How to distinguish whitespace in string after using "read" in bash shell - bash

Question

I'm trying to writing a vim-like editor using shell. And I find that I cannot distinguish whitespace. I read 4 character because some special characters like arrows have 3 bytes. But it will be a mess if you enter keys at a fast speed.
So how can I distinguish space? (If you can tell me a better way to deal with the "entering too fast" problem will be nicer.)
while read -rsN1 key
do
if [ $key==$'\e' ];then
read -sN1 -t 0.0001 k1
read -sN1 -t 0.0001 k2
read -sN1 -t 0.0001 k3
key+=${k1}${k2}${k3}
fi
case $key in
$'\e[A')
echo "up" ;;
' ')
echo "space" ;; #It doesn't work here!!!
i)
echo "insert" ;;
esac
done

Answer 1

You can try this.
Instead of trying that there are a lot of things you can learn when using vim/vi/vim.exe/vi.exe in any operating system (Windows cygwin/mingw, AIX, Linux HP-UX/OSF1/IRIX/SunOS/UNIX)
Hence try learning vi.
However I have updated your code only for my knowledge transfer:
Here goes my coding:
#!/bin/bash
echo "Use any one of the following keys:"
UP=$(echo $'\U2190')
#echo -n $'\U2190' | od -bc
#echo -e "\0342\0206\0220" # LEFT
LEFT=$(echo $'\U2191')
#echo -e "\0342\0206\0221" # UP
RIGHT=$(echo $'\U2192')
#echo -e "\0342\0206\0222" # RIGHT
DOWN=$(echo $'\U2193')
#echo -e "\0342\0206\0223" # DOWN
echo SPACEBAR
while read -rsN1 key
do
if [ $'\e' == "$key" ]
then
read -sN1 -t 0.0001 k1
read -sN1 -t 0.0001 k2
read -sN1 -t 0.0001 k3
key+=${k1}${k2}${k3}
fi
case $key in
$'[A')
echo -n "$UP"
;;
$'[B')
echo -n "$DOWN"
;;
$'[C')
echo -n "$RIGHT"
;;
$'[D')
echo -n "$LEFT"
;;
' ')
echo -n " "
;;
#It doesn't work here!!!
i)
echo "insert"
;;
esac
done
My output:
$ 73172247.sh
Use any one of the following keys:
SPACEBAR
↑↓←→↓↑ ↑↑ ↑ →←↑
Example pdf:
https://www.jics.utk.edu/files/images/csure-reu/PDF-DOC/VI-TUTORIAL.pdf
Textpad.exe/notepad++.exe at windows
gedit at Linux.