#!/bin/sh
#-----------------------------------------------------------------------------#
# Copyright (C) 1998 The University of Melbourne.
# This file may only be copied under the terms of the GNU General
# Public License - see the file COPYING in the Mercury distribution.
#-----------------------------------------------------------------------------#
#
# IMPORTANT: the manpage is produced automatically from this help
# message, so if you change the help message, don't forget to check
# that the manpage still looks OK.
Help="\
Name:	mdb - Mercury debugger
Usage:	mdb [<options>] <executable> [<args>]...
Description:
	\`mdb' invokes the specified command \`<executable> <args>...'
	with Mercury debugging enabled.  If that command is a Mercury
	program that was compiled with debugging enabled (e.g. using
	the \`--debug' option), or if that command invokes such a
	program, then mdb will cause the program to be executed under
	the supervision of the Mercury internal debugger.  Otherwise,
	mdb will execute the command line as if the mdb prefix weren't
	there.

	By default, all the output of the debugger and the output of the
	program being debugged will be interleaved on the same terminal
	window.  This can be avoided using the \`--tty' or \`--window'
	options described below.

Options:
	-t <file-name>, --tty <file-name>
		Redirect all of the I/O for the debugger to the device
		specified by <file-name>.  The I/O for the program
		being debugged will not be redirected.

	-w, --window
		Run the program in a new window, with the program's I/O
		going to that window, but with mdb's I/O going to the
		current terminal.

	-c <window-command>, --window-command <window-command>
		Specify the command used by the \`--window' option for
		executing a command in a new window.  The default such
		command is \`xterm -e'.

Environment variables:
	MERCURY_OPTIONS, MERCURY_DEBUGGER_INIT.
"

tty=
window=false
window_cmd="xterm -e"

#-----------------------------------------------------------------------------#
#
# process the command line options
#

case $# in
	0)	echo "Usage: mdb [<options>] <executable> [<arg> ...]" 1>&2
		exit 1 ;;
esac

while : ; do
	case "$1" in
		--help)
			echo "$Help"
			exit 0 ;;
		-t|--tty)
			tty="$2";
			shift; shift ;;
		-t*)
			tty="` expr $1 : '-t\(.*\)' `"
			shift ;;
		-w|--window)
			window=true
			shift ;;
		-w-|--no-window)
			window=false
			shift ;;
		-c|--window-command)
			window_cmd="$2";
			shift; shift ;;
		--)
			shift; break ;;
		-*)
			echo "$0: unknown option \`$1'" 1>&2
			exit 1 ;;
		*)
			break ;;
	esac
done

#-----------------------------------------------------------------------------#
#
# Figure out how we should invoke the command
#

invoke_cmd=
case "$window" in true)
	invoke_cmd="$window_cmd"
	#
	# If windowing is enabled, check that DISPLAY is set, and if not,
	# issue a warning message.  This is needed because the default error
	# message from xterm is very poor.
	#
	case "$DISPLAY" in "")
	    echo "$0: warning: environment variable \`DISPLAY' not set" 1>&2 ;;
	esac ;;
esac

#-----------------------------------------------------------------------------#
#
# Figure out if/how we should redirect the mdb I/O streams
#

case "$tty" in
    "")
	case "$window" in
	    true)
		#
		# On Linux, we can use special files in /proc
		# that refer to the file descriptors for a
		# particular process.
		#
		stdin=/proc/$$/fd/0
		stdout=/proc/$$/fd/1
		stderr=/proc/$$/fd/2
		if [ -f $stdin -a -f $stdout -a -f $stderr ]; then
			redirect_opts="
				--mdb-in $stdin
				--mdb-out $stdout
				--mdb-err $stderr
			"
		else
			# In the general case, we can use the `tty' command.
			# But that will only work if we're actually running
			# on a terminal.
			tty="`tty`"
			case "$tty" in ""|"not a tty")
				echo "$0: standard input stream is not a tty" 1>&2
				exit 1
				;;
			esac
			redirect_opts="--mdb-tty $tty"
		fi
		;;
	    false)
		redirect_opts=""
		;;
	esac ;;
    *)
	redirect_opts="--mdb-tty $tty"
	;;
esac

#-----------------------------------------------------------------------------#
#
# Set the environment variables used by the Mercury runtime to the
# the appropriate values to enabled debugging and to redirect mdb I/O,
# and then finally use $invoke_cmd to invoke the command.
#

enable_mdb_opt="-Di"
MERCURY_OPTIONS="$MERCURY_OPTIONS $redirect_opts $enable_mdb_opt"
export MERCURY_OPTIONS
MERCURY_DEBUGGER_INIT=${MERCURY_DEBUGGER_INIT-@DEFAULT_MERCURY_DEBUGGER_INIT_DIR@/mdbrc}
export MERCURY_DEBUGGER_INIT
exec $invoke_cmd "$@"

#-----------------------------------------------------------------------------#