How to reply a message with Gmail API in Ruby?

Question

I have configured Google api's with my Ruby on Rails project. Also, I have set webhooks for incoming emails. I have successfully implemented login via Google and get user's inbox messages.

Now, I'm implementing a message reply, but I'm getting "BadRequest" in response.

My code.

uri = URI.parse("https://www.googleapis.com/gmail/v1/users/me/messages/send?access_token=#{access_token}")
          request = Net::HTTP::Post.new(uri)
          request.content_type = "application/json"
          request.body = JSON.dump({
              "References" => "\u003cCAAY2B8p2CjEjDKz+sXVBQBrda5i5Lz=Dd4fVC21kfx8fhLLCdg@mail.gmail.com\u003e" ,
              "In-Reply-To" => "\u003cCAAY2B8p2CjEjDKz+sXVBQBrda5i5Lz=Dd4fVC21kfx8fhLLCdg@mail.gmail.com\u003e" ,
              "Subject" => "Re: Test02" ,
              "From" => "[email protected]" ,
              "To" => "[email protected]" ,
              "threadId"=> "1764cc4c5efa6855",
              # "body" => "This is where the response text will go"
          })

          req_options = {
            use_ssl: uri.scheme == "https",
          }

          response = Net::HTTP.start(uri.hostname, uri.port, req_options) do |http|
            http.request(request)
          end

API call response.

response =>  #<Net::HTTPBadRequest 400 Bad Request readbody=true>

I need to send a reply using google API.

Thanks in advance.

Answer 1

In order to reply to a message using Google API, I have used this method.

client_secrets = Google::APIClient::ClientSecrets.load("#{Rails.root}/config/client_secrets.json")
      auth_client = client_secrets.to_authorization
      auth_client.update!(
        :scope => 'https://mail.google.com/ https://www.googleapis.com/auth/gmail.modify https://www.googleapis.com/auth/gmail.readonly https://www.googleapis.com/auth/pubsub',
        :redirect_uri => 'http://localhost:3000/google_code',
        :additional_parameters => {
          "access_type" => "offline",         # offline access
          "include_granted_scopes" => "true"  # incremental auth
        }
      )

      auth_client.code = auth_code

        gmail = Google::Apis::GmailV1::GmailService.new
        
          gmail.authorization = auth_client

          message              = Mail.new
          message.date         = Time.now
          message.subject      = "Re: Test02" 
          message.from         = "[email protected]"
          message.to           = "[email protected]"
          message.message_id   = "\u003cCAFVVPDvD-zK6Akj8djj+uam35ZxFTf2EW4AefW1Ri7OV7AxFVA@mail.gmail.com\u003e"

          message.part content_type: 'multipart/alternative' do |part|
              part.html_part = Mail::Part.new(body: "Using service Account.", content_type: 'text/html; charset=UTF-8')
          end

          msg = message.encoded
            
          message_object = Google::Apis::GmailV1::Message.new(raw:message.to_s, thread_id: "1764cc4c5efa6855", content_type: 'message/rfc822')
          
          gmail.send_user_message('me', message_object)