import SwiftUI

#if os(macOS)
import AppKit
#else
import UIKit
#endif

private enum CompactMailTab: Hashable {
    case inbox
    case search
    case compose
    case activity
}

enum MailLayoutMode {
    case compact
    case regular
}

struct MailRootView: View {
    @Bindable var model: AppViewModel
    @Environment(\.horizontalSizeClass) private var horizontalSizeClass
    @State private var preferredCompactColumn: NavigationSplitViewColumn = .content
    @State private var compactTab: CompactMailTab = .inbox
    @State private var lastCompactTab: CompactMailTab = .inbox
    @State private var regularColumnVisibility: NavigationSplitViewVisibility = .all
    @AppStorage("sio.readingPane") private var readingPaneRawValue = ReadingPanePreference.right.rawValue

    var body: some View {
        Group {
            if usesCompactLayout {
                compactScene
            } else {
                regularScene
            }
        }
        .overlay {
            if model.isCommandPalettePresented {
                CommandPaletteView(model: model)
            }
        }
        .overlay(alignment: .topLeading) {
            if !usesCompactLayout {
                CommandPaletteShortcut(model: model)
            }
        }
        .task {
            await model.load()
        }
        .task {
            await model.beginBackendControl()
        }
        .onAppear {
            syncRegularColumns()
        }
        .onChange(of: readingPaneRawValue) {
            syncRegularColumns()
        }
        .onChange(of: model.mailboxNavigationToken) {
            if usesCompactLayout {
                compactTab = .inbox
            }
        }
        .onChange(of: model.threadNavigationToken) {
            if usesCompactLayout {
                compactTab = .inbox
            }
        }
        .onChange(of: model.isComposing) {
            syncRegularColumns()
        }
        .alert("Something went wrong", isPresented: errorPresented) {
            Button("OK") {
                model.errorMessage = nil
            }
        } message: {
            Text(model.errorMessage ?? "")
        }
    }

    private var compactScene: some View {
        TabView(selection: $compactTab) {
            NavigationStack {
                ThreadListView(model: model, layoutMode: .compact)
                    .navigationTitle(model.selectedMailbox.title)
                    .compactInboxNavigation(searchText: searchTextBinding)
                    .navigationDestination(isPresented: compactThreadPresented) {
                        ThreadReadingView(model: model)
                    }
            }
            .tabItem {
                Label("Inbox", systemImage: "tray.full")
            }
            .tag(CompactMailTab.inbox)

            NavigationStack {
                SearchView(model: model)
            }
            .tabItem {
                Label("Search", systemImage: "magnifyingglass")
            }
            .tag(CompactMailTab.search)

            Color.clear
                .tabItem {
                    Label("Compose", systemImage: "square.and.pencil")
                }
                .tag(CompactMailTab.compose)

            NavigationStack {
                ActivityView(model: model)
            }
            .tabItem {
                Label("Activity", systemImage: "bolt.horizontal")
            }
            .tag(CompactMailTab.activity)
        }
        .sheet(isPresented: compactComposePresented) {
            ComposeView(model: model)
                .presentationDetents([.large])
        }
        .onChange(of: compactTab) {
            guard compactTab == .compose else {
                lastCompactTab = compactTab
                return
            }

            model.startCompose()
            compactTab = lastCompactTab
        }
    }

    private var regularScene: some View {
        NavigationSplitView(
            columnVisibility: $regularColumnVisibility,
            preferredCompactColumn: $preferredCompactColumn
        ) {
            SidebarView(model: model)
        } content: {
            ThreadListView(model: model, layoutMode: .regular)
                .navigationTitle(model.selectedMailbox.title)
        } detail: {
            if model.isComposing {
                ComposeView(model: model)
            } else {
                ThreadReadingView(model: model)
            }
        }
        .readingPaneNavigationStyle(readingPanePreference)
        .sheet(isPresented: regularThreadSheetPresented) {
            NavigationStack {
                ThreadReadingView(model: model)
            }
            .frame(minWidth: 760, minHeight: 620)
        }
        .toolbar {
            ToolbarItem(placement: .primaryAction) {
                Button {
                    model.startCompose()
                } label: {
                    Label("Compose", systemImage: "square.and.pencil")
                }
            }

            ToolbarItem(placement: .automatic) {
                Button {
                    model.isCommandPalettePresented = true
                } label: {
                    Label("Command Palette", systemImage: "command")
                }
                .keyboardShortcut("k", modifiers: .command)
            }
        }
    }

    private var searchTextBinding: Binding<String> {
        Binding(
            get: { model.searchText },
            set: { model.setSearchText($0) }
        )
    }

    private var compactThreadPresented: Binding<Bool> {
        Binding(
            get: { model.selectedThreadID != nil && !model.isComposing },
            set: { isPresented in
                if !isPresented {
                    model.dismissThreadSelection()
                }
            }
        )
    }

    private var compactComposePresented: Binding<Bool> {
        Binding(
            get: { model.isComposing },
            set: { isPresented in
                if !isPresented {
                    model.dismissCompose()
                }
            }
        )
    }

    private var regularThreadSheetPresented: Binding<Bool> {
        Binding(
            get: {
                !usesCompactLayout &&
                    readingPanePreference == .off &&
                    model.selectedThreadID != nil &&
                    !model.isComposing
            },
            set: { isPresented in
                if !isPresented {
                    model.dismissThreadSelection()
                }
            }
        )
    }

    private var errorPresented: Binding<Bool> {
        Binding(
            get: { model.errorMessage != nil },
            set: { isPresented in
                if !isPresented {
                    model.errorMessage = nil
                }
            }
        )
    }

    private var usesCompactLayout: Bool {
        #if os(iOS)
        UIDevice.current.userInterfaceIdiom == .phone || horizontalSizeClass == .compact
        #else
        false
        #endif
    }

    private var readingPanePreference: ReadingPanePreference {
        ReadingPanePreference(rawValue: readingPaneRawValue) ?? .right
    }

    private func syncRegularColumns() {
        guard !usesCompactLayout else { return }
        regularColumnVisibility = readingPanePreference == .off && !model.isComposing ? .doubleColumn : .all
    }
}

struct SidebarView: View {
    @Bindable var model: AppViewModel

    var body: some View {
        List {
            Section {
                SidebarAccountHeader(model: model)
                    .listRowInsets(EdgeInsets(top: 8, leading: 10, bottom: 12, trailing: 10))
                    .listRowBackground(Color.clear)
            }

            Section("Inbox") {
                inboxAllRow
                laneRow(.feed)
                laneRow(.paper)
                laneRow(.people)
            }

            Section("Smart") {
                mailboxRow(.starred)
                mailboxRow(.snoozed)
                mailboxRow(.screener, accessibilityID: "mailbox.screener")
            }

