import SwiftUI
import NucleicProtocol

/// Chooses the navigation shell by width so one universal binary serves both idioms:
///   • **compact** (iPhone, and iPad in Slide Over / narrow split) → the five-tab `TabView`.
///   • **regular** (iPad full-screen / Stage Manager) → the Mac's sidebar + detail split.
///
/// Both render the SAME `RemoteStore` projection — the iPad is a third renderer of the one host
/// authority (UX_MACOS §8), not a fork. The store holds all real state, so a size-class flip
/// (e.g. resizing a Stage Manager window) only swaps chrome; sessions, connection, and the open
/// transcript survive it.
struct AdaptiveRootView: View {
    @Environment(\.horizontalSizeClass) private var sizeClass

    var body: some View {
        if sizeClass == .regular {
            SplitRootView()
        } else {
            CompactRootView()
        }
    }
}

// MARK: - Compact (iPhone / narrow multitasking)

/// The original iPhone shell, relocated verbatim from `RootView`: a five-tab `TabView`. A
/// notification tap routes to the Sessions tab, where `SessionsView` consumes `pendingRoute`
/// and pushes the detail.
struct CompactRootView: View {
    @EnvironmentObject var store: RemoteStore
    // Initial tab; overridable via NUCLEIC_TAB for offline UI previews.
    @State private var tab = Int(ProcessInfo.processInfo.environment["NUCLEIC_TAB"] ?? "") ?? 0

    var body: some View {
        TabView(selection: $tab) {
            HomeView()
                .tabItem { Label("Home", systemImage: "house") }.tag(0)
            SessionsView()
                .tabItem { Label("Sessions", systemImage: "square.stack.3d.up") }
                .badge(store.needsYouCount).tag(1)
            ProjectsView()
                .tabItem { Label("Projects", systemImage: "folder") }.tag(2)
            TodosView()
                .tabItem { Label("To-dos", systemImage: "checklist") }.tag(3)
            SettingsView()
                .tabItem { Label("Settings", systemImage: "gearshape") }.tag(4)
        }
        // A notification tap routes to its session by jumping to the Sessions tab.
        .onChange(of: store.pendingRoute) { _, route in
            if route != nil { tab = 1 }
        }
        // A Live Activity tap with work running but nothing waiting: show the Sessions list.
        .onChange(of: store.pendingSessionsList) { _, show in
            if show { tab = 1; store.pendingSessionsList = false }
        }
    }
}

// MARK: - Regular (iPad sidebar + detail)

/// What the sidebar can select. Mirrors the Mac sidebar: a few global destinations plus the
/// live sessions themselves (grouped by project). Projects are reached through the `projects`
/// destination (`ProjectsView`), which also hosts the scoped "start a chat here" composer.
enum SidebarItem: Hashable {
    case home
    case projects
    case todos
    case settings
    case session(SessionID)
}

/// The Mac's information architecture on iPad: a two-column `NavigationSplitView` whose leading
/// column carries the destinations + the project→session tree, and whose detail is the selected
/// session (or a destination view). Selection lives here and binds the same `openSessionID`
/// lifecycle the iPhone push/pop path uses — the detail is keyed by session id so switching one
/// session for another fires `open`/`closeOpen` exactly as a push/pop would.
struct SplitRootView: View {
    @EnvironmentObject var store: RemoteStore
    @State private var selection: SidebarItem? = .home
    @State private var columnVisibility: NavigationSplitViewVisibility = .all
    /// One-shot: a Cmd+N sets this, the Home composer consumes it to grab focus.
    @State private var focusNewChat = false

    var body: some View {
        NavigationSplitView(columnVisibility: $columnVisibility) {
            SplitSidebar(selection: $selection, focusNewChat: $focusNewChat)
        } detail: {
            SplitDetail(selection: selection, focusNewChat: $focusNewChat)
        }
        .navigationSplitViewStyle(.balanced)
        .background { keyboardShortcuts }
        // Notification tap → select its session directly (the regular-width analogue of the
        // compact path's jump-to-Sessions-tab). Then clear the request so it isn't re-consumed.
        .onChange(of: store.pendingRoute) { _, route in
            guard let route else { return }
            selection = .session(route)
            store.pendingRoute = nil
        }
        // A Live Activity tap with work running but nothing waiting: reveal the sidebar, which
        // always lists the live sessions (the regular-width analogue of the Sessions tab).
        .onChange(of: store.pendingSessionsList) { _, show in
            guard show else { return }
            columnVisibility = .all
            store.pendingSessionsList = false
        }
        .onAppear {
            // Offline UI previews (NUCLEIC_DEMO): open straight into one session.
            if let raw = ProcessInfo.processInfo.environment["NUCLEIC_DEMO_SESSION"], !raw.isEmpty {
                selection = .session(SessionID(rawValue: raw))
            }
        }
    }

    /// Hardware-keyboard shortcuts (Magic Keyboard on iPad), the remote's echo of the Mac's menu
    /// commands: ⌘N new chat, ⌘1–4 jump to a destination, ⌘R refresh. Carried by hidden buttons —
    /// SwiftUI still routes a shortcut to a zero-opacity button that's in the hierarchy.
    private var keyboardShortcuts: some View {
        Group {
            Button("New chat") { selection = .home; focusNewChat = true }
                .keyboardShortcut("n", modifiers: .command)
            Button("Home") { selection = .home }.keyboardShortcut("1", modifiers: .command)
            Button("Projects") { selection = .projects }.keyboardShortcut("2", modifiers: .command)
            Button("To-dos") { selection = .todos }.keyboardShortcut("3", modifiers: .command)
            Button("Settings") { selection = .settings }.keyboardShortcut("4", modifiers: .command)
            Button("Refresh") { store.refreshSessions() }.keyboardShortcut("r", modifiers: .command)
        }
        .opacity(0)
        .accessibilityHidden(true)
    }
}

