import SwiftUI

struct MainView: View {
  @EnvironmentObject var settings: SettingsManager
  @State private var selectedTab: Int = 0
  @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
        manager.selectedPost = nil
      }
      .onAppear(perform: initializeManager)
      .onChange(of: settings.providerCredentials) { initializeManager() }
      #if os(macOS)
        .onChange(of: selectedTab) { _, newValue in
          if newValue == 0 {
            Task(priority: .userInitiated) {
              await manager.fetchPosts()
            }
          }
        }
      #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)
          }
        }

        #if os(macOS)
          Tab("Search History", systemImage: "clock.arrow.circlepath", value: 3) {
            PostGridSearchHistoryView(
              selectedTab: $selectedTab,
              isPresented: .constant(false)
            )
          }
        #endif

        #if DEBUG || !os(macOS)
          Tab("Settings", systemImage: "gear", value: 2) {
            SettingsView()
          }
        #endif
      }
    } 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)

        #if os(macOS)
          NavigationStack {
            PostGridSearchHistoryView(
              selectedTab: $selectedTab,
              isPresented: .constant(false)
            )
          }
          .tabItem { Label("Search History", systemImage: "clock.arrow.circlepath") }
          .tag(3)
        #endif

        #if DEBUG || !os(macOS)
          SettingsView()
            .tabItem { Label("Settings", systemImage: "gear") }
            .tag(2)
        #endif
      }
    }
  }

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

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

    manager = BooruManager(
      provider,
      credentials: settings.providerCredentials
        .first { $0.provider == settings.preferredBooru }
    )
    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 }
    )

    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
}