Screencast Downloader

download.rb

# Forcing the app to load the dynamic libxml2 library instead of the older system version of libxml2 loaded by gems that failed to specify which library to load.
require 'nokogiri'
require 'open-uri'

Bundler.setup
Bundler.require(:default)

require 'ostruct'

ROOT_URL = 'https://www.URL.com'

def download_screencasts
  login

  all_screencasts do |screencast|
    download screencast unless File.exists? screencast.filename
  end
end

def all_screencasts(&block)
  screencasts_links do |link|
    download_page = Nokogiri::HTML(open url(link))
    download_link = ios_download_link download_page

    filename = "#{link.split('/').last}.mov"

    yield OpenStruct.new filename: filename, download_link: download_link
  end
end

def authenticity_token
  page = Nokogiri::HTML(open url('/screencasts/users/sign_in'))
  page.css('input[name=authenticity_token]').first[:value]
end

def download(screencast)
  link     = screencast.download_link
  filename = screencast.filename

  Curl::Easy.new(link) do |curl|
    curl.follow_location = true
    curl.cookies = @cookies.join " "
    progress_bar = nil

    curl.on_header do |header|
      if header =~ /Content-Length: (\d*)/
        length = $1.to_i
        progress_bar = ProgressBar.create title: filename, total: length, format: '%a |%b>>%i| %p%% %t'
      end

      header.length
    end

    curl.on_body do |data|
      File.open(filename, 'a') { |f| f.write data }
      progress_bar.progress += data.length

      data.length
    end

    curl.perform
  end
end

def login
  curl = Curl::Easy.new(url '/screencasts/users/sign_in')
  curl.follow_location = true
  curl.enable_cookies  = true

  # Extract cookies in response.
  @cookies = []
  curl.on_header { |header|
    # Parse cookies from the headers (yes, this is a naive implementation but it's fast).
    @cookies << "#{$1}=#{$2}" if header =~ /^Set-Cookie: ([^=]*)=([^;]+;)/

    header.length
  }

  curl.http_post(
    Curl::PostField.content('authenticity_token', authenticity_token),
    Curl::PostField.content('user[email]', 'EMAIL'),
    Curl::PostField.content('user[password]', 'PASSWORD')
  )

  # Reset the on_header handler.
  curl.on_header
end

def ios_download_link(page)
  links = page.css('.downloads a').map { |link| url(link[:href]) }
  links.find { |link| link =~ /ios/ }
end

def screencasts_links(&block)
  page = Nokogiri::HTML(open url('/screencasts'))
  page.css('.screencast a').each { |link| yield link[:href] }
end

def url(link)
  "#{ROOT_URL}#{link}"
end

download_screencasts

Gemfile

source :rubygems

gem 'curb'
gem 'nokogiri'
gem 'ruby-progressbar'

group :test, :development do
  gem 'pry'
end