import SwiftUI
import SwiftCN

/// A styled SwiftUI action surface presented in an anchored SwiftUI popover.
public struct CNDropdownMenu<Label: View, Content: View>: View {
    @State private var presented = false
    @FocusState private var triggerFocused: Bool
    private let externalPresentation: Binding<Bool>?
    private let classes: TWClasses
    private let contentClasses: TWClasses
    private let edge: Edge
    private let label: Label
    private let content: () -> Content
    public init(_ classes: TWClasses = "", isPresented: Binding<Bool>? = nil,
                contentClasses: TWClasses = "", arrowEdge: Edge = .top,
                @ViewBuilder content: @escaping () -> Content, @ViewBuilder label: () -> Label) {
        self.classes = classes; self.externalPresentation = isPresented
        self.contentClasses = contentClasses; self.edge = arrowEdge
        self.content = content; self.label = label()
    }
    public init(_ title: LocalizedStringKey, classes: TWClasses = "", isPresented: Binding<Bool>? = nil,
                contentClasses: TWClasses = "", arrowEdge: Edge = .top,
                @ViewBuilder content: @escaping () -> Content) where Label == Text {
        self.init(classes, isPresented: isPresented, contentClasses: contentClasses,
                  arrowEdge: arrowEdge, content: content) { Text(title) }
    }
    private var presentation: Binding<Bool> { externalPresentation ?? $presented }
    public var body: some View {
        Button(action: { presentation.wrappedValue.toggle() }) { label }
            .focusable().focusEffectDisabled().focused($triggerFocused)
            .buttonStyle(.tw(cn("button-outline", classes), state: .init(isFocused: triggerFocused)))
            .accessibilityValue(presentation.wrappedValue ? Text("Expanded") : Text("Collapsed"))
            .onKeyPress(keys: [.return, .space, .downArrow]) { key in
                if key.key == .downArrow { presentation.wrappedValue = true }
                else { presentation.wrappedValue.toggle() }
                return .handled
            }
            .cnPopover(isPresented: presentation, arrowEdge: edge) {
                CNDropdownMenuContent(contentClasses, isPresented: presentation,
                                      onDismiss: { presentation.wrappedValue = false }, content: content)
            }
            .onChange(of: presentation.wrappedValue) { _, value in if !value { triggerFocused = true } }
    }
}

/// Also usable as an inline surface for previews or application-owned presentation.
public struct CNDropdownMenuContent<Content: View>: View {
    @FocusState private var focusedID: UUID?
    @Namespace private var focusScope
    @Binding private var isPresented: Bool
    @State private var itemIDs: [UUID] = []
    private let classes: TWClasses
    private let onDismiss: () -> Void
    private let autofocus: Bool
    private let content: Content
    public init(_ classes: TWClasses = "", autofocus: Bool = true, isPresented: Binding<Bool>? = nil,
                onDismiss: @escaping () -> Void = {}, @ViewBuilder content: () -> Content) {
        _isPresented = isPresented ?? .constant(true)
        self.classes = classes; self.autofocus = autofocus; self.onDismiss = onDismiss; self.content = content()
    }
    public var body: some View {
        VStack(alignment: .leading, spacing: 2) { content }
            .tw(cn("dropdown-content", classes))
            .environment(\.cnDropdownMenuContext, .init(focusedID: $focusedID, dismiss: onDismiss, navigate: navigate))
            .onPreferenceChange(CNMenuItemIDs.self) { ids in
                itemIDs = ids
                if autofocus && !ids.contains(where: { $0 == focusedID }) { focusedID = ids.first }
            }
            .defaultFocus($focusedID, autofocus ? itemIDs.first : nil)
            #if os(macOS)
            .focusScope(focusScope)
            #endif
            .task(id: isPresented) {
                guard autofocus else { return }
                focusedID = nil
                guard isPresented else { return }
                // Let the focusable rows attach before entering this scope.
                // Presentation changes cancel this request, including reversals.
                await Task.yield()
                guard !Task.isCancelled, isPresented else { return }
                focusedID = itemIDs.first
            }
            .onKeyPress(keys: [.upArrow, .downArrow, .home, .end, .escape]) { key in
                navigate(key.key)
            }
    }
    private func navigate(_ key: KeyEquivalent) -> KeyPress.Result {
        switch key {
        case .escape: onDismiss()
        case .home: focusedID = itemIDs.first
        case .end: focusedID = itemIDs.last
        case .upArrow: focusedID = CNMenuNavigation.next(itemIDs, current: focusedID, step: -1)
        case .downArrow: focusedID = CNMenuNavigation.next(itemIDs, current: focusedID, step: 1)
        default: return .ignored
        }
        return .handled
    }
}

