import SwiftUI
#if canImport(UIKit)
import UIKit
#endif

struct FeedbackView: View {
    @State private var suggestion: String = ""
    @State private var submittedFeedback: SubmittedFeedback? = nil
    @State private var isSubmitting: Bool = false
    @State private var showSubmissionMessage: Bool = false
    @State private var feedbackCategory: FeedbackCategory = .idea
    @State private var rating: Int = 0
    @State private var wantsResponse: Bool = false
    @State private var contactEmail: String = ""
    @FocusState private var focusedField: Field?

    private let gridColumns = [GridItem(.adaptive(minimum: 120), spacing: 12)]

    var body: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 24) {
                headerSection
                infoSection
                categorySection
                ratingSection
                suggestionSection
                contactSection

                Button(action: submitSuggestion) {
                    HStack(spacing: 10) {
                        if isSubmitting {
                            ProgressView()
                                .progressViewStyle(CircularProgressViewStyle())
                        }
                        Text(isSubmitting
                             ? NSLocalizedString("Отправляем...", comment: "feedback: sending state")
                             : NSLocalizedString("Отправить отзыв", comment: "feedback: submit button"))
                            .fontWeight(.semibold)
                    }
                    .frame(maxWidth: .infinity)
                    .padding()
                    .background(buttonBackgroundColor)
                    .foregroundColor(.white)
                    .cornerRadius(16)
                }
                .disabled(!canSubmit)

                if let submission = submittedFeedback, showSubmissionMessage {
                    successSection(for: submission)
                        .transition(.move(edge: .top).combined(with: .opacity))
                }

                Spacer(minLength: 16)
            }
            .padding(.vertical, 32)
            .padding(.horizontal, 20)
        }
        .background(Color(.systemGroupedBackground).ignoresSafeArea())
        .navigationTitle(NSLocalizedString("Обратная связь", comment: "feedback: navigation title"))
        .navigationBarTitleDisplayMode(.inline)
        .simultaneousGesture(
            TapGesture().onEnded {
                dismissKeyboardIfNeeded()
            }
        )
        .onChange(of: wantsResponse) { wants in
            if !wants {
                contactEmail = ""
            }
        }
    }

    private var headerSection: some View {
        VStack(alignment: .leading, spacing: 12) {
            Text(NSLocalizedString("Расскажите о своём опыте", comment: "feedback: header title"))
                .font(.title2)
                .fontWeight(.bold)
            Text(NSLocalizedString("Мы читаем каждый отзыв и используем его, чтобы сделать Yobble полезнее для вас.", comment: "feedback: header subtitle"))
                .foregroundColor(.secondary)
        }
    }

    private var infoSection: some View {
        VStack(alignment: .leading, spacing: 8) {
            Label {
                Text(NSLocalizedString("Поделитесь идеями, сообщите об ошибке или расскажите, что работает отлично.", comment: "feedback: info detail"))
            } icon: {
                Image(systemName: "bubble.left.and.bubble.right.fill")
                    .foregroundColor(.accentColor)
            }
            .font(.callout)
        }
        .padding()
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(
            RoundedRectangle(cornerRadius: 16, style: .continuous)
                .fill(Color.accentColor.opacity(0.08))
        )
    }

    private var categorySection: some View {
        VStack(alignment: .leading, spacing: 12) {
            sectionTitle(NSLocalizedString("Что вы хотите обсудить?", comment: "feedback: category title"))
            LazyVGrid(columns: gridColumns, alignment: .leading, spacing: 12) {
                ForEach(FeedbackCategory.allCases) { category in
                    categoryButton(for: category)
                }
            }
        }
    }

    private var ratingSection: some View {
        VStack(alignment: .leading, spacing: 12) {
            sectionTitle(NSLocalizedString("Насколько вам нравится Yobble?", comment: "feedback: rating title"))
            HStack(spacing: 8) {
                ForEach(1...5, id: \.self) { value in
                    Button {
                        rating = value
                    } label: {
                        Image(systemName: rating >= value ? "star.fill" : "star")
                            .foregroundColor(rating >= value ? Color.yellow : Color(.systemGray3))
                            .font(.title3)
                            .padding(.vertical, 4)
                    }
                    .buttonStyle(.plain)
                    .accessibilityLabel(Text(String(format: NSLocalizedString("Оценка %d", comment: "feedback: rating accessibility"), value)))
                    .accessibilityAddTraits(rating == value ? .isSelected : [])
                }
            }

