# bashdb.fns - Bourne-Again Shell Debugger functions

_BUFSIZ=100

# Here after each statement in script being debugged.
# Handle single-step and breakpoints.
_steptrap() {
	let _curline=$1-1		# no. of line that just ran
	let "$_curline < 1" && let _curline=1

	let "$_curline > $_firstline+$_BUFSIZ" && _readin $_curline

	let " $_trace" &&
		_msg "$PS4, line $_curline: ${_lines[$(($_curline-$_firstline+1))]}"


	# if in step mode, decrement counter
	let " $_steps >= 0" && let _steps="$_steps - 1"

	# first check if line num or string brkpt. reached
	if _at_linenumbp || _at_stringbp; then
		_msg "Reached breakpoint at line $_curline"
		_cmdloop		# enter debugger

	# if not, check whether break condition exists and is true
	elif [ -n "$_brcond" ] && eval $_brcond; then
		_msg "Break condition $_brcond true at line $_curline"
		_cmdloop		# enter debugger

	# next, check if step mode and no. of steps is up
	elif let "$_steps == 0"; then
		_msg "Stopped at line $_curline"
		_cmdloop		# enter debugger
	fi
}


# Debugger command loop.
# Here at start of debugger session, when brkpt. reached, or after single-step.
_cmdloop() {
	local cmd args

# added support for default command (last one entered)

	while read -e -p "bashdb> [$lastcmd $lastargs] " cmd args; do
		if [ -z "$cmd" ]; then
			cmd=$lastcmd
			args=$lastargs 
		fi

		lastcmd="$cmd"
		lastargs=$args

# made commands to be debugger commands by default, no need for '*' prefix

		case $cmd in
		bp ) _setbp $args ;;	#set brkpt at line num or string

		bc ) _setbc $args ;;	# set break condition

		cb ) _clearbp ;;	# clear all brkpts.

		g ) return ;;		# start/resume execution

		s ) let _steps=${args:-1} 
		    return ;;		# single-step N times(default 1)

		x ) _xtrace ;;	# toggle execution trace

		pr ) _print $args ;;	# print lines in file

		\? | h | help ) _menu ;; # print command menu

		hi ) history ;;		# show command history

		q ) _cleanup; exit ;;		# quit

		\! ) eval $args ;;	# run shell command

		* ) _msg "Invalid command: $cmd" ; _menu ;;
		esac
	done
}


# see if next line no. is a brkpt.
_at_linenumbp() {
	if [ -z "${_linebp}" ]; then
		return 1
	fi
	echo "${_curline}" | grep -E "(${_linebp%\|})" >/dev/null 2>&1
	return $?
}


# search string brkpts to see if next line in script matches.
_at_stringbp() {
	local l;

	if [ -z "$_stringbp" ]; then
		return 1;
	fi
	l=${_lines[$_curline-$_firstline+1]}
	echo "${l}" | grep -E "\\*(${_stringbp%\|})\\*" >/dev/null 2>&1
	return $?
}


# print message to stderr
_msg() {
	echo -e "$@" >&2
}


# set brkpt(s) at given line numbers and/or strings
# by appending lines to brkpt file
_setbp() {
	declare -i n
	case "$1" in
	"")	_listbp ;;
	[0-9]*)	#number, set brkpt at that line
		n=$1
		_linebp="${_linebp}$n|"
		_msg "Breakpoint at line " $1
		;;
	*)	#string, set brkpt at next line w/string
		_stringbp="${_stringbp}$@|"
		_msg "Breakpoint at next line containing $@."
		;;
	esac
}


# list brkpts and break condition.
_listbp() {
	_msg "Breakpoints at lines:"
	_msg "${_linebp//\|/ }"
	_msg "Breakpoints at strings:"
	_msg "${_stringbp//\|/ }"
	_msg "Break on condition:"
	_msg "$_brcond"
}


# set or clear break condition
_setbc() {
	if [ -n "$@" ] ; then
		_brcond=$args
		_msg "Break when true: $_brcond"
	else
		_brcond=
		_msg "Break condition cleared"
	fi
}


# clear all brkpts
_clearbp() {
	_linebp=
	_stringbp=
	_msg "All breakpoints cleared"
}


# toggle execution trace feature
_xtrace() {
	let _trace="! $_trace"

	_msg "Execution trace \c"
	let " $_trace" && _msg "on." || _msg "off."
}


# print command menu
_menu() {

# made commands to be debugger commands by default, no need for '*' prefix

	_msg 'bashdb commands:
	bp N			set breakpoint at line N
	bp string		set breakpoint at next line containing "string"
	bp			list breakpoints and break condition
	bc string		set break condition to "string"
	bc			clear break condition
	cb			clear all breakpoints
	g			start/resume execution
	s [N]			execute N statements (default 1)
	x			toggle execution trace on/off (default on)
	pr [start|.] [cnt]	print "cnt" lines from line no. "start"
	?, h, help		print this menu
	hi			show command history	
	q			quit

	! cmd [args]		execute command "cmd" with "args"

	default:		last command (in "[ ]" at the prompt)

	Readline command line editing (emacs/vi mode) is available'
}


# erase temp files before exiting
_cleanup() {
	rm $_dbgfile 2>/dev/null
}


# read $_BUFSIZ lines from $_guineapig into _lines array, starting from line $1
# save number of first line read in _firstline
_readin() {
	declare -i _i=1			
	let _firstline=$1

	SEDCMD="$_firstline,$(($_firstline+$_BUFSIZ))p"

	sed -n "$SEDCMD" $_guineapig > /tmp/_script.$$
	while read -r _lines[$_i]; do
		_i=_i+1
	done  < /tmp/_script.$$
	rm -f /tmp/_script.$$ 2>/dev/null
}

_print() {
	typeset _start _cnt

	if [ -z "$1" ] || [ "$1" = . ]; then
		_start=$_curline
	else
		_start=$1
	fi

	_cnt=${2:-9}

	SEDCMD="$_start,$(($_start+$_cnt))p"

	pr -tn $_guineapig | sed -n "$SEDCMD"
}