            Section("Mailboxes") {
                mailboxRow(.sent)
                mailboxRow(.drafts)
                mailboxRow(.archive)
                mailboxRow(.trash)
            }

            if !model.folderNames.isEmpty {
                Section("Folders") {
                    ForEach(model.folderNames, id: \.self) { folder in
                        HStack(spacing: 12) {
                            Image(systemName: "folder")
                                .foregroundStyle(.secondary)
                            Text(folder)
                        }
                        .font(.subheadline)
                    }
                }
            }
        }
        .listStyle(.sidebar)
        .scrollContentBackground(.hidden)
        .background(platformBackground.ignoresSafeArea())
    }

    private var inboxAllRow: some View {
        Button {
            model.selectMailbox(.inbox)
            model.setLaneFilter(nil)
        } label: {
            SidebarMailboxLabel(
                title: "All",
                systemImage: Mailbox.inbox.systemImage,
                isSelected: model.selectedMailbox == .inbox && model.laneFilter == nil
            )
        }
        .buttonStyle(.plain)
        .badge(model.threadCount(in: .inbox))
        .accessibilityIdentifier("mailbox.inbox")
    }

    private func mailboxRow(_ mailbox: Mailbox, accessibilityID: String? = nil) -> some View {
        Button {
            model.selectMailbox(mailbox)
            if mailbox != .inbox {
                model.setLaneFilter(nil)
            }
        } label: {
            SidebarMailboxLabel(
                title: mailbox.title,
                systemImage: mailbox.systemImage,
                isSelected: model.selectedMailbox == mailbox
            )
        }
        .buttonStyle(.plain)
        .badge(model.threadCount(in: mailbox))
        .accessibilityIdentifier(accessibilityID ?? "mailbox.\(mailbox.id)")
    }

    private func laneRow(_ lane: Lane) -> some View {
        Button {
            model.selectMailbox(.inbox)
            model.setLaneFilter(lane)
        } label: {
            HStack(spacing: 12) {
                RoundedRectangle(cornerRadius: 3, style: .continuous)
                    .fill(lane.color)
                    .frame(width: 14, height: 14)
                Text(lane.label)
                    .font(.subheadline.weight(model.selectedMailbox == .inbox && model.laneFilter == lane ? .semibold : .regular))
                    .foregroundStyle(model.selectedMailbox == .inbox && model.laneFilter == lane ? lane.color : Color.primary)
                Spacer(minLength: 0)
            }
            .padding(.vertical, 4)
        }
        .buttonStyle(.plain)
        .badge(model.laneCount(lane, in: .inbox))
        .accessibilityIdentifier("mailbox.lane.\(lane.rawValue)")
    }
}

private struct SidebarAccountHeader: View {
    @Bindable var model: AppViewModel

    var body: some View {
        VStack(alignment: .leading, spacing: 14) {
            HStack(spacing: 12) {
                AvatarView(name: model.currentUser.name, color: SIO.tint, size: 42)

                VStack(alignment: .leading, spacing: 2) {
                    Text(model.currentUser.name)
                        .font(.headline)
                    Text(model.currentUser.email)
                        .font(.subheadline)
                        .foregroundStyle(.secondary)
                }
            }

            HStack(spacing: 12) {
                compactSummary(title: "Unread", value: model.totalUnreadCount, tint: SIO.tint)
                compactSummary(title: "Starred", value: model.threadCount(in: .starred), tint: .yellow)
            }
        }
        .padding(16)
        .sioCardBackground(tint: SIO.tint)
    }

    private func compactSummary(title: String, value: Int, tint: Color) -> some View {
        VStack(alignment: .leading, spacing: 4) {
            Text(title)
                .font(.caption)
                .foregroundStyle(.secondary)
            Text(value, format: .number)
                .font(.headline.weight(.semibold))
                .foregroundStyle(tint)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
    }
}

private struct SidebarMailboxLabel: View {
    let title: String
    let systemImage: String
    let isSelected: Bool

    var body: some View {
        HStack(spacing: 12) {
            Image(systemName: systemImage)
                .foregroundStyle(isSelected ? SIO.tint : Color.secondary)
            Text(title)
                .font(.subheadline.weight(isSelected ? .semibold : .regular))
                .foregroundStyle(isSelected ? SIO.tint : Color.primary)
            Spacer(minLength: 0)
        }
        .padding(.vertical, 4)
    }
}

struct ThreadListView: View {
    @Bindable var model: AppViewModel
    let layoutMode: MailLayoutMode
    @AppStorage("sio.density") private var densityRawValue = ""

    var body: some View {
        VStack(spacing: 0) {
            if layoutMode == .regular {
                ThreadListSearchHeader(model: model)
            }

            if layoutMode == .compact && model.selectedMailbox == .inbox {
                CompactLaneOverview(model: model)
                    .padding(.horizontal, 16)
                    .padding(.top, 8)
            }

            LaneFilterStrip(model: model)
                .padding(.vertical, 10)

            Divider()

            Group {
                if model.isLoading {
                    ProgressView("Loading mail...")
                        .frame(maxWidth: .infinity, maxHeight: .infinity)
                } else if model.selectedMailbox == .screener {
                    ScreenerListView(model: model)
                } else if model.filteredThreads.isEmpty {
                    ContentUnavailableView(
                        "No Messages",
                        systemImage: "tray",
                        description: Text("Try another mailbox or relax the filters.")
                    )
                    .frame(maxWidth: .infinity, maxHeight: .infinity)
                } else {
                    List(model.filteredThreads) { thread in
                        Button {
                            Haptics.selection()
                            model.openThread(withID: thread.id)
                        } label: {
                            ThreadRow(
                                thread: thread,
                                density: density,
                                isSelected: thread.id == model.selectedThreadID
                            )
                            .contentShape(Rectangle())
                        }
                        .buttonStyle(.plain)
                        .listRowInsets(EdgeInsets(top: 8, leading: 14, bottom: 8, trailing: 14))
                        .listRowBackground(Color.clear)
                        .listRowSeparator(.hidden)
                        .contextMenu {
                            Button(thread.isUnread ? "Mark Read" : "Mark Unread") {
                                model.toggleRead(for: thread)
                            }

                            Button(thread.isStarred ? "Remove Star" : "Star") {
                                model.toggleStar(for: thread)
                            }

                            Button("Archive") {
                                model.moveThread(withID: thread.id, to: .archive)
                            }
                        }
                    }
                    .listStyle(.plain)
                    .scrollContentBackground(.hidden)
                }
            }
        }
        .background(platformBackground.ignoresSafeArea())
        .safeAreaInset(edge: .bottom) {
            if layoutMode == .compact {
                FloatingComposeButton(model: model)
            }
        }
    }

    private var density: ThreadRowDensity {
        if let stored = ThreadRowDensity(rawValue: densityRawValue) {
            return stored
        }

        #if os(macOS)
        return .cozy
        #else
        return .comfortable
        #endif
    }
}

private struct ThreadListSearchHeader: View {
    @Bindable var model: AppViewModel

    var body: some View {
        VStack(alignment: .leading, spacing: 12) {
            MailSearchField(
                text: Binding(
                    get: { model.searchText },
                    set: { model.setSearchText($0) }
                ),
                placeholder: "Search mail"
            )

