#!/usr/bin/env sh

# This script generates a menu from the given list of items. Choosing an item runs the command for that item.
# Usage: menu "Please choose" "item1 item2 item3" "ls cat command3"
# Use up/down arrow keys to select a menu item, then press Enter. Or cancel with ESC.

. colors

description=$1
items=($2)
commands=($3)
selected=0
displayed=0

# Calculate the position of the menu
menu_x=$((0))
menu_y=$(fathom-cursor -y)

# Calculate the number of rows that the menu will occupy
num_rows=${#items[@]}

# Calculate the maximum length of the item names
max_name_length=$(max-length "${items[*]}")
max_name_length=$((max_name_length))

# Define the function to display the menu
display_menu() {
  # Get the dimensions of the terminal window (again each time in case window is resized)
  window_width=$(fathom-terminal -w)
  window_height=$(fathom-terminal -h)
  
  # Recalculate the position of the menu
  menu_y=$(fathom-cursor -y)
  
  # Move the cursor to the correct position
  if [ $displayed -eq 0 ]; then
    # Don't move the cursor or clear the screen the first time
    displayed=1
  else
    if [ $((menu_y + num_rows)) -ge $window_height ]; then
    	menu_y=$((window_height))
    fi
    move-cursor $menu_x $((menu_y - num_rows)) 
  fi
  
  # Print the items and commands
  for i in "${!items[@]}"; do
    if [ $i -eq $selected ]; then
      printf "${CYAN}> %-${max_name_length}s${RESET} ${GREY}%s${RESET}\n" "${items[$i]}" "${commands[$i]}"
    else
    	# Print the menu item plus extra spaces to cover up its command, since it's not selected
      printf "  %-${max_name_length}s %*s\n" "${items[$i]}" "${#commands[$i]}"
    fi
  done
}

# Define the function to handle key presses
handle_key() {
  key=$(await-keypress)
  case "$key" in
    up)
      selected=$((selected - 1))
      if [ $selected -lt 0 ]; then
        selected=$((num_rows - 1))
      fi
      ;;
    down)
      selected=$((selected + 1))
      if [ $selected -ge $num_rows ]; then
        selected=0
      fi
      ;;
    enter)
      cursor-blink on
      command="${commands[$selected]}"
      printf "\n"
      eval $command 
      exit 0
      ;;
    escape) 
      cursor-blink on
      echo ESC
      exit
      ;;
    esac
}

cursor-blink off

# Display the menu's description
echo $description

# Menu loop
while true; do
  display_menu
  handle_key $key
done