swift-composable-architecture-mirror/Examples/CaseStudies/SwiftUICaseStudies/FactClient.swift

import Combine
import ComposableArchitecture
import XCTestDynamicOverlay

struct FactClient {
  var fetch: (Int) -> Effect<String, Error>

  struct Error: Swift.Error, Equatable {}
}

extension FactClient {
  // This is the "live" fact dependency that reaches into the outside world to fetch trivia.
  // Typically this live implementation of the dependency would live in its own module so that the
  // main feature doesn't need to compile it.
  static let live = Self(
    fetch: { number in
    URLSession.shared.dataTaskPublisher(for: URL(string: "http://numbersapi.com/\(number)/trivia")!)
      .map { data, _ in String(decoding: data, as: UTF8.self) }
      .catch { _ in
        // Sometimes numbersapi.com can be flakey, so if it ever fails we will just
        // default to a mock response.
        Just("\(number) is a good number Brent")
          .delay(for: 1, scheduler: DispatchQueue.main)
      }
      .setFailureType(to: Error.self)
      .eraseToEffect()
  })
}

extension FactClient {
  // This is the "unimplemented" fact dependency that is useful to plug into tests that you want
  // to prove do not need the dependency.
  static let unimplemented = Self(
    fetch: { _ in
    XCTFail("\(Self.self).fact is unimplemented.")
    return .none
  })
}