#!/usr/bin/env bash

# Renders a text based list of options that can be selected by the
# user using up, down and enter keys and returns the chosen option.
#
#   Arguments   : list of options, maximum of 256
#                 "opt1" "opt2" ...
#   Return value: selected index (0 for opt1, 1 for opt2 ...)
function select_option {

    # little 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 " $1 "; }
    print_selected()   { printf "$ESC[7m $1 $ESC[27m"; }
    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; 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=0
    while true; do
        # print options by overwriting the last lines
        local idx=0
        for opt; 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
    printf "\n"
    cursor_blink_on

    return $selected
}

function multi_select_option {
    # little 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()     { in=$1
                         c=$2
                         if [[ $in != "Wipe" && $in != "Exit" ]];
                         then 
                             printf " [${choices[$c]}] $in ";
                         else
                             printf " $in "
                         fi
                        }
    print_selected()   { in=$1
                         if [[ $in != "Wipe" && $in != "Exit" ]]; then
                             printf "$ESC[7m [${choices[$2]}] $1$ESC[27m"; 
                         else
                             printf "$ESC[7m $1$ESC[27m"; 
                         fi
                        }
    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; }
    
    checker()   { idx=$1;
                  if [[ "${choices[$idx]}" != " " && \
                      "${choices[$idx]}" != "*" \
                  ]]; then
                      choices[$idx]=" " 
                  fi
                }

    local wipe_part=false
    local stop_loop=false
    # 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 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=0
    while true; do
        # print options by overwriting the last lines
        local idx=0
        for opt; do
            cursor_to $(($startrow + $idx))
            checker $idx
            if [ $idx -eq $selected ]; then
                print_selected "$opt" "$idx"
            else
                print_option "$opt" "$idx"
            fi
            ((idx++))
        done
        # user key control
        case `key_input` in
            enter)  if [[ $selected == $(($idx-1)) ]]; then
                        stop_loop=true
                    elif [[ $selected == $(($idx-2)) ]]; then
                        printf "\n"
                        confirm_question
                        if [[ $? -eq 0 ]];then
                            wipe_part=true;
                            stop_loop=true
                        else
                            choices=()
                            wipe_part=false
                            main
                        fi
                    else
                    [[ "${choices[selected]}" == "*" ]] &&
                       choices[selected]=" " || \
                       choices[selected]='*'
                    fi
                ;;

            up)    ((selected--));
                   if [ $selected -lt 0 ]; then selected=$(($# - 1)); fi;;
            down)  ((selected++));
                   if [ $selected -ge $# ]; then selected=0; fi;;
        esac
        if [[ $stop_loop == true ]]; then
            break
        fi
    done

    # cursor position back to normal
    cursor_to $lastrow
    printf "\n"
    cursor_blink_on
    if [[ $wipe_part == true ]];then
        return 0
    else
        return 1
    fi
}