Bash script - Using spaces as string - bash

Question

I'm trying to build a really simple TODO list with a bash script. It should allow user to add and remove a task and also see the entire list.
I've done it with the following script. But I've issues allowing a given task to take a whitespace as a string. For instance, if I'm adding a task with the command: ./programme_stack.sh add 1 start projet n1, it will only add a task with "start".
I've read a couple of things online, I know, I should double quote the variables but after trying this, it doesn't work. I must be missing something on the road.
Here is my script:
#!/bin/bash
TACHES=$HOME/.todo_list
# functions
function remove() {
res_remove=$(sed -n "$1p" $TACHES)
sed -i "$1d" $TACHES
}
function list() {
nl $TACHES
}
function add() {
if [ ""$(($(wc -l $TACHES | cut -d " " -f 1) + 1))"" == "$1" ]
then
echo "- $2" >> $TACHES
else
sed -i "$1i - $2" $TACHES
fi
echo "Task \"$2\" has been add to the index $1"
}
function isNumber() {
re='^[0-9]+$'
if ! [[ $# =~ $re ]] ; then
res_isNumber=true
else
res_isNumber=false
fi
}
# application
case $1 in
list)
list
;;
done)
shift
isNumber $#
if ! [[ "$res_isNumber" = false ]] ; then
echo "done must be followed by an index number"
else
nb_taches=$(wc -l $TACHES | cut -d " " -f 1)
if [ "$1" -ge 1 ] && [ "$1" -le $nb_taches ]; then
remove $1
echo "Well done! Task $i ($res_remove) is completed"
else
echo "this task doesn't exists"
fi
fi
;;
add)
shift
isNumber $1
if ! [[ "$res_isNumber" = false ]] ; then
echo "add must be followed by an index number"
else
index_max=$(($(wc -l $TACHES | cut -d " " -f 1) + 1))
if [ "$1" -ge 1 ] && [ "$1" -le $index_max ]; then
add $1 $2
else
echo "Idex must be between 1 and $index_max"
fi
fi
;;
*)
echo "./programme_stack.sh (list|add|done) [args]"
;;
esac
Can you guys see what I'm missing?
Many thanks!!

Answer 1

To get the script to support embedded spaces, 2 changes are needed
1) Accept embedded space - either
1A) Pass in the task name in quote script add nnn "say hello", OR
1B) Concatenate all the input parameters into single string.
2) Quote the task name to prevent it from being broken into individual words
In the code, implement 1B and 2
add)
...
if [ "$1" -ge 1 ] && [ "$1" -le $index_max ]; then
num=$1
shift
# Combine all remaining arguments
todo="$#"
add "$num" "$todo"
...