public struct CNDropdownMenuItem<Label: View>: View {
    @Environment(\.cnDropdownMenuContext) private var context
    @Environment(\.isEnabled) private var isEnabled
    @FocusState private var localFocus: UUID?
    @State private var id = UUID()
    private let role: ButtonRole?
    private let dismissOnSelect: Bool
    private let classes: TWClasses
    private let action: () -> Void
    private let label: Label
    public init(role: ButtonRole? = nil, dismissOnSelect: Bool = true, classes: TWClasses = "",
                action: @escaping () -> Void, @ViewBuilder label: () -> Label) {
        self.role = role; self.dismissOnSelect = dismissOnSelect; self.classes = classes
        self.action = action; self.label = label()
    }
    public init(_ title: LocalizedStringKey, role: ButtonRole? = nil, dismissOnSelect: Bool = true,
                classes: TWClasses = "", action: @escaping () -> Void) where Label == Text {
        self.init(role: role, dismissOnSelect: dismissOnSelect, classes: classes, action: action) { Text(title) }
    }
    private var focus: FocusState<UUID?>.Binding { context.focusedID ?? $localFocus }
    private var focused: Bool { focus.wrappedValue == id }
    private var minimumHeight: TWClasses {
        #if os(iOS)
        "min-h-[44]"
        #else
        "min-h-[32]"
        #endif
    }
    private func activate() {
        guard isEnabled else { return }
        if dismissOnSelect { context.dismiss() }
        action()
    }
    public var body: some View {
        Button(role: role, action: activate) {
            HStack(spacing: 8) { label }.frame(maxWidth: .infinity, alignment: .leading).contentShape(Rectangle())
        }
        .focusable().focusEffectDisabled().focused(focus, equals: id)
        .buttonStyle(.tw(cn("dropdown-item", minimumHeight, role == .destructive ? "text-destructive" : "", classes),
                          state: .init(isFocused: focused)))
        .preference(key: CNMenuItemIDs.self, value: isEnabled ? [id] : [])
        .onHover { hovering in
            guard hovering, isEnabled, !focused else { return }
            // Pointer focus must move with the highlight, without inheriting
            // the popup's entry animation or cross-fading two active rows.
            var transaction = Transaction()
            transaction.disablesAnimations = true
            withTransaction(transaction) { focus.wrappedValue = id }
        }
        .onKeyPress(keys: [.return, .space]) { _ in activate(); return .handled }
        .onKeyPress(keys: [.upArrow, .downArrow, .home, .end, .escape]) { context.navigate($0.key) }
    }
}
public struct CNDropdownMenuLink<Label: View>: View {
    @Environment(\.openURL) private var openURL
    private let destination: URL
    private let classes: TWClasses
    private let label: Label
    public init(destination: URL, classes: TWClasses = "", @ViewBuilder label: () -> Label) {
        self.destination = destination; self.classes = classes; self.label = label()
    }
    public init(_ title: LocalizedStringKey, destination: URL, classes: TWClasses = "") where Label == Text {
        self.init(destination: destination, classes: classes) { Text(title) }
    }
    public var body: some View {
        CNDropdownMenuItem(classes: classes, action: { openURL(destination) }) { label }
            .accessibilityAddTraits(.isLink)
    }
}
public struct CNDropdownMenuLabel<Content: View>: View {
    private let classes: TWClasses
    private let content: Content
    public init(_ classes: TWClasses = "", @ViewBuilder content: () -> Content) { self.classes = classes; self.content = content() }
    public init(_ title: LocalizedStringKey, classes: TWClasses = "") where Content == Text {
        self.init(classes) { Text(title) }
    }
    public var body: some View { content.tw(cn("dropdown-label", classes)).accessibilityAddTraits(.isHeader) }
}
public struct CNDropdownMenuSeparator: View {
    private let classes: TWClasses
    public init(_ classes: TWClasses = "") { self.classes = classes }
    public var body: some View { Color.clear.tw(cn("h-[1] w-full bg-border", classes)).tw("py-1").accessibilityHidden(true) }
}
public struct CNDropdownMenuShortcut: View {
    private let text: String
    public init(_ text: String) { self.text = text }
    public var body: some View { Text(text).tw("text-xs text-mutedForeground").accessibilityHidden(true) }
}
public struct CNDropdownMenuCheckboxItem<Label: View>: View {
    @Binding private var isOn: Bool
    private let classes: TWClasses
    private let label: Label
    public init(isOn: Binding<Bool>, classes: TWClasses = "", @ViewBuilder label: () -> Label) {
        _isOn = isOn; self.classes = classes; self.label = label()
    }
    public var body: some View {
        CNDropdownMenuItem(dismissOnSelect: false, classes: classes, action: { isOn.toggle() }) {
            Image(systemName: "checkmark").tw("w-4 text-xs").opacity(isOn ? 1 : 0).accessibilityHidden(true)
            label
        }.accessibilityValue(isOn ? Text("On") : Text("Off"))
            .accessibilityAddTraits(isOn ? [.isSelected] : [])
    }
}
private struct CNMenuItemIDs: PreferenceKey {
    static let defaultValue: [UUID] = []
    static func reduce(value: inout [UUID], nextValue: () -> [UUID]) { value += nextValue() }
}
// Pure ordering logic also covers disabled-item removal and focus loss.
enum CNMenuNavigation {
    static func next<ID: Equatable>(_ ids: [ID], current: ID?, step: Int) -> ID? {
        guard !ids.isEmpty else { return nil }
        guard let current, let index = ids.firstIndex(of: current) else { return step < 0 ? ids.last : ids.first }
        return ids[(index + (step < 0 ? -1 : 1) + ids.count) % ids.count]
    }
}