            ScrollView(.horizontal, showsIndicators: false) {
                HStack(spacing: 8) {
                    FilterChip(title: "From:", subtitle: model.selectedThread?.participants.first?.name ?? "Anyone")
                    FilterChip(title: "Has attachment", isSelected: model.filteredThreads.contains(where: \.hasAttachments))
                    FilterChip(title: "Last 30 days", isSelected: true)
                    FilterChip(title: "Lane:", subtitle: model.laneFilter?.label ?? "All")
                }
            }
        }
        .padding(.horizontal, 16)
        .padding(.top, 14)
        .padding(.bottom, 10)
    }
}

private struct LaneFilterStrip: View {
    @Bindable var model: AppViewModel

    var body: some View {
        ScrollView(.horizontal, showsIndicators: false) {
            HStack(spacing: 8) {
                filterButton(title: "All", lane: nil)
                ForEach(Lane.allCases) { lane in
                    filterButton(title: lane.label, lane: lane)
                }
                unreadButton
            }
            .padding(.horizontal, 16)
        }
    }

    private func filterButton(title: String, lane: Lane?) -> some View {
        Button {
            model.setLaneFilter(lane)
        } label: {
            HStack(spacing: 8) {
                if let lane {
                    RoundedRectangle(cornerRadius: 3, style: .continuous)
                        .fill(lane.color)
                        .frame(width: 10, height: 10)
                }
                Text(title)
                if model.unreadCount(for: lane) > 0 {
                    Text(model.unreadCount(for: lane), format: .number)
                        .font(.caption2.weight(.bold))
                        .padding(.horizontal, 6)
                        .padding(.vertical, 2)
                        .background((lane?.color ?? SIO.tint).opacity(0.14), in: Capsule())
                }
            }
            .font(.subheadline.weight(.semibold))
            .foregroundStyle(model.laneFilter == lane ? (lane?.color ?? SIO.tint) : Color.primary)
            .padding(.horizontal, 12)
            .padding(.vertical, 8)
            .background(
                Capsule(style: .continuous)
                    .fill(model.laneFilter == lane ? (lane?.color ?? SIO.tint).opacity(0.12) : Color.secondary.opacity(0.08))
            )
        }
        .buttonStyle(.plain)
    }

    private var unreadButton: some View {
        Button {
            model.setUnreadOnly(!model.showUnreadOnly)
        } label: {
            HStack(spacing: 8) {
                Image(systemName: model.showUnreadOnly ? "line.3.horizontal.decrease.circle.fill" : "line.3.horizontal.decrease.circle")
                Text("Unread")
            }
            .font(.subheadline.weight(.semibold))
            .foregroundStyle(model.showUnreadOnly ? SIO.tint : Color.primary)
            .padding(.horizontal, 12)
            .padding(.vertical, 8)
            .background(
                Capsule(style: .continuous)
                    .fill(model.showUnreadOnly ? SIO.tint.opacity(0.12) : Color.secondary.opacity(0.08))
            )
        }
        .buttonStyle(.plain)
        .accessibilityIdentifier("filter.unread")
    }
}

private struct ScreenerListView: View {
    @Bindable var model: AppViewModel

    var body: some View {
        if model.screenerThreads.isEmpty {
            ContentUnavailableView(
                "The Screener is Empty",
                systemImage: "person.crop.circle.badge.checkmark",
                description: Text("New first-contact mail will land here before it reaches the inbox.")
            )
            .frame(maxWidth: .infinity, maxHeight: .infinity)
        } else {
            List(model.screenerThreads) { thread in
                VStack(alignment: .leading, spacing: 14) {
                    ThreadRow(thread: thread, density: .comfortable, isSelected: false)

                    HStack(spacing: 10) {
                        Button("Approve") {
                            model.applyScreenerDecision(.approve, to: thread.id)
                        }
                        .buttonStyle(PrimaryActionStyle())

                        Button("Send to Paper") {
                            model.applyScreenerDecision(.sendToPaper, to: thread.id)
                        }
                        .buttonStyle(SecondaryActionStyle())

                        Button("Block") {
                            model.applyScreenerDecision(.block, to: thread.id)
                        }
                        .buttonStyle(DestructiveStyle())
                    }
                }
                .listRowInsets(EdgeInsets(top: 12, leading: 14, bottom: 12, trailing: 14))
                .listRowBackground(Color.clear)
                .listRowSeparator(.hidden)
            }
            .listStyle(.plain)
            .scrollContentBackground(.hidden)
        }
    }
}

private struct FloatingComposeButton: View {
    @Bindable var model: AppViewModel

    var body: some View {
        HStack {
            Spacer()
            Button {
                model.startCompose()
            } label: {
                HStack(spacing: 10) {
                    Image(systemName: "square.and.pencil")
                    Text("Compose")
                }
                .font(.headline.weight(.semibold))
                .foregroundStyle(.white)
                .padding(.horizontal, 18)
                .padding(.vertical, 14)
                .sioGlassSurface(in: Capsule(), tint: SIO.tint)
            }
            .buttonStyle(.plain)
        }
        .padding(.horizontal, 16)
        .padding(.top, 8)
        .padding(.bottom, 12)
    }
}

private struct CompactLaneOverview: View {
    @Bindable var model: AppViewModel

    var body: some View {
        HStack(spacing: 10) {
            ForEach(Lane.allCases) { lane in
                Button {
                    model.selectMailbox(.inbox)
                    model.setLaneFilter(lane)
                } label: {
                    VStack(alignment: .leading, spacing: 6) {
                        HStack(spacing: 6) {
                            Circle()
                                .fill(lane.color)
                                .frame(width: 7, height: 7)
                            Text(lane.label.uppercased())
                                .font(.caption2.weight(.semibold))
                                .foregroundStyle(.secondary)
                        }

                        Text(model.unreadCount(for: lane), format: .number)
                            .font(.title2.weight(.bold))
                            .foregroundStyle(model.laneFilter == lane ? lane.color : Color.primary)
                    }
                    .frame(maxWidth: .infinity, alignment: .leading)
                    .padding(.horizontal, 14)
                    .padding(.vertical, 12)
                    .background(
                        RoundedRectangle(cornerRadius: 16, style: .continuous)
                            .fill(model.laneFilter == lane ? lane.color.opacity(0.12) : Color.secondary.opacity(0.08))
                    )
                    .overlay(
                        RoundedRectangle(cornerRadius: 16, style: .continuous)
                            .strokeBorder(model.laneFilter == lane ? lane.color.opacity(0.24) : Color.primary.opacity(0.06), lineWidth: 1)
                    )
                }
                .buttonStyle(.plain)
            }
        }
    }
}

private struct ThreadRow: View {
    let thread: MailThread
    let density: ThreadRowDensity
    let isSelected: Bool

    var body: some View {
        VStack(alignment: .leading, spacing: 10) {
            HStack(alignment: .top, spacing: 10) {
                unreadDot

                AvatarView(name: senderName, color: thread.lane.color, size: density.avatarSize)

