Why is it important to create interfaces for remote data sources in the system?

Creating interfaces for remote data sources is important for several reasons:

• Abstraction and isolation: The interface hides implementation details, allowing changes to the data source (e.g., from REST API to GraphQL or local database) without altering the rest of the code.
• Testability: Mocks can be easily substituted through the interface for unit tests, simplifying the verification of business logic without real network connections.
• Maintainability: A clearly defined interaction contract makes the code easier to understand and support.
• Flexibility: It allows implementing different data retrieval options (cache, network, database) with the same interface.

Example of an interface in Kotlin for a remote data source:

interface RemoteDataSource {
    suspend fun fetchData(): List<DataItem>
}

class ApiRemoteDataSource(private val apiService: ApiService) : RemoteDataSource {
    override suspend fun fetchData(): List<DataItem> {
        return apiService.getData()
    }
}