support posting private messages

lib/flowdock.rb

@@ -146,6 +146,18 @@ def chat_message(params)
       post(event + 's', params.merge(tags: tags, event: event))
     end
 
+    def private_message(params)
+      raise InvalidParameterError, "Message must have :content" if blank?(params[:content])
+      raise InvalidParameterError, "Message must have :user_id" if blank?(params[:user_id])
+
+      user_id = params.delete(:user_id)
+
+      params = params.clone
+      event = "message"
+
+      post("private/#{user_id}/messages", params.merge(event: event))
+    end
+
     def post(path, data = {})
       resp = self.class.post(api_url(path), :body => MultiJson.dump(data), :basic_auth => {:username => @api_token, :password => ''}, :headers => headers)
       handle_response(resp)

spec/flowdock_spec.rb

@@ -375,6 +375,16 @@ def join_tokens(tokens)
         expect(res).to eq({"id" => 1234})
       }.not_to raise_error
     end
+    it 'posts to /private/:user_id/messages' do
+      expect {
+        stub_request(:post, "https://#{token}:@api.flowdock.com/v1/private/12345/messages").
+          with(:body => MultiJson.dump(content: "foobar", event: "message"), :headers => {"Accept" => "application/json", "Content-Type" => "application/json"}).
+          to_return(:status => 201, :body => '{"id":1234}', :headers => {"Content-Type" => "application/json"})
+        res = client.private_message(user_id: "12345", content: 'foobar')
+        expect(res).to eq({"id" => 1234})
+      }.not_to raise_error
+    end
+
     it 'raises without flow' do
       expect {
         client.chat_message(content: 'foobar')