ContentView.swift

//
//  ContentView.swift
//  AsyncMuxDemo
//
//  Created by Hovik Melikyan on 07/01/2023.
//

import SwiftUI
import AsyncMux


// TODO: a function to add a custom location by city name


private let backgroundURL = URL(string: "https://images.unsplash.com/photo-1513051265668-0ebab31671ae")!


struct ContentView: View {

    @State var placeNames = WeatherAPI.defaultPlaceNames
    @State var weather: [String: WeatherItem] = [:]

    @State private var error: Error?

    var body: some View {
        listView()
            .background(backgroundImageView())
            .preferredColorScheme(.dark)

            .task {
                guard !Globals.isPreview else { return }
                await reload()
            }

            .refreshable {
                guard !Globals.isPreview else { return }
                await WeatherAPI.map.refresh()
                await reload()
            }

            .errorAlert($error)

            // Handle internet connection recovery by refreshing the data; this is also called at app startup
            .onReceive(NotificationCenter.default.publisher(for: .networkDidChangeStatus)) { output in
                if let connected = output.object as? Bool, connected {
                    print("Connection is back...")
                    Task {
                        await WeatherAPI.map.refresh()
                        await reload()
                    }
                }
            }

            // Purge memory caches on memory warnings from the OS
            .onReceive(NotificationCenter.default.publisher(for: UIApplication.didReceiveMemoryWarningNotification)) { _ in
                Task {
                    await MuxRepository.clearMemory()
                    ImageCache.clear()
                }
            }
    }

    private func listView() -> some View {
        ScrollView(.vertical, showsIndicators: false) {
            VStack(spacing: 0) {
                ForEach(placeNames, id: \.self) { placeName in
                    HStack {
                        Text(placeName)
                        Spacer()
                        if let item = weather[placeName] {
                            Text(item.weather.map { "\(Int(round($0.currentWeather.temperature)))ºC" } ?? "-")
                        }
                    }
                    .padding(.vertical)
                    Divider()
                }
            }
        }
        .padding()
        .font(.title2)
    }

    private func backgroundImageView() -> some View {
        RemoteImage(url: backgroundURL) { image in
            image
                .resizable()
                .aspectRatio(contentMode: .fill)
                .ignoresSafeArea()
        } placeholder: { error in
            if error != nil {
                Image(systemName: "exclamationmark.triangle")
                    .font(.system(size: 28))
                    .opacity(0.3)
            }
            else {
                ProgressView()
            }
        }
    }

    @MainActor
    private func reload() async {
        do {
            // Create an array of actions for the zipper
            let actions = placeNames.map { name in
                { @Sendable in
                    try await WeatherAPI.map.request(key: name)
                }
            }
            // Execute the array of actions in parallel, get the results in an array and convert them to a dictionary to be used in the UI
            weather = try await Zip(actions: actions)
                .result
                .reduce(into: [String: WeatherItem]()) {
                    $0[$1.name] = $1
                }
        }
        catch {
            self.error = error
        }
    }
}


#Preview {
    ContentView(
        placeNames: ["London, UK", "Paris, FR"],
        weather: [
            "London, UK": .init(name: "London, UK", place: .init(city: "London", countryCode: "GB", lat: 51.51, lon: -0.13), weather: .init(currentWeather: .init(temperature: 8.1, weathercode: 2))),
            "Paris, FR": .init(name: "Paris, FR", place: .init(city: "Paris", countryCode: "FR", lat: 48.84, lon: 2.36), weather: .init(currentWeather: .init(temperature: 10.2, weathercode: 3)))
        ]
    )
}