Weather App

An offline first weather app to showcase a microservices architecture, having clean architecture and TDD in mind.

• The app has a minimal material UI. The UI is fully implemented using Jetpack Compose.
• The app contains only a single screen in which there are three main sections:
  • Units toolbar: It's possible to toggle between celsius and fahrenheit for temperature, and between km/h and mp/h for wind speed respectively.
  • NowWeather: Displays the weather at the current moment with a margin of 1 hour.
  • TodayWeather: Displays the weather of the following hours of the current day.
• The following errors are handled gracefully:
  • Missing permission to access coarse and fine location
  • Gps/Location is disabled
  • No internet connection
  • Unknown errors!
• Large screens are supported. The app will switch to a horizontal layout on larger screens, or in landscape mode of some devices.
• Offline support: The last displayed data is always cached locally and can be displayed when offline.

Run the App

An authentication free service is used for accessing weather data, so, no authentication is required. Just run the app.

Architecture

• The app follows UDF (unidirectional data flow), using kotlin flow.
• It also respects separation of concerns, having data, api, feature, and ui layers.
• The architecture is based on microservices, MVI, and clean architecture.

Layers

• Networking: Is in charge of network communication, including headers interception, serialization adapters implementation, and generic response handling. All responses are translated to an ApiResponse object, with well-defined success and error cases.
• Service: Provides feature-specific networking and local service - namely, fetching weather data - using the networking module. Ideally, every feature should have a respective service module. However, connected features can share a single service module.
• Design: Implements the design language, including theming, components, and dimensions.
• Feature: Ideally, a feature module is a microservice which includes only a single feature which is a set of connected functionalities by definition. In case of the current app, only a single feature was needed, as such, it was named feature!
• Plugins: Provides version catalogs. It could also contain other plugins, e.g., lint, build, etc.

Feature module

Technically, this module is a microservice. It's completely isolated from the app module. It has the following layers internally:

• Api: Exposes a couple of interfaces, explaining what's the expected behavior of this microservice. It also contains all the domain models.
• Data: Provides all the data that the domain layer expects, e.g., weather data, permissions, gps, etc..
• Domain: Provides an implementation to the api layer. Ideally, the domain module must be platform agnostic.
• Feature: This is the module that going to be exposed to the outside world. It's in charge of gluing all the layer together.
• Demo: This layer is not implemented, however, it can be easily. With this layer, a microservice can showcase it's functionalities using fake data and a demo app.

Naming conventions

• Network data models are suffixed with Dto
• Local data models are suffixed with Dao
• Domain data models aren't suffixed with anything
• Ui data models are suffixed with Param
• Mappers are in charge of mapping these models across layers

Libraries

• Retrofit: A REST API communication framework
• Coroutines: A asynchronous or non-blocking programming framework
• OkHttp: A HTTP client
• Koin A lightweight dependency injection (service locator) framework
• Kotlin Serialization: A JSON serialization library
• Mockk: A mocking framework
• JetPack Compose: Google's recommended declarative UI framework for building native UI

Future Improvements

• Extract the platform specific parts of the feature microservice, including all the providers implementations, e.g., GpsProviderImpl, LocationProviderImpl, etc..
• All layers must be fully covered with unit/ui tests. Not all the layers are fully covered with tests at the moment.
• A plugin can be useful for aggregating the build.gradle boilerplate scripts.