import SwiftUI

#if canImport(UIKit)
import UIKit
#elseif canImport(AppKit)
import AppKit
#endif

/// User-selected appearance, applied once at the `WindowGroup`.
///
/// Deliberately applied in exactly one place. The app previously carried 16
/// separate `.preferredColorScheme(.dark)` calls scattered across view bodies,
/// which is how it became impossible to reach light mode at all — re-applying
/// per view is what let the lock spread unnoticed.
enum AppAppearance: String, CaseIterable, Identifiable {
    case system
    case light
    case dark

    static let userDefaultsKey = "appAppearance"

    var id: String { rawValue }

    var title: String {
        switch self {
        case .system:
            return "System"
        case .light:
            return "Light"
        case .dark:
            return "Dark"
        }
    }

    /// `nil` hands control back to the system setting.
    var colorScheme: ColorScheme? {
        switch self {
        case .system:
            return nil
        case .light:
            return .light
        case .dark:
            return .dark
        }
    }
}

enum AppDensity: String, CaseIterable, Identifiable {
    case compact
    case comfortable

    static let userDefaultsKey = "appDensity"

    var id: String { rawValue }

    var title: String {
        switch self {
        case .compact:
            return "Compact"
        case .comfortable:
            return "Comfortable"
        }
    }

    var metrics: AppDensityMetrics {
        switch self {
        case .compact:
            return AppDensityMetrics(
                sectionSpacing: 14,
                cardSpacing: 6,
                cardPadding: 10,
                rowSpacing: 4,
                rowMinHeight: 30,
                controlVerticalPadding: 10,
                // Was 42, which put every control using it under the 44pt
                // minimum in compact density — section headers, Run, Run Batch.
                controlMinHeight: AppLayout.minimumTapTarget,
                cardCornerRadius: 10
            )
        case .comfortable:
            return AppDensityMetrics(
                sectionSpacing: 18,
                cardSpacing: 10,
                cardPadding: 14,
                rowSpacing: 7,
                rowMinHeight: 38,
                controlVerticalPadding: 14,
                controlMinHeight: 48,
                cardCornerRadius: 14
            )
        }
    }

    func font(_ textStyle: Font.TextStyle, design: Font.Design = .monospaced, weight: Font.Weight? = nil) -> Font {
        var font = Font.system(textStyle, design: design)
        if let weight {
            font = font.weight(weight)
        }
        return font
    }
}

/// Layout constants that are not density-dependent.
enum AppLayout {
    /// The HIG minimum for an interactive control, and WCAG 2.5.8's floor.
    /// Controls scale up from here with Dynamic Type; none may sit below it.
    static let minimumTapTarget: CGFloat = 44
}

struct AppDensityMetrics: Equatable {
    let sectionSpacing: CGFloat
    let cardSpacing: CGFloat
    let cardPadding: CGFloat
    let rowSpacing: CGFloat
    let rowMinHeight: CGFloat
    let controlVerticalPadding: CGFloat
    let controlMinHeight: CGFloat
    let cardCornerRadius: CGFloat
}

private struct AppDensityKey: EnvironmentKey {
    static let defaultValue: AppDensity = .compact
}

extension EnvironmentValues {
    var appDensity: AppDensity {
        get { self[AppDensityKey.self] }
        set { self[AppDensityKey.self] = newValue }
    }
}

/// A status colour pairing: the foreground and the surface it sits on.
///
/// These travel together because they cannot be derived from one another. The
/// badge fill used to be `foreground.opacity(0.16)`, which forced every
/// foreground dark enough to stay legible against its own wash — that is how the
/// light palette ended up olive-and-mud rather than amber-and-green. Decoupling
/// them lets the foregrounds stay fully saturated.
///
/// See `Docs/ACCESSIBILITY.md` for the measured ratios.
enum AppStatusTone {
    case positive
    case warning
    case critical
    case info
    case neutral

    var foreground: Color {
        switch self {
        case .positive:
            return Color(.statusPositive)
        case .warning:
            return Color(.statusWarning)
        case .critical:
            return Color(.statusCritical)
        case .info:
            return Color(.statusInfo)
        case .neutral:
            return Color(.statusNeutral)
        }
    }

