#!/usr/bin/env bash

## Function start
function select_option {
    local nformat
    local optcount=$#
    printf -v nformat "%%%dd. " ${#optcount}
    local max_opt=0
    local multiselected=()
    local choices=()
    local shortcuts=()
    local idx=0
    local clean_opt
    for opt; do
      multiselected+=(0)
      if [[ "$opt" =~ ^\[.\]* ]]; then # choice starts with [x]
        shortcuts+=( "${opt:1:1}" )
        choices+=( "${opt:3}" )
      else
        shortcuts+=( "${opt:0:1}" )
        choices+=( "$opt" )
      fi
      if [[ "${#choices[$idx]}" -gt $max_opt ]]; then
        max_opt="${#choices[$idx]}"
      fi
      ((idx++))
    done

    # 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"; }
    if [[ $SELECT_MONOCHROME -eq 1 ]]; then
        print_option()     { printf "  $ESC[30m%s $ESC[0m%s  %s   $ESC[30m%s$ESC[0m$ESC[K" "$1" "$2" "$3" "$4"; }
        print_selected()   { printf "  $ESC[30m%s $ESC[0m%s{ $ESC[1m%s$ESC[0m } $ESC[30m%s$ESC[0m$ESC[K" "$1" "$2" "$3" "$4"; }
        print_multiselected()   { printf "$ESC[30;1m*$ESC[0m"; }
    else
        print_option()     { printf "  $ESC[30m%s $ESC[33m%s  %s$ESC[0m   $ESC[30m%s$ESC[0m$ESC[K" "$1" "$2" "$3" "$4"; }
        print_selected()   { printf "  $ESC[30m%s $ESC[35;1m%s{ $ESC[37;1m%s$ESC[0;35;1m } $ESC[0;30m%s$ESC[0m$ESC[K" "$1" "$2" "$3" "$4"; }
        print_multiselected()   { printf "$ESC[32;1m*$ESC[0m"; }
    fi
    get_cursor_row()   { IFS=';' read -sdR -p $'\E[6n' ROW COL; echo ${ROW#*[}; }
    key_input()        { read -s -n1 key1 2>/dev/null >&2
                         read -s -n2 -t 0.1 key2 2>/dev/null >&2
                         local idx=$selected
                         while true; do
                           idx=$(( ($idx + 1) % $optcount ))
                           if [[ "$key1" = "${shortcuts[$idx]}" ]]; then
                             echo $idx; return;
                           fi
                           if [[ $idx -eq $selected ]]; then break; fi
                         done
                         if [[ $key1$key2 = $ESC[A ]]; then echo up; return; fi
                         if [[ $key1$key2 = $ESC[B ]]; then echo down; return; fi
                         if [[ $key1$key2 = $ESC[C ]]; then echo left; return; fi
                         if [[ $key1$key2 = $ESC[D ]]; then echo right; return; fi
                         if [[ $key1 = $'\e'  ]]; then echo esc; return;   fi
                         if [[ $key1 = x      ]]; then echo multiselect; return;   fi
                         if [[ $key1 = q      ]]; then echo esc; return;   fi
                         if [[ $key1 = ""     ]]; then echo enter; return; fi
                    }
    reset_display()  {
        cursor_blink_on; stty echo; printf '\n';
    }
    # initially print empty new lines (scroll down if at bottom of screen)
    for opt; do printf "\n"; done
    # Extras for top and bottom
    printf "\n\n"

    # determine current screen position for overwriting the options
    local lastrow=`get_cursor_row`
    local startrow=$(( $lastrow - $# - 2 ))
    local toprow="+~~--"
    local bottomrow="--~~+"
    local lborderchars="|:'"
    local rborderchars="|:."

    # ensure cursor and input echoing back on upon a ctrl+c during read -s
    trap "cursor_blink_on; stty echo; printf '\n'; exit 1" 2
    cursor_blink_off

    local selected=0
    local bottomlength=$(( 10 + $max_opt ))
    local multiselect_pos=6
    if [[ $SELECT_NUMBERS  -eq 1 ]]; then
        bottomlength=$(( $bottomlength + 3 ))
        multiselect_pos=$(( $multiselect_pos + 3 ))
    fi
    if [[ $SELECT_SHORTCUTS -eq 1 ]]; then
        bottomlength=$(( $bottomlength + 3 ))
        multiselect_pos=$(( $multiselect_pos + 3 ))
    fi

    while true; do
        # print options by overwriting the last lines
        local idx=0
        local nidx
        local shortcut
        cursor_to $startrow
        if [ $selected -lt 0 ]; then selected=$(($# - 1)); fi
        if [ $selected -ge $# ]; then selected=0; fi
        printf "  $ESC[30m%s$ESC[0m$ESC[K  " "$toprow"

        for opt; do
            opt="${choices[$idx]}"
            local lborder="${lborderchars:$idx:1}"
            if [ -z "$lborder" ]; then lborder=" "; fi
            local rborder="${rborderchars:$(( $optcount - $idx - 1)):1}"
            if [ -z "$rborder" ]; then rborder=" "; fi
            if [[ $SELECT_UNDERSCORES -eq 1 ]]; then
                opt=${opt//_/ }
            fi
            if [[ $SELECT_NUMBERS  -eq 1 ]]; then
                printf -v nidx "$nformat" $(( idx + 1 ))
            fi
            if [[ $SELECT_SHORTCUTS -eq 1 ]]; then
                printf -v shortcut "%s) " "${shortcuts[$idx]}"
            fi
            printf -v padopt "%-${max_opt}s" "$opt"
            cursor_to $(($startrow + $idx + 1))
            if [ $idx -eq $selected ]; then
                print_selected "$lborder" "$nidx$shortcut" "$padopt"  "$rborder"
            else
                print_option "$lborder" "$nidx$shortcut" "$padopt" "$rborder"
            fi
            if (( ${multiselected[$idx]} )); then
              cursor_to $(($startrow + $idx + 1)) $multiselect_pos
              print_multiselected
            fi
            ((idx++))
        done
        cursor_to $(($startrow + $idx + 1))
        printf "$ESC[K$ESC[30m%${bottomlength}s$ESC[0m  " "$bottomrow"