                VStack(alignment: .leading, spacing: 6) {
                    HStack(alignment: .firstTextBaseline, spacing: 8) {
                        Text(senderName)
                            .font(.subheadline.weight(thread.isUnread ? .bold : .semibold))
                            .foregroundStyle(isSelected ? SIO.tint : Color.primary)
                            .lineLimit(1)

                        if thread.messageCount > 1 {
                            Text(thread.messageCount, format: .number)
                                .font(.caption2.weight(.bold))
                                .foregroundStyle(.secondary)
                                .padding(.horizontal, 6)
                                .padding(.vertical, 2)
                                .background(Color.secondary.opacity(0.12), in: Capsule())
                        }

                        Spacer(minLength: 0)

                        if thread.isStarred {
                            Image(systemName: "star.fill")
                                .foregroundStyle(.yellow)
                        }

                        if thread.hasAttachments {
                            Image(systemName: "paperclip")
                                .foregroundStyle(.secondary)
                        }

                        Text(thread.lastUpdated.formatted(date: .abbreviated, time: .shortened))
                            .font(.caption)
                            .foregroundStyle(.secondary)
                    }

                    Text(thread.subject)
                        .font(.headline)
                        .lineLimit(1)

                    Text(thread.previewText)
                        .font(.subheadline)
                        .foregroundStyle(.secondary)
                        .lineLimit(density.previewLineLimit)

                    if density.showsMetaChips {
                        HStack(spacing: 8) {
                            LaneChip(lane: thread.lane)

                            if thread.summary != nil {
                                HStack(spacing: 6) {
                                    Image(systemName: "sparkles")
                                    Text("AI Summary")
                                }
                                .font(.caption.weight(.semibold))
                                .padding(.horizontal, 8)
                                .padding(.vertical, 5)
                                .background(SIO.tint.opacity(0.12), in: RoundedRectangle(cornerRadius: SIO.chipRadius, style: .continuous))
                                .foregroundStyle(SIO.tint)
                            }
                        }
                    }
                }
            }
        }
        .padding(density.rowPadding)
        .background(
            RoundedRectangle(cornerRadius: SIO.cardRadius, style: .continuous)
                .fill(isSelected ? SIO.tint.opacity(0.12) : Color.secondary.opacity(0.06))
        )
        .overlay(
            RoundedRectangle(cornerRadius: SIO.cardRadius, style: .continuous)
                .strokeBorder(isSelected ? SIO.tint.opacity(0.18) : Color.primary.opacity(0.06), lineWidth: 1)
        )
        .accessibilityIdentifier("thread.\(thread.routeID)")
    }

    private var senderName: String {
        thread.latestMessage?.sender.name ?? thread.participants.first?.name ?? "Unknown Sender"
    }

    @ViewBuilder
    private var unreadDot: some View {
        Circle()
            .fill(thread.isUnread ? SIO.tint : Color.clear)
            .frame(width: 8, height: 8)
            .padding(.top, density.avatarSize > 24 ? 10 : 8)
    }
}

struct ThreadReadingView: View {
    @Bindable var model: AppViewModel
    @State private var replyText = ""

    var body: some View {
        Group {
            if let thread = model.selectedThread {
                ScrollViewReader { proxy in
                    ScrollView {
                        VStack(alignment: .leading, spacing: 18) {
                            ReadingHeader(thread: thread)

                            if let summary = thread.summary {
                                AISummaryCard(count: thread.messageCount, bullets: summary)
                            }

                            ForEach(thread.messages) { message in
                                MessageCard(
                                    message: message,
                                    isFocused: message.routeID == model.focusedMessageRouteID,
                                    isLatest: message.id == thread.latestMessage?.id
                                )
                                .id(message.routeID)
                            }
                        }
                        .padding(20)
                        .frame(maxWidth: 920, alignment: .leading)
                        .frame(maxWidth: .infinity, alignment: .topLeading)
                    }
                    .background(platformBackground.ignoresSafeArea())
                    .safeAreaInset(edge: .top) {
                        if !isPhone {
                            ReadingToolbar(model: model, thread: thread)
                        }
                    }
                    .safeAreaInset(edge: .bottom) {
                        InlineReplyComposer(
                            text: $replyText,
                            placeholder: "Reply to \(replyTargetName(for: thread))..."
                        ) {
                            model.sendInlineReply(replyText, in: thread.id)
                            replyText = ""
                            Haptics.success()
                        }
                    }
                    .onAppear {
                        scrollToFocusedMessage(using: proxy, animated: false)
                    }
                    .onChange(of: model.focusedMessageRouteID) {
                        scrollToFocusedMessage(using: proxy)
                    }
                    .onChange(of: thread.routeID) {
                        scrollToFocusedMessage(using: proxy, animated: false)
                    }
                }
            } else {
                ContentUnavailableView(
                    "Select a Thread",
                    systemImage: "envelope.open",
                    description: Text("Choose a conversation to read or compose a new message.")
                )
                .frame(maxWidth: .infinity, maxHeight: .infinity)
                .background(platformBackground.ignoresSafeArea())
            }
        }
    }

    private var isPhone: Bool {
        #if os(iOS)
        UIDevice.current.userInterfaceIdiom == .phone
        #else
        false
        #endif
    }

    private func replyTargetName(for thread: MailThread) -> String {
        thread.latestMessage?.sender.name ?? thread.participants.first(where: { $0.email != model.currentUser.email })?.name ?? "sender"
    }

    private func scrollToFocusedMessage(using proxy: ScrollViewProxy, animated: Bool = true) {
        guard let focusedMessageRouteID = model.focusedMessageRouteID else { return }

        if animated {
            withAnimation(.easeInOut(duration: 0.25)) {
                proxy.scrollTo(focusedMessageRouteID, anchor: .center)
            }
        } else {
            proxy.scrollTo(focusedMessageRouteID, anchor: .center)
        }
    }
}

private struct ReadingHeader: View {
    let thread: MailThread

    var body: some View {
        VStack(alignment: .leading, spacing: 14) {
            Text(thread.subject)
                .font(.title.weight(.bold))

            HStack(alignment: .center, spacing: 12) {
                participantStack

                LaneChip(lane: thread.lane)

                Text("\(thread.messageCount) \(thread.messageCount == 1 ? "message" : "messages")")
                    .font(.subheadline)
                    .foregroundStyle(.secondary)

                Spacer(minLength: 0)

