Doubtfire Downloader for lazy CS Students - Ruby

# Welcome lazy students, this program will download all the task PDFs and Resources from your units
# Get your auth token by 'right-click > copy link location' of one of the download buttons (Download PDF/Resources)
# From that link, copy the stuff after 'auth_token=' and paste it just here:
$auth_token = 'AUTH TOKEN HERE'
# From the same link, copy the unit ID here (it's the part after '/units/unit id is here'):
$unit = 185
# Run the script and it'll download and sort all the files in target_dir, heads up that it WILL update all files, so if the tutors update a file, make sure you re-run this
$target_dir = './Tasks/' # Don't forget the trailing '/'
# You're welcome, love Zac

require 'json'
require 'net/http'

# Doubtfire Documentation at: https://doubtfire.ict.swin.edu.au/api/docs/
unit_url = URI("https://doubtfire.ict.swin.edu.au/api/units/#{$unit}.json?auth_token=#{$auth_token}")
def file_url (task_id, type)
    return URI("https://doubtfire.ict.swin.edu.au/api/units/#{$unit}/task_definitions/#{task_id}/#{type}.json?auth_token=#{$auth_token}")
end

# Handles downloading and saving of our files
def download_file (url, destination)
    response = Net::HTTP.get_response(url)
    f = File.new($target_dir + destination, 'wb')
    f.write(response.body)
    f.close()
end

# Removes illegal characters from out filenames, will lead to some weird names, blame the tutors
def remove_illegal_characters (string)
    illegalChars = /[\/\?<>\\\\:\*\|\"]/
    return string.gsub(illegalChars, ' ')
end

# Handle a missing target directory
if (!Dir.exists?($target_dir))
    puts "Target Directory: \"#{$target_dir}\" does not exist, create it? (y/n)   "
    if ('y' == gets.chomp)
        Dir.mkdir($target_dir)
    else
        exit(0)
    end
end

# Download student data and iterate through tasks, downloading
student_info = JSON.parse(Net::HTTP.get_response(unit_url).body)
for task in student_info['task_definitions']
    safe_dir_name = task['abbreviation'] + ' - ' + remove_illegal_characters(task['name'])

    if (!Dir.exists?($target_dir + safe_dir_name))
        Dir.mkdir($target_dir + safe_dir_name)
    end

    if (task['has_task_pdf'] == true)
        destination = "#{safe_dir_name}/#{remove_illegal_characters(task['name'])} Brief.pdf"
        download_file(file_url(task['id'], 'task_pdf'), destination)
    end

    if (task['has_task_resources'] == true)
        destination = "#{safe_dir_name}/#{remove_illegal_characters(task['name'])} Resources.zip"
        download_file(file_url(task['id'], 'task_resources'), destination)
    end
end