Enable batch processing in Sonos worker

From now on, the Sonos worker dumps the Sonos state before the first
request and restores it only after the last request.
This resolved the issue of often not resuming playback
when more than one query was enqueued.

app/src/main/java/com/bartlomiejpluta/ttsserver/core/sonos/worker/SonosWorker.kt

@@ -4,7 +4,10 @@ import com.bartlomiejpluta.ttsserver.core.tts.engine.TTSEngine
 import com.bartlomiejpluta.ttsserver.core.web.dto.SonosDTO
 import com.bartlomiejpluta.ttsserver.service.foreground.ForegroundService
 import com.bartlomiejpluta.ttsserver.service.state.ServiceState
+import com.vmichalak.sonoscontroller.Snapshot
+import com.vmichalak.sonoscontroller.SonosDevice
 import com.vmichalak.sonoscontroller.SonosDiscovery
+import com.vmichalak.sonoscontroller.model.PlayState
 import java.util.concurrent.BlockingQueue
 
 class SonosWorker(
@@ -12,6 +15,7 @@ class SonosWorker(
    private val address: String,
    private val queue: BlockingQueue<SonosDTO>
 ) : Runnable {
+   private var snapshot: Snapshot? = null
 
    override fun run() = try {
       while (ForegroundService.state == ServiceState.RUNNING) {
@@ -23,9 +27,36 @@ class SonosWorker(
 
    private fun consume(data: SonosDTO) =
       SonosDiscovery.discover().firstOrNull { it.zoneGroupState.name == data.zone }?.let {
-         val file = tts.createTTSFile(data.text, data.language)
-         val filename = file.name
-         val url = "$address/sonos/$filename"
-         it.clip(url, data.volume, "")
+         updateSnapshotIfFirst(it)
+         val url = prepareTTSFile(data)
+         announce(it, data, url)
+         restoreSnapshotIfLast()
       }
+
+   private fun prepareTTSFile(data: SonosDTO): String {
+      val filename = tts.createTTSFile(data.text, data.language).name
+      return "$address/sonos/$filename"
+   }
+
+   private fun announce(device: SonosDevice, data: SonosDTO, url: String) {
+      device.stop()
+      device.volume = data.volume
+      device.playUri(url, "")
+      while (device.playState != PlayState.STOPPED) {
+         Thread.sleep(500)
+      }
+   }
+
+   private fun updateSnapshotIfFirst(it: SonosDevice) {
+      if (snapshot == null) {
+         snapshot = it.snapshot()
+      }
+   }
+
+   private fun restoreSnapshotIfLast() {
+      if (queue.isEmpty()) {
+         snapshot!!.restore()
+         snapshot = null
+      }
+   }
 }