                Text(thread.lastUpdated.formatted(date: .abbreviated, time: .shortened))
                    .font(.subheadline)
                    .foregroundStyle(.secondary)
            }
        }
        .padding(18)
        .sioCardBackground(tint: thread.lane.color)
    }

    private var participantStack: some View {
        HStack(spacing: -10) {
            ForEach(Array(thread.participants.prefix(3))) { participant in
                AvatarView(name: participant.name, color: thread.lane.color, size: 28)
            }
        }
    }
}

private struct ReadingToolbar: View {
    @Bindable var model: AppViewModel
    let thread: MailThread

    var body: some View {
        ScrollView(.horizontal, showsIndicators: false) {
            HStack(spacing: 10) {
                toolbarButton("Archive", systemImage: "archivebox", key: "E") {
                    model.moveThread(withID: thread.id, to: .archive)
                }
                .keyboardShortcut("e", modifiers: [])

                toolbarButton("Move", systemImage: "tray.and.arrow.down", key: "I") {
                    model.moveThread(withID: thread.id, to: .inbox)
                }
                .keyboardShortcut("i", modifiers: [])

                toolbarButton("Delete", systemImage: "trash", key: "⌫", destructive: true) {
                    model.moveThread(withID: thread.id, to: .trash)
                }

                toolbarButton("Reply", systemImage: "arrowshape.turn.up.left", key: "R") {
                    model.startReply(to: thread.id)
                }
                .keyboardShortcut("r", modifiers: [])

                toolbarButton("Reply all", systemImage: "arrowshape.turn.up.left.2", key: "⇧R") {
                    model.startReply(to: thread.id, replyAll: true)
                }
                .keyboardShortcut("r", modifiers: [.shift])

                toolbarButton("Forward", systemImage: "arrowshape.turn.up.right", key: "F") {
                    model.startReply(to: thread.id, forward: true)
                }
                .keyboardShortcut("f", modifiers: [])
            }
            .padding(.horizontal, 20)
            .padding(.top, 12)
            .padding(.bottom, 6)
        }
        .background(platformBackground.opacity(0.92))
    }

    private func toolbarButton(
        _ title: String,
        systemImage: String,
        key: String,
        destructive: Bool = false,
        action: @escaping () -> Void
    ) -> some View {
        Button(action: action) {
            HStack(spacing: 10) {
                Image(systemName: systemImage)
                Text(title)
                KeyboardHint(title: key)
            }
            .font(.subheadline.weight(.semibold))
            .padding(.horizontal, 12)
            .padding(.vertical, 10)
            .background(.regularMaterial, in: RoundedRectangle(cornerRadius: SIO.controlRadius, style: .continuous))
            .foregroundStyle(destructive ? Color.red : Color.primary)
        }
        .buttonStyle(.plain)
    }
}

private struct MessageCard: View {
    let message: MailMessage
    let isFocused: Bool
    let isLatest: Bool

    var body: some View {
        VStack(alignment: .leading, spacing: 14) {
            HStack(alignment: .top, spacing: 12) {
                AvatarView(name: message.sender.name, color: SIO.tint, size: 32)

                VStack(alignment: .leading, spacing: 3) {
                    Text(message.sender.name)
                        .font(.headline)
                    Text("to \(message.recipients.map(\.email).joined(separator: ", "))")
                        .font(.caption)
                        .foregroundStyle(.secondary)
                }

                Spacer(minLength: 0)

                Text(message.sentAt.formatted(date: .abbreviated, time: .shortened))
                    .font(.caption)
                    .foregroundStyle(.secondary)
            }

            Text(message.body)
                .sioProse()
                .textSelection(.enabled)

            if !message.attachments.isEmpty {
                ScrollView(.horizontal, showsIndicators: false) {
                    HStack(spacing: 8) {
                        ForEach(message.attachments) { attachment in
                            HStack(spacing: 6) {
                                Image(systemName: "doc")
                                Text(attachment.name)
                                Text(attachment.size)
                                    .foregroundStyle(.secondary)
                                Image(systemName: "arrow.down.circle")
                            }
                            .font(.caption2.weight(.semibold))
                            .padding(.horizontal, 10)
                            .padding(.vertical, 8)
                            .background(Color.secondary.opacity(0.08), in: RoundedRectangle(cornerRadius: 10, style: .continuous))
                        }
                    }
                }
            }
        }
        .padding(18)
        .background(
            RoundedRectangle(cornerRadius: SIO.cardRadius, style: .continuous)
                .fill(isFocused ? SIO.tint.opacity(0.12) : (isLatest ? SIO.tint.opacity(0.08) : Color.secondary.opacity(0.05)))
        )
        .overlay(
            RoundedRectangle(cornerRadius: SIO.cardRadius, style: .continuous)
                .strokeBorder(isFocused ? SIO.tint.opacity(0.22) : Color.primary.opacity(0.06), lineWidth: 1)
        )
        .accessibilityIdentifier("message.\(message.routeID)")
    }
}

private struct InlineReplyComposer: View {
    @Binding var text: String
    let placeholder: String
    let onSend: () -> Void

    var body: some View {
        HStack(alignment: .bottom, spacing: 12) {
            ZStack(alignment: .leading) {
                if text.isEmpty {
                    Text(placeholder)
                        .foregroundStyle(.secondary)
                        .padding(.horizontal, 14)
                        .padding(.vertical, 12)
                }

                TextEditor(text: $text)
                    .font(.system(size: 15.5))
                    .scrollContentBackground(.hidden)
                    .frame(minHeight: 44, maxHeight: min(140, 44 + CGFloat(max(0, text.components(separatedBy: "\n").count - 1)) * 22))
                    .padding(.horizontal, 10)
                    .padding(.vertical, 6)
                    .background(Color.clear)
            }
            .background(.regularMaterial, in: RoundedRectangle(cornerRadius: 22, style: .continuous))

            Button(action: onSend) {
                Image(systemName: "arrow.up")
                    .font(.headline.weight(.bold))
                    .foregroundStyle(.white)
                    .frame(width: 42, height: 42)
                    .background(SIO.tint, in: Circle())
            }
            .buttonStyle(.plain)
            .disabled(text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
        }
        .padding(.horizontal, 16)
        .padding(.top, 8)
        .padding(.bottom, 12)
        .background(platformBackground.opacity(0.94))
    }
}

struct ComposeView: View {
    @Environment(\.dismiss) private var dismiss
    @Bindable var model: AppViewModel

    var body: some View {
        VStack(spacing: 0) {
            HStack {
                Button("Cancel") {
                    model.dismissCompose()
                    dismiss()
                }
                .buttonStyle(SecondaryActionStyle())

                Spacer(minLength: 0)

                Text("New Message")
                    .font(.headline.weight(.semibold))

                Spacer(minLength: 0)

                Button(model.isSending ? "Sending..." : "Send") {
                    Task {
                        let didSend = await model.sendCurrentDraft()
                        if didSend {
                            Haptics.success()
                            dismiss()
                        } else {
                            Haptics.warning()
                        }
                    }
                }
                .buttonStyle(PrimaryActionStyle())
                .disabled(model.isSending || model.composeDraft.to.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty || model.composeDraft.body.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty)
                .accessibilityIdentifier("compose.send")
            }
            .padding(16)

            Divider()

            ScrollView {
                VStack(alignment: .leading, spacing: 14) {
                    ComposeHeaderRow(title: "To") {
                        RecipientTokenInput(text: $model.composeDraft.to, placeholder: "name@example.com", accessibilityID: "compose.to")
                    }

                    ComposeHeaderRow(title: "Cc") {
                        RecipientTokenInput(text: $model.composeDraft.cc, placeholder: "Optional")
                    }

