import SwiftUI

// MARK: - Models

enum UserRole: String, CaseIterable, Codable {
    case admin    = "Admin"
    case manager  = "Manager"
    case op       = "Operator"
    case viewer   = "Viewer"

    var tint: Color {
        switch self {
        case .admin:   return Color(.systemRed)
        case .manager: return Color(.systemOrange)
        case .op:      return Color(.systemBlue)
        case .viewer:  return Color(.systemGreen)
        }
    }

    var icon: String {
        switch self {
        case .admin:   return "crown.fill"
        case .manager: return "person.badge.shield.checkmark.fill"
        case .op:      return "wrench.and.screwdriver.fill"
        case .viewer:  return "eye.fill"
        }
    }
}

struct User: Identifiable, Hashable {
    var id: UUID
    var name: String
    var email: String
    var role: UserRole
    var isOnline: Bool
    var lastSeen: Date?

    var initials: String {
        name.components(separatedBy: " ")
            .prefix(2)
            .compactMap(\.first)
            .map(String.init)
            .joined()
            .uppercased()
    }

    var avatarTint: Color {
        let palette: [Color] = [
            Color(.systemBlue), Color(.systemGreen), Color(.systemOrange),
            Color(.systemRed),  Color(.systemPurple), Color(.systemTeal)
        ]
        return palette[abs(name.hashValue) % palette.count]
    }
}

extension User {
    static let samples: [User] = [
        User(id: UUID(), name: "Anna Lindström",  email: "anna@aamos.io",   role: .admin,   isOnline: true,  lastSeen: nil),
        User(id: UUID(), name: "Bernt Johansson", email: "bernt@aamos.io",  role: .manager, isOnline: true,  lastSeen: nil),
        User(id: UUID(), name: "Carl Eriksson",   email: "carl@aamos.io",   role: .op,      isOnline: false, lastSeen: Date().addingTimeInterval(-3_600)),
        User(id: UUID(), name: "Diana Svensson",  email: "diana@aamos.io",  role: .viewer,  isOnline: false, lastSeen: Date().addingTimeInterval(-86_400)),
        User(id: UUID(), name: "Erik Nilsson",    email: "erik@aamos.io",   role: .op,      isOnline: true,  lastSeen: nil),
        User(id: UUID(), name: "Frida Karlsson",  email: "frida@aamos.io",  role: .manager, isOnline: false, lastSeen: Date().addingTimeInterval(-7_200)),
    ]
}

// MARK: - ViewModel

@Observable
final class UsersViewModel {
    var users: [User]    = User.samples
    var searchText       = ""
    var showInviteSheet  = false

    var filtered: [User] {
        guard !searchText.isEmpty else { return users }
        return users.filter {
            $0.name.localizedCaseInsensitiveContains(searchText) ||
            $0.email.localizedCaseInsensitiveContains(searchText) ||
            $0.role.rawValue.localizedCaseInsensitiveContains(searchText)
        }
    }

    func delete(_ user: User) {
        users.removeAll { $0.id == user.id }
    }

    func update(_ updated: User) {
        guard let i = users.firstIndex(where: { $0.id == updated.id }) else { return }
        users[i] = updated
    }

    func invite(name: String, email: String, role: UserRole) {
        users.insert(
            User(id: UUID(), name: name, email: email, role: role, isOnline: false),
            at: 0
        )
    }
}

// MARK: - UsersView

struct UsersView: View {
    @State private var vm = UsersViewModel()

