import SwiftUI

struct FrontPageView: View {
    @EnvironmentObject private var subscriptions: SubscriptionManager
    @State private var viewModel = FrontPageViewModel()
    @State private var paywallViewModel = PaywallViewModel()
    @State private var postGeneratorViewModel = PostGeneratorViewModel()
    @State private var titleOptimizerViewModel = TitleOptimizerViewModel()
    @State private var commentWriterViewModel = CommentWriterViewModel()
    @State private var settingsViewModel = SettingsViewModel()

    var body: some View {
        ZStack {
            HStack(spacing: 0) {
                SidebarView(
                    viewModel: viewModel,
                    isPremium: subscriptions.hasPremiumAccess
                )

                mainContent
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
                    .environment(\.requirePremiumAccess, {
                        if subscriptions.hasPremiumAccess { return true }
                        viewModel.showPaywall()
                        return false
                    })
            }

            if viewModel.isPaywallPresented {
                PaywallView(viewModel: paywallViewModel) {
                    viewModel.dismissPaywall()
                }
                .frame(maxWidth: .infinity, maxHeight: .infinity)
                .ignoresSafeArea()
                .zIndex(1)
                .transition(.opacity)
            }
        }
        .animation(.easeInOut(duration: 0.2), value: viewModel.isPaywallPresented)
        .onChange(of: subscriptions.hasPremiumAccess) { hasPremium in
            if hasPremium {
                viewModel.dismissPaywall()
            }
        }
        .frame(minWidth: AppWindow.minWidth, minHeight: AppWindow.minHeight)
        .background(AppTheme.background)
        .alert("Sign-in issue", isPresented: authErrorBinding) {
            Button("OK") {
                viewModel.clearAuthError()
            }
        } message: {
            Text(viewModel.authErrorMessage ?? "")
        }
    }

    private var authErrorBinding: Binding<Bool> {
        Binding(
            get: { viewModel.authErrorMessage != nil },
            set: { isPresented in
                if !isPresented {
                    viewModel.clearAuthError()
                }
            }
        )
    }

    @ViewBuilder
    private var mainContent: some View {
        VStack(spacing: 0) {
            if viewModel.isRedditActive, viewModel.redditCanGoBack {
                RedditWebBackBar(
                    canGoBack: true,
                    onBack: { viewModel.goBackInReddit() }
                )
            }

            ZStack {
                RedditWebView(
                    url: viewModel.redditLoadURL,
                    reloadTrigger: viewModel.redditReloadTrigger,
                    goBackTrigger: viewModel.redditGoBackTrigger,
                    onCanGoBackChange: { viewModel.updateRedditCanGoBack($0) },
                    onAuthError: { viewModel.showAuthError($0) }
                )
                .id("reddit-webview")
                .frame(maxWidth: .infinity, maxHeight: .infinity)
                .allowsHitTesting(viewModel.isRedditActive)
                .accessibilityHidden(!viewModel.isRedditActive)

                if viewModel.isSettingsActive {
                    SettingsView(viewModel: settingsViewModel)
                } else if !viewModel.isRedditActive, let item = viewModel.selectedNavItem {
                    toolContent(for: item)
                }
            }
        }
        .background(AppTheme.background)
    }

    @ViewBuilder
    private func toolContent(for item: SidebarNavItem) -> some View {
        switch item.iconKind {
        case .postGenerator:
            PostGeneratorView(viewModel: postGeneratorViewModel) { url in
                viewModel.openReddit(at: url)
            }
        case .titleOptimizer:
            TitleOptimizerView(viewModel: titleOptimizerViewModel)
        case .commentWriter:
            CommentWriterView(viewModel: commentWriterViewModel)
        default:
            ToolPlaceholderView(item: item)
        }
    }
}

private struct ToolPlaceholderView: View {
    let item: SidebarNavItem

    var body: some View {
        VStack(spacing: 12) {
            ModernSidebarIconView(kind: item.iconKind, size: 56)

            Text(item.title)
                .font(.system(size: 20, weight: .semibold))
                .foregroundStyle(AppTheme.textPrimary)

            Text(item.subtitle)
                .font(.system(size: 13))
                .foregroundStyle(AppTheme.textSecondary)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .background(AppTheme.background)
    }
}

#Preview {
    FrontPageView()
        .environmentObject(SubscriptionManager())
        .frame(width: AppWindow.width, height: AppWindow.height)
}