//
//  ContentView.swift
//  Gemini
//
//  Created by Shadowfacts on 7/12/20.
//

import SwiftUI
import GeminiFormat
import GeminiRenderer
import GeminiProtocol

struct ContentView: View {
    let navigator: NavigationManager
    @State var task: GeminiDataTask?
    @State var document: Document?
    @State var errorMessage: String?
    
    var body: some View {
        mainView
            .frame(minWidth: 480, maxWidth: .infinity, minHeight: 300, maxHeight: .infinity)
            .onReceive(navigator.$currentURL, perform: self.urlChanged)
    }
    
    @ViewBuilder
    private var mainView: some View {
        if let document = document {
            DocumentView(document: document, changeURL: navigator.changeURL)
        } else if let errorMessage = errorMessage {
            VStack {
                Text("An error occurred")
                    .font(.headline)
                Text(errorMessage)
            }
        } else {
            loadingView
                .onAppear(perform: self.loadDocument)
        }
    }
    
    @ViewBuilder
    private var loadingView: some View {
        if #available(macOS 10.16, iOS 14.0, *) {
            ProgressView("Loading...")
        } else {
            Text("Loading...")
        }
    }
    
    private func loadDocument() {
        let url = navigator.currentURL
        task = try! GeminiDataTask(url: url, completion: { (response) in
            switch response {
            case let .failure(error):
                self.errorMessage = error.localizedDescription
            case let .success(response):
                guard let text = response.bodyText else {
                    self.errorMessage = "Response had no body text"
                    return
                }
                self.document = GeminiParser.parse(text: text, baseURL: url)
            }
            self.task = nil
        })
        task!.resume()
    }
    
    private func urlChanged(_ newValue: URL) {
        self.task = nil
        self.document = nil
        self.errorMessage = nil
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView(navigator: NavigationManager(url: URL(string: "gemini://localhost/overview.gmi")!))
    }
}