import SwiftUI

private enum NativeDesign {
    static let accent = Color(red: 108 / 255, green: 58 / 255, blue: 237 / 255)
    static func background(_ dark: Bool) -> Color {
        dark
            ? Color(red: 25 / 255, green: 24 / 255, blue: 22 / 255)
            : Color(red: 245 / 255, green: 243 / 255, blue: 237 / 255)
    }
    static func surface(_ dark: Bool) -> Color {
        dark ? Color(red: 43 / 255, green: 40 / 255, blue: 37 / 255) : .white
    }
}

private struct NativeDraft: Identifiable {
    let id = UUID()
    let recordID: Int?
    let page: NativePage
    var title: String
    var detail: String
    var priority = "none"
    var date = ""
}

struct NativeRootView: View {
    @StateObject private var store = NativeStore()
    @Environment(\.colorScheme) private var scheme
    @Environment(\.scenePhase) private var phase
    @State private var draft: NativeDraft?
    @State private var forget = false
    @State private var deletePath: String?

    var body: some View {
        ZStack {
            NativeDesign.background(scheme == .dark).ignoresSafeArea()
            if store.user == nil { authentication } else { application }
            if phase != .active {
                NativeDesign.background(scheme == .dark).ignoresSafeArea()
                NativeBrandMark().frame(width: 64, height: 64)
            }
        }
        .tint(NativeDesign.accent)
        .task { await store.restore() }
        .sheet(item: $draft) { entry in
            NativeEditor(draft: entry, busy: store.busy, error: store.error) { body in
                let path: String
                let method: String
                switch entry.page {
                case .tasks:
                    path = entry.recordID.map { "/tasks/\($0)" } ?? "/tasks"
                    method = entry.recordID == nil ? "POST" : "PUT"
                case .notes:
                    path = entry.recordID.map { "/notes/\($0)" } ?? "/notes"
                    method = entry.recordID == nil ? "POST" : "PUT"
                case .shopping:
                    path =
                        entry.recordID.map { "/shopping/items/\($0)" } ?? store.selectedList.map {
                            "/shopping/\($0.id)/items"
                        } ?? "/shopping"
                    method = entry.recordID == nil ? "POST" : "PATCH"
                default: return false
                }
                return await store.mutate(path, method: method, body: body)
            }
        }
        .alert("Server entfernen?", isPresented: $forget) {
            Button("Lokal entfernen", role: .destructive) { Task { await store.forget() } }
            Button("Abbrechen", role: .cancel) {}
        } message: {
            Text(
                "Die native Sitzung und geladene Inhalte werden lokal gelöscht. Melde dich möglichst zuerst ab, um die Sitzung auch auf dem Server zu widerrufen."
            )
        }
        .alert(
            "Eintrag löschen?", isPresented: Binding(get: { deletePath != nil }, set: { if !$0 { deletePath = nil } })
        ) {
            Button("Löschen", role: .destructive) {
                if let path = deletePath { Task { _ = await store.mutate(path, method: "DELETE") } }
                deletePath = nil
            }
            Button("Abbrechen", role: .cancel) { deletePath = nil }
        } message: {
            Text("Der Eintrag wird auf deinem Server gelöscht.")
        }
    }

    private var authentication: some View {
        NativeAuthenticationScreen(store: store, forget: { forget = true })
    }

