module ShopifyAPI

  class ValidationException < StandardError
  end

  class Session
    cattr_accessor :api_key
    cattr_accessor :secret
    cattr_accessor :protocol
    self.protocol = 'https'

    attr_accessor :url, :token, :name

    class << self

      def setup(params)
        params.each { |k,value| send("#{k}=", value) }
      end

      def temp(domain, token, &block)
        session = new(domain, token)
        begin
          original_domain = host_with_port(ShopifyAPI::Base.site.to_s)
        rescue URI::InvalidURIError
        end
        original_token   = ShopifyAPI::Base.headers['X-Shopify-Access-Token']
        original_session = new(original_domain, original_token)

        begin
          ShopifyAPI::Base.activate_session(session)
          yield
        ensure
          ShopifyAPI::Base.activate_session(original_session)
        end
      end

      def prepare_url(url)
        return nil if url.blank?
        url.gsub!(/https?:\/\//, '')                            # remove http:// or https://
        url.concat(".myshopify.com") unless url.include?('.')   # extend url to myshopify.com if no host is given
      end

      def validate_signature(params)
        params = params.with_indifferent_access
        return false unless signature = params[:signature]

        sorted_params = params.except(:signature, :action, :controller).collect{|k,v|"#{k}=#{v}"}.sort.join
        Digest::MD5.hexdigest(secret + sorted_params) == signature
      end

      def host_with_port(site)
        parsed_site = URI.parse(site)
        host = parsed_site.host or return
        port = parsed_site.port
        if (protocol == 'http' && port == 80) || (protocol == 'https' && port == 443)
          host
        else
          "#{host}:#{port}"
        end
      end

    end

    def initialize(url, token = nil)
      self.url, self.token = url, token
      self.class.prepare_url(self.url)
    end

    def create_permission_url(scope, redirect_uri = nil)
      params = {:client_id => api_key, :scope => scope.join(',')}
      params[:redirect_uri] = redirect_uri if redirect_uri
      "#{protocol}://#{url}/admin/oauth/authorize?#{parameterize(params)}"
    end

    def request_token(params)
      return token if token

      unless self.class.validate_signature(params) && params[:timestamp].to_i > 24.hours.ago.utc.to_i
        raise ShopifyAPI::ValidationException, "Invalid Signature: Possible malicious login"
      end

      code = params['code']

      response = access_token_request(code)

      if response.code == "200"
        token = JSON.parse(response.body)['access_token']
      else
        raise RuntimeError, response.msg
      end
    end

    def shop
      Shop.current
    end

    def site
      "#{protocol}://#{url}/admin"
    end

    def valid?
      url.present? && token.present?
    end

    private
      def parameterize(params)
        URI.escape(params.collect{|k,v| "#{k}=#{v}"}.join('&'))
      end

      def access_token_request(code)
        uri = URI.parse("#{protocol}://#{url}/admin/oauth/access_token")
        https = Net::HTTP.new(uri.host, uri.port)
        https.use_ssl = true
        request = Net::HTTP::Post.new(uri.request_uri)
        request.set_form_data({"client_id" => api_key, "client_secret" => secret, "code" => code})
        https.request(request)
      end
  end
end