add some tests (#537)

* add some tests

* spotless

+/*
+ * Copyright 2024 LiveKit, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.livekit.android.audio
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import java.nio.ByteBuffer
+
+class AudioBufferCallbackDispatcherTest {
+
+    @Test
+    fun callsThrough() {
+        val dispatcher = AudioBufferCallbackDispatcher()
+        val audioBuffer = ByteBuffer.allocateDirect(0)
+        var called = false
+        val callback = object : AudioBufferCallback {
+            override fun onBuffer(buffer: ByteBuffer, audioFormat: Int, channelCount: Int, sampleRate: Int, bytesRead: Int, captureTimeNs: Long): Long {
+                assertEquals(audioBuffer, buffer)
+                called = true
+                return captureTimeNs
+            }
+        }
+        dispatcher.bufferCallback = callback
+        dispatcher.onBuffer(
+            buffer = audioBuffer,
+            audioFormat = 0,
+            channelCount = 1,
+            sampleRate = 48000,
+            bytesRead = 0,
+            captureTimeNs = 0L,
+        )
+
+        assertTrue(called)
+    }
+}

+/*
+ * Copyright 2024 LiveKit, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.livekit.android.audio
+
+import android.media.AudioFormat
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import java.nio.ByteBuffer
+import java.nio.ByteOrder
+
+class MixerAudioBufferCallbackTest {
+
+    @Test
+    fun mixesByte() {
+        val mixer = IncrementMixer()
+        val buffer = ByteBuffer.allocateDirect(1).order(ByteOrder.nativeOrder())
+        buffer.put(0, 0.toByte())
+        mixer.onBuffer(
+            buffer = buffer,
+            audioFormat = AudioFormat.ENCODING_PCM_8BIT,
+            channelCount = 1,
+            sampleRate = 1,
+            bytesRead = 1,
+            captureTimeNs = 0,
+        )
+
+        assertEquals((0 + INCREMENT).toByte(), buffer.get(0))
+    }
+
+    @Test
+    fun mixesShort() {
+        val mixer = IncrementMixer()
+        val buffer = ByteBuffer.allocateDirect(2).order(ByteOrder.nativeOrder())
+        val shortBuffer = buffer.asShortBuffer()
+        shortBuffer.put(0, 0.toShort())
+        mixer.onBuffer(
+            buffer = buffer,
+            audioFormat = AudioFormat.ENCODING_PCM_16BIT,
+            channelCount = 1,
+            sampleRate = 1,
+            bytesRead = 2,
+            captureTimeNs = 0,
+        )
+
+        assertEquals((0 + INCREMENT).toShort(), shortBuffer.get(0))
+    }
+
+    @Test
+    fun mixesFloat() {
+        val mixer = IncrementMixer()
+        val buffer = ByteBuffer.allocateDirect(4).order(ByteOrder.nativeOrder())
+        val floatBuffer = buffer.asFloatBuffer()
+        floatBuffer.put(0, 0.toFloat())
+        mixer.onBuffer(
+            buffer = buffer,
+            audioFormat = AudioFormat.ENCODING_PCM_FLOAT,
+            channelCount = 1,
+            sampleRate = 1,
+            bytesRead = 1,
+            captureTimeNs = 0,
+        )
+
+        assertEquals((0 + INCREMENT).toFloat(), floatBuffer.get(0))
+    }
+
+    companion object {
+        const val INCREMENT = 1
+    }
+
+    class IncrementMixer : MixerAudioBufferCallback() {
+        override fun onBufferRequest(originalBuffer: ByteBuffer, audioFormat: Int, channelCount: Int, sampleRate: Int, bytesRead: Int, captureTimeNs: Long): BufferResponse? {
+            val byteBuffer = ByteBuffer.allocateDirect(4).order(ByteOrder.nativeOrder())
+
+            when (audioFormat) {
+                AudioFormat.ENCODING_PCM_8BIT -> {
+                    byteBuffer.put(0, INCREMENT.toByte())
+                }
+
+                AudioFormat.ENCODING_PCM_16BIT -> {
+                    byteBuffer.asShortBuffer().put(0, INCREMENT.toShort())
+                }
+
+                AudioFormat.ENCODING_PCM_FLOAT -> {
+                    byteBuffer.asFloatBuffer().put(0, INCREMENT.toFloat())
+                }
+
+                AudioFormat.ENCODING_INVALID -> throw IllegalArgumentException("Bad audio format $audioFormat")
+            }
+
+            return BufferResponse(byteBuffer)
+        }
+    }
+}
+
+private fun getBytesPerSample(audioFormat: Int): Int {
+    return when (audioFormat) {
+        AudioFormat.ENCODING_PCM_8BIT -> 1
+        AudioFormat.ENCODING_PCM_16BIT, AudioFormat.ENCODING_IEC61937, AudioFormat.ENCODING_DEFAULT -> 2
+        AudioFormat.ENCODING_PCM_FLOAT -> 4
+        AudioFormat.ENCODING_INVALID -> throw IllegalArgumentException("Bad audio format $audioFormat")
+        else -> throw IllegalArgumentException("Bad audio format $audioFormat")
+    }
+}