    private var application: some View {
        NavigationStack {
            ScrollView {
                VStack(alignment: .leading, spacing: 16) {
                    if store.busy { ProgressView().frame(maxWidth: .infinity) }
                    if let error = store.error {
                        Text(error).foregroundStyle(.red).accessibilityIdentifier("native-error")
                    }
                    switch store.page {
                    case .home: dashboard
                    case .tasks: taskList
                    case .notes: noteList
                    case .shopping: shopping
                    case .more: more
                    }
                }
                .padding(16)
                .frame(maxWidth: 760)
                .frame(maxWidth: .infinity)
            }
            .background(NativeDesign.background(scheme == .dark))
            .navigationTitle(store.selectedList?.name ?? store.page.title)
            .toolbar {
                ToolbarItem(placement: .topBarTrailing) {
                    Button("Aktualisieren", systemImage: "arrow.clockwise") { Task { await store.refresh() } }.disabled(
                        store.busy)
                }
                if [.tasks, .notes, .shopping].contains(store.page),
                    store.permissions?.access(store.page.rawValue) == "write"
                {
                    ToolbarItem(placement: .topBarTrailing) {
                        Button("Hinzufügen", systemImage: "plus") {
                            draft = NativeDraft(recordID: nil, page: store.page, title: "", detail: "")
                        }.disabled(store.busy)
                    }
                }
            }
            .safeAreaInset(edge: .bottom) {
                HStack(spacing: 0) {
                    ForEach(
                        NativePage.allCases.filter {
                            [.home, .more].contains($0) || store.permissions?.access($0.rawValue) != "none"
                        }
                    ) { page in
                        Button {
                            Task { await store.navigate(page) }
                        } label: {
                            VStack(spacing: 4) {
                                Image(systemName: page.symbol).font(.system(size: 21))
                                Text(page.title).font(.system(size: 11))
                            }
                            .foregroundStyle(store.page == page ? NativeDesign.accent : .secondary)
                            .frame(maxWidth: .infinity).padding(.vertical, 10)
                        }
                        .disabled(store.busy).accessibilityIdentifier("nav-\(page.rawValue)")
                    }
                }
                .padding(6).background(.regularMaterial, in: Capsule()).shadow(
                    color: .black.opacity(0.08), radius: 12, y: 4
                ).padding(.horizontal, 12).padding(.bottom, 8)
            }
        }
    }

    @ViewBuilder private var dashboard: some View {
        VStack(alignment: .leading, spacing: 6) {
            Text("Hallo, \(store.user?.displayName ?? "")").font(.title2.bold())
            Text(Date.now, format: .dateTime.weekday(.wide).day().month(.wide)).foregroundStyle(.secondary)
        }
        if let data = store.dashboard {
            if store.permissions?.access("tasks") != "none", store.permissions?.showsWidget("tasks") == true {
                NativeCard("Aufgaben", subtitle: "\(data.openTaskCount.map(String.init) ?? "—") offen") {
                    if data.urgentTasks.isEmpty { empty("Keine dringenden Aufgaben") }
                    ForEach(data.urgentTasks) { item in row(item.title, detail: item.dueDate ?? "") }
                    Button("Alle Aufgaben") { Task { await store.navigate(.tasks) } }
                }
            }
            if store.permissions?.access("calendar") != "none", store.permissions?.showsWidget("calendar") == true {
                NativeCard("Kalender", subtitle: "Nächste Termine") {
                    if data.upcomingEvents.isEmpty { empty("Keine anstehenden Termine") }
                    ForEach(data.upcomingEvents) { item in
                        row(
                            item.title,
                            detail: String(item.startDatetime.replacingOccurrences(of: "T", with: " ").prefix(16)))
                    }
                }
            }
            if store.permissions?.access("shopping") != "none", store.permissions?.showsWidget("shopping") == true {
                NativeCard("Einkauf", subtitle: "\(data.shoppingOpenCount.map(String.init) ?? "—") offene Artikel") {
                    if data.shoppingLists.isEmpty { empty("Alles eingekauft") }
                    ForEach(data.shoppingLists) { item in row(item.name, detail: "\(item.openCount ?? 0) offen") }
                    Button("Alle Listen") { Task { await store.navigate(.shopping) } }
                }
            }
            if store.permissions?.access("notes") != "none", store.permissions?.showsWidget("notes") == true {
                NativeCard("Notizen", subtitle: "Angeheftet") {
                    if data.pinnedNotes.isEmpty { empty("Noch keine Notizen") }
                    ForEach(data.pinnedNotes) { item in
                        row(item.title ?? "Notiz", detail: String(item.content.prefix(140)))
                    }
                    Button("Alle Notizen") { Task { await store.navigate(.notes) } }
                }
            }
        }
    }

    @State private var search = ""
    @State private var taskStatus = "open"
    private var canWrite: Bool { !store.busy && store.permissions?.access(store.page.rawValue) == "write" }