    var surface: Color {
        switch self {
        case .positive:
            return Color(.statusPositiveSurface)
        case .warning:
            return Color(.statusWarningSurface)
        case .critical:
            return Color(.statusCriticalSurface)
        case .info:
            return Color(.statusInfoSurface)
        case .neutral:
            return Color(.statusNeutralSurface)
        }
    }
}

struct AppStatusBadgeModel: Equatable {
    let title: String
    let systemImage: String?
    let foregroundColor: Color
    let backgroundColor: Color
}

enum AppStatusFactory {
    static func availability(_ status: DomainAvailabilityStatus?) -> AppStatusBadgeModel {
        switch status {
        case .available:
            return .init(title: "Available", systemImage: "checkmark.circle.fill", foregroundColor: Color(.statusPositive), backgroundColor: Color(.statusPositiveSurface))
        case .registered:
            return .init(title: "Registered", systemImage: "circle.fill", foregroundColor: Color(.statusWarning), backgroundColor: Color(.statusWarningSurface))
        case .unknown, .none:
            return .init(title: "Unknown", systemImage: "questionmark.circle", foregroundColor: Color(.appTextSecondary), backgroundColor: Color(.appSurfaceElevated))
        }
    }

    static func tls(sslInfo: SSLCertificateInfo?, error: String?) -> AppStatusBadgeModel {
        if error != nil || sslInfo == nil {
            return .init(title: "Invalid", systemImage: "xmark.octagon.fill", foregroundColor: Color(.statusCritical), backgroundColor: Color(.statusCriticalSurface))
        }
        if let sslInfo, sslInfo.daysUntilExpiry <= 14 {
            return .init(title: "Expiring", systemImage: "exclamationmark.triangle.fill", foregroundColor: Color(.statusWarning), backgroundColor: Color(.statusWarningSurface))
        }
        return .init(title: "Valid", systemImage: "lock.fill", foregroundColor: Color(.statusPositive), backgroundColor: Color(.statusPositiveSurface))
    }

    static func email(_ result: EmailSecurityResult?, error: String?) -> AppStatusBadgeModel {
        guard error == nil, let result else {
            return .init(title: "Missing", systemImage: "minus.circle", foregroundColor: Color(.appTextSecondary), backgroundColor: Color(.appSurfaceElevated))
        }

        let foundCount = [result.spf.found, result.dmarc.found, result.dkim.found].filter { $0 }.count
        switch foundCount {
        case 3:
            return .init(title: "Secure", systemImage: "checkmark.shield.fill", foregroundColor: Color(.statusPositive), backgroundColor: Color(.statusPositiveSurface))
        case 1, 2:
            return .init(title: "Partial", systemImage: "shield.lefthalf.filled", foregroundColor: Color(.statusWarning), backgroundColor: Color(.statusWarningSurface))
        default:
            return .init(title: "Missing", systemImage: "minus.circle", foregroundColor: Color(.appTextSecondary), backgroundColor: Color(.appSurfaceElevated))
        }
    }

    static func change(_ summary: DomainChangeSummary?) -> AppStatusBadgeModel {
        guard let summary else {
            return .init(title: "Unchanged", systemImage: "circle", foregroundColor: Color(.appTextSecondary), backgroundColor: Color(.appSurfaceElevated))
        }
        if summary.hasChanges {
            return .init(title: "Changed", systemImage: "arrow.triangle.2.circlepath", foregroundColor: Color(.statusInfo), backgroundColor: Color(.statusInfoSurface))
        }
        return .init(title: "Unchanged", systemImage: "checkmark.circle", foregroundColor: Color(.appTextSecondary), backgroundColor: Color(.appSurfaceElevated))
    }
}

struct AppStatusBadgeView: View {
    @Environment(\.appDensity) private var appDensity

    let model: AppStatusBadgeModel

    var body: some View {
        HStack(spacing: 6) {
            if let systemImage = model.systemImage {
                Image(systemName: systemImage)
                    .font(.caption2)
            }
            Text(model.title)
        }
        .font(appDensity.font(.caption, weight: .semibold))
        .foregroundStyle(model.foregroundColor)
        .padding(.horizontal, 9)
        .padding(.vertical, 5)
        .background(model.backgroundColor)
        .clipShape(Capsule())
    }
}

struct AppCopyButton: View {
    @Environment(\.appDensity) private var appDensity
    @State private var didCopy = false

