Gemini Nano Integration

val availability = generativeModel.checkAvailability()
if (availability != AvailabilityStatus.AVAILABLE) {
    return Result.Failure(ModelUnavailableException(availability))
}

2. TextChunker

• Interface at data/TextChunker.kt; implementation is TextChunkerImpl, injected via Hilt.
• Splits input into chunks capped at MAX_CHUNK_TOKENS (a const val in the companion object).
• Accepts an optional seed: Long parameter for deterministic selection in tests.
• Returns a random excerpt as a String.

interface TextChunker {
    fun randomExcerpt(text: String, seed: Long = Random.nextLong()): String

    companion object {
        const val MAX_CHUNK_TOKENS = 3_000 // leaves room for prompt overhead
    }
}

class TextChunkerImpl @Inject constructor() : TextChunker {
    override fun randomExcerpt(text: String, seed: Long): String { … }
}

3. PromptBuilder

• Interface at domain/PromptBuilder.kt; implementation is PromptBuilderImpl, injected via Hilt.
• Accepts the excerpt string and returns a fully-formed prompt String.
• Prompt must instruct Gemini Nano to return only a JSON array — no markdown fences.

interface PromptBuilder {
    fun build(excerpt: String): String
}

class PromptBuilderImpl @Inject constructor() : PromptBuilder {
    override fun build(excerpt: String): String =
        """
        Generate a 5-question multiple-choice quiz based on the following text.
        Return ONLY a JSON array with this structure (no markdown, no explanation):
        [{"question":"…","options":["A)…","B)…","C)…","D)…"],"answer":"A)…"}]
        
        Text:
        $excerpt
        """.trimIndent()
}

4. JSON Parsing

Use Kotlinx Serialization. Define:

@Serializable
data class QuizQuestion(
    val question: String,
    val options: List<String>,
    val answer: String,
)

Parse with:

val questions = Json { ignoreUnknownKeys = true }
    .decodeFromString<List<QuizQuestion>>(rawJson)

Wrap in try/catch and surface as Result.Failure(ParseException(…)) on error.

5. FakeQuizGeneratorRepository

Provide this for emulator/CI where AICore is unavailable:

class FakeQuizGeneratorRepository(
    private val response: Result<List<QuizQuestion>> = Result.Success(FAKE_QUESTIONS),
) : QuizGeneratorRepository {
    override suspend fun generateQuiz(text: String): Result<List<QuizQuestion>> = response
}

Keep FAKE_QUESTIONS as a const/top-level property in the same file.

Key Dependencies

// build.gradle.kts (app)
implementation("com.google.ai.edge.aicore:aicore:<version>")
implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:<version>")