    @ViewBuilder private var taskList: some View {
        TextField("Suchen", text: $search).textFieldStyle(.roundedBorder)
        Picker("Status", selection: $taskStatus) {
            Text("Offen").tag("open")
            Text("Erledigt").tag("done")
            Text("Alle").tag("all")
        }.pickerStyle(.segmented)
        let filtered = store.tasks.filter {
            (search.isEmpty || ($0.title + ($0.description ?? "")).localizedCaseInsensitiveContains(search))
                && (taskStatus == "all" || (taskStatus == "done" ? $0.status == "done" : $0.status != "done"))
        }
        if filtered.isEmpty && !store.busy { empty("Hier gibt es noch keine passenden Aufgaben.") }
        ForEach(filtered) { item in
            NativeCard {
                HStack {
                    Button {
                        Task {
                            _ = await store.mutate(
                                "/tasks/\(item.id)/status", method: "PATCH",
                                body: ["status": .string(item.status == "done" ? "open" : "done")])
                        }
                    } label: {
                        Image(systemName: item.status == "done" ? "checkmark.circle.fill" : "circle").font(.title2)
                    }.disabled(!canWrite).accessibilityLabel(item.status == "done" ? "Wieder öffnen" : "Erledigen")
                    Button {
                        draft = NativeDraft(
                            recordID: item.id, page: .tasks, title: item.title, detail: item.description ?? "",
                            priority: item.priority, date: item.dueDate ?? "")
                    } label: {
                        row(
                            item.title,
                            detail: [item.category, item.dueDate].compactMap { $0 }.joined(separator: " · "))
                    }.buttonStyle(.plain).disabled(!canWrite)
                    Spacer()
                    deleteButton("/tasks/\(item.id)")
                }
            }
        }
    }

    @ViewBuilder private var noteList: some View {
        TextField("Suchen", text: $search).textFieldStyle(.roundedBorder)
        let filtered = store.notes.filter {
            search.isEmpty || (($0.title ?? "") + $0.content).localizedCaseInsensitiveContains(search)
        }
        if filtered.isEmpty && !store.busy { empty("Hier gibt es noch keine passenden Notizen.") }
        ForEach(filtered) { item in
            NativeCard {
                Button {
                    draft = NativeDraft(recordID: item.id, page: .notes, title: item.title ?? "", detail: item.content)
                } label: {
                    row(item.title ?? "Notiz", detail: item.content)
                }.buttonStyle(.plain).disabled(!canWrite)
                HStack {
                    Button(item.pinned == 1 ? "Lösen" : "Anheften") {
                        Task { _ = await store.mutate("/notes/\(item.id)/pin", method: "PATCH") }
                    }.disabled(!canWrite)
                    Spacer()
                    deleteButton("/notes/\(item.id)")
                }
            }
        }
    }

    @ViewBuilder private var shopping: some View {
        if store.selectedList != nil {
            Button("Alle Listen") { Task { await store.navigate(.shopping) } }.disabled(store.busy)
            if store.items.isEmpty && !store.busy { empty("Diese Liste ist noch leer.") }
            ForEach(store.items) { item in
                NativeCard {
                    HStack {
                        Button {
                            Task {
                                _ = await store.mutate(
                                    "/shopping/items/\(item.id)", method: "PATCH",
                                    body: ["is_checked": .number(item.isChecked == 1 ? 0 : 1)])
                            }
                        } label: {
                            Image(systemName: item.isChecked == 1 ? "checkmark.circle.fill" : "circle").font(.title2)
                        }.disabled(!canWrite).accessibilityLabel(item.isChecked == 1 ? "Wieder öffnen" : "Abhaken")
                        Button {
                            draft = NativeDraft(
                                recordID: item.id, page: .shopping, title: item.name, detail: item.quantity ?? "")
                        } label: {
                            row(item.name, detail: item.quantity ?? "")
                        }.buttonStyle(.plain).disabled(!canWrite)
                        Spacer()
                        deleteButton("/shopping/items/\(item.id)")
                    }
                }
            }
        } else {
            if store.lists.isEmpty && !store.busy { empty("Hier gibt es noch keine Einkaufslisten.") }
            ForEach(store.lists) { list in
                NativeCard {
                    HStack {
                        Button {
                            Task { await store.open(list) }
                        } label: {
                            row(list.name, detail: "\(list.itemTotal ?? 0) Artikel")
                        }.buttonStyle(.plain).disabled(store.busy)
                        Spacer()
                        deleteButton("/shopping/\(list.id)")
                    }
                }
            }
        }
    }

    private var more: some View {
        VStack(spacing: 16) {
            NativeCard("Dein Haushalt", subtitle: store.appName) {
                Text(store.user?.displayName ?? "")
                Text(store.server).foregroundStyle(.secondary)
            }
            NativeCard("Konto") {
                Button("Abmelden") { Task { await store.logout() } }.disabled(store.busy)
                Button("Server und lokale Sitzung entfernen", role: .destructive) { forget = true }.disabled(store.busy)
            }
            NativeCard("Nativer Neubau", subtitle: "Noch keine vollständige PWA-Parität") {
                Text(
                    "Die weiteren Module und Einstellungen werden separat nativ nachgebaut. Es gibt keinen Browser-Fallback."
                )
            }
        }
    }

