freeletics_login.rb

require 'active_support/all'

class FreeleticsLogin
  def self.log(*args)
    new(*args).log
  end

  def initialize(email, password)
    self.login_url = 'https://www.freeletics.com/api/user/v1/auth/password/login'
    self.email = email
    self.password = password
    self.headers = {
        'Host:' => 'www.freeletics.com',
        'Connection:' => 'keep-alive',
        'Content-Length:' => '71',
        'Accept:' => 'application/json, text/plain, */*',
        'Origin:' => 'https://www.freeletics.com',
        'Accept-Language:' => 'pt',
        'User-Agent:' => 'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36',
        'Content-Type:' => 'application/json;charset=UTF-8',
        'DNT:' => '1',
        'Referer:' => 'https://www.freeletics.com/pt/login',
        'Accept-Encoding:' => 'gzip, deflate, br',
        'Cookie:' => 'country_code=BR; PRUM_EPISODES=s=1474572369951&r=https%3A//www.freeletics.com/pt/bodyweight/users/2768424/feed'
      }
  end

  def log
    JSON.parse(`curl -s '#{login_url}' #{ headers.map { |k, v| "-H '#{k} #{v}'" }.join(" ")} --data-binary '{"login":{"email":"#{email}","password":"#{password}"}}' --compressed`)
  end

  protected

  attr_accessor :login_url, :email, :password, :headers
end

puts  "Email:"
email    = gets.chomp
puts  "Password:"
password = gets.chomp
p FreeleticsLogin.log email, password