nav

#!/bin/bash

GLOBAL_J=0
GLOBAL_Y=0

GLOBAL_LS_ARR=()

IFS=$'\n'

_print_help() {
	cat << EOF
nav is a simple tool for navigating your directory in less
keystrokes!

If you want, you can technically even execute commands from inside
it. (NOTE: This has a LOT of glitches and unwanted side-effects
currently; it makes use of the dreaded 'exec'... so use it at your
own risk! This functionality can be disabled with an argument as seen
later.)

~~~~~~~~~~~~~~~~~~~~~~~~~ USING NAV: BASICS ~~~~~~~~~~~~~~~~~~~~~~~~~
nav makes use of 'ls' to list your directory contents with numbers
beside them. To navigate to one of them, key in that number and press
ENTER, plain and simple! To go back, use '..'. And if you have
'just-nav' mode disabled, ANYTHING ELSE will be exec-ed as a command!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

~~~~~~~~~~~~~~~~~~~~ ARGUMENTS WHEN STARTING NAV ~~~~~~~~~~~~~~~~~~~~
-e or --exposit
	Display the contents of the current directory without
	interactivity.

	NOTE! ALWAYS PLACE THIS ARGUMENT LAST! THE PROGRAM WILL DISPLAY
	AND EXIT AS SOON AS IT PARSES THIS!

-? or --help
	Display this help page.

	NOTE! '-h' DOES NOT TRIGGER HELP; IT PASSES THE '-h' ARGUMENT TO
	THE INTERNAL 'ls' COMMAND! (More on this below)

-j or --just-nav
	A safe mode; disables the internal usage of 'exec' to execute
	user commands from within nav.

-y or --yump
	Sets nav up to auto-exit after one directory change.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


~~~~~~~~~~~~~~~~~ CONTROLLING INTERNAL 'ls' COMMAND ~~~~~~~~~~~~~~~~~
nav uses an internal 'ls' command to facilitate the display of
directory contents. Thus, it is an option to pass arguments to this
internal 'ls' command to tweak the display you want.

Any argument you give nav that starts with a hyphen and is not one 
of the above-listed arguments will be passed to the internal 'ls' 
command when displaying directories.

Please note however that not all 'ls' arguments may function as
expected, or indeed at all, with nav.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


~~~~~~~~~~~~~~~~~~ ADDING SOURCE NAV THROUGH ALIAS ~~~~~~~~~~~~~~~~~~
It is also suggested to alias "snav" for "source nav". This will 
allow your shift in directory to be retained after moving, although
there are some disorienting side-effects after launching any program 
through snav, for example that your working directory might be left
at some bin directory that nav or that program accessed.

NOTE!!! IF THAT PROGRAM SELF-TERMINATES WITH AN EXIT SIGNAL, YOUR
ENTIRE TERMINAL SESSION WILL SELF-TERMINATE AS WELL!

Should you choose to alias "snav" for "source nav", this can be done
by adding the following in its own line in either your .bash_aliases
or .bashrc files:

		alias snav='source nav'
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



EOF
}

_print_usage() {
	cat << EOF
USAGE: nav [<arguments>...]

These arguments can be either for nav itself, or for its internal
'ls' command (explained further in 'nav --help')

Enter 'nav --help' for further assistance.

NOTE: THE ARGUMENT '-e' or '--exposit' MUST ALWAYS BE THE LAST
PARAMETER!

EOF
}

_flag_check() {
	shopt -s extglob
	while [ $# -gt 0 ]; do
		case $1 in
			-e|--exposit)
				_show_settings
				_display
				kill -INT $$
				;;
			-j|--just-nav)
				GLOBAL_J=1
				;;
			-y|--yump)
				GLOBAL_Y=1
				;;
			-\?|--help)
				_print_help
				kill -INT $$
				;;
			\-*)
				GLOBAL_LS_ARR+=($1)
				;;
			*)
				_print_usage
				kill -INT $$
				;;
		esac

		shift
	done
}

_display() {

	echo "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"
	echo "CURRENT DIRECTORY: $PWD"
	echo "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"
	echo ""

	COUNT=1
	CONT_ARR=()
	CHOICE=0
        
        COLUMN_ARR=()

	for content in `ls ${GLOBAL_LS_ARR[@]} $PWD`; do
		CONT_ARR+=($content)
		COLUMN_ARR+="$COUNT: ${CONT_ARR[COUNT-1]} \n"
		((COUNT=COUNT+1))
	done
        
        NO_OF_COLS=$(tput cols)
        
        echo -e $COLUMN_ARR | column -c $NO_OF_COLS
}

_choice() {
	echo ""
	_show_settings
	echo ""
	read -p "SELECT CHOICE: " CHOICE

	clear

	CD_TRUNC_CHOICE=`echo $CHOICE | cut -c -3`

	if echo $CHOICE | grep -x -E "[0-9]+"; then
		cd ./${CONT_ARR[CHOICE-1]}
	elif [ $CHOICE = ".." -o $CHOICE = "." ]; then
		cd $CHOICE
	elif [ $CHOICE = "cd" ]; then
		cd
	elif [ $CD_TRUNC_CHOICE = "cd " ] ; then
		cd `echo $CHOICE | cut -c 4-`
	elif [ $CHOICE = "," ]; then
		echo "---------------- EXIT COMMAND DETECTED ----------------"
		echo "ARGUMENTS PASSED TO 'ls' COMMAND: ${GLOBAL_LS_ARR[*]}"
		_display
		echo "---------------- EXIT COMMAND DETECTED ----------------"
		kill -INT $$
	else
		if [ $GLOBAL_J -eq 1 ]; then
			echo "INVALID INPUT. PLEASE ENTER A NUMBER FROM 1 TO $COUNT."
			echo ""
			echo "If you wish to enable execution of user commands from within nav,"
			echo "activate nav with the '-j' or the '--just-nav' arguments. "
			echo ""
			echo "(NOT RECOMMENDED. VERY VERY GLITCHY AND UNPREDICTABLE.)"
			echo ""
		else
			echo "EXECUTING COMMAND: $CHOICE"
			(exec /bin/bash -c $CHOICE)
		fi
	fi
}

_ending() {

	if [ $GLOBAL_Y -eq 1 ]; then
		_display
		echo STOP.
	else
		_nav_loop
	fi

}

_show_settings() {
	if [ $GLOBAL_J -eq 1 ]; then
		echo "SAFE MODE ('-j' or '--just-nav') ENABLED."
		echo ""
	else
		echo "USER COMMANDS PERMITTED."
		echo ""
	fi

	if [ $GLOBAL_Y -eq 1 ]; then
		echo "NAV WILL AUTO-EXIT AFTER ONE DIRECTORY CHANGE ('-y' or '--yump')."
		echo ""
	fi

	if [ ${#GLOBAL_LS_ARR[@]} -gt 0 ]; then
		echo "ARGUMENTS PASSED TO 'ls' COMMAND: ${GLOBAL_LS_ARR[*]}"
		echo ""
	else
		echo "NO ARGUMENTS PASSED TO 'ls' COMMAND"
		echo ""
	fi
}

_nav_loop() {

	_display
	_choice
	_ending

}

_flag_check "$@"

_nav_loop