    private func deleteButton(_ path: String) -> some View {
        Button("Löschen", systemImage: "trash", role: .destructive) { deletePath = path }.labelStyle(.iconOnly)
            .disabled(!canWrite)
    }
    private func row(_ title: String, detail: String) -> some View {
        VStack(alignment: .leading, spacing: 4) {
            Text(title).fontWeight(.semibold)
            if !detail.isEmpty { Text(detail).font(.subheadline).foregroundStyle(.secondary) }
        }.frame(maxWidth: .infinity, alignment: .leading)
    }
    private func empty(_ text: String) -> some View {
        Text(text).foregroundStyle(.secondary).padding(.vertical, 16).frame(maxWidth: .infinity)
    }
}

private struct NativeAuthenticationScreen: View {
    @ObservedObject var store: NativeStore
    let forget: () -> Void
    @State private var address = ""
    @State private var username = ""
    @State private var password = ""
    @State private var name = ""
    @State private var code = ""
    @State private var invalidAddress = false
    @State private var sso = false

    var body: some View {
        ScrollView {
            VStack(spacing: 16) {
                NativeCard {
                    VStack(spacing: 16) {
                        NativeBrandMark().frame(width: 64, height: 64).accessibilityHidden(true)
                        Text(store.appName).font(.system(size: 34, weight: .bold))
                        Text(
                            store.server.isEmpty ? "Dein Zuhause. Dein Server." : "Alles für euren Alltag an einem Ort."
                        ).foregroundStyle(.secondary).multilineTextAlignment(.center)
                        if store.server.isEmpty {
                            TextField("Server-Adresse", text: $address).keyboardType(.URL).textContentType(.URL)
                                .textInputAutocapitalization(.never).autocorrectionDisabled().textFieldStyle(
                                    .roundedBorder
                                ).accessibilityIdentifier("server-url")
                            if invalidAddress {
                                Text("Bitte eine gültige HTTPS-Adresse ohne Unterpfad eingeben.").foregroundStyle(.red)
                                    .accessibilityIdentifier("invalid-server")
                            }
                            Text("HTTPS · eigener Server · keine zentrale Cloud").font(.caption).foregroundStyle(
                                .secondary)
                            Button("Verbinden") {
                                guard (try? ServerAddress(address)) != nil else {
                                    invalidAddress = true
                                    return
                                }
                                invalidAddress = false
                                Task { await store.connect(address) }
                            }.buttonStyle(.borderedProminent).disabled(store.busy || address.isEmpty)
                                .accessibilityIdentifier("connect")
                        } else if store.twoFactor {
                            TextField("Code oder Wiederherstellungscode", text: $code).textContentType(.oneTimeCode)
                                .textFieldStyle(.roundedBorder)
                            Button("Bestätigen") {
                                let value = code
                                code = ""
                                Task { await store.verify(value) }
                            }.buttonStyle(.borderedProminent).disabled(store.busy || code.isEmpty)
                            Button("Zurück zur Anmeldung") { store.cancelTwoFactor() }.disabled(store.busy)
                        } else {
                            if store.setup { TextField("Anzeigename", text: $name).textFieldStyle(.roundedBorder) }
                            if store.passwordAllowed || store.setup {
                                TextField("Benutzername", text: $username).textContentType(.username)
                                    .textInputAutocapitalization(.never).autocorrectionDisabled().textFieldStyle(
                                        .roundedBorder
                                    ).accessibilityIdentifier("username")
                                SecureField("Passwort", text: $password).textContentType(.password).textFieldStyle(
                                    .roundedBorder
                                ).accessibilityIdentifier("password")
                                Button(store.setup ? "Haushalt einrichten" : "Anmelden") {
                                    let submitted = password
                                    password = ""
                                    Task {
                                        await store.login(username: username, password: submitted, displayName: name)
                                    }
                                }.buttonStyle(.borderedProminent).disabled(
                                    store.busy || username.isEmpty || password.isEmpty
                                ).accessibilityIdentifier("login")
                            }
                            if store.oidc { Button("SSO – noch in Umsetzung") { sso = true } }
                            Button("Anderen Server verwenden", action: forget).disabled(store.busy)
                        }
                        if store.busy { ProgressView() }
                        if let error = store.error {
                            Text(error).foregroundStyle(.red).accessibilityIdentifier("auth-error")
                        }
                    }
                    .padding(8)
                }
                .frame(maxWidth: 412)
            }
            .padding(16).frame(maxWidth: .infinity)
            .containerRelativeFrame(.vertical) { height, _ in max(height, 500) }
        }
        .alert("Native Anmeldung", isPresented: $sso) {
            Button("Verstanden", role: .cancel) {}
        } message: {
            Text(
                "SSO wird für den nativen API-Client noch nicht unterstützt. Es wird keine Browser-Sitzung als native Anmeldung vorgetäuscht."
            )
        }
    }
}