    var body: some View {
        NavigationStack {
            // List gives native swipe-actions; row style matches LazyVStack card design.
            List {
                if vm.filtered.isEmpty {
                    emptyState
                        .listRowBackground(Color.clear)
                        .listRowSeparator(.hidden)
                } else {
                    ForEach(vm.filtered) { user in
                        NavigationLink(value: user) {
                            UserRow(user: user)
                        }
                        .listRowBackground(Color.clear)
                        .listRowSeparator(.hidden)
                        .listRowInsets(EdgeInsets(top: 4, leading: 16, bottom: 4, trailing: 16))
                        .swipeActions(edge: .trailing, allowsFullSwipe: true) {
                            Button(role: .destructive) {
                                withAnimation(.spring(duration: 0.3)) { vm.delete(user) }
                            } label: {
                                Label("Ta bort", systemImage: "trash")
                            }
                        }
                    }
                }
            }
            .listStyle(.plain)
            .scrollContentBackground(.hidden)
            .background(Color(.systemGroupedBackground))
            .navigationTitle("Användare")
            .navigationBarTitleDisplayMode(.large)
            .searchable(
                text: $vm.searchText,
                placement: .navigationBarDrawer(displayMode: .always),
                prompt: "Sök namn, e-post eller roll"
            )
            .toolbar {
                ToolbarItem(placement: .topBarTrailing) {
                    Button {
                        vm.showInviteSheet = true
                    } label: {
                        Label("Bjud in", systemImage: "person.badge.plus")
                    }
                }
            }
            .navigationDestination(for: User.self) { user in
                UserDetailView(user: user, onSave: vm.update)
            }
            .sheet(isPresented: $vm.showInviteSheet) {
                InviteUserView(onInvite: vm.invite)
            }
        }
    }

    private var emptyState: some View {
        VStack(spacing: 16) {
            Image(systemName: vm.searchText.isEmpty ? "person.3" : "magnifyingglass")
                .font(.system(size: 48))
                .foregroundStyle(Color(.systemGray3))
            Text(
                vm.searchText.isEmpty
                    ? "Inga användare"
                    : "Inga träffar för \"\(vm.searchText)\""
            )
            .font(.headline)
            .foregroundStyle(Color(.secondaryLabel))
        }
        .frame(maxWidth: .infinity)
        .padding(.top, 60)
    }
}

// MARK: - UserRow

struct UserRow: View {
    let user: User

    var body: some View {
        HStack(spacing: 12) {
            AvatarView(user: user, size: 44)

            VStack(alignment: .leading, spacing: 4) {
                HStack(alignment: .center, spacing: 6) {
                    Text(user.name)
                        .font(.body.weight(.medium))
                        .foregroundStyle(Color(.label))
                    Spacer()
                    RoleBadge(role: user.role)
                }
                Text(user.email)
                    .font(.subheadline)
                    .foregroundStyle(Color(.secondaryLabel))
                    .lineLimit(1)
            }

            Image(systemName: "chevron.right")
                .font(.caption.weight(.semibold))
                .foregroundStyle(Color(.tertiaryLabel))
        }
        .padding(12)
        .background(Color(.systemBackground))
        .clipShape(RoundedRectangle(cornerRadius: 12))
        .shadow(color: .black.opacity(0.05), radius: 4, x: 0, y: 2)
    }
}

// MARK: - AvatarView

struct AvatarView: View {
    let user: User
    let size: CGFloat

    private var dotSize: CGFloat { size * 0.3 }

    var body: some View {
        ZStack(alignment: .bottomTrailing) {
            Circle()
                .fill(user.avatarTint.opacity(0.18))
                .frame(width: size, height: size)
                .overlay {
                    Text(user.initials)
                        .font(.system(size: size * 0.36, weight: .semibold))
                        .foregroundStyle(user.avatarTint)
                }

            Circle()
                .fill(Color(.systemBackground))
                .frame(width: dotSize + 4, height: dotSize + 4)
                .overlay {
                    Circle()
                        .fill(user.isOnline ? Color(.systemGreen) : Color(.systemGray4))
                        .frame(width: dotSize, height: dotSize)
                }
                .offset(x: 2, y: 2)
        }
    }
}

// MARK: - RoleBadge

struct RoleBadge: View {
    let role: UserRole

    var body: some View {
        Label(role.rawValue, systemImage: role.icon)
            .font(.system(size: 11, weight: .semibold))
            .labelStyle(.titleAndIcon)
            .padding(.horizontal, 7)
            .padding(.vertical, 3)
            .background(role.tint.opacity(0.14))
            .foregroundStyle(role.tint)
            .clipShape(Capsule())
    }
}

