Now Bot keeps channel purpose as a reminder at last message in channel.

src/main/scala/com/maqdev/SlackApi.scala

@@ -2,13 +2,14 @@ package com.maqdev
 
 import akka.actor.ActorSystem
 import com.typesafe.config.ConfigFactory
-import play.api.libs.json.{JsValue, Json}
+import play.api.libs.json.{JsValue, Json, Reads}
 import spray.client.pipelining._
 import spray.http.Uri
 
 import scala.concurrent.{Await, Future}
 import scala.concurrent.duration._
 import scala.util.matching._
+import java.util.concurrent.ConcurrentHashMap
 
 object SlackApi {
   import scala.concurrent.ExecutionContext.Implicits.global
@@ -23,11 +24,21 @@ object SlackApi {
 
   val htmlEntities = Map("lt" → "<", "gt" → ">", "amp" → "&", "quot" → "\"", "apos" → "'") map { case (s, c) ⇒ c → ("&%s;" format s) }
 
+  var slackChannels = new ConcurrentHashMap[String, (String, String)]();
+
   def postMessageToSlack(m: SkypeMessage, slackChannelId: String) = {
     val strippedMessage = """<[^< ][^>]+?>""".r replaceAllIn (m.message replaceAllLiterally ("<quote", "> <quote"), "")
     val sanitizedMessage = htmlEntities.foldLeft(strippedMessage) { case (result, (chr, ent)) ⇒ result replaceAllLiterally (ent, chr) }
 
-    slackRequest("chat.postMessage", Map(
+    if (slackChannels.get(slackChannelId) != null) {
+      slackRequest[SlackChannelsInfoResult]("channels.info", Map(
+        "channel" → slackChannelId
+      )) map { result =>
+        slackChannels.put(slackChannelId, (result.channel.purpose.value, ""))
+      }
+    }
+
+    slackRequest[SlackChatResult]("chat.postMessage", Map(
       "channel" → slackChannelId,
       "username" → s"${m.authorName} @ Skype",
       "icon_url" → s"http://api.skype.com/users/${m.author}/profile/avatar",
@@ -36,44 +47,78 @@ object SlackApi {
       "unfurl_links" → s"true",
       "unfurl_media" → s"true",
       "text" → sanitizedMessage
-    ))
-  }
+    )) map { response ⇒
+      Option(slackChannels.get(response.channel)) foreach { case (uri, ts) ⇒
+        if (ts.nonEmpty) {
+          slackRequest[SlackChatResult]("chat.delete", Map(
+            "channel" → response.channel,
+            "ts" → ts
+          ))
+        }
 
-  case class SlackChannel(id: String, name: String)
-  def getChannelsFromSlack: Future[List[SlackChannel]] = {
-    implicit val slackChannelReads = Json.reads[SlackChannel]
-
-    slackRequest("channels.list") map {
-      json ⇒
-        val channelsJson = json \ "channels"
-        Json.fromJson[List[SlackChannel]](channelsJson).get
+        if (uri.nonEmpty) {
+          slackRequest[SlackChatResult]("chat.postMessage", Map(
+            "channel" → response.channel,
+            "username" → "SkypeBot",
+            "icon_url" → "http://en.gravatar.com/userimage/6208733/1129353ced07ece051aefd7e63d8b2f8.jpg",
+            "text" → uri
+          )) map { result =>
+            slackChannels.put(slackChannelId, (uri, result.ts))
+          }
+        }
+      }
     }
   }
 
-  def getChannelsFromSlackSync: List[SlackChannel] = {
+  def getChannelsFromSlack: Future[List[SlackChannelInfo]] = {
+    slackRequest[SlackChannelsListResult]("channels.list") map (_.channels)
+  }
+
+  def getChannelsFromSlackSync: List[SlackChannelInfo] = {
     // todo: remove sync version
     Await.result(getChannelsFromSlack, 30 seconds)
   }
 
   class SlackException(json: JsValue) extends Exception("Slack call failed: " + json.toString())
-  case class SlackRequestResult(ok: Boolean)
 
-  def slackRequest(method: String, data: Map[String,String] = Map()): Future[JsValue] = {
-    implicit val slackRequestResultReads = Json.reads[SlackRequestResult]
+  trait SlackRequestResult {
+    val ok: Boolean = false
+  }
+
+  case class SlackChannelPurpose(value: String)
+  case class SlackChannelInfo(id: String, name: String, purpose: SlackChannelPurpose)
+
+  case class SlackChannelsListResult(channels: List[SlackChannelInfo]) extends SlackRequestResult
+  case class SlackChannelsInfoResult(channel: SlackChannelInfo) extends SlackRequestResult
+  case class SlackChatResult(channel: String, ts: String) extends SlackRequestResult
+
+  implicit val slackChannelPurposeReads = Json.reads[SlackChannelPurpose]
+  implicit val slackChannelInfo = Json.reads[SlackChannelInfo]
+
+  implicit val slackChannelsListResultReads = Json.reads[SlackChannelsListResult]
+  implicit val slackChannelsInfoResultReads = Json.reads[SlackChannelsInfoResult]
+  implicit val slackChatResultReads = Json.reads[SlackChatResult]
+
+  def slackRequest[T <: SlackRequestResult : Reads](method: String, data: Map[String,String] = Map()): Future[T] = {
 
     val uri = Uri(s"https://slack.com/api/$method").withQuery(
       Map("token" → slackAuthToken) ++ data
     )
+
     log.debug("--> slack: {}", uri)
+
     val pipeline = sendReceive ~> unmarshal[String]
+
     pipeline {
       Get(uri)
     } map { s ⇒
       log.debug("<-- slack: {} ", s)
+
       val json = Json.parse(s)
-      val r = Json.fromJson[SlackRequestResult](json).get
+      val r = Json.fromJson[T](json).get
+
       if (r.ok) {
-        json
+        r
       }
       else {
         throw new SlackException(json)

src/main/scala/com/maqdev/SlackReportMessagesActor.scala

@@ -4,7 +4,7 @@ import java.io.File
 
 import akka.actor.Actor
 import akka.event.Logging
-import com.maqdev.SlackApi.SlackChannel
+import com.maqdev.SlackApi.SlackChannelInfo
 import com.typesafe.config.ConfigFactory
 
 import scala.collection.mutable
@@ -50,7 +50,7 @@ class SlackReportMessagesActor extends Actor {
     }
 
     defaultChannelId = SlackApi.getChannelsFromSlackSync.collect {
-      case x: SlackChannel if x.name.compareToIgnoreCase(defaultChannel) == 0 ⇒ x.id
+      case x: SlackChannelInfo if x.name.compareToIgnoreCase(defaultChannel) == 0 ⇒ x.id
     }.headOption
   }
 
@@ -133,7 +133,7 @@ class SlackReportMessagesActor extends Actor {
     }
   }
 
-  def channels: Future[(List[SkypeChat], List[SlackChannel])] = {
+  def channels: Future[(List[SkypeChat], List[SlackChannelInfo])] = {
     import context.dispatcher
     val f = SlackApi.getChannelsFromSlack
     val db = new SkypeDb(dbPath)