                    ComposeHeaderRow(title: "From") {
                        Menu {
                            Button(model.currentUser.email) {
                                model.composeDraft.from = model.currentUser.email
                            }
                        } label: {
                            HStack {
                                Text(model.composeDraft.from.isEmpty ? model.currentUser.email : model.composeDraft.from)
                                Spacer(minLength: 0)
                                Image(systemName: "chevron.up.chevron.down")
                                    .foregroundStyle(.secondary)
                            }
                            .font(.body)
                            .padding(.vertical, 4)
                        }
                        .buttonStyle(.plain)
                    }

                    ComposeHeaderRow(title: "Subject") {
                        TextField("What's this about?", text: $model.composeDraft.subject)
                            .textFieldStyle(.plain)
                            .accessibilityIdentifier("compose.subject")
                    }

                    VStack(alignment: .leading, spacing: 10) {
                        TextEditor(text: $model.composeDraft.body)
                            .font(.system(size: 15.5))
                            .scrollContentBackground(.hidden)
                            .frame(minHeight: 320)
                            .accessibilityIdentifier("compose.body")

                        ComposeFormatToolbar()
                    }
                    .padding(14)
                    .background(.regularMaterial, in: RoundedRectangle(cornerRadius: SIO.cardRadius, style: .continuous))
                }
                .padding(16)
            }
        }
        .background(platformBackground.ignoresSafeArea())
        .accessibilityIdentifier("compose.view")
        .onChange(of: model.composeDraft) {
            model.queueDraftAutosave()
        }
    }
}

private struct ComposeHeaderRow<Content: View>: View {
    let title: String
    let content: Content

    init(title: String, @ViewBuilder content: () -> Content) {
        self.title = title
        self.content = content()
    }

    var body: some View {
        HStack(alignment: .top, spacing: 14) {
            Text(title)
                .font(.subheadline.weight(.semibold))
                .foregroundStyle(.secondary)
                .frame(width: 56, alignment: .leading)

            content
                .frame(maxWidth: .infinity, alignment: .leading)
        }
        .padding(14)
        .background(.regularMaterial, in: RoundedRectangle(cornerRadius: SIO.cardRadius, style: .continuous))
    }
}

private struct RecipientTokenInput: View {
    @Binding var text: String
    let placeholder: String
    var accessibilityID: String?

    var body: some View {
        VStack(alignment: .leading, spacing: 8) {
            if !tokens.isEmpty {
                ScrollView(.horizontal, showsIndicators: false) {
                    HStack(spacing: 8) {
                        ForEach(tokens, id: \.self) { token in
                            Text(token)
                                .font(.caption.weight(.semibold))
                                .padding(.horizontal, 10)
                                .padding(.vertical, 6)
                                .background(SIO.tint.opacity(0.12), in: Capsule())
                                .foregroundStyle(SIO.tint)
                        }
                    }
                }
            }

            TextField(placeholder, text: $text)
                .textFieldStyle(.plain)
                .recipientAutocapitalization()
                .accessibilityIdentifier(accessibilityID ?? "")
        }
    }

    private var tokens: [String] {
        text.split(separator: ",")
            .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
            .filter { !$0.isEmpty }
    }
}

private struct ComposeFormatToolbar: View {
    var body: some View {
        HStack(spacing: 10) {
            formatButton("Aa")
            formatButton("B")
            formatButton("I")
            formatButton("U")
            iconButton("paperclip")
            iconButton("camera")
            Spacer(minLength: 0)
        }
    }

    private func formatButton(_ title: String) -> some View {
        Button(title) {}
            .buttonStyle(SecondaryActionStyle())
    }

    private func iconButton(_ systemImage: String) -> some View {
        Button {
        } label: {
            Image(systemName: systemImage)
        }
        .buttonStyle(SecondaryActionStyle())
    }
}

struct SearchView: View {
    @Bindable var model: AppViewModel
    @State private var attachmentsOnly = false
    @State private var last30DaysOnly = false
    @State private var selectedLane: Lane?

    var body: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 16) {
                MailSearchField(
                    text: Binding(
                        get: { model.searchText },
                        set: { model.setSearchText($0) }
                    ),
                    placeholder: "Search messages",
                    showsCancel: true,
                    onLongPress: {
                        model.isCommandPalettePresented = true
                    }
                )

                ScrollView(.horizontal, showsIndicators: false) {
                    HStack(spacing: 8) {
                        FilterChip(title: "From:", subtitle: model.topSearchResult?.participants.first?.name ?? "Anyone")
                        Button {
                            attachmentsOnly.toggle()
                        } label: {
                            FilterChip(title: "Has attachment", isSelected: attachmentsOnly)
                        }
                        .buttonStyle(.plain)

                        Button {
                            last30DaysOnly.toggle()
                        } label: {
                            FilterChip(title: "Last 30 days", isSelected: last30DaysOnly)
                        }
                        .buttonStyle(.plain)

                        Menu {
                            Button("All") { selectedLane = nil }
                            ForEach(Lane.allCases) { lane in
                                Button(lane.label) { selectedLane = lane }
                            }
                        } label: {
                            FilterChip(title: "Lane:", subtitle: selectedLane?.label ?? "All")
                        }
                    }
                }

                if filteredResults.isEmpty {
                    ContentUnavailableView(
                        "Search mail",
                        systemImage: "magnifyingglass",
                        description: Text("Use search to find senders, subjects, summaries, and attachments.")
                    )
                    .frame(maxWidth: .infinity)
                    .padding(.top, 40)
                } else {
                    if let topHit = filteredResults.first {
                        SearchResultSection(title: "Top hit") {
                            resultButton(for: topHit)
                        }
                    }

                    let remaining = Array(filteredResults.dropFirst())
                    if !remaining.isEmpty {
                        SearchResultSection(title: "Messages (\(remaining.count))") {
                            ForEach(remaining) { thread in
                                resultButton(for: thread)
                            }
                        }
                    }
                }
            }
            .padding(16)
        }
        .background(platformBackground.ignoresSafeArea())
        .navigationTitle("Search")
    }

    private var filteredResults: [MailThread] {
        model.searchResults.filter { thread in
            let matchesAttachments = !attachmentsOnly || thread.hasAttachments
            let matchesDate = !last30DaysOnly || thread.lastUpdated > .now.addingTimeInterval(-30 * 24 * 60 * 60)
            let matchesLane = selectedLane == nil || thread.lane == selectedLane
            return matchesAttachments && matchesDate && matchesLane
        }
    }

    private func resultButton(for thread: MailThread) -> some View {
        Button {
            model.selectMailbox(thread.mailbox)
            model.openThread(withID: thread.id)
        } label: {
            ThreadRow(thread: thread, density: .comfortable, isSelected: false)
        }
        .buttonStyle(.plain)
    }
}

private struct SearchResultSection<Content: View>: View {
    let title: String
    let content: Content

    init(title: String, @ViewBuilder content: () -> Content) {
        self.title = title
        self.content = content()
    }

    var body: some View {
        VStack(alignment: .leading, spacing: 10) {
            Text(title)
                .font(.caption.weight(.semibold))
                .foregroundStyle(.secondary)

