import SwiftUI
import WebKit

/// Phase ζ-1: SwiftUI-Hülle um `WKWebView`. Eine `WebShellView`-Instanz
/// gehört zu einem Tab und behält ihren Web-State (Scroll-Position,
/// Browser-History) während der Tab aktiv bleibt.
///
/// **Verhalten:**
/// - Lädt `target` beim ersten Auftauchen.
/// - Wechselt `target` während die View lebt → lädt neue URL.
/// - Pull-to-Refresh über `UIRefreshControl` (iOS).
/// - External-Links (anderer Host, `target=_blank`) öffnen im System-
///   Browser via `openURL`-Environment, nicht im WebView.
/// - Cookies werden über das default `WKWebsiteDataStore` geteilt,
///   sodass `CookieBridge` einmal injizierte `mana.access`-Cookies
///   sichtbar sind.
struct WebShellView: View {
    let target: WebTarget

    @State private var navState = WebNavState()
    @Environment(\.openURL) private var openURL

    var body: some View {
        VStack(spacing: 0) {
            if navState.isLoading {
                ProgressView(value: navState.estimatedProgress)
                    .progressViewStyle(.linear)
                    .frame(height: 2)
            }
            #if canImport(UIKit)
                WebViewRepresentable(
                    target: target,
                    navState: navState,
                    openURL: openURL
                )
                .background(ZitareTheme.background)
            #elseif canImport(AppKit)
                MacWebViewRepresentable(
                    target: target,
                    navState: navState,
                    openURL: openURL
                )
                .background(ZitareTheme.background)
            #endif
            if let error = navState.lastError {
                errorBar(error)
            }
        }
    }

    private func errorBar(_ message: String) -> some View {
        HStack(spacing: 12) {
            Image(systemName: "exclamationmark.triangle.fill")
                .foregroundStyle(ZitareTheme.warning)
            Text(message)
                .font(.caption)
                .lineLimit(2)
            Spacer()
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 8)
        .background(ZitareTheme.muted)
    }
}

/// URL + monoton wachsende `reloadToken`. Ein neuer Token zwingt den
/// WebView, dieselbe URL nochmal zu laden — wird gebraucht wenn der
/// User auf einen Universal-Link tappt, der zur aktuellen URL führt.
struct WebTarget: Equatable {
    let url: URL
    let reloadToken: Int

    init(url: URL, reloadToken: Int = 0) {
        self.url = url
        self.reloadToken = reloadToken
    }
}

/// Reactive Navigation-State, geteilt zwischen SwiftUI und Coordinator.
@Observable
final class WebNavState {
    var isLoading: Bool = false
    var estimatedProgress: Double = 0
    var lastError: String?
    var currentURL: URL?
    var canGoBack: Bool = false
}

#if canImport(UIKit)
    import UIKit

    private struct WebViewRepresentable: UIViewRepresentable {
        let target: WebTarget
        let navState: WebNavState
        let openURL: OpenURLAction

        func makeCoordinator() -> WebShellCoordinator {
            WebShellCoordinator(navState: navState, openURL: openURL)
        }

        func makeUIView(context: Context) -> WKWebView {
            let config = WKWebViewConfiguration()
            config.websiteDataStore = .default()
            config.applicationNameForUserAgent = "ZitareNative/0.1 (iOS)"
            config.userContentController.addUserScript(WebShellScripts.hideWebHeader)
            let webView = WKWebView(frame: .zero, configuration: config)
            webView.navigationDelegate = context.coordinator
            webView.uiDelegate = context.coordinator
            webView.allowsBackForwardNavigationGestures = true
            webView.scrollView.refreshControl = makeRefreshControl(
                webView: webView,
                coordinator: context.coordinator
            )
            context.coordinator.observe(webView: webView)
            context.coordinator.load(target.url, into: webView)
            return webView
        }

        func updateUIView(_ webView: WKWebView, context: Context) {
            let coord = context.coordinator
            if coord.lastTarget != target {
                coord.load(target.url, into: webView)
                coord.lastTarget = target
            }
        }

        private func makeRefreshControl(
            webView: WKWebView,
            coordinator: WebShellCoordinator
        ) -> UIRefreshControl {
            let refresh = UIRefreshControl()
            coordinator.attachRefresh(refresh, webView: webView)
            return refresh
        }
    }

#elseif canImport(AppKit)
    import AppKit

    private struct MacWebViewRepresentable: NSViewRepresentable {
        let target: WebTarget
        let navState: WebNavState
        let openURL: OpenURLAction

        func makeCoordinator() -> WebShellCoordinator {
            WebShellCoordinator(navState: navState, openURL: openURL)
        }

        func makeNSView(context: Context) -> WKWebView {
            let config = WKWebViewConfiguration()
            config.websiteDataStore = .default()
            config.applicationNameForUserAgent = "ZitareNative/0.1 (macOS)"
            config.userContentController.addUserScript(WebShellScripts.hideWebHeader)
            let webView = WKWebView(frame: .zero, configuration: config)
            webView.navigationDelegate = context.coordinator
            webView.uiDelegate = context.coordinator
            webView.allowsBackForwardNavigationGestures = true
            context.coordinator.observe(webView: webView)
            context.coordinator.load(target.url, into: webView)
            return webView
        }

        func updateNSView(_ webView: WKWebView, context: Context) {
            let coord = context.coordinator
            if coord.lastTarget != target {
                coord.load(target.url, into: webView)
                coord.lastTarget = target
            }
        }
    }
#endif