A PoC client for Slack's "Custom Integrations" implemented as a Lagom Service.

SlackService.scala

package com.example.hello.api

import akka.NotUsed
import com.example.hello.api.SlackCustomIntegration.Message
import com.lightbend.lagom.scaladsl.api.{Descriptor, Service, ServiceCall}
import com.lightbend.lagom.scaladsl.api.Service._
import com.lightbend.lagom.scaladsl.api.transport.Method
import play.api.libs.json._
import play.api.libs.functional.syntax._


trait SlackService extends Service {

  // Slack's custom integrations create an incoming webhook with the pattern:
  //    https://hooks.slack.com/services/T000000/B000000/XXXXXXXXXX
  // I'm not familiar with the meaning of the codes so I made up this names
  //  T000000 --> slackId
  //  B000000 --> slackTeamCode
  //  XXXXXXXXXX --> slackTeamKey
  //
  // Go to https://api.slack.com/custom-integrations for details on getting custom integrations webhooks for your team.

  override def descriptor: Descriptor =
    named("slack").withCalls(
      restCall(Method.POST, 
               "/services/T000000/B000000/XXXXXXXXXX", // TODO: read these 3 values from conf.
               sendMessage _)
    )

  def sendMessage(): ServiceCall[Message, NotUsed]
  // alternatively, delegate the use of slackId, slackTeamCode and slackTeamKey to every invocation
  // def sendMessageWithIds(slackId: String, 
  //                        slackTeamCode: String, 
  //                        slackTeamKey: String): ServiceCall[Message, NotUsed]
  // Then replace the restCall above with:
  //       restCall(Method.POST, "/services/:id/:team/:key", sendMessageWithIds _)
}

object SlackCustomIntegration {
  // TODO: use stronger typing on title_link
  case class Attachment(titles: String, title_link: String, test: String)
  case class Message(text: String,attachments: Option[Attachment] = None,
                     channel: Option[String] = None, // use #channel or @user for DM's
                     username: Option[String] = None, icon_emoji: Option[String] = None
                    )

  object Message{ implicit val format: Format[Message] = Json.format }
  object Attachment{ implicit val format: Format[Attachment] = Json.format }

}