tool makes it possible to run scripts in a full CASA environment from
# the command line in the sanest way I can muster (for my personal definition
# of "sane"). Expected usage is in a hashbang line in the script:
#
#   #! /usr/bin/env casa-script
#   # -*- python -*-
#   ...
#
# The elements of sanity are:
#
# - casapy is invoked in a temporary directory, so that the logfile turds it
#   likes to drop everywhere get cleaned up.
# - command-line arguments are made accessible to the script in a clean-ish
#   way (last I checked, this didn't work with straight-up casapy)
# - output is redirected so that casapy's incessant chatter can be silenced
# - the GUI is disabled
#
# Unfortunately I am unable to do anything about casapy's terrible startup
# time.
#
# Inside the temporary directory, the invocation directory of this script is
# symlinked under the name 'data'. All file paths should begin with 'data/',
# with special care for command-line arguments, which will need post-processing.
#
# The command-line arguments to the invoked script are saved, separated by
# **NULs**, in a file in the temporary directory called 'args'. These can be
# retrieved with:
#
#   argv = open ('args').read ().split ('\0')[2:-1]
#   # or
#   args = open ('args').read ().split ('\0')[3:-1]
#
# The output of casapy is redirected to files 'stdout' and 'stderr' in the
# temporary working directory. The standard output and error of this script
# are linked to FIFOs in the work directory named 'csout' and 'cserr'.
# Therefore, to selectively output data to the invoker, do
#
#   csout, cserr = open ('csout', 'w', 1), open ('cserr', 'w', 1)
#   ...
#   print >>csout, 'info: this script works'
#   ...
#   print >>cserr, 'warning: your data are broken'
#
# Keep in mind that the script is being executed in CASA's IPython
# environment, so the environment is highly non-vanilla. Because IPython
# just prints exceptions to the screen, you need to wrap the entire program
# in a try/except block and handle them manually:
#
#  # after setting up cserr
#  try:
#    ... entire program ...
#  except SystemExit:
#    pass
#  except:
#    import os, sys, traceback
#    traceback.print_exception (*sys.exc_info (), file=cserr)
#    os._exit (1)
#
# Note that we need to use os._exit() to be able to actually exit with an
# error return code. Do not use sys.exit() or (CASA's) exit().

# Set up a fully-qualified path name to the input script so that CASA can
# always find it, even when we hop around in subdirectories. Otherwise it
# tries to evaluate the filename as a line of Python.

script=$(cd $(dirname $1) && pwd)/$(basename $1)
if [ ! -e "$script" ] ; then
    echo >&2 "error: cannot find input script \"$1\"; should be at \"$script\""
    exit 1
fi

workdir=`mktemp -d casascript.XXXXXXXXX`
cd "$workdir"
ln -s .. data
cp /proc/$$/cmdline args
mkfifo csout cserr || exit 1

# Process group management insanity:
# http://stackoverflow.com/a/1645157/3760486 I'm sure I could do a
# better/cleaner job of this, but I'm pretty sure this code errs on the side
# of safety, and that's my priority.

trap : SIGTERM SIGINT
cat csout &
killpids="-$!"
cat cserr >&2 &
killpids="$killpids -$!"
casapy --log2term --nogui -c "$script" </dev/null >stdout 2>stderr &
killpids="$killpids -$!"
wait $!
retval=$?

if [ $retval -gt 128 ] ; then
    kill -- $killpids
fi

if [ $retval -ne 0 ] ; then
    echo >&2 "error: casapy exited with error code $retval; preserving work directory $workdir"
else
    cd ..
    [ x"$CASASCRIPT_DEBUG_WORK" != x ] || rm -rf "$workdir"
fi

exit $retval