Exercise 2: Fetching and Displaying a Joke with async/await and .task — Possible Solution
================================================================================================

struct Joke: Decodable {
    let setup: String
    let punchline: String
}

func fetchJoke() async throws -> Joke {
    let url = URL(string: "https://api.example.com/joke")!
    let (data, response) = try await URLSession.shared.data(from: url)

    guard let httpResponse = response as? HTTPURLResponse,
          httpResponse.statusCode == 200 else {
        throw URLError(.badServerResponse)
    }

    return try JSONDecoder().decode(Joke.self, from: data)
}

struct JokeView: View {
    @State private var joke: Joke?
    @State private var errorMessage: String?

    var body: some View {
        Group {
            if let joke {
                VStack(alignment: .leading, spacing: 8) {
                    Text(joke.setup)
                    Text(joke.punchline).font(.headline)
                }
            } else if let errorMessage {
                Text("Error: \(errorMessage)")
            } else {
                ProgressView()
            }
        }
        .task {
            do {
                joke = try await fetchJoke()
            } catch {
                errorMessage = error.localizedDescription
            }
        }
    }
}

HOW IT WORKS: fetchJoke() follows the chapter's own fetchQuote()
pattern exactly - marked async throws, using
URLSession.shared.data(from:) with try await, checking for a real
200 status code, and decoding the response Data into a real Joke
value via JSONDecoder().decode(Joke.self, from: data). Joke conforms
to Decodable, so its two properties (setup and punchline) are matched
automatically against the JSON response's own matching keys.

JokeView holds two optional @State properties - joke (nil until
loaded) and errorMessage (nil unless something goes wrong) - and its
body branches on which one is currently set, showing a ProgressView
while both remain nil. The .task {} modifier runs its own async
closure once the view appears, calling fetchJoke() inside a
do/catch block - a successful result sets joke, while any thrown
error is caught and its description stored in errorMessage instead of
crashing or silently failing.

ANSWER: A Joke struct conforming to Decodable, an async throws
fetchJoke() function following the chapter's own URLSession/JSONDecoder
pattern, and a JokeView using .task with do/catch to load and display
either the joke, an error message, or a loading indicator, correctly
implements the requested networking flow end to end.

WHY THIS WORKS AS AN ANSWER
------------------------------
This correctly mirrors the chapter's own fetchQuote()/.task pattern for
a new Decodable type, including proper error handling via do/catch
rather than omitting it.