private struct NativeEditor: View {
    @Environment(\.dismiss) private var dismiss
    @State var draft: NativeDraft
    let busy: Bool
    let error: String?
    let save: ([String: NativeValue]) async -> Bool

    var body: some View {
        NavigationStack {
            Form {
                TextField(draft.page == .shopping ? "Name" : "Titel", text: $draft.title)
                TextField(draft.page == .shopping ? "Menge" : "Inhalt", text: $draft.detail, axis: .vertical).lineLimit(
                    3...10)
                if draft.page == .tasks {
                    Picker("Priorität", selection: $draft.priority) {
                        Text("Keine").tag("none")
                        Text("Niedrig").tag("low")
                        Text("Mittel").tag("medium")
                        Text("Hoch").tag("high")
                        Text("Dringend").tag("urgent")
                    }
                    TextField("Fällig am (JJJJ-MM-TT)", text: $draft.date)
                }
                if let error { Text(error).foregroundStyle(.red) }
            }
            .navigationTitle(draft.recordID == nil ? "Hinzufügen" : "Bearbeiten").navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .cancellationAction) { Button("Abbrechen") { dismiss() }.disabled(busy) }
                ToolbarItem(placement: .confirmationAction) {
                    Button("Speichern") {
                        var body: [String: NativeValue] = [
                            draft.page == .shopping ? "name" : "title": .string(draft.title)
                        ]
                        if draft.page == .notes { body["content"] = .string(draft.detail) }
                        if draft.page == .tasks {
                            body["description"] = .string(draft.detail)
                            body["priority"] = .string(draft.priority)
                            body["due_date"] = draft.date.isEmpty ? .null : .string(draft.date)
                        }
                        if draft.page == .shopping { body["quantity"] = .string(draft.detail) }
                        Task { if await save(body) { dismiss() } }
                    }.disabled(
                        busy || (draft.title.isEmpty && draft.page != .notes)
                            || (draft.page == .notes && draft.detail.isEmpty))
                }
            }
        }.interactiveDismissDisabled(busy)
    }
}

private struct NativeCard<Content: View>: View {
    @Environment(\.colorScheme) private var scheme
    let title: String?
    let subtitle: String?
    let content: Content
    init(_ title: String? = nil, subtitle: String? = nil, @ViewBuilder content: () -> Content) {
        self.title = title
        self.subtitle = subtitle
        self.content = content()
    }
    var body: some View {
        VStack(alignment: .leading, spacing: 12) {
            if let title { Text(title).font(.title3.weight(.semibold)) }
            if let subtitle { Text(subtitle).font(.subheadline).foregroundStyle(.secondary) }
            content
        }.frame(maxWidth: .infinity, alignment: .leading).padding(16).background(
            NativeDesign.surface(scheme == .dark), in: RoundedRectangle(cornerRadius: 16))
    }
}

private struct NativeBrandMark: View {
    var body: some View {
        Canvas { context, size in
            let shape = Path(roundedRect: CGRect(origin: .zero, size: size), cornerRadius: size.width * 0.225)
            context.fill(
                shape,
                with: .linearGradient(
                    Gradient(colors: [Color(red: 139 / 255, green: 92 / 255, blue: 246 / 255), NativeDesign.accent]),
                    startPoint: .zero, endPoint: CGPoint(x: size.width, y: size.height)))
            for (x, y, radius) in [(64.0, 72.0, 27.0), (100.0, 78.0, 25.0), (80.0, 106.0, 24.0)] {
                let rect = CGRect(
                    x: (x - radius) * size.width / 160, y: (y - radius) * size.height / 160,
                    width: radius * 2 * size.width / 160, height: radius * 2 * size.height / 160)
                context.fill(Path(ellipseIn: rect), with: .color(.white.opacity(0.82)))
            }
        }
    }
}