#  Arguments:
#    index of preselected option
#    array of options
#
#  Return value:
#    selected index (0 for opt1, 1 for opt2 ...)
#
function select_option {
    start_idx=$1
    shift
    options=("$@")

    # helpers for terminal print control and key input
    ESC=$(printf "\033")
    cursor_blink_on()   { printf "$ESC[?25h"; }
    cursor_blink_off()  { printf "$ESC[?25l"; }
    cursor_to()         { printf "$ESC[$1;${2:-1}H"; }
    print_option()      { printf "   $1 "; }
    print_selected()    { printf "${COLOR_GREEN}  $ESC[7m $1 $ESC[27m${NC}"; }
    get_cursor_row()    { IFS=';' read -sdR -p $'\E[6n' ROW COL; echo ${ROW#*[}; }
    key_input()         { read -s -n3 key 2>/dev/null >&2
                         if [[ $key = $ESC[A ]]; then echo up; fi
                         if [[ $key = $ESC[B ]]; then echo down; fi
                         if [[ $key = ""     ]]; then echo enter; fi; }

    # initially print empty new lines (scroll down if at bottom of screen)
    for opt in "${options[@]}"; do printf "\n"; done

    # determine current screen position for overwriting the options
    local lastrow=`get_cursor_row`
    local startrow=$(($lastrow - $#))

    # 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 selected=$start_idx
    while true; do
        # print options by overwriting the last lines
        local idx=0
        for opt in "${options[@]}"; do
            cursor_to $(($startrow + $idx))
            if [ $idx -eq $selected ]; then
                print_selected "$opt"
            else
                print_option "$opt"
            fi
            ((idx++))
        done

        # user key control
        case `key_input` in
            enter) break;;
            up) ((selected--));
                    if [ $selected -lt 0 ]; then selected=$(($# - 1)); fi;;
            down)  ((selected++));
                    if [ $selected -ge $# ]; then selected=0; fi;;
        esac
    done

    # cursor position back to normal
    cursor_to $lastrow
    cursor_blink_on
    echo

    return $selected
}


# Usage:
deployment_targets=('staging' 'production')
default_target_idx=0

select_option $default_target_idx "${deployment_targets[@]}"