#!/bin/dash

### FUNCTIONS
usage(){
	echo "USAGE: qobackup BACKUP_FILENAME   BACKUP_DIRECTORY\n" >&2
}

die(){
	msg=$1
	echo "\n$msg\n" >&2
	usage
	exit 1
}

timestamp(){
	date +_%Y_%m_%d_%H_%M_%S
}

### VARIABLE SETTINGS
[ $# = 2 ] || die "Must have two arguments."
backup_directory="$2" 
file_to_back_up="$1"
file_to_back_up=`basename "$file_to_back_up"`
file_to_back_up="${file_to_back_up%.*}"
fullpath_to_back_up="$HOME/qownNotes/$file_to_back_up.md"
backup_interval_seconds="10"
prev_buppathname="/this_should_never_be_a_real_file.fake"

### MAIN ROUTINE CODE
echo "WAIT at least $backup_interval_seconds before editing $fullpath_to_back_up!!!"
sleep 1
mkdir -p $backup_directory || die "Could not create backup dir $backup_directory."
while /bin/true; do
	# copy
	ts=`timestamp`
	buppathname=$backup_directory/${ts}__$file_to_back_up.md
	cp $fullpath_to_back_up $buppathname

	# break logic / delete if unchanged
	status="firstime"
	[ -f $prev_buppathname ] && status="different"
	[ "$status" = "different" ] && \
		diff $buppathname $prev_buppathname > /dev/null \
		&& status="same"
	[ "$status" = "firstime"  ]  && prev_buppathname=$buppathname
        [ "$status" = "different" ] && prev_buppathname=$buppathname	
	[ "$status" = "same" ] && rm $buppathname

	# delay
	sleep $backup_interval_seconds
done