// MARK: - UserDetailView

struct UserDetailView: View {
    @Environment(\.dismiss) private var dismiss

    @State private var draft: User
    @State private var isEditing = false
    @State private var confirmDelete = false

    let onSave: (User) -> Void

    init(user: User, onSave: @escaping (User) -> Void) {
        _draft  = State(initialValue: user)
        self.onSave = onSave
    }

    var body: some View {
        ZStack {
            Color(.systemGroupedBackground).ignoresSafeArea()

            ScrollView {
                LazyVStack(spacing: 16) {
                    avatarSection
                    infoSection
                    roleSection
                    if isEditing { saveButton }
                    dangerSection
                }
                .padding(.horizontal, 16)
                .padding(.top, 24)
                .padding(.bottom, 48)
            }
        }
        .navigationTitle(isEditing ? "Redigera" : draft.name)
        .navigationBarTitleDisplayMode(.inline)
        .toolbar {
            ToolbarItem(placement: .topBarTrailing) {
                Button(isEditing ? "Klar" : "Redigera") {
                    if isEditing { onSave(draft) }
                    withAnimation(.spring(duration: 0.28)) { isEditing.toggle() }
                }
                .fontWeight(isEditing ? .semibold : .regular)
                .foregroundStyle(Color(.systemBlue))
            }
        }
        .confirmationDialog(
            "Ta bort \(draft.name)?",
            isPresented: $confirmDelete,
            titleVisibility: .visible
        ) {
            Button("Ta bort", role: .destructive) { dismiss() }
            Button("Avbryt", role: .cancel) {}
        } message: {
            Text("Användaren förlorar omedelbart åtkomst till AAMOS.")
        }
    }

    // MARK: Avatar

    private var avatarSection: some View {
        VStack(spacing: 10) {
            AvatarView(user: draft, size: 80)
            statusLabel
        }
    }

    private var statusLabel: some View {
        Group {
            if draft.isOnline {
                Label("Online", systemImage: "circle.fill")
                    .foregroundStyle(Color(.systemGreen))
            } else if let seen = draft.lastSeen {
                let rel = RelativeDateTimeFormatter()
                Text("Senast \(rel.localizedString(for: seen, relativeTo: Date()))")
                    .foregroundStyle(Color(.secondaryLabel))
            } else {
                Text("Offline").foregroundStyle(Color(.secondaryLabel))
            }
        }
        .font(.caption)
    }

    // MARK: Info

    private var infoSection: some View {
        Card {
            DetailField(
                icon: "person.fill", tint: Color(.systemBlue),
                label: "Namn", value: $draft.name,
                isEditing: isEditing,
                keyboardType: .default,
                capitalization: .words
            )
            Divider().padding(.leading, 52)
            DetailField(
                icon: "envelope.fill", tint: Color(.systemBlue),
                label: "E-post", value: $draft.email,
                isEditing: isEditing,
                keyboardType: .emailAddress,
                capitalization: .never
            )
        }
    }

    // MARK: Role

    private var roleSection: some View {
        Card {
            VStack(alignment: .leading, spacing: 12) {
                Label("Roll", systemImage: "shield.lefthalf.filled")
                    .font(.subheadline)
                    .foregroundStyle(Color(.secondaryLabel))

                if isEditing {
                    LazyVGrid(
                        columns: [GridItem(.flexible()), GridItem(.flexible())],
                        spacing: 8
                    ) {
                        ForEach(UserRole.allCases, id: \.self) { role in
                            RoleOptionButton(role: role, selected: $draft.role)
                        }
                    }
                    .transition(.opacity.combined(with: .scale(scale: 0.97)))
                } else {
                    RoleBadge(role: draft.role)
                }
            }
            .animation(.spring(duration: 0.25), value: isEditing)
        }
    }

    // MARK: Save

    private var saveButton: some View {
        Button {
            onSave(draft)
            withAnimation { isEditing = false }
        } label: {
            Label("Spara ändringar", systemImage: "checkmark")
                .font(.body.weight(.semibold))
                .frame(maxWidth: .infinity)
                .padding(.vertical, 14)
                .background(Color(.systemBlue))
                .foregroundStyle(.white)
                .clipShape(RoundedRectangle(cornerRadius: 12))
        }
        .transition(.opacity.combined(with: .move(edge: .bottom)))
    }

