Bash: two loops inside while loop - bash

Question

As a beginner I'm not sure if this is the best way to do multiple loops!! though it works well, please suggest me if there is an elegant way of doing this (I'm not restricted to bash but I'm not familiar with other languages)
#!/bin/bash
while :; do
read -n1 -e -p"Top Levels 1-5: " top_levels
if [ "$top_levels" == "1" ]; then
echo "top level 1"
elif [ "$top_levels" == "2" ]; then
while :; do
read -n1 -e -p"Sub Levels 1-5: " sub_levels
if [ "$sub_levels" == "1" ]; then
echo "sub level 1"
elif [ "$sub_levels" == "2" ]; then
echo "sub level 2"
elif [ "$sub_levels" == "3" ]; then
while :; do
read -n1 -e -p"Final Levels 1-5: " final_levels
if [ "$final_levels" == "1" ]; then
echo "Final level 1"
elif [ "$final_levels" == "2" ]; then
echo "Final level 2"
elif [ "$final_levels" == "3" ]; then
echo "Final level 3"
elif [ "$final_levels" == "4" ]; then
echo "Final level 4"
else
echo "bye"
break
fi
done
elif [ "$sub_levels" == "4" ]; then
echo "sub level 4"
else
echo "bye"
break
fi
done
elif [ "$top_levels" == "3" ]; then
echo "top level 3"
elif [ "$top_levels" == "4" ]; then
echo "top level 4"
else
echo "bye"
exit
fi
done

Answer 1

I'd write it like this
#!/bin/bash
process_final_levels() {
while :; do
read -n1 -e -p"### Final Levels 1-5: " final_levels
case $final_levels in
1) echo "Final level 1";;
2) echo "Final level 2";;
3) echo "Final level 3";;
4) echo "Final level 4";;
*) echo "returning to sub levels"
break;;
esac
done
}
process_sub_levels() {
while :; do
read -n1 -e -p"# Sub Levels 1-5: " sub_levels
case "$sub_levels" in
1) echo "sub level 1" ;;
2) echo "sub level 2" ;;
3) process_final_levels;;
4) echo "sub level 4" ;;
*) echo "returning to top levels"
break;;
esac
done
}
while :; do
# get top levels to work with
read -n1 -e -p"Top Levels 1-5: " top_levels
case "$top_levels" in
1) echo "top level 1" ;;
2) process_sub_levels ;;
3) echo "top level 3" ;;
4) echo "top level 4" ;;
*) echo "Bye"
exit;;
esac
done
I changed the prompt and exiting strings to be more intuitive as to what level you are working on. I didn't add comments, b/c I have no idea what's this for. I functionalized, b/c any code that needs to be modified, tested, or maintained should be functionalized.