#!/bin/bash

if [ "a$1" == "a--help" ] || [ "a$1" == "a-h" ]; then
  cat <<EOF
Usage: $0 [-i] \`tty\` "Option A" "Option B"
Displays the user in the provided tty all the options and lets the user select an option with their keys.

Prints the selected option (or the (0-based) index of that option with the -i flag) to the default stdout.

Exits with code 1 if the user aborted the selection with q.
EOF
fi

printidx=0
if [ "a$1" == "a-i" ]; then
  printidx=1
  shift
fi

tty="$1"
shift
options=("${@}")
optionslength=${#options[@]}
sel=0
printf "\e[s" >"$tty"
while true; do
  printf "\e[u\e[s\e[K" >"$tty"
  for ((i = 0; i < optionslength; i++)); do
    if [ "$i" -eq $sel ]; then
      printf "\e[30;47m" >"$tty"
    fi
    printf "%s\e[40;37m " "${options[$i]}" >"$tty"
  done
  case "$(./readkey <"$tty")" in
  left)
    sel=$((sel - 1))
    ;;
  right)
    sel=$((sel + 1))
    ;;
  q)
    printf "\e[u\e[KSelection aborted\n" >"$tty"
    exit 1
    ;;
  enter)
    break
    ;;
  esac
  if ((sel < 0)); then
    sel=0
  fi
  if ((sel >= optionslength)); then
    sel=$((optionslength - 1))
  fi

done
printf "\e[u\e[KSelected %s\n" "${options[$sel]}" >"$tty"

if [ "$printidx" -eq 1 ]; then
  echo "$sel"
else
  echo "${options[$sel]}"
fi