    // MARK: Danger

    private var dangerSection: some View {
        Card {
            Button(role: .destructive) {
                confirmDelete = true
            } label: {
                Label("Ta bort användare", systemImage: "trash")
                    .frame(maxWidth: .infinity, alignment: .leading)
            }
        }
    }
}

// MARK: - RoleOptionButton

private struct RoleOptionButton: View {
    let role: UserRole
    @Binding var selected: UserRole

    var isSelected: Bool { selected == role }

    var body: some View {
        Button {
            withAnimation(.spring(duration: 0.22)) { selected = role }
        } label: {
            VStack(spacing: 6) {
                Image(systemName: role.icon)
                    .font(.system(size: 18))
                Text(role.rawValue)
                    .font(.system(size: 13, weight: .semibold))
            }
            .frame(maxWidth: .infinity)
            .padding(.vertical, 12)
            .background(isSelected ? role.tint.opacity(0.15) : Color(.secondarySystemBackground))
            .foregroundStyle(isSelected ? role.tint : Color(.secondaryLabel))
            .clipShape(RoundedRectangle(cornerRadius: 10))
            .overlay {
                if isSelected {
                    RoundedRectangle(cornerRadius: 10)
                        .strokeBorder(role.tint.opacity(0.5), lineWidth: 1.5)
                }
            }
        }
        .buttonStyle(.plain)
    }
}

// MARK: - DetailField

private struct DetailField: View {
    let icon: String
    let tint: Color
    let label: String
    @Binding var value: String
    let isEditing: Bool
    let keyboardType: UIKeyboardType
    let capitalization: TextInputAutocapitalization

    var body: some View {
        HStack(spacing: 12) {
            Image(systemName: icon)
                .font(.system(size: 14))
                .foregroundStyle(tint)
                .frame(width: 32, height: 32)
                .background(tint.opacity(0.12))
                .clipShape(RoundedRectangle(cornerRadius: 8))

            VStack(alignment: .leading, spacing: 2) {
                Text(label)
                    .font(.caption)
                    .foregroundStyle(Color(.secondaryLabel))

                if isEditing {
                    TextField(label, text: $value)
                        .font(.body)
                        .keyboardType(keyboardType)
                        .textInputAutocapitalization(capitalization)
                        .autocorrectionDisabled()
                } else {
                    Text(value)
                        .font(.body)
                        .foregroundStyle(Color(.label))
                }
            }

            Spacer()
        }
        .padding(.vertical, 4)
    }
}

// MARK: - Card

private struct Card<Content: View>: View {
    @ViewBuilder let content: () -> Content

    var body: some View {
        VStack(spacing: 0) {
            content()
        }
        .padding(16)
        .background(Color(.systemBackground))
        .clipShape(RoundedRectangle(cornerRadius: 12))
        .shadow(color: .black.opacity(0.05), radius: 4, x: 0, y: 2)
    }
}

// MARK: - InviteUserView

struct InviteUserView: View {
    @Environment(\.dismiss) private var dismiss

    @State private var name         = ""
    @State private var email        = ""
    @State private var selectedRole = UserRole.viewer
    @State private var isSending    = false

    @FocusState private var focus: Field?
    enum Field { case name, email }

    let onInvite: (String, String, UserRole) -> Void

    private var isValid: Bool {
        !name.trimmingCharacters(in: .whitespaces).isEmpty &&
        email.contains("@") && email.contains(".")
    }

    var body: some View {
        NavigationStack {
            ZStack {
                Color(.systemGroupedBackground).ignoresSafeArea()

                ScrollView {
                    LazyVStack(spacing: 20) {
                        header
                        formCard
                        roleGrid
                        sendButton
                    }
                    .padding(.horizontal, 16)
                    .padding(.top, 24)
                    .padding(.bottom, 48)
                }
            }
            .navigationTitle("Bjud in användare")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .topBarLeading) {
                    Button("Avbryt") { dismiss() }
                        .foregroundStyle(Color(.systemBlue))
                }
            }
        }
    }

