import SwiftUI
import SwiftData

struct CategoryView: View {
    @Environment(\.modelContext) private var modelContext
    @State private var viewModel = CategoryViewModel()
    @State private var showAddSheet = false

    var body: some View {
        ZStack {
            Theme.background.ignoresSafeArea()
            Group {
                if viewModel.categories.isEmpty {
                    emptyState
                } else {
                    categoryList
                }
            }
        }
        .navigationTitle(String(localized: "tab.category"))
        .toolbar {
            ToolbarItem(placement: .navigationBarTrailing) {
                Button { showAddSheet = true } label: {
                    Image(systemName: "plus")
                        .foregroundStyle(Theme.green)
                }
            }
        }
        .sheet(isPresented: $showAddSheet) {
            AddCategorySheet { name, colorHex in
                viewModel.addCategory(name: name, colorHex: colorHex)
            }
        }
        .onAppear { viewModel.setup(context: modelContext) }
    }

    private var emptyState: some View {
        VStack(spacing: 16) {
            Image(systemName: "folder.badge.plus")
                .font(.system(size: 56))
                .foregroundStyle(Theme.green.opacity(0.6))
            Text(String(localized: "category.empty"))
                .foregroundStyle(Theme.primaryText.opacity(0.6))
        }
    }

    private var categoryList: some View {
        List {
            ForEach(viewModel.categories) { category in
                CategoryRow(category: category, taskCount: viewModel.taskCount(for: category))
                    .listRowBackground(Theme.surface)
                    .swipeActions(edge: .trailing, allowsFullSwipe: false) {
                        Button(role: .destructive) {
                            viewModel.deleteCategory(category)
                        } label: {
                            Label(String(localized: "category.delete"), systemImage: "trash")
                        }
                    }
            }
        }
        .listStyle(.plain)
        .scrollContentBackground(.hidden)
    }
}

// MARK: - Category Row

private struct CategoryRow: View {
    let category: Category
    let taskCount: Int

    var body: some View {
        HStack(spacing: 12) {
            Circle()
                .fill(Color(hex: category.colorHex))
                .frame(width: 14, height: 14)

            Text(category.name)
                .font(.body)
                .fontWeight(.medium)
                .foregroundStyle(Theme.primaryText)

            Spacer()

            Text("\(taskCount) \(String(localized: "category.task.count"))")
                .font(.caption)
                .foregroundStyle(Theme.primaryText.opacity(0.5))
                .padding(.horizontal, 8)
                .padding(.vertical, 4)
                .background(Theme.green.opacity(0.12), in: Capsule())
        }
        .padding(.vertical, 6)
    }
}

// MARK: - Add Category Sheet

private struct AddCategorySheet: View {
    @Environment(\.dismiss) private var dismiss
    @State private var name = ""
    @State private var selectedColor = CategoryViewModel.presetColors[0]

    let onAdd: (String, String) -> Void

    var body: some View {
        NavigationStack {
            Form {
                Section {
                    TextField(String(localized: "category.name"), text: $name)
                }

                Section(String(localized: "category.color")) {
                    LazyVGrid(columns: Array(repeating: GridItem(.flexible()), count: 4), spacing: 16) {
                        ForEach(CategoryViewModel.presetColors, id: \.self) { colorHex in
                            Circle()
                                .fill(Color(hex: colorHex))
                                .frame(width: 42, height: 42)
                                .overlay(alignment: .center) {
                                    if selectedColor == colorHex {
                                        Image(systemName: "checkmark")
                                            .font(.caption)
                                            .fontWeight(.bold)
                                            .foregroundStyle(.white)
                                    }
                                }
                                .overlay(
                                    Circle()
                                        .strokeBorder(
                                            selectedColor == colorHex ? Theme.primaryText.opacity(0.4) : Color.clear,
                                            lineWidth: 2
                                        )
                                )
                                .onTapGesture { selectedColor = colorHex }
                        }
                    }
                    .padding(.vertical, 8)
                }
            }
            .navigationTitle(String(localized: "category.add"))
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button(String(localized: "button.cancel")) { dismiss() }
                }
                ToolbarItem(placement: .confirmationAction) {
                    Button(String(localized: "button.add")) {
                        let trimmed = name.trimmingCharacters(in: .whitespaces)
                        guard !trimmed.isEmpty else { return }
                        onAdd(trimmed, selectedColor)
                        dismiss()
                    }
                    .disabled(name.trimmingCharacters(in: .whitespaces).isEmpty)
                }
            }
        }
    }
}

// MARK: - Color Hex Extension

extension Color {
    init(hex: String) {
        let hex = hex.trimmingCharacters(in: CharacterSet.alphanumerics.inverted)
        var int: UInt64 = 0
        Scanner(string: hex).scanHexInt64(&int)
        let r = Double((int >> 16) & 0xFF) / 255
        let g = Double((int >> 8) & 0xFF) / 255
        let b = Double(int & 0xFF) / 255
        self.init(red: r, green: g, blue: b)
    }
}

#Preview {
    NavigationStack {
        CategoryView()
    }
}