            if rating > 0 {
                Text(ratingDescription(for: rating))
                    .font(.caption)
                    .foregroundColor(.secondary)
            } else {
                Text(NSLocalizedString("Выберите оценку — это поможет нам понять настроение.", comment: "feedback: rating hint"))
                    .font(.caption)
                    .foregroundColor(.secondary)
            }
        }
    }

    private var suggestionSection: some View {
        VStack(alignment: .leading, spacing: 12) {
            sectionTitle(feedbackCategory.promptTitle)

            TextEditor(text: $suggestion)
                .frame(minHeight: 140)
                .padding(12)
                .background(
                    RoundedRectangle(cornerRadius: 14, style: .continuous)
                        .fill(Color(.systemBackground))
                )
                .overlay(
                    RoundedRectangle(cornerRadius: 14, style: .continuous)
                        .stroke(Color(.systemGray4), lineWidth: 1)
                )
                .overlay(
                    Group {
                        if suggestion.isEmpty {
                            Text(feedbackCategory.placeholder)
                                .foregroundColor(.secondary)
                                .padding(.horizontal, 18)
                                .padding(.vertical, 16)
                                .allowsHitTesting(false)
                        }
                    }
                )
                .focused($focusedField, equals: .suggestion)
                .autocorrectionDisabled(false)

            Text(String(format: NSLocalizedString("%d символов", comment: "feedback: character count"), suggestion.count))
                .font(.caption2)
                .foregroundColor(.secondary)
        }
    }

    private var contactSection: some View {
        VStack(alignment: .leading, spacing: 12) {
            sectionTitle(NSLocalizedString("Нужно ли вам ответить?", comment: "feedback: contact title"))

            Toggle(NSLocalizedString("Получить ответ от команды", comment: "feedback: contact toggle"), isOn: $wantsResponse)
                .toggleStyle(SwitchToggleStyle(tint: .accentColor))

            if wantsResponse {
                VStack(alignment: .leading, spacing: 6) {
                    TextField(NSLocalizedString("Ваш e-mail", comment: "feedback: email placeholder"), text: $contactEmail)
                        .textContentType(.emailAddress)
                        .textInputAutocapitalization(.never)
                        .keyboardType(.emailAddress)
                        .autocorrectionDisabled(true)
                        .padding(12)
                        .background(
                            RoundedRectangle(cornerRadius: 14, style: .continuous)
                                .fill(Color(.systemBackground))
                        )
                        .overlay(
                            RoundedRectangle(cornerRadius: 14, style: .continuous)
                                .stroke(emailBorderColor, lineWidth: 1)
                        )
                        .focused($focusedField, equals: .email)

                    if !contactEmail.isEmpty && !emailIsValid {
                        Text(NSLocalizedString("Пожалуйста, введите корректный e-mail.", comment: "feedback: email error"))
                            .font(.caption)
                            .foregroundColor(.red)
                    } else {
                        Text(NSLocalizedString("Мы используем адрес только для ответа на ваш запрос.", comment: "feedback: email hint"))
                            .font(.caption)
                            .foregroundColor(.secondary)
                    }
                }
            }
        }
    }

    private var canSubmit: Bool {
        suggestionIsValid && emailIsValid && !isSubmitting
    }

    private var suggestionIsValid: Bool {
        !suggestion.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty
    }

    private var emailIsValid: Bool {
        guard wantsResponse else { return true }
        let trimmed = contactEmail.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else { return false }
        return trimmed.contains("@") && trimmed.contains(".")
    }

    private var buttonBackgroundColor: Color {
        suggestionIsValid && emailIsValid ? Color.accentColor : Color(.systemGray4)
    }

    private var emailBorderColor: Color {
        if contactEmail.isEmpty { return Color(.systemGray4) }
        return emailIsValid ? Color.accentColor : .red
    }

    private func sectionTitle(_ text: String) -> some View {
        Text(text)
            .font(.headline)
    }

    private func categoryButton(for category: FeedbackCategory) -> some View {
        let isSelected = feedbackCategory == category

