final class AppSaga {
  typealias Effect = Redux.Saga.Effect

  /// The app's saga branches.
  static func sagas(_ api: AppRepositoryType) -> [Effect<AppState, Any>] {
    return [
      Redux.Saga.Effect.takeLatest(
        paramExtractor: self.autocompleteParam,
        effectCreator: {self.verboseAutocompleteSaga(api, $0)},
        options: .default())
    ]
  }

  /// Extract the autocomplete query from an action.
  static func autocompleteParam(_ action: AppAction) -> String? {
    switch action {
    case .updateAutocompleteInput(let input): return input
    default: return nil
    }
  }

  /// Verbose saga to demonstrate full use of helper functions.
  static func verboseAutocompleteSaga(_ api: AppRepositoryType, _ input: String)
    -> Redux.Saga.Effect<AppState, Any>
  {
    /// Create an Effect wrapper from the input string.
    let inputEffect = Redux.Saga.Effect<AppState, String>.just(input)

    /// Create a CallEffect to invoke the search API on the query.
    let callEffect = Redux.Saga.Effect
      .call(with: inputEffect, callCreator: api.searchITunes)

    /// Create a PutEffect to deposit search results into the Redux Store.
    return Redux.Saga.Effect
      .put(callEffect, actionCreator: AppAction.updateITunesResults)
  }
}