DenisBronx

// A wrapper for handling failing requests
sealed class Result<T> {

    data class Success<T>(val value: T) : Result<T>()

    data class Failure<T>(val throwable: Throwable) : Result<T>()

}
// A DataStore for the SharedPreferences
interface ProductPreferences {

DenisBronx

// Entity
data class Product( 
    val id: String,
    val name: String,
    val price: Price
) {
    // Value object
    data class Price( 
        val nowPrice: Double,
        val wasPrice: Double

DenisBronx

// Network DTO
data class NetworkProduct(
    @SerializedName("id")
    val id: String?,
    @SerializedName("name")
    val name: String?,
    @SerializedName("nowPrice")
    val nowPrice: Double?,
    @SerializedName("wasPrice")
    val wasPrice: Double?

DenisBronx

// Database DTO
@Entity(tableName = "Product")
data class DBProduct(
    @PrimaryKey                
    @ColumnInfo(name = "id")                
    val id: String,                
    @ColumnInfo(name = "name")                
    val name: String,
    @ColumnInfo(name = "nowPrice")
    val nowPrice: Double,

DenisBronx

// Non-nullable to Non-nullable
interface ListMapper<I, O>: Mapper<List<I>, List<O>>

class ListMapperImpl<I, O>(
    private val mapper: Mapper<I, O>
) : ListMapper<I, O> {
    override fun map(input: List<I>): List<O> {
        return input.map { mapper.map(it) }
    }
}

DenisBronx

// Nullable to Non-nullable
interface NullableInputListMapper<I, O>: Mapper<List<I>?, List<O>>

class NullableInputListMapperImpl<I, O>(
    private val mapper: Mapper<I, O>
) : NullableInputListMapper<I, O> {
    override fun map(input: List<I>?): List<O> {
        return input?.map { mapper.map(it) }.orEmpty()
    }
}

DenisBronx

// Non-nullable to Nullable
interface NullableOutputListMapper<I, O>: Mapper<List<I>, List<O>?>

class NullableOutputListMapperImpl<I, O>(
    private val mapper: Mapper<I, O>
) : NullableOutputListMapper<I, O> {
    override fun map(input: List<I>): List<O>? {
        return if (input.isEmpty()) null else input.map { mapper.map(it) }
    }
}

DenisBronx

@Entity(tableName = "Product")
data class ProductDTO(
    @PrimaryKey                
    @ColumnInfo(name = "id")    
    @SerializedName("id")
    val id: String?,
    @ColumnInfo(name = "name")
    @SerializedName("name")
    val name: String?,
    @ColumnInfo(name = "nowPrice")

DenisBronx

// Entity
data class Product( 
    val id: String,
    val name: String,
    val price: Price,
    val isFavourite: Boolean
) {
// Value object
    data class Price( 
        val nowPrice: Double,

DenisBronx

class ProductRepositoryImpl(
    private val productApiService: ProductApiService,
    private val productDataMapper: Mapper<DataProduct, Product>,
    private val productPreferences: ProductPreferences
) : ProductRepository {

    override fun getProducts(): Single<Result<List<Product>>> {
        return productApiService.getProducts().map {
            when(it) {
                is Result.Success -> Result.Success(mapProducts(it.value))