    /// Grows with Dynamic Type. The `max(_, minimumTapTarget)` floor matters
    /// because `@ScaledMetric` also scales *down* below the default text size,
    /// which would push this back under the 44pt minimum.
    @ScaledMetric(relativeTo: .caption) private var size: CGFloat = AppLayout.minimumTapTarget

    let value: String
    let label: String

    var body: some View {
        Button {
            AppClipboard.copy(value)
            AppHaptics.copy()
            withAnimation(.easeInOut(duration: 0.18)) {
                didCopy = true
            }
            Task {
                try? await Task.sleep(nanoseconds: 900_000_000)
                await MainActor.run {
                    withAnimation(.easeInOut(duration: 0.18)) {
                        didCopy = false
                    }
                }
            }
        } label: {
            Image(systemName: didCopy ? "checkmark" : "doc.on.doc")
                .font(appDensity.font(.caption))
                .foregroundStyle(didCopy ? Color(.statusPositive) : Color(.appTextSecondary))
                .frame(width: max(size, AppLayout.minimumTapTarget), height: max(size, AppLayout.minimumTapTarget))
                .background(Color(.appSurfaceElevated))
                .clipShape(RoundedRectangle(cornerRadius: 8))
        }
        .buttonStyle(.plain)
        .accessibilityLabel(didCopy ? "\(label) copied" : label)
    }
}

enum AppClipboard {
    static func copy(_ value: String) {
        #if canImport(UIKit)
        UIPasteboard.general.string = value
        #elseif canImport(AppKit)
        NSPasteboard.general.clearContents()
        NSPasteboard.general.setString(value, forType: .string)
        #endif
    }
}

enum AppHaptics {
    static func copy() {
        #if canImport(UIKit)
        let generator = UINotificationFeedbackGenerator()
        generator.notificationOccurred(.success)
        #endif
    }

    static func refresh() {
        #if canImport(UIKit)
        let generator = UIImpactFeedbackGenerator(style: .light)
        generator.impactOccurred()
        #endif
    }

    static func track() {
        #if canImport(UIKit)
        let generator = UIImpactFeedbackGenerator(style: .soft)
        generator.impactOccurred()
        #endif
    }
}

struct EmptyStateCardView: View {
    @Environment(\.appDensity) private var appDensity

    let title: String
    let message: String
    let suggestion: String
    let systemImage: String
    let showsCardBackground: Bool

    init(
        title: String,
        message: String,
        suggestion: String,
        systemImage: String,
        showsCardBackground: Bool = true
    ) {
        self.title = title
        self.message = message
        self.suggestion = suggestion
        self.systemImage = systemImage
        self.showsCardBackground = showsCardBackground
    }

    var body: some View {
        VStack(alignment: .leading, spacing: appDensity.metrics.cardSpacing) {
            // `Text(message)` already carried `fixedSize`; the title and
            // suggestion did not, which is why the audit reported the *title*
            // clipped on every empty state while the body beneath it wrapped.
            // Deliberately an HStack rather than `Label`. `Label` constrains its
            // own title text and `.fixedSize` applied to the Label does not
            // reach the Text inside, so every empty-state heading reported as
            // clipped. Splitting it lets the modifier land on the Text itself.
            // Verified: doing this alone cleared the finding on all four empty
            // states; changing the font design did not.
            HStack(alignment: .firstTextBaseline, spacing: 8) {
                // Decorative. `Label` used to fold the icon into the title's
                // element; splitting them exposed it as its own, announcing the
                // raw SF Symbol name ("checklist.unchecked") to VoiceOver.
                Image(systemName: systemImage)
                    .accessibilityHidden(true)
                Text(title)
                    .fixedSize(horizontal: false, vertical: true)
                    .multilineTextAlignment(.leading)
            }
                .font(appDensity.font(.headline, weight: .semibold))
                .foregroundStyle(.primary)

