Select Option Function

select_option() {
    # little helpers for terminal print control and key input
    ESC=$( printf "\033")
    cursor_blink_on()   { printf "%s[?25h" "$ESC"; }
    cursor_blink_off()  { printf "%s[?25l" "$ESC"; }
    cursor_to()         { printf "%s[%s;%sH" "$ESC" "$1" "${2:-1}"; }
    print_option()      { printf "%s   %s " "$2" "$1"; }
    print_selected()    { printf "%s  %s[7m %s %s[27m" "$2" "$ESC" "$1" "$ESC"; }
    get_cursor_row()    { IFS=';' read -sdR -p $'\E[6n' ROW COL; echo "${ROW#*[}"; }
    get_cursor_col()    { IFS=';' read -sdR -p $'\E[6n' ROW COL; echo "${COL#*[}"; }
    key_input()         {
        local key
        IFS= read -rsn1 key 2>/dev/null >&2
        if [[ $key = ""      ]]; then echo enter; fi
        if [[ $key = $'\x20' ]]; then echo space; fi
        if [[ $key = "k" ]]; then echo up; fi
        if [[ $key = "j" ]]; then echo down; fi
        if [[ $key = "h" ]]; then echo left; fi
        if [[ $key = "l" ]]; then echo right; fi
        if [[ $key = "a" ]]; then echo all; fi
        if [[ $key = "n" ]]; then echo none; fi
        if [[ $key = $'\x1b' ]]; then
            read -rsn2 key
            if [[ $key = [A || $key = k ]]; then echo up; fi
            if [[ $key = [B || $key = j ]]; then echo down; fi
            if [[ $key = [C || $key = l ]]; then echo right; fi
            if [[ $key = [D || $key = h ]]; then echo left; fi
        fi
    }
    print_options_multicol() {
        # print options by overwriting the last lines
        local curr_col=$1
        local curr_row=$2
        local curr_idx=0

        local idx=0
        local row=0
        local col=0

        curr_idx=$(( curr_col + curr_row * colmax ))

        for option in "${options[@]}"; do

            row=$(( idx / colmax ))
            col=$(( idx - row * colmax ))

            cursor_to $(( startrow + row + 1 )) $(( offset * col + 1 ))
            if [[ $idx -eq $curr_idx ]]; then
                print_selected "$option"
            else
                print_option "$option"
            fi
            ((idx++))
        done
    }

    # initially print empty new lines (scroll down if at bottom of screen)
    for opt; do printf "\n"; done

    # determine current screen position for overwriting the options
    # local return_value=$1
    local lastrow=$(get_cursor_row)
    # local lastcol=$(get_cursor_col)
    local startrow=$(( lastrow - $# ))
    # local startcol=1
    # local lines=$( tput lines )
    local cols=$(tput cols)
    local colmax=$2
    local offset=$(( cols / colmax ))

    # local size=$4
    shift 4

    # ensure cursor and input echoing back on upon a ctrl+c during read -s
    trap "cursor_blink_on; stty echo; printf '\n'; exit" 2
    cursor_blink_off

    local active_row=0
    local active_col=0
    while true; do
        print_options_multicol $active_col $active_row
        # user key control
        case $(key_input) in

            enter)  break;;

            up)     (( active_row-- ));
                    if [[ "$active_row" -lt 0 ]]; then active_row=0; fi;;

            down)   (( active_row++ ));
                    if [[ $(( ${#options[@]} % colmax )) -ne 0 ]]; then
                        if [[ "$active_row" -ge $(( ${#options[@]} / colmax )) ]]; then
                            active_row=$(( ${#options[@]} / colmax ));
                        fi
                    else
                        if [[ "$active_row" -ge $(( ${#options[@]} / colmax -1 )) ]]; then
                            active_row=$(( ${#options[@]} / colmax -1 ));
                        fi
                    fi;;

            left)   (( active_col = active_col - 1 ));
                    if [[ "$active_col" -lt 0 ]]; then active_col=0; fi;;

            right)  (( active_col = active_col + 1 ));
                    if [[ "$active_col" -ge "$colmax" ]]; then active_col=$(( colmax - 1 )) ; fi;;

        esac
    done

    # cursor position back to normal
    cursor_to $(( lastrow - $# + ( $# / colmax ) - 1 ))
    printf "\n"
    cursor_blink_on

    return $(( active_col + active_row * colmax ))
}

#!/bin/bash

select_option() {
    .
    .
    .
}

options=("Apple" "Banana" "Orange" "Exit")
select_option $? NUM_OF_COLUMN "${options[@]}"
case $? in 
0) echo "You selected Apple";;
1) echo "You selected Banana";;
2) echo "You selected Orange";;
3) echo "You selected Exit";
    exit;;
esac

exit 0