    // MARK: Header

    private var header: some View {
        VStack(spacing: 8) {
            ZStack {
                Circle()
                    .fill(Color(.systemBlue).opacity(0.12))
                    .frame(width: 72, height: 72)
                Image(systemName: "person.badge.plus")
                    .font(.system(size: 28))
                    .foregroundStyle(Color(.systemBlue))
            }
            Text("Nytt konto")
                .font(.title3.weight(.semibold))
            Text("Användaren får en inbjudan via e-post.")
                .font(.subheadline)
                .foregroundStyle(Color(.secondaryLabel))
                .multilineTextAlignment(.center)
        }
    }

    // MARK: Form

    private var formCard: some View {
        Card {
            HStack(spacing: 12) {
                iconBox("person.fill", tint: Color(.systemBlue))
                TextField("Fullständigt namn", text: $name)
                    .font(.body)
                    .textInputAutocapitalization(.words)
                    .autocorrectionDisabled()
                    .focused($focus, equals: .name)
                    .submitLabel(.next)
                    .onSubmit { focus = .email }
            }
            .padding(.vertical, 2)

            Divider().padding(.leading, 52)

            HStack(spacing: 12) {
                iconBox("envelope.fill", tint: Color(.systemBlue))
                TextField("E-postadress", text: $email)
                    .font(.body)
                    .keyboardType(.emailAddress)
                    .textInputAutocapitalization(.never)
                    .autocorrectionDisabled()
                    .focused($focus, equals: .email)
                    .submitLabel(.done)
            }
            .padding(.vertical, 2)
        }
    }

    private func iconBox(_ symbol: String, tint: Color) -> some View {
        Image(systemName: symbol)
            .font(.system(size: 14))
            .foregroundStyle(tint)
            .frame(width: 32, height: 32)
            .background(tint.opacity(0.12))
            .clipShape(RoundedRectangle(cornerRadius: 8))
    }

    // MARK: Role grid

    private var roleGrid: some View {
        VStack(alignment: .leading, spacing: 12) {
            Label("Roll", systemImage: "shield.lefthalf.filled")
                .font(.subheadline.weight(.medium))
                .foregroundStyle(Color(.secondaryLabel))
                .padding(.leading, 4)

            LazyVGrid(
                columns: [GridItem(.flexible()), GridItem(.flexible())],
                spacing: 8
            ) {
                ForEach(UserRole.allCases, id: \.self) { role in
                    RoleOptionButton(role: role, selected: $selectedRole)
                }
            }
        }
    }

    // MARK: Send button

    private var sendButton: some View {
        Button {
            guard isValid, !isSending else { return }
            isSending = true
            Task {
                try? await Task.sleep(for: .milliseconds(350))
                onInvite(
                    name.trimmingCharacters(in: .whitespaces),
                    email.lowercased().trimmingCharacters(in: .whitespaces),
                    selectedRole
                )
                dismiss()
            }
        } label: {
            HStack(spacing: 8) {
                if isSending {
                    ProgressView().tint(.white).scaleEffect(0.85)
                } else {
                    Image(systemName: "paperplane.fill")
                }
                Text(isSending ? "Skickar…" : "Skicka inbjudan")
                    .fontWeight(.semibold)
            }
            .frame(maxWidth: .infinity)
            .padding(.vertical, 14)
            .background(isValid ? Color(.systemBlue) : Color(.systemGray4))
            .foregroundStyle(isValid ? .white : Color(.systemGray2))
            .clipShape(RoundedRectangle(cornerRadius: 12))
        }
        .disabled(!isValid || isSending)
        .animation(.easeInOut(duration: 0.15), value: isValid)
    }
}

// MARK: - Previews

#Preview("UsersView") {
    UsersView()
}

#Preview("UserRow — online") {
    UserRow(user: User.samples[0])
        .padding()
        .background(Color(.systemGroupedBackground))
}

#Preview("UserRow — offline") {
    UserRow(user: User.samples[2])
        .padding()
        .background(Color(.systemGroupedBackground))
}

#Preview("UserDetailView") {
    NavigationStack {
        UserDetailView(user: User.samples[0], onSave: { _ in })
    }
}

#Preview("InviteUserView") {
    InviteUserView(onInvite: { _, _, _ in })
}