        return Button {
            feedbackCategory = category
        } label: {
            VStack(alignment: .leading, spacing: 6) {
                Image(systemName: category.iconName)
                    .font(.subheadline)
                    .foregroundColor(isSelected ? .accentColor : .secondary)
                Text(category.title)
                    .fontWeight(.semibold)
                    .foregroundColor(.primary)
                Text(category.subtitle)
                    .font(.caption)
                    .foregroundColor(.secondary)
            }
            .frame(maxWidth: .infinity, alignment: .leading)
            .padding(.vertical, 14)
            .padding(.horizontal, 16)
            .background(
                RoundedRectangle(cornerRadius: 16, style: .continuous)
                    .fill(isSelected ? Color.accentColor.opacity(0.12) : Color(.systemBackground))
            )
            .overlay(
                RoundedRectangle(cornerRadius: 16, style: .continuous)
                    .stroke(isSelected ? Color.accentColor : Color(.systemGray4), lineWidth: isSelected ? 2 : 1)
            )
        }
        .buttonStyle(.plain)
    }

    private func ratingDescription(for rating: Int) -> String {
        switch rating {
        case 1:
            return NSLocalizedString("Что-то пошло не так. Расскажите подробности ниже.", comment: "feedback: rating description 1")
        case 2:
            return NSLocalizedString("Мы постараемся всё исправить. Напишите, что смутило.", comment: "feedback: rating description 2")
        case 3:
            return NSLocalizedString("Неплохо, но можно лучше — что добавить?", comment: "feedback: rating description 3")
        case 4:
            return NSLocalizedString("Спасибо! Что поможет нам добраться до пятёрки?", comment: "feedback: rating description 4")
        case 5:
            return NSLocalizedString("Прекрасно! Расскажите, что понравилось больше всего.", comment: "feedback: rating description 5")
        default:
            return ""
        }
    }

    private func submitSuggestion() {
        guard canSubmit else { return }

        let trimmedSuggestion = suggestion.trimmingCharacters(in: .whitespacesAndNewlines)
        let trimmedEmail = contactEmail.trimmingCharacters(in: .whitespacesAndNewlines)

        dismissKeyboardIfNeeded()

        isSubmitting = true
        showSubmissionMessage = false

        DispatchQueue.main.asyncAfter(deadline: .now() + 0.7) {
            submittedFeedback = SubmittedFeedback(
                suggestion: trimmedSuggestion,
                category: feedbackCategory,
                rating: rating,
                email: wantsResponse ? trimmedEmail : nil
            )
            suggestion = ""
            rating = 0
            if !wantsResponse {
                contactEmail = ""
            }
            withAnimation {
                showSubmissionMessage = true
            }
            isSubmitting = false
        }
    }

    private func successSection(for submission: SubmittedFeedback) -> some View {
        VStack(alignment: .leading, spacing: 10) {
            Label {
                Text(NSLocalizedString("Спасибо! Мы получили ваш отзыв", comment: "feedback: success title"))
            } icon: {
                Image(systemName: "checkmark.seal.fill")
                    .foregroundColor(.accentColor)
            }
            .font(.headline)

            Text(String(format: NSLocalizedString("Тема: %@", comment: "feedback: success category"), submission.category.title))
                .font(.subheadline)

            if submission.rating > 0 {
                Text(String(format: NSLocalizedString("Оценка: %d из 5", comment: "feedback: success rating"), submission.rating))
                    .font(.subheadline)
            }

            if !submission.suggestion.isEmpty {
                Text(submission.suggestion)
                    .font(.callout)
                    .foregroundColor(.secondary)
            }

            if let email = submission.email, !email.isEmpty {
                Text(String(format: NSLocalizedString("Мы свяжемся с вами по адресу %@, как только ответим.", comment: "feedback: success email"), email))
                    .font(.footnote)
                    .foregroundColor(.secondary)
            }
        }
        .padding()
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(
            RoundedRectangle(cornerRadius: 16, style: .continuous)
                .fill(Color.accentColor.opacity(0.12))
        )
    }

    private func dismissKeyboardIfNeeded() {
        guard focusedField != nil else { return }
        focusedField = nil

#if canImport(UIKit)
        