Multiple Select Option Function

multi_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_inactive()    { printf "%s   %s " "$2" "$1"; }
    print_active()      { 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#*[}"; }

    # local lines=$(tput lines)
    local cols=$(tput cols)
    local return_value=$1
    local colmax=$2
    local offset=$(( cols / colmax ))
    local -n options=$3
    # local -n defaults=$4
    local defaults=()

    local selected=()
    for ((i=0; i<${#options[@]}; i++)); do
        if [[ ${defaults[i]} = "true" ]]; then
            selected+=("true")
        else
            selected+=("false")
        fi
        printf "\n"
    done

    # determine current screen position for overwriting the options
    local lastrow=$(get_cursor_row)
    # local lastcol=$(get_cursor_col)
    local startrow=$(( lastrow - ${#options[@]} + 1 ))
    # local startcol=1

    # 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

    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 
    }

    toggle_option() {
        local option=$1
        if [[ ${selected[option]} == true ]]; then
            selected[option]=false
        else
            selected[option]=true
        fi
    }

    toggle_option_multicol() {
        local option_row=$1
        local option_col=$2

        if [[ $option_row -eq -10 ]] && [[ $option_row -eq -10 ]]; then
            for ((option=0;option<${#selected[@]};option++)); do
                selected[option]=true
            done
        else
            if [[ $option_row -eq -100 ]] && [[ $option_row -eq -100 ]]; then
                for ((option=0;option<${#selected[@]};option++)); do
                    selected[option]=false
                done
            else
                option=$(( option_col + option_row * colmax )) 
                if [[ ${selected[option]} == true ]]; then
                    selected[option]=false
                else
                    selected[option]=true
                fi
            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
            local prefix="[ ]"
            if [[ ${selected[idx]} == "true" ]]; then
                prefix="[✓]"
            fi

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

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


    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
            space)  toggle_option_multicol $active_row $active_col;;
            enter)  print_options_multicol -1 -1; 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;;
            all)    toggle_option_multicol -10 -10 ;;
            none)   toggle_option_multicol -100 -100 ;;
        esac
    done

    # cursor position back to normal
    cursor_to $(( startrow + ( ${#options[@]} / colmax ) + 2 ))
    printf "\n"
    cursor_blink_on

    eval "$return_value"='("${selected[@]}")'
}

#!/bin/bash

multi_select_option() {
    .
    .
    .
}

choices=("One" "Two" "Three" "Four" "Five" "Six")
multi_select_option results NUM_OF_COLUMN choices
if ! echo ${results[@]} | grep true &>/dev/null; then
    echo "Nothing is selected. So exited."
    exit
fi
idx=0
for choice in "${choices[@]}"; do
    if [[ "${results[idx]}" == "true" ]]; then
        echo $choice is selected.
    fi
    ((idx++))
done

exit 0