import SwiftUI

struct MainView: View {
  private enum MainSidebarSection: Int, CaseIterable, Hashable {
    case posts = 0
    case bookmarks = 1
    case favorites = 2

    var title: String {
      switch self {
      case .posts:
        "Posts"

      case .bookmarks:
        "Bookmarks"

      case .favorites:
        "Favorites"
      }
    }

    var systemImage: String {
      switch self {
      case .posts:
        "rectangle.stack"

      case .bookmarks:
        "bookmark"

      case .favorites:
        "heart"
      }
    }
  }

  @EnvironmentObject var settings: SettingsManager
  @State private var selectedTab: Int = 0
  @State private var selectedSidebarSection: MainSidebarSection? = .posts
  @State private var manager = BooruManager(.yandere)

  var body: some View {
    platformSpecificContent
      .environmentObject(settings)
      .environmentObject(manager)
      .onChange(of: settings.preferredBooru) { _, newState in
        updateManager(newState)
      }
      .onChange(of: manager.historyIndex) { _, _ in
        if manager.isNavigatingHistory {
          manager.selectedPost = nil
        }
      }
      .onAppear(perform: initializeManager)
      .onChange(of: settings.providerCredentials) { updateManager(settings.preferredBooru) }
      .onChange(of: settings.showHeldMoebooruPosts) { updateManager(settings.preferredBooru) }
      .onChange(of: settings.sendBooruUserAgent) { updateManager(settings.preferredBooru) }
      .onChange(of: settings.customBooruUserAgent) { updateManager(settings.preferredBooru) }
      #if os(macOS)
        .onChange(of: selectedSidebarSection) { _, newValue in
          guard let newValue else { return }

          selectedTab = newValue.rawValue

          if newValue == .posts {
            Task(priority: .userInitiated) {
              await manager.fetchPosts()
            }
          }
        }
        .onChange(of: selectedTab) { _, newValue in
          selectedSidebarSection = MainSidebarSection(rawValue: newValue) ?? .posts
        }
      #endif
  }

  @ViewBuilder private var tabViewContent: some View {
    if #available(iOS 26, macOS 15.0, *) {
      TabView(selection: $selectedTab) {
        Tab("Posts", systemImage: "rectangle.stack", value: 0) {
          ContentView(selectedTab: $selectedTab)
        }

        Tab("Bookmarks", systemImage: "bookmark", value: 1) {
          NavigationStack {
            BookmarksView(selectedTab: $selectedTab)
          }
        }

        Tab("Favorites", systemImage: "heart", value: 2) {
          NavigationStack {
            FavoritesView(selectedTab: $selectedTab, isPresented: .constant(false))
          }
        }
      }
    } else {
      TabView(selection: $selectedTab) {
        ContentView(selectedTab: $selectedTab)
          .tabItem { Label("Posts", systemImage: "rectangle.stack") }
          .tag(0)

        NavigationStack {
          BookmarksView(selectedTab: $selectedTab)
        }
        .tabItem { Label("Bookmarks", systemImage: "bookmark") }
        .tag(1)

        NavigationStack {
          FavoritesView(selectedTab: $selectedTab, isPresented: .constant(false))
        }
        .tabItem { Label("Favorites", systemImage: "heart") }
        .tag(2)
      }
    }
  }

  #if os(macOS)
    @ViewBuilder private var sidebarContent: some View {
      List(selection: $selectedSidebarSection) {
        ForEach(MainSidebarSection.allCases, id: \.self) { section in
          Label(section.title, systemImage: section.systemImage)
            .tag(section)
        }
      }
      .navigationTitle("Sora")
    }

    @ViewBuilder private var sidebarDetailContent: some View {
      switch selectedSidebarSection ?? .posts {
      case .posts:
        ContentView(selectedTab: $selectedTab)

      case .bookmarks:
        NavigationStack {
          BookmarksView(selectedTab: $selectedTab)
        }

      case .favorites:
        NavigationStack {
          FavoritesView(selectedTab: $selectedTab, isPresented: .constant(false))
        }
      }
    }
  #endif

  @ViewBuilder private var platformSpecificContent: some View {
    #if os(macOS)
      NavigationSplitView {
        sidebarContent
      } detail: {
        sidebarDetailContent
      }
    #else
      if #available(iOS 26, *) {
        tabViewContent
          .tabBarMinimizeBehavior(.onScrollDown)
      } else {
        tabViewContent
      }
    #endif
  }

  private func updateManager(_ provider: BooruProvider) {
    let previousSearchText = manager.searchText

    manager = BooruManager(
      provider,
      credentials: settings.providerCredentials
        .first { $0.provider == settings.preferredBooru },
      sendUserAgent: settings.sendBooruUserAgent,
      customUserAgent: settings.customBooruUserAgent,
      showHeldMoebooruPosts: settings.showHeldMoebooruPosts
    )
    manager.searchText = previousSearchText

    Task(priority: .userInitiated) {
      if manager.searchText.isEmpty {
        await manager.fetchPosts()
      } else {
        await manager.performSearch(settings: settings)
      }
    }
  }

  private func initializeManager() {
    manager = BooruManager(
      settings.preferredBooru,
      credentials: settings.providerCredentials
        .first { $0.provider == settings.preferredBooru },
      sendUserAgent: settings.sendBooruUserAgent,
      customUserAgent: settings.customBooruUserAgent,
      showHeldMoebooruPosts: settings.showHeldMoebooruPosts
    )

    Task(priority: .userInitiated) {
      if manager.posts.isEmpty {
        await manager.fetchPosts()
      }
    }
  }
}

#Preview {
  #if os(macOS)
    let screenSize = NSScreen.main?.frame.size ?? CGSize(width: 1_920, height: 1_080)
    let heightCoefficient = screenSize.height / 1_080
    let widthCoefficient = screenSize.width / 1_440
  #endif

  MainView()
    .environmentObject(SettingsManager())
    #if os(macOS)
      .frame(
        width: screenSize.width / widthCoefficient,
        height: screenSize.height / heightCoefficient
      )
    #endif
}