import SwiftUI

struct GoalEditorView: View {
    @Environment(\.dismiss) private var dismiss
    @State private var name = ""
    @State private var targetAmount = ""
    @State private var targetDate = Date()
    @State private var includeTargetDate = false
    @State private var didLoadGoal = false
    @State private var selectedCategoryId: UUID?

    @StateObject private var categoryRepository = CategoryRepository()

    let account: Account?
    let goal: Goal?
    private let goalRepository = GoalRepository()

    init(account: Account?, goal: Goal? = nil) {
        self.account = account
        self.goal = goal
    }

    private var currencySymbol: String {
        if let account = account, let code = account.currency, !code.isEmpty {
            return CurrencyFormatter.symbol(for: code)
        }
        return AppSettings.getOrCreate(in: CoreDataStack.shared.viewContext).currencySymbol
    }

    private var currencyCode: String {
        if let account = account, let code = account.currency, !code.isEmpty {
            return code
        }
        return AppSettings.getOrCreate(in: CoreDataStack.shared.viewContext).currency
    }

    var body: some View {
        NavigationStack {
            Form {
                Section {
                    TextField("Goal name", text: $name)
                    HStack {
                        Text(currencySymbol)
                            .foregroundStyle(.secondary)
                        TextField("Target amount", text: $targetAmount)
                            .keyboardType(.decimalPad)
                    }

                    Toggle("Add target date", isOn: $includeTargetDate)
                    if includeTargetDate {
                        DatePicker("Target date", selection: $targetDate, displayedComponents: .date)
                            .datePickerStyle(.graphical)
                    }
                } header: {
                    Text("Goal Details")
                }

                Section {
                    Picker(String(localized: "goal_scope_category"), selection: $selectedCategoryId) {
                        Text("goal_scope_all_categories").tag(UUID?.none)
                        ForEach(categoryRepository.categories) { category in
                            Label(category.name, systemImage: category.icon)
                                .tag(UUID?.some(category.id))
                        }
                    }
                } header: {
                    Text("goal_scope_section")
                } footer: {
                    Text(selectedCategoryId == nil
                         ? String(localized: "goal_scope_footer_all")
                         : String(localized: "goal_scope_footer_category"))
                }
            }
            .navigationTitle(goal == nil ? "New Goal" : "Edit Goal")
            .toolbar {
                ToolbarItem(placement: .topBarLeading) {
                    Button("Cancel") { dismiss() }
                }
                ToolbarItem(placement: .topBarTrailing) {
                    Button("Save") { saveGoal() }
                        .disabled(!isValid)
                }
            }
        }
        .presentationDetents([.medium, .large])
        .presentationDragIndicator(.visible)
        .onAppear {
            guard let goal, !didLoadGoal else { return }
            name = goal.name
            if let amount = goal.targetAmount?.decimalValue {
                targetAmount = formatDecimalForInput(amount)
            }
            if let target = goal.targetDate {
                includeTargetDate = true
                targetDate = target
            }
            selectedCategoryId = goal.category?.safeId
            didLoadGoal = true
        }
    }

    private var isValid: Bool {
        !name.trimmingCharacters(in: .whitespaces).isEmpty && parseDecimal(targetAmount) != nil
    }

    private var selectedCategory: Category? {
        guard let selectedCategoryId else { return nil }
        return categoryRepository.categories.first { $0.safeId == selectedCategoryId }
    }

    private func saveGoal() {
        guard let value = parseDecimal(targetAmount) else { return }
        let category = selectedCategory
        if let goal {
            goalRepository.updateGoal(
                goal,
                name: name,
                targetAmount: value,
                targetDate: includeTargetDate ? targetDate : nil,
                clearTargetDate: !includeTargetDate,
                category: category,
                clearCategory: category == nil
            )
        } else {
            goalRepository.createGoal(
                name: name,
                targetAmount: value,
                targetDate: includeTargetDate ? targetDate : nil,
                account: account,
                category: category
            )
        }
        dismiss()
    }

    private func parseDecimal(_ value: String) -> Decimal? {
        let locale = CurrencyFormatter.locale(for: currencyCode)
        let stripped = value
            .replacingOccurrences(of: currencySymbol, with: "")
            .trimmingCharacters(in: .whitespaces)

        guard !stripped.isEmpty else { return nil }

        let decimalSep = locale.decimalSeparator ?? "."
        let groupingSep = locale.groupingSeparator ?? ""

        // Detect alternate decimal BEFORE removing separators
        let usesAlternateDecimal =
            (decimalSep == "," && stripped.contains(".") && !stripped.contains(",")) ||
            (decimalSep == "." && stripped.contains(",") && !stripped.contains("."))

        if usesAlternateDecimal {
            let normalized = stripped
                .replacingOccurrences(of: groupingSep, with: "")
                .replacingOccurrences(of: ",", with: ".")
            let formatter = NumberFormatter()
            formatter.numberStyle = .decimal
            formatter.locale = Locale(identifier: "en_US_POSIX")
            return formatter.number(from: normalized)?.decimalValue
        }

        let cleaned = stripped.replacingOccurrences(of: groupingSep, with: "")
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.locale = locale

        if let result = formatter.number(from: cleaned)?.decimalValue {
            return result
        }

        // Fallback for mixed locale input
        let normalized = cleaned
            .replacingOccurrences(of: decimalSep, with: ".")
            .replacingOccurrences(of: ",", with: ".")
        formatter.locale = Locale(identifier: "en_US_POSIX")
        return formatter.number(from: normalized)?.decimalValue
    }

    private func formatDecimalForInput(_ decimal: Decimal) -> String {
        let locale = CurrencyFormatter.locale(for: currencyCode)
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.locale = locale
        formatter.minimumFractionDigits = 0
        formatter.maximumFractionDigits = 2
        formatter.groupingSeparator = ""
        return formatter.string(from: decimal as NSDecimalNumber) ?? ""
    }
}

#Preview {
    GoalEditorView(account: nil)
}