            VStack(spacing: 10) {
                content
            }
        }
    }
}

private struct MailSearchField: View {
    @Binding var text: String
    let placeholder: String
    var showsCancel = false
    var onLongPress: (() -> Void)?

    var body: some View {
        HStack(spacing: 10) {
            Image(systemName: "magnifyingglass")
                .foregroundStyle(.secondary)

            TextField(placeholder, text: $text)
                .textFieldStyle(.plain)

            if !text.isEmpty {
                Button {
                    text = ""
                } label: {
                    Image(systemName: "xmark.circle.fill")
                        .foregroundStyle(.secondary)
                }
                .buttonStyle(.plain)
            }

            if showsCancel && !text.isEmpty {
                Button("Cancel") {
                    text = ""
                }
                .buttonStyle(.plain)
            }
        }
        .padding(.horizontal, 12)
        .padding(.vertical, 10)
        .background(.regularMaterial, in: RoundedRectangle(cornerRadius: 12, style: .continuous))
        .onLongPressGesture {
            onLongPress?()
        }
    }
}

private struct FilterChip: View {
    let title: String
    var subtitle: String? = nil
    var isSelected = false

    var body: some View {
        HStack(spacing: 6) {
            Text(title)
            if let subtitle {
                Text(subtitle)
                    .foregroundStyle(.secondary)
            }
        }
        .font(.caption.weight(.semibold))
        .padding(.horizontal, 10)
        .padding(.vertical, 8)
        .background(isSelected ? SIO.tint.opacity(0.12) : Color.secondary.opacity(0.08), in: Capsule())
        .foregroundStyle(isSelected ? SIO.tint : Color.primary)
    }
}

private struct ActivityView: View {
    @Bindable var model: AppViewModel

    var body: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 16) {
                Text("Activity")
                    .font(.largeTitle.weight(.bold))

                HStack(spacing: 12) {
                    activityCard(title: "Unread", value: model.totalUnreadCount, tint: SIO.tint)
                    activityCard(title: "Snoozed", value: model.threadCount(in: .snoozed), tint: .orange)
                }

                if let summaryThread = model.threads.first(where: { $0.summary != nil }) {
                    AISummaryCard(count: summaryThread.messageCount, bullets: summaryThread.summary ?? [])
                }

                AppearanceSettingsCard()
            }
            .padding(16)
        }
        .background(platformBackground.ignoresSafeArea())
        .navigationTitle("Activity")
    }

    private func activityCard(title: String, value: Int, tint: Color) -> some View {
        VStack(alignment: .leading, spacing: 6) {
            Text(title)
                .font(.caption)
                .foregroundStyle(.secondary)
            Text(value, format: .number)
                .font(.title2.weight(.bold))
                .foregroundStyle(tint)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(16)
        .sioCardBackground(tint: tint)
    }
}

struct CommandPaletteView: View {
    @Bindable var model: AppViewModel
    @State private var selectedIndex = 0

    var body: some View {
        ZStack {
            Rectangle()
                .fill(Color.black.opacity(0.32))
                .ignoresSafeArea()
                .onTapGesture {
                    model.isCommandPalettePresented = false
                }

            VStack(alignment: .leading, spacing: 18) {
                ForEach(Array(sectionedItems.enumerated()), id: \.offset) { _, section in
                    VStack(alignment: .leading, spacing: 8) {
                        Text(section.title)
                            .font(.caption.weight(.semibold))
                            .foregroundStyle(.secondary)

                        VStack(spacing: 6) {
                            ForEach(Array(section.items.enumerated()), id: \.element.id) { _, item in
                                paletteRow(for: item)
                            }
                        }
                    }
                }
            }
            .padding(20)
            .frame(maxWidth: 640)
            .background(.regularMaterial, in: RoundedRectangle(cornerRadius: SIO.cardRadius, style: .continuous))
            .overlay(
                RoundedRectangle(cornerRadius: SIO.cardRadius, style: .continuous)
                    .strokeBorder(Color.primary.opacity(0.08), lineWidth: 1)
            )
            .sioGlassChrome()
            .focusable()
            .onAppear {
                selectedIndex = 0
            }
            .onKeyPress(.upArrow) {
                selectedIndex = max(0, selectedIndex - 1)
                return .handled
            }
            .onKeyPress(.downArrow) {
                selectedIndex = min(items.count - 1, selectedIndex + 1)
                return .handled
            }
            .onKeyPress(.escape) {
                model.isCommandPalettePresented = false
                return .handled
            }
            .onKeyPress(.return) {
                guard items.indices.contains(selectedIndex) else { return .ignored }
                items[selectedIndex].action()
                model.isCommandPalettePresented = false
                return .handled
            }
        }
        .accessibilityIdentifier("commandPalette")
    }

    private func paletteRow(for item: CommandPaletteItem) -> some View {
        let index = items.firstIndex(where: { $0.id == item.id }) ?? 0

        return Button {
            selectedIndex = index
            item.action()
            model.isCommandPalettePresented = false
        } label: {
            HStack(spacing: 12) {
                Image(systemName: item.systemImage)
                    .frame(width: 18)
                Text(item.title)
                    .frame(maxWidth: .infinity, alignment: .leading)
                KeyboardHint(title: item.keyHint)
            }
            .font(.subheadline.weight(.semibold))
            .padding(.horizontal, 12)
            .padding(.vertical, 11)
            .background(
                RoundedRectangle(cornerRadius: 10, style: .continuous)
                    .fill(index == selectedIndex ? SIO.tint.opacity(0.12) : Color.clear)
            )
        }
        .buttonStyle(.plain)
        .accessibilityIdentifier("commandPalette.action.\(item.id)")
    }

    private var items: [CommandPaletteItem] {
        let selectedThreadID = model.selectedThreadID

        return [
            CommandPaletteItem(id: "reply", section: "Actions", title: "Reply", systemImage: "arrowshape.turn.up.left", keyHint: "R") {
                if let selectedThreadID {
                    model.startReply(to: selectedThreadID)
                }
            },
            CommandPaletteItem(id: "replyAll", section: "Actions", title: "Reply all", systemImage: "arrowshape.turn.up.left.2", keyHint: "⇧R") {
                if let selectedThreadID {
                    model.startReply(to: selectedThreadID, replyAll: true)
                }
            },
            CommandPaletteItem(id: "forward", section: "Actions", title: "Forward", systemImage: "arrowshape.turn.up.right", keyHint: "F") {
                if let selectedThreadID {
                    model.startReply(to: selectedThreadID, forward: true)
                }
            },
            CommandPaletteItem(id: "archive", section: "Actions", title: "Archive", systemImage: "archivebox", keyHint: "E") {
                if let selectedThreadID {
                    model.moveThread(withID: selectedThreadID, to: .archive)
                }
            },
            CommandPaletteItem(id: "jumpPeople", section: "Jump to", title: "Inbox - People", systemImage: "person.2", keyHint: "G I") {
                model.selectMailbox(.inbox)
                model.setLaneFilter(.people)
            },
            CommandPaletteItem(id: "jumpStarred", section: "Jump to", title: "Starred", systemImage: "star", keyHint: "G S") {
                model.selectMailbox(.starred)
            },
            CommandPaletteItem(id: "jumpSent", section: "Jump to", title: "Sent", systemImage: "paperplane", keyHint: "G T") {
                model.selectMailbox(.sent)
            },
            CommandPaletteItem(id: "snoozeTomorrow", section: "Snooze", title: "Tomorrow morning", systemImage: "clock.badge", keyHint: "H 1") {
                if let selectedThreadID {
                    model.snoozeThread(withID: selectedThreadID)
                }
            },
            CommandPaletteItem(id: "snoozeEvening", section: "Snooze", title: "This evening", systemImage: "moon.stars", keyHint: "H 2") {
                if let selectedThreadID {
                    model.snoozeThread(withID: selectedThreadID)
                }
            },
            CommandPaletteItem(id: "snoozeNextWeek", section: "Snooze", title: "Next week", systemImage: "calendar", keyHint: "H 3") {
                if let selectedThreadID {
                    model.snoozeThread(withID: selectedThreadID)
                }
            }
        ]
    }

