import ManaAuthUI
import ManaCore
import SwiftUI

/// Top-Level-View: TabBar mit drei Tabs (Decks / Entdecken / Account).
/// Kein harter Login-Gate mehr — Cardecky läuft auch im Guest-Modus
/// (lokale Decks lernen, Marketplace browsen). Schreibende Server-
/// Aktionen werden über ``ManaAuthGate`` einzeln auf Login eskaliert.
struct RootView: View {
    @Environment(AuthClient.self) private var auth
    @Environment(ManaAuthGate.self) private var authGate
    @State private var selectedTab: AppTab = .decks
    @State private var pendingDeepLinkSlug: String?
    @State private var showCreateDeck = false
    @State private var showSignUpSheet = false
    @State private var showForgotSheet = false
    @State private var resetPasswordToken: String?

    private let sourceAppUrl = URL(string: "https://cardecky.mana.how/auth/verify")!
    private let resetUniversalLink = URL(string: "https://cardecky.mana.how/auth/reset")!

    var body: some View {
        mainTabs
            .onOpenURL { url in handle(url: url) }
            .onContinueUserActivity(NSUserActivityTypeBrowsingWeb) { activity in
                if let url = activity.webpageURL { handle(url: url) }
            }
            .manaBrand(CardsBrand.manaBrand)
            .manaAuthGate(authGate) {
                gateSignInContent
            }
            .sheet(item: Binding(
                get: { resetPasswordToken.map(IdentifiedString.init) },
                set: { resetPasswordToken = $0?.value }
            )) { token in
                ManaResetPasswordView(
                    token: token.value,
                    auth: auth,
                    onDone: { resetPasswordToken = nil }
                )
                .manaBrand(CardsBrand.manaBrand)
            }
            .task {
                // DEBUG: Auto-Login mit DebugCredentials, falls signedOut.
                // Release: no-op. Danach in Guest-Mode wechseln, wenn weder
                // signedIn noch eingebuchtet — Cardecky soll *immer* nutzbar
                // sein, auch ohne Account.
                await auth.ensureSignedIn()
                if case .signedOut = auth.status {
                    do {
                        _ = try auth.enterGuestMode()
                    } catch {
                        Log.auth.warning(
                            "Guest-Mode konnte nicht aktiviert werden: \(String(describing: error), privacy: .public)"
                        )
                    }
                }
            }
    }

    /// Content für das ``ManaAuthGate``-Sheet — wenn ein gegateter Button
    /// gedrückt wird, fliegt der User in den Sign-In-Flow. Sign-Up und
    /// Forgot-Password werden als verschachtelte Sheets aufgeklappt,
    /// damit aus dem Gate-Sheet alle Auth-Pfade erreichbar bleiben.
    private var gateSignInContent: some View {
        NavigationStack {
            ManaLoginView(
                auth: auth,
                onSignUpTapped: { showSignUpSheet = true },
                onForgotTapped: { showForgotSheet = true }
            )
            .manaBrand(CardsBrand.manaBrand)
            .sheet(isPresented: $showSignUpSheet) {
                ManaSignUpView(
                    auth: auth,
                    sourceAppUrl: sourceAppUrl,
                    onDone: { showSignUpSheet = false }
                )
                .manaBrand(CardsBrand.manaBrand)
            }
            .sheet(isPresented: $showForgotSheet) {
                ManaForgotPasswordView(
                    auth: auth,
                    resetUniversalLink: resetUniversalLink,
                    onDone: { showForgotSheet = false }
                )
                .manaBrand(CardsBrand.manaBrand)
            }
        }
    }

    private var mainTabs: some View {
        TabView(selection: $selectedTab) {
            DeckListView(showCreate: $showCreateDeck)
                .tabItem { Label("Decks", systemImage: "rectangle.stack") }
                .tag(AppTab.decks)

            ExploreView(deepLinkSlug: $pendingDeepLinkSlug)
                .tabItem { Label("Entdecken", systemImage: "sparkles") }
                .tag(AppTab.explore)

            NavigationStack {
                AccountView()
            }
            .tabItem { Label("Account", systemImage: "person.crop.circle") }
            .tag(AppTab.account)
        }
        .decksCreateAccessory(visible: selectedTab == .decks) {
            authGate.require(reason: "deck-create-accessory") {
                showCreateDeck = true
            }
        }
    }

    /// Universal-Link- und URL-Scheme-Handler:
    /// - `https://cardecky.mana.how/d/<slug>` → Explore-Tab + PublicDeckView
    /// - `https://cardecky.mana.how/auth/reset?token=…` → ManaResetPasswordView
    /// - `cards://study/<deckId>` → später (β-6 Notifications)
    private func handle(url: URL) {
        Log.app.info("Open URL: \(url.absoluteString, privacy: .public)")
        guard url.host == "cardecky.mana.how" || url.scheme == "cards" else { return }

        let parts = url.pathComponents.filter { $0 != "/" }

        // Auth-Reset-Link aus der Passwort-Vergessen-Email.
        if parts == ["auth", "reset"] {
            let components = URLComponents(url: url, resolvingAgainstBaseURL: false)
            if let token = components?.queryItems?.first(where: { $0.name == "token" })?.value {
                resetPasswordToken = token
                return
            }
        }

        if parts.count >= 2, parts[0] == "d" {
            pendingDeepLinkSlug = parts[1]
            selectedTab = .explore
        }
    }
}

/// Helper für `.sheet(item:)` mit einem String-Value (Reset-Token).
private struct IdentifiedString: Identifiable {
    let value: String
    var id: String {
        value
    }
}

enum AppTab: Hashable {
    case decks
    case explore
    case account
}

private extension View {
    /// iOS 26: floating „Neues Deck"-Pille via `.tabViewBottomAccessory`,
    /// nur sichtbar wenn der Decks-Tab aktiv ist. iOS 18 fällt auf den
    /// bestehenden `.bottomBar`-„+"-Toolbar-Button in `DeckListView` zurück.
    ///
    /// Den Modifier nur konditional anwenden — sonst rendert das System
    /// auch bei leerem Inhalt die leere Glass-Hülle (sichtbar als toter
    /// Streifen über der TabBar auf Entdecken/Account).
    @ViewBuilder
    func decksCreateAccessory(visible: Bool, onTap: @escaping () -> Void) -> some View {
        if #available(iOS 26.0, *), visible {
            tabViewBottomAccessory {
                DeckCreateAccessoryPill(action: onTap)
            }
        } else {
            self
        }
    }
}

@available(iOS 26.0, *)
private struct DeckCreateAccessoryPill: View {
    let action: () -> Void

    var body: some View {
        Button(action: action) {
            Label("Neues Deck", systemImage: "plus")
                .font(.subheadline.weight(.semibold))
        }
        .buttonStyle(.glass)
        .tint(CardsTheme.primary)
        .accessibilityLabel("Neues Deck erstellen")
    }
}