Basis for a Ruby Freemius HTTP API client.

freemius-api-client.rb

module Freemius
  API_HOST = 'api.freemius.com'
  SANDBOX_HOST = 'sandbox-api.freemius.com'

  class Base
    # Options taken from http://docs.freemius.apiary.io/#introduction/the-authentication-header
    # * host                 Default is api.freemius.com
    # * api_version          Default is v1
    # * scope_entity         Default is 'plugin'. Could also be 'developer', 'install', 'site', 'user'
    # * scope_entity_id      Required.
    # * public_key           Required.
    # * secret_key           Required.
    def initialize(options)
      Freemius.host         = options.fetch(:host)             { API_HOST }
      Freemius.api_version  = options.fetch(:api_version)      { 'v1' }
      Freemius.scope_entity = options.fetch(:scope_entity)     { 'plugin' }
      Freemius.scope_entity_id  = options.fetch(:scope_entity_id) do 
        raise ArgumentError.new('Scope entity ID is required to initialize Freemius') if Freemius.scope_entity_id.nil?
      end
      Freemius.public_key  = options.fetch(:public_key) do 
        raise ArgumentError.new('Public key is required to initialize Freemius') if Freemius.public_key.nil?
      end
      Freemius.secret_key  = options.fetch(:secret_key) do 
        raise ArgumentError.new('Secret key is required to initialize Freemius') if Freemius.secret_key.nil?
      end
    end

    def base_url
      "https://#{Freemius.host}#{base_path}"
    end

    def base_path
      "/#{Freemius.api_version}/#{Freemius.scope_entity.pluralize}/#{Freemius.scope_entity_id}"
    end

    def submit(method, path, data = {})
      body = [:put, :post].include?(method) ? data.to_json : ''
      headers = headers(method, "#{base_path}/#{path.split('?').first}", body)
      response = http_client.run_request(method, path, body, headers)
      JSON.parse(response.body)
    end
      
    private
      
      def http_client
        @http_client ||= Faraday.new(base_url, :ssl => { :ca_file => ENV['CERT_PATH'], :version => :TLSv1 }) 
      end

      def headers(method, path, body)
        formatted_date = Time.now.strftime('%a, %e %b %Y %H:%M:%S %z')
        content_type = 'application/json'
        md5 = body.empty? ? '' : Digest::MD5.hexdigest(body)
        signature_content = "#{method.to_s.upcase}\n#{md5}\n#{content_type}\n#{formatted_date}\n#{path}"
        digest = OpenSSL::Digest.new('sha256')
        signature = base64_url_encode(OpenSSL::HMAC.hexdigest(digest, Freemius.secret_key, signature_content))
        { 
          'Authorization' => "FS #{Freemius.scope_entity_id}:#{Freemius.public_key}:#{signature}",
          'Content-Type' => content_type,
          'Date' => formatted_date
        }
      end

      def base64_url_encode(data)
        Base64::encode64( data ).tr('+/', '-_').gsub('=', '').gsub("\n", '')
      end

  end

  class << self
    attr_accessor :host,
                  :scope_entity,
                  :scope_entity_id,
                  :public_key,
                  :secret_key,
                  :api_version

    def configure
      yield self
      true
    end
    alias :config :configure
  end
end