/// The leading column: global destinations, then the live sessions grouped under their projects
/// (attention-first within each group), mirroring the Mac sidebar tree. The persistent
/// connection status sits in the footer — one home for it, versus the phone's per-tab inset.
private struct SplitSidebar: View {
    @EnvironmentObject var store: RemoteStore
    @Binding var selection: SidebarItem?
    var focusNewChat: Binding<Bool> = .constant(false)

    /// Live sessions grouped under their project (dashboard order), with anything whose project
    /// isn't in the dashboard collected into a trailing "Other" group. Attention-first sort.
    private var projectGroups: [(name: String, rows: [WireSessionSummary])] {
        let live = store.liveSessions.sorted {
            let a = StatusStyle.sortRank($0), b = StatusStyle.sortRank($1)
            return a == b ? $0.updatedAt > $1.updatedAt : a < b
        }
        var groups: [(name: String, rows: [WireSessionSummary])] = []
        var placed = Set<SessionID>()
        for project in store.dashboard.projects {
            let rows = live.filter { $0.projectID == project.id.rawValue }
            guard !rows.isEmpty else { continue }
            groups.append((project.name, rows))
            rows.forEach { placed.insert($0.sessionID) }
        }
        let orphans = live.filter { !placed.contains($0.sessionID) }
        if !orphans.isEmpty { groups.append(("Other", orphans)) }
        return groups
    }

    var body: some View {
        List(selection: $selection) {
            Section {
                Label("Home", systemImage: "house").tag(SidebarItem.home)
                Label("Projects", systemImage: "folder").tag(SidebarItem.projects)
                Label("To-dos", systemImage: "checklist").tag(SidebarItem.todos)
                Label("Settings", systemImage: "gearshape").tag(SidebarItem.settings)
            }
            if projectGroups.isEmpty {
                Section("Sessions") {
                    Text(store.connectivity.isLive
                        ? "Start a session from Home or the Mac to see it here."
                        : "Waiting to connect to your Mac…")
                        .font(.callout).foregroundStyle(.secondary)
                }
            } else {
                ForEach(projectGroups, id: \.name) { group in
                    Section(group.name) {
                        ForEach(group.rows, id: \.sessionID) { summary in
                            SessionRow(summary: summary, showProjectName: false)
                                .tag(SidebarItem.session(summary.sessionID))
                                .listRowBackground(SessionRowWash(summary: summary))
                                .swipeActions(edge: .leading) {
                                    Button {
                                        store.setFavorite(summary.sessionID, !summary.favorite)
                                    } label: {
                                        Label("Favorite", systemImage: summary.favorite ? "star.slash" : "star.fill")
                                    }.tint(.yellow)
                                }
                                .swipeActions(edge: .trailing) {
                                    Button(role: .destructive) {
                                        store.deleteSession(summary.sessionID)
                                    } label: { Label("Delete", systemImage: "trash") }
                                    Button {
                                        store.setArchived(summary.sessionID, !summary.archived)
                                    } label: {
                                        Label(summary.archived ? "Unarchive" : "Archive",
                                              systemImage: summary.archived ? "tray.and.arrow.up" : "archivebox")
                                    }.tint(.gray)
                                }
                        }
                    }
                }
            }
        }
        .listStyle(.sidebar)
        // Every Mac's sessions are merged into this sidebar (mesh P3), so a single host name would
        // misrepresent it — title it for the app.
        .navigationTitle("Nucleic")
        .toolbar {
            ToolbarItem(placement: .primaryAction) {
                Button {
                    selection = .home
                    focusNewChat.wrappedValue = true
                } label: {
                    Image(systemName: "square.and.pencil")
                }
                .help("New chat (⌘N)")
                .disabled(!store.canControl)
            }
            ToolbarItem(placement: .primaryAction) {
                Button { store.refreshSessions() } label: {
                    Image(systemName: "arrow.clockwise")
                }
                .help("Refresh (⌘R)")
            }
        }
        .safeAreaInset(edge: .bottom) {
            ConnectionChip().padding(.bottom, 10)
        }
    }
}

/// The detail column. A selected session reuses the existing `SessionDetailView` unchanged
/// (it owns its own subscribe/unsubscribe on appear/disappear); it's keyed `.id(sessionID)` so
/// switching sessions remounts and drives that lifecycle. The destination views already embed
/// their own `NavigationStack`, so they're shown directly.
private struct SplitDetail: View {
    let selection: SidebarItem?
    var focusNewChat: Binding<Bool> = .constant(false)

    var body: some View {
        switch selection {
        case .home, .none:
            HomeView(focusNewChat: focusNewChat)
        case .projects:
            ProjectsView()
        case .todos:
            TodosView()
        case .settings:
            SettingsView()
        case .session(let id):
            NavigationStack {
                SessionDetailView(sessionID: id)
            }
            .id(id)
        }
    }
}