import SwiftUI
import WebKit

/// Static/stable anchor ids matching the `<a id="...">` markers hand-placed in `Manual.md`
/// (tab-/step-anchors) and auto-generated by `build-manual.py`'s `schema_anchor()` (Experte
/// menus) — the two sides are kept in sync by construction: this is the exact same string
/// transform as the Python function, not a generated file, so there's nothing to regenerate
/// when a schema's `menuPath` doesn't change.
enum ManualAnchor {
    static let tabConnect = "tab-connect"
    static let stepWAN = "step-wan"
    static let stepLAN = "step-lan"
    static let stepVLAN = "step-vlan"
    static let stepWifi = "step-wifi"
    static let stepFirewall = "step-firewall"
    static let stepReview = "step-review"
    static let tabOverview = "tab-overview"
    static let tabDevices = "tab-devices"
    static let tabExpert = "tab-expert"
    static let tabBackup = "tab-backup"
    static let tabSettings = "tab-settings"

    /// Mirrors `build-manual.py`'s `schema_anchor(menu_path)` exactly.
    static func schema(_ menuPath: String) -> String {
        let trimmed = menuPath.trimmingCharacters(in: CharacterSet(charactersIn: "/"))
        return "schema-" + trimmed.replacingOccurrences(of: " ", with: "-")
    }
}

/// Shared across the app (one instance, injected as an `@StateObject` in
/// `RouterOSAssistantApp`) so any "?"-help button anywhere can request the Handbuch window
/// jump to a specific section, whether or not that window is already open.
@MainActor
final class ManualNavigator: ObservableObject {
    @Published var pendingAnchor: String?

    func go(to anchor: String) {
        // Reassigning the same value wouldn't trigger `didSet`/a fresh `onChange` in
        // `ManualView` if the user clicks the same help button twice in a row — nil the
        // slot first so every request, including a repeat, actually re-scrolls.
        pendingAnchor = nil
        DispatchQueue.main.async { self.pendingAnchor = anchor }
    }
}

private struct ManualWebView: NSViewRepresentable {
    @ObservedObject var navigator: ManualNavigator
    let language: String

    /// One HTML file per language (`Manual.html` for "de", `Manual_en.html`, later
    /// `Manual_es.html`, ...) — `build-manual.py` names them the same way (`suffix = ""
    /// if lang == "de" else f"_{lang}"`), so a new language needs no Swift change here,
    /// only a new `Manual.<lang>.md` + an entry in `LANGUAGES` in that script.
    final class Coordinator {
        var loadedLanguage: String?
    }

    func makeCoordinator() -> Coordinator { Coordinator() }

    func makeNSView(context: Context) -> WKWebView {
        let webView = WKWebView()
        load(language, into: webView, coordinator: context.coordinator)
        return webView
    }

    func updateNSView(_ webView: WKWebView, context: Context) {
        if context.coordinator.loadedLanguage != language {
            load(language, into: webView, coordinator: context.coordinator)
        }
        guard let anchor = navigator.pendingAnchor else { return }
        // The page is already loaded — scrolling via JS instead of re-navigating to
        // "Manual.html#anchor" avoids a full page reload/flash on every help-button click.
        webView.evaluateJavaScript(
            "document.getElementById(\(String(reflecting: anchor)))?.scrollIntoView({behavior: 'smooth', block: 'start'});"
        )
    }

    private func load(_ language: String, into webView: WKWebView, coordinator: Coordinator) {
        let resourceName = language == "de" ? "Manual" : "Manual_\(language)"
        // Falls back to the German file if this language has no translated manual yet
        // (e.g. a language the app UI supports but the manual hasn't been translated
        // into) rather than showing a blank window.
        guard let url = Bundle.main.url(forResource: resourceName, withExtension: "html")
            ?? Bundle.main.url(forResource: "Manual", withExtension: "html") else { return }
        webView.loadFileURL(url, allowingReadAccessTo: url)
        coordinator.loadedLanguage = language
    }
}

struct ManualView: View {
    @EnvironmentObject private var navigator: ManualNavigator
    @AppStorage("appLanguage") private var appLanguage: String = "de"

    var body: some View {
        ManualWebView(navigator: navigator, language: appLanguage)
            .frame(minWidth: 640, minHeight: 480)
    }
}

/// Drop-in "?" toolbar button for any screen — opens (or focuses, if already open) the
/// Handbuch window scrolled straight to `anchor`. One shared implementation so every tab/
/// wizard-step/Experte-schema screen wires help the same way.
struct ManualHelpButton: View {
    let anchor: String
    @AppStorage("appLanguage") private var appLanguage: String = "de"
    @EnvironmentObject private var navigator: ManualNavigator
    @Environment(\.openWindow) private var openWindow

    var body: some View {
        Button {
            navigator.go(to: anchor)
            openWindow(id: "manual")
        } label: {
            Image(systemName: "questionmark.circle")
        }
        .help(L10n.t("Hilfe zu diesem Bereich im Handbuch öffnen", appLanguage))
    }
}