/// Compose native links, navigation links, and submenu controls without owning the application's navigation path.
public struct CNNavigationMenu<Content: View>: View {
    private let classes: TWClasses
    private let content: Content
    public init(_ classes: TWClasses = "", @ViewBuilder content: () -> Content) { self.classes = classes; self.content = content() }
    public var body: some View {
        ScrollView(.horizontal) { HStack(spacing: 12) { content } }.tw(cn("menu", classes))
    }
}
/// In-window menu strip. For application menu-bar commands, use SwiftUI Scene.commands instead.
public struct CNMenubar<Content: View>: View {
    private let classes: TWClasses
    private let content: Content
    public init(_ classes: TWClasses = "", @ViewBuilder content: () -> Content) { self.classes = classes; self.content = content() }
    public var body: some View { HStack(spacing: 8) { content }.tw(cn("menu p-1 bg-surface border rounded-md", classes)) }
}

/// Attach native contextual actions to any content, including rows and images.
public struct CNContextMenu<Content: View, MenuItems: View>: View {
    private let classes: TWClasses
    private let content: Content
    private let menuItems: () -> MenuItems
    public init(_ classes: TWClasses = "", @ViewBuilder menuItems: @escaping () -> MenuItems, @ViewBuilder content: () -> Content) {
        self.classes = classes; self.menuItems = menuItems; self.content = content()
    }
    public var body: some View { content.tw(classes).contextMenu(menuItems: menuItems) }
}