diff --git a/app/src/main/java/io/bartek/tts/TTS.kt b/app/src/main/java/io/bartek/tts/TTS.kt
new file mode 100644
index 0000000..852e838
--- /dev/null
+++ b/app/src/main/java/io/bartek/tts/TTS.kt
@@ -0,0 +1,67 @@
+package io.bartek.tts
+
+import android.content.Context
+import android.speech.tts.TextToSpeech
+import android.speech.tts.UtteranceProgressListener
+import java.io.BufferedInputStream
+import java.io.FileInputStream
+import java.io.InputStream
+import java.lang.RuntimeException
+import java.util.*
+
+data class SpeechData(val stream: InputStream, val size: Long)
+
+class TTS(context: Context, initListener: TextToSpeech.OnInitListener) {
+    private val tts = TextToSpeech(context, initListener)
+
+    fun performTTS(text: String, language: Locale): SpeechData {
+        val file = createTempFile("tmp_tts_server", ".wav")
+
+        val uuid = UUID.randomUUID().toString()
+        val lock = Lock()
+        tts.setOnUtteranceProgressListener(TTSProcessListener(uuid, lock))
+
+        synchronized(lock) {
+            tts.language = language
+            tts.synthesizeToFile(text, null, file, uuid)
+            lock.wait()
+        }
+
+        if (!lock.success) {
+            throw RuntimeException("TTS failed")
+        }
+
+        val stream = BufferedInputStream(FileInputStream(file))
+        val length = file.length()
+
+        file.delete()
+
+        return SpeechData(stream, length)
+    }
+}
+
+private data class Lock(var success: Boolean = false) : Object()
+
+private class TTSProcessListener(private val uuid: String, private val lock: Lock) :
+    UtteranceProgressListener() {
+
+    override fun onDone(utteranceId: String?) {
+        if (utteranceId == uuid) {
+            synchronized(lock) {
+                lock.success = true
+                lock.notifyAll()
+            }
+        }
+    }
+    override fun onError(utteranceId: String?) {
+        if (utteranceId == uuid) {
+            synchronized(lock) {
+                lock.success = false
+                lock.notifyAll()
+            }
+        }
+    }
+
+    override fun onStart(utteranceId: String?) {}
+
+}
diff --git a/app/src/main/java/io/bartek/web/TTSServer.kt b/app/src/main/java/io/bartek/web/TTSServer.kt
index d2b6166..d55107c 100644
--- a/app/src/main/java/io/bartek/web/TTSServer.kt
+++ b/app/src/main/java/io/bartek/web/TTSServer.kt
@@ -2,57 +2,24 @@ package io.bartek.web
 
 import android.content.Context
 import android.speech.tts.TextToSpeech
-import android.speech.tts.UtteranceProgressListener
 import android.widget.Toast
 import fi.iki.elonen.NanoHTTPD
 import fi.iki.elonen.NanoHTTPD.Response.Status.*
 import io.bartek.R
+import io.bartek.tts.TTS
 import org.json.JSONObject
-import java.io.BufferedInputStream
-import java.io.FileInputStream
-import java.io.InputStream
-import java.lang.RuntimeException
 import java.util.*
-import kotlin.collections.HashMap
 
-data class TTSRequestData(val text: String, val language: Locale)
+private data class TTSRequestData(val text: String, val language: Locale)
 
-data class Lock(var success: Boolean = false) : Object()
-
-data class SpeechData(val stream: InputStream, val size: Long)
-
-class TTSProcessListener(private val uuid: String, private val lock: Lock) :
-    UtteranceProgressListener() {
-    override fun onDone(utteranceId: String?) {
-        if (utteranceId == uuid) {
-            synchronized(lock) {
-                lock.success = true
-                lock.notifyAll()
-            }
-        }
-    }
-
-    override fun onError(utteranceId: String?) {
-        if (utteranceId == uuid) {
-            synchronized(lock) {
-                lock.success = false
-                lock.notifyAll()
-            }
-        }
-    }
-
-    override fun onStart(utteranceId: String?) {}
-}
 
 class TTSServer(port: Int, private val context: Context) : NanoHTTPD(port),
     TextToSpeech.OnInitListener {
-    private val tts = TextToSpeech(context, this)
+    private val tts = TTS(context, this)
 
     override fun serve(session: IHTTPSession?): Response {
         try {
-            val (text, language) = getRequestData(validateRequest(session))
-            val (stream, size) = performTTS(text, language)
-            return newFixedLengthResponse(OK, "audio/x-wav", stream, size)
+            return tryToServe(session)
         } catch (e: ResponseException) {
             throw e
         } catch (e: Exception) {
@@ -60,6 +27,12 @@ class TTSServer(port: Int, private val context: Context) : NanoHTTPD(port),
         }
     }
 
+    private fun tryToServe(session: IHTTPSession?): Response {
+        val (text, language) = getRequestData(validateRequest(session))
+        val (stream, size) = tts.performTTS(text, language)
+        return newFixedLengthResponse(OK, "audio/x-wav", stream, size)
+    }
+
     private fun validateRequest(session: IHTTPSession?): IHTTPSession {
         if (session == null) {
             throw ResponseException(BAD_REQUEST, "")
@@ -81,40 +54,12 @@ class TTSServer(port: Int, private val context: Context) : NanoHTTPD(port),
         return session
     }
 
-    private fun performTTS(text: String, language: Locale): SpeechData {
-        val file = createTempFile("tmp_tts_server", ".wav")
-
-        val uuid = UUID.randomUUID().toString()
-        val lock = Lock()
-        tts.setOnUtteranceProgressListener(TTSProcessListener(uuid, lock))
-
-        synchronized(lock) {
-            tts.language = language
-            tts.synthesizeToFile(text, null, file, uuid)
-            lock.wait()
-        }
-
-        if (!lock.success) {
-            throw RuntimeException("TTS failed")
-        }
-
-        val stream = BufferedInputStream(FileInputStream(file))
-        val length = file.length()
-
-        file.delete()
-
-        return SpeechData(stream, length)
-    }
-
     private fun getRequestData(session: IHTTPSession): TTSRequestData {
         val map = mutableMapOf<String, String>()
         session.parseBody(map)
         val json = JSONObject(map["postData"] ?: "{}")
         val language = Locale(json.optString("language", "en_US"))
-        val text = json.optString("text") ?: throw ResponseException(
-            BAD_REQUEST,
-            "The missing 'text' field is required."
-        )
+        val text = json.optString("text") ?: throw ResponseException(BAD_REQUEST, "")
         return TTSRequestData(text, language)
     }