        # user key control
        local user_input=`key_input`
        case "$user_input" in
            enter) break;;
            esc)   reset_display; exit 1;;
            up)    ((selected--));;
            down)  ((selected++));;
            multiselect)  if (( $SELECT_MULTI )); then
                            multiselected[$selected]=$(( 1 - ${multiselected[$selected]} ));
                            ((selected++));
                          fi;;
            ?) selected=$user_input;;
        esac
    done

    # cursor position back to normal
    cursor_to $lastrow
    reset_display
    local returnvalue=0
    local idx=0
    if (( $SELECT_MULTI )); then
      if [[ -n "$SELECT_TOFILE" ]]; then printf "" > "$SELECT_TOFILE"; fi
      for opt; do
        if (( ${multiselected[$idx]} )); then
          if [[ -n "$SELECT_TOFILE" ]]; then echo "${choices[$idx]}" >> "$SELECT_TOFILE"; fi
          returnvalue=$(( $returnvalue + 2**$idx ))
        fi
        ((idx++))
      done
    else
    # Single choice
      returnvalue=$selected
      if [[ -n "$SELECT_TOFILE" ]]; then
        echo "${choices[$selected]}" > "$SELECT_TOFILE"
      fi
    fi

    return $(( $returnvalue + 10 ))
}
## Function end

[[ $_ == $0 ]] && {
_help() {
  SELF=$( basename "$0" )
  echo "Select Option [Pure BASH]
  Adapted from: https://unix.stackexchange.com/questions/146570/arrow-key-enter-menu

  Usage: $SELF [-nms_] [--nc] [-o File] list of options
    -n       Show item number
    -m       Multiple choice selection. Note that only 7 options can be encoded
             reliably in return value. Use File output for more options.
    -s       Show shortcuts
    --nc     No colors
    -o File  Save the choice(s) in a file.
    -_       Print spaces instead of underscores, workaround for
             shell arguments containing spaces.
    --package Special option to base64 encode this program, to be
              used in your own programs

  User interface:
    Enter          Select option
    Esc / Ctrl-c   Exit
    x              Multi-selection
    other keys     Shortcut, defaults to first letter of choice

  Returns:
    Single selection:
      - (10 + index) of selection (first option = 10)
      - 1 if ctrl-c or ESC pressed
      - If output file is defined, choice is printed there.
    Multiple selection:
      - (10 + 2**index) encoded multiple values (no options = 10). See example.
      - 1 if ctrl-c or ESC pressed
      - All choices separately in the output File.

  Example:
    Single choice:
      > $SELF -n one two three
      > EC=\$?
      > [[ \$EC -lt 10 ]] && { echo Exited..; } || { echo You selected \$(( \$EC - 9 )); }
    Single choice with shortcuts, press 1 2 3 or c to move in the menu:
      > $SELF -s [1]One [2]Two [3]Three [c]Cancel

    Multi choice:
      > $SELF -m one two three four five six seven -o choice.txt
      > C=\$?; C=\$(( \$C - 10 ))
      > if (( \$C == 0 )); then printf 'No selection'; else printf 'Selections: '; fi
      > for b in 7 6 5 4 3 2 1 0; do
      >   if (( \$C >= 2**\$b )); then printf '%d, ' \$(( \$b + 1 )); C=\$(( \$C - 2**\$b )); fi
      > done; printf '\\n'

"
  exit
}
_package_self() {
  grep ^SELECT_ "$0"
  printf "source <( echo '"
  awk '/^## Function start/{flag=1;next}/^## Function end/{flag=0}flag' "$0" | \
    base64 -w 0
  printf "' | base64 -d )\n"
  printf 'select_option one two three || choice=$(( $? - 9 ))\n'
}


SELECT_MONOCHROME=0
SELECT_SHORTCUTS=0
SELECT_NUMBERS=0
SELECT_UNDERSCORES=0
SELECT_MULTI=0
SELECT_TOFILE=""
for (( i=1; i<=$#; i++ )); do
  value=${!i}
  j=$(( i + 1 ))
  [[ "$value" = "--help" ]] && _help
  [[ "$value" = "--nc" ]] && { SELECT_MONOCHROME=1; continue; }
  [[ "$value" = "--package" ]] && { _package_self; exit; }
  [[ "${value}" = "-"* ]] && {
    [[ "$value" =~ -.*h ]] && { _help; }
    [[ "$value" =~ -.*m ]] && { SELECT_MULTI=1; }
    [[ "$value" =~ -.*s ]] && { SELECT_SHORTCUTS=1; }
    [[ "$value" =~ -.*n ]] && { SELECT_NUMBERS=1; }
    [[ "$value" =~ -.*_ ]] && { SELECT_UNDERSCORES=1; }
    [[ "$value" =~ -.*o ]] && {
        SELECT_TOFILE="${!j}"; ((i++));
        [[ -z "$SELECT_TOFILE" ]] && { echo Output file name missing; exit 1; }
    }
    continue
  }

  opts+=( "$value" )
done

select_option "${opts[@]}"
exit $?
}