LocalDataSource.kt

interface LocalDataSource {
    fun getPlanetsFlow(): Flow<WorkResult<List<Planet>>>
    fun getPlanetFlow(planetId: String): Flow<WorkResult<Planet?>>
    suspend fun setPlanets(planets: List<Planet>)
    suspend fun addPlanet(planet: Planet)
    suspend fun deletePlanet(planetId: String)
}

RemoteDataSource.kt

interface RemoteDataSource {
    suspend fun getPlanets(): List<Planet>
    suspend fun addPlanet(planet: Planet): Planet
    suspend fun deletePlanet(planetId: String)
}