Build an AI Voice-Notes App for Android

class VoiceRecorder(private val context: Context) {
    private var recorder: MediaRecorder? = null

    /** Requires RECORD_AUDIO permission granted. */
    fun start(output: File) {
        recorder = MediaRecorder(context).apply {
            setAudioSource(MediaRecorder.AudioSource.MIC)
            setOutputFormat(MediaRecorder.OutputFormat.MPEG_4)
            setAudioEncoder(MediaRecorder.AudioEncoder.AAC)
            setAudioSamplingRate(16_000)
            setAudioEncodingBitRate(64_000)
            setOutputFile(output)
            prepare()
            start()
        }
    }

    fun stop() {
        recorder?.runCatching { stop() }       // stop() throws if nothing was recorded
        recorder?.release()
        recorder = null
    }
}
// MediaRecorder(Context) requires API 31+; use the deprecated no-arg constructor on older versions.

suspend fun transcribe(model: GenerativeModel, audio: File): String {
    val response = model.generateContent(content {
        inlineData(audio.readBytes(), "audio/mp4")
        text("Transcribe this voice note verbatim. Mark unclear words as [inaudible].")
    })
    return response.text.orEmpty()
}
// Inline data has size limits; for long recordings, split audio or use file upload options per the docs.

@Serializable
data class Enrichment(val title: String, val summary: String, val actionItems: List<String>)

suspend fun enrich(model: GenerativeModel, transcript: String): Enrichment {
    val response = model.generateContent(
        "From this voice note transcript, return JSON with: title (max 6 words), " +
        "summary (max 2 sentences), actionItems (list, only explicit tasks; empty if none). " +
        "Use only information in the transcript.\n\nTranscript:\n$transcript"
    )
    return Json { ignoreUnknownKeys = true }.decodeFromString(response.text.orEmpty())
}
// Configure the model with responseMimeType = "application/json" and a schema for reliability.

@HiltWorker
class ProcessNoteWorker @AssistedInject constructor(
    @Assisted ctx: Context, @Assisted params: WorkerParameters,
    private val notes: NoteRepository,
    private val ai: VoiceAi,
) : CoroutineWorker(ctx, params) {
    override suspend fun doWork(): Result {
        val id = inputData.getLong("noteId", -1)
        val note = notes.get(id) ?: return Result.failure()
        return try {
            val transcript = note.transcript ?: ai.transcribe(File(note.audioPath)).also { notes.saveTranscript(id, it) }
            if (note.summary == null) notes.saveEnrichment(id, ai.enrich(transcript))
            Result.success()
        } catch (e: IOException) {
            Result.retry()
        }
    }
}
// Enqueue with a CONNECTED network constraint as unique work per note.