package dev.privacyllc.period.di

import android.content.Context
import androidx.datastore.core.DataStore
import androidx.datastore.preferences.core.PreferenceDataStoreFactory
import androidx.datastore.preferences.core.Preferences
import androidx.datastore.preferences.preferencesDataStoreFile
import dagger.Module
import dagger.Provides
import dagger.hilt.InstallIn
import dagger.hilt.android.qualifiers.ApplicationContext
import dagger.hilt.components.SingletonComponent
import dev.privacyllc.period.core.data.CycleData
import dev.privacyllc.period.core.data.CycleRepository
import dev.privacyllc.period.core.datastore.UserPreferencesRepository
import dev.privacyllc.period.domain.prediction.BaselinePredictionEngine
import dev.privacyllc.period.domain.prediction.PredictionEngine
import java.time.Clock
import javax.inject.Singleton

/**
 * Where the app learns what a file path is, and the only place it does.
 *
 * Note what is absent: no `PeriodDatabase`, no DAO, no Room import anywhere in
 * this module or anywhere above it. `CycleData.repository` hands back a
 * repository and keeps the storage to itself — see
 * docs/architecture/README.md.
 */
@Module
@InstallIn(SingletonComponent::class)
object DataModule {

    /**
     * Singleton because Room and DataStore both are: two instances over one
     * file is a corruption bug that only shows up under concurrency.
     */
    @Provides
    @Singleton
    fun cycleRepository(
        @ApplicationContext context: Context,
        engine: PredictionEngine,
        clock: Clock,
    ): CycleRepository = CycleData.repository(context, engine, clock)

    @Provides
    @Singleton
    fun preferencesDataStore(@ApplicationContext context: Context): DataStore<Preferences> =
        PreferenceDataStoreFactory.create {
            context.preferencesDataStoreFile("user_preferences")
        }

    @Provides
    @Singleton
    fun userPreferencesRepository(store: DataStore<Preferences>) = UserPreferencesRepository(store)

    /**
     * Batch 02 replaces this binding, and only this binding.
     *
     * The rest of the app depends on [PredictionEngine], never on an
     * implementation — so swapping in the real engine is one line here, and the
     * §51 acceptance tests can run against both to show the replacement is
     * better rather than merely different.
     */
    @Provides
    @Singleton
    fun predictionEngine(): PredictionEngine = BaselinePredictionEngine()

    /** Injected rather than read from the environment, so §50's date edge cases stay testable. */
    @Provides
    @Singleton
    fun clock(): Clock = Clock.systemDefaultZone()
}