    private var sectionedItems: [CommandPaletteSection] {
        ["Actions", "Jump to", "Snooze"].compactMap { title in
            let matchingItems = items.filter { $0.section == title }
            guard !matchingItems.isEmpty else { return nil }
            return CommandPaletteSection(title: title, items: matchingItems)
        }
    }
}

private struct CommandPaletteShortcut: View {
    @Bindable var model: AppViewModel

    var body: some View {
        Button("Command Palette") {
            model.isCommandPalettePresented = true
        }
        .keyboardShortcut("k", modifiers: .command)
        .opacity(0.01)
        .frame(width: 1, height: 1)
        .accessibilityHidden(true)
    }
}

private struct CommandPaletteItem: Identifiable {
    let id: String
    let section: String
    let title: String
    let systemImage: String
    let keyHint: String
    let action: () -> Void
}

private struct CommandPaletteSection {
    let title: String
    let items: [CommandPaletteItem]
}

struct AppearanceSettingsView: View {
    var body: some View {
        Form {
            AppearanceSettingsContent()
        }
        .formStyle(.grouped)
    }
}

private struct AppearanceSettingsCard: View {
    var body: some View {
        VStack(alignment: .leading, spacing: 14) {
            Text("Appearance")
                .font(.headline)
            AppearanceSettingsContent()
        }
        .padding(16)
        .sioCardBackground(tint: SIO.tint)
    }
}

private struct AppearanceSettingsContent: View {
    @AppStorage("sio.density") private var densityRawValue = ""
    @AppStorage("sio.theme") private var themeRawValue = ThemePreference.system.rawValue
    @AppStorage("sio.readingPane") private var readingPaneRawValue = ReadingPanePreference.right.rawValue

    var body: some View {
        VStack(alignment: .leading, spacing: 12) {
            preferenceRow(title: "Theme") {
                Picker("Theme", selection: $themeRawValue) {
                    ForEach(ThemePreference.allCases) { preference in
                        Text(preference.label).tag(preference.rawValue)
                    }
                }
                .pickerStyle(.segmented)
            }

            preferenceRow(title: "Density") {
                Picker("Density", selection: densityBinding) {
                    ForEach(ThreadRowDensity.allCases) { density in
                        Text(density.rawValue.capitalized).tag(density.rawValue)
                    }
                }
                .pickerStyle(.segmented)
            }

            preferenceRow(title: "Reading Pane") {
                Picker("Reading Pane", selection: $readingPaneRawValue) {
                    ForEach(ReadingPanePreference.allCases) { preference in
                        Text(preference.label).tag(preference.rawValue)
                    }
                }
                .pickerStyle(.segmented)
            }
        }
    }

    private var densityBinding: Binding<String> {
        Binding(
            get: {
                if let stored = ThreadRowDensity(rawValue: densityRawValue) {
                    return stored.rawValue
                }

                #if os(macOS)
                return ThreadRowDensity.cozy.rawValue
                #else
                return ThreadRowDensity.comfortable.rawValue
                #endif
            },
            set: { densityRawValue = $0 }
        )
    }

    private func preferenceRow<Content: View>(title: String, @ViewBuilder content: () -> Content) -> some View {
        VStack(alignment: .leading, spacing: 8) {
            Text(title)
                .font(.subheadline.weight(.semibold))
            content()
        }
    }
}

#if os(macOS)
private let platformBackground = Color(nsColor: .windowBackgroundColor)
#else
private let platformBackground = Color(uiColor: .systemBackground)
#endif

private extension View {
    @ViewBuilder
    func compactInboxNavigation(searchText: Binding<String>) -> some View {
        #if os(iOS)
        navigationBarTitleDisplayMode(.inline)
            .searchable(text: searchText, placement: .navigationBarDrawer(displayMode: .automatic), prompt: "Search mail")
        #else
        self
        #endif
    }

    @ViewBuilder
    func recipientAutocapitalization() -> some View {
        #if os(iOS)
        textInputAutocapitalization(.never)
        #else
        self
        #endif
    }

    @ViewBuilder
    func readingPaneNavigationStyle(_ preference: ReadingPanePreference) -> some View {
        if preference == .bottom {
            navigationSplitViewStyle(.prominentDetail)
        } else {
            navigationSplitViewStyle(.balanced)
        }
    }
}

#Preview("Thread List Light") {
    NavigationStack {
        ThreadListView(model: previewModel(), layoutMode: .regular)
    }
}

#Preview("Thread List Dark") {
    NavigationStack {
        ThreadListView(model: previewModel(), layoutMode: .regular)
            .preferredColorScheme(.dark)
    }
}

#Preview("Thread List XL") {
    NavigationStack {
        ThreadListView(model: previewModel(), layoutMode: .regular)
            .dynamicTypeSize(.xxxLarge)
    }
}

#Preview("Thread Reading") {
    NavigationStack {
        ThreadReadingView(model: previewSelectedModel())
    }
}

#Preview("Compose") {
    ComposeView(model: previewModel())
}

#Preview("Sidebar") {
    SidebarView(model: previewModel())
        .frame(width: 320)
}

#Preview("Command Palette") {
    ZStack {
        platformBackground
        CommandPaletteView(model: previewSelectedModel())
    }
}

@MainActor
private func previewModel() -> AppViewModel {
    let model = AppViewModel(service: MockMailService(), controlService: StubPreviewControlService())
    model.threads = MockMailService().previewThreads()
    model.selectMailbox(.inbox)
    return model
}

@MainActor
private func previewSelectedModel() -> AppViewModel {
    let model = previewModel()
    if let firstThread = model.threads.first {
        model.openThread(withID: firstThread.id)
    }
    return model
}

private struct StubPreviewControlService: AppControlServicing {
    func commands() -> AsyncStream<AppNavigationCommand> {
        AsyncStream { continuation in
            continuation.finish()
        }
    }
}