import ManaCore
import SwiftUI

/// Top-Level-View: TabView mit drei Tabs.
///
/// **Phase ζ-0 — Setup.** Tabs zeigen aktuell nur Placeholder-Views.
/// Ab Phase ζ-1 wird der Lesen-Tab durch `WebShellView` ersetzt,
/// der `zitare.com` im `WKWebView` rendert.
struct RootView: View {
    @Environment(AuthClient.self) private var auth
    @State private var selectedTab: AppTab = .read
    @State private var healthStatus: HealthStatus = .unknown

    var body: some View {
        TabView(selection: $selectedTab) {
            placeholderView(
                title: "Lesen",
                subtitle: "ζ-1: WebShellView gegen zitare.com",
                systemImage: "book"
            )
            .tabItem { Label("Lesen", systemImage: "book") }
            .tag(AppTab.read)

            placeholderView(
                title: "Erkunden",
                subtitle: "ζ-1: WebShell auf zitare.com/explore",
                systemImage: "sparkle.magnifyingglass"
            )
            .tabItem { Label("Erkunden", systemImage: "sparkle.magnifyingglass") }
            .tag(AppTab.explore)

            AccountView(healthStatus: healthStatus)
                .tabItem { Label("Konto", systemImage: "person.circle") }
                .tag(AppTab.account)
        }
        .task {
            await probeHealth()
        }
        .onOpenURL { url in
            handle(url: url)
        }
        .onContinueUserActivity(NSUserActivityTypeBrowsingWeb) { activity in
            if let url = activity.webpageURL { handle(url: url) }
        }
    }

    /// Phase ζ-0 Probe: ein Aufruf gegen `/healthz` bei App-Start.
    /// Ab Phase ζ-1 wandert das in einen Service, der den Status global
    /// trackt und im AccountView anzeigt.
    private func probeHealth() async {
        let api = ZitareAPI(auth: auth)
        do {
            let ok = try await api.healthCheck()
            healthStatus = ok ? .ok : .down
            Log.api.info("Healthz: \(ok ? "OK" : "DOWN")")
        } catch {
            healthStatus = .down
            Log.api.warning(
                "Healthz fehlgeschlagen: \(String(describing: error), privacy: .public)"
            )
        }
    }

    /// Deep-Link-Routing. Phase ζ-0: nur loggen. Phase ζ-1: in den
    /// passenden Tab + Pfad routen.
    private func handle(url: URL) {
        Log.app.info("Deep-Link empfangen: \(url.absoluteString, privacy: .public)")
        // ζ-1 TODO: parse zitare.com/q/<slug>, /a/<slug>, /c/<slug>
        // und in WebShellView mit entsprechender URL laden.
    }

    private func placeholderView(
        title: String,
        subtitle: String,
        systemImage: String
    ) -> some View {
        VStack(spacing: 16) {
            Image(systemName: systemImage)
                .font(.system(size: 48))
                .foregroundStyle(ZitareTheme.primary)
            Text(title)
                .font(.title2)
                .fontWeight(.semibold)
            Text(subtitle)
                .font(.callout)
                .foregroundStyle(ZitareTheme.mutedForeground)
                .multilineTextAlignment(.center)
                .padding(.horizontal, 32)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .background(ZitareTheme.background)
    }
}

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

enum HealthStatus {
    case unknown
    case ok
    case down
}