            Text(message)
                .font(appDensity.font(.body))
                .foregroundStyle(Color(.appTextSecondary))
                .fixedSize(horizontal: false, vertical: true)

            Text(suggestion)
                .font(appDensity.font(.caption))
                .foregroundStyle(Color(.statusInfo))
                .fixedSize(horizontal: false, vertical: true)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .padding(appDensity.metrics.cardPadding)
        .background(showsCardBackground ? Color(.appSurface) : Color.clear)
        .clipShape(RoundedRectangle(cornerRadius: appDensity.metrics.cardCornerRadius))
    }
}

struct CollapsibleSectionView<HeaderTrailing: View, Content: View>: View {
    @Environment(\.appDensity) private var appDensity

    let title: String
    @Binding var isCollapsed: Bool
    let subtitle: String?
    @ViewBuilder let trailing: () -> HeaderTrailing
    @ViewBuilder let content: () -> Content

    init(
        title: String,
        isCollapsed: Binding<Bool>,
        subtitle: String? = nil,
        @ViewBuilder trailing: @escaping () -> HeaderTrailing = { EmptyView() },
        @ViewBuilder content: @escaping () -> Content
    ) {
        self.title = title
        self._isCollapsed = isCollapsed
        self.subtitle = subtitle
        self.trailing = trailing
        self.content = content
    }

    var body: some View {
        VStack(alignment: .leading, spacing: appDensity.metrics.cardSpacing) {
            Button {
                withAnimation(.easeInOut(duration: 0.2)) {
                    isCollapsed.toggle()
                }
            } label: {
                HStack(alignment: .center, spacing: 10) {
                    VStack(alignment: .leading, spacing: 3) {
                        Text(title)
                            .font(appDensity.font(.headline, weight: .semibold))
                            .foregroundStyle(.primary)
                        if let subtitle {
                            Text(subtitle)
                                .font(appDensity.font(.caption))
                                .foregroundStyle(Color(.appTextSecondary))
                        }
                    }
                    Spacer(minLength: 8)
                    trailing()
                    Image(systemName: isCollapsed ? "chevron.down" : "chevron.up")
                        .font(.caption.weight(.semibold))
                        .foregroundStyle(Color(.appTextSecondary))
                }
                .contentShape(Rectangle())
                .frame(minHeight: appDensity.metrics.controlMinHeight, alignment: .center)
            }
            .buttonStyle(.plain)

            if !isCollapsed {
                content()
                    .transition(.opacity.combined(with: .move(edge: .top)))
            }
        }
    }
}

/// A horizontally scrolling row of read-only tag chips, e.g. for a tracked
/// domain's detail view.
struct TagChipRowView: View {
    let tags: [String]

    var body: some View {
        ScrollView(.horizontal, showsIndicators: false) {
            HStack(spacing: 8) {
                ForEach(tags, id: \.self) { tag in
                    Text(tag)
                        .font(.caption)
                        .padding(.horizontal, 10)
                        .padding(.vertical, 5)
                        .background(Color(.appSurfaceElevated), in: Capsule())
                }
            }
        }
    }
}

/// A horizontally scrolling row of selectable tag chips used to filter a list,
/// with an "All" chip to clear the selection.
struct TagFilterChipRowView: View {
    let tags: [String]
    @Binding var selection: String?

    var body: some View {
        ScrollView(.horizontal, showsIndicators: false) {
            HStack(spacing: 8) {
                filterChip(title: "All", isSelected: selection == nil) {
                    selection = nil
                }
                ForEach(tags, id: \.self) { tag in
                    filterChip(title: tag, isSelected: selection == tag) {
                        selection = (selection == tag) ? nil : tag
                    }
                }
            }
        }
    }

    private func filterChip(title: String, isSelected: Bool, action: @escaping () -> Void) -> some View {
        Button(action: action) {
            Text(title)
                .font(.caption)
                .padding(.horizontal, 10)
                .padding(.vertical, 5)
                .background(isSelected ? Color(.statusInfoSurface) : Color(.appSurfaceElevated), in: Capsule())
                .foregroundStyle(isSelected ? Color(.statusInfo) : Color.primary)
        }
        .buttonStyle(.plain)
    }
}