directory.rb

@students = [] #global empty array

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 the menu and ask user what to do
  print_menu
  #get user input and pass it to the process method
  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"
    load_students
  when "9"
    exit
  else
    puts "I don't know what you mean, try again"
  end
end

def input_students
  puts "Please enter the names of the students"
  puts "To finish just hit return twice"
  #get the first name
  name = STDIN.gets.chomp
  #while the name is not empty repeat this code
  while !name.empty? do
    #add the student hash to the array
    @students << {name: name, cohort: :november}
    puts "Now we have #{@students.count} students"
    #get another name from the user
    name = STDIN.gets.chomp
  end
end

def show_students
  print_header
  print_student_list
  print_footer
end

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

def print_student_list
  @students.each_with_index do |student, index|
    puts "#{index + 1}. #{student[:name]} (#{student[:cohort]} cohort)" 
  end
end

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

def save_students
  #open the file for writing
  file = File.open("students.csv", "w")
  #iterate over the array of students
  @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 #first arg from the command line
  return if filename.nil? #get out of the method if it isn't given
  if File.exists?(filename) #if it exists
    load_students(filename)
    puts "Loaded #{@students.count} from #{filename}"
  else #if it doesn't exist
    puts "Sorry, #{filename} doesn't exist."
    exit #quit the program
  end
end

#nothing happens until we call all the methods
try_load_students
interactive_menu