directory.rb

@students = [] # an empty array accessible to all methods

def print_menu
  puts "1. Input the students"
  puts "2. Show the students"
  puts "3. Save the list to students.csv"
  puts "4. Load the list from students.csv"
  puts "9. Exit"
end

def interactive_menu
  loop do
    print_menu
    process(STDIN.gets.chomp)
  end
end

def process(selection)
  case selection
  when "1"
    input_students
  when "2"
    show_students
  when "3"
    save_students
  when "4"
    try_load_students
  when "9"
    exit 
  else
    puts "I don't know what you meant, try again"
  end
end

def input_students
  puts "Please enter the name of the students"
  puts "To finish, just hit return twice"
  name = STDIN.gets.chomp
  while !name.empty? do
    @students << {name: name, cohort: :november}
    puts "Now we have #{@students.count} students"
    name = STDIN.gets.chomp
  end
end

def show_students
  print_header
  print_students_list
  print_footer
end

def print_header
  puts "The students of Villians Academy"
  puts "-----------------"
end

def print_students_list
  @students.each do |student|
    puts "#{student[:name]} (#{student[:cohort]} cohort)"
  end
end

def print_footer
  puts "Overall, we have #{@students.count} great students"
end

def save_students
  file = File.open("students.csv", "w")
  @students.each do |student|
    student_data = [student[:name], student[:cohort]]
    csv_line = student_data.join(",")
    file.puts csv_line
  end
  file.close
end

def load_students(filename = "students.csv")
  file = File.open(filename, "r")
  file.readlines.each do |line| 
  name, cohort = line.chomp.split(',')
    @students << {name: name, cohort: cohort.to_sym}
  end
  file.close
end

def try_load_students
  filename = ARGV.first
  if filename.nil?
     load_students
     puts "Loaded #{@students.count} students from 'students.csv'"
  elsif File.exist?(filename)
    load_students(filename)
    puts "Loaded #{@students.count} students from #{filename}"
  else
    puts "Sorry, #{filename} doesn't exist."
    exit
  end
end

try_load_students
interactive_menu