Improve shared installer to allow picking and choosing of modules

[joshuacurtiss]

Right now, the user selects how far in the installation process they want to go. In the future, though, this will become less straightforward, and it will be beneficial to allow the user to pick and choose which modules will be ran.

Replace the existing list with a process that lets the user check/uncheck the different modules, and then just the checked modules will run.

[joshuacurtiss]

Here's a nice multiple select menu function:

# Multi-select menu in pure bash
multi_select_menu() {
  local cursor=0
  local key
  local options=("$@")
  local selected=()

  # Find the length of the longest option, and set selections to false
  local maxlen=0
  for ((i=0; i<${#options[@]}; i++)); do
    (( ${#options[i]} > maxlen )) && maxlen=${#options[i]}
    selected[i]=false
  done
  local padlen=$((maxlen + 7))

  tput sc >&2 && tput civis >&2
  while true; do
    tput rc >&2
    for ((i=0; i<${#options[@]}; i++)); do
      tput el >&2
      box=○ && ${selected[i]} && box=◉
      printf -v line "%-*s" "$padlen" " $box ${options[i]}"
      ((cursor==i)) && tput setab 4 >&2 && tput setaf 7 >&2
      echo "$line" >&2
      tput sgr0 >&2
    done
    tput dim >&2
    echo "Use ↑/↓ to move, SPACE to select/deselect, ENTER to confirm." >&2
    tput sgr0 >&2

    # Read key
    IFS= read -rsn1 key
    if [[ $key == $'\x1b' ]]; then
      read -rsn2 key
      if [[ $key == "[A" ]]; then
        ((cursor--))
        ((cursor<0)) && cursor=$((${#options[@]}-1))
      elif [[ $key == "[B" ]]; then
        ((cursor++))
        ((cursor>=${#options[@]})) && cursor=0
      fi
    elif [[ $key == " " ]]; then
      if ${selected[cursor]}; then selected[cursor]=false; else selected[cursor]=true; fi
    elif [[ $key == "" ]]; then
      break
    fi
  done

  # Show cursor
  tput cnorm >&2

  # Collect selected items
  local result=()
  for ((i=0; i<${#selected[@]}; i++)); do
    ${selected[i]} && result+=("$i")
  done
  echo "${result[@]}"
}

Example usage:

choices=("Apple //e" "Mac Classic" "Atari 2600" "Apple IIgs" "Newton MessagePad")
echo "$(tput bold)Choose your favorite retro gear:$(tput sgr0)"
while true; do
  selected_items=$(multi_select_menu "${choices[@]}")
  # Error handling:
  [[ -z $selected_items ]] && tput setaf 1 && echo 'Select at least one item.' && tput rc
  # Valid handling:
  [[ -n $selected_items ]] && tput el && break
done

# Print selected items
echo
echo "You selected these items:"
for index in $selected_items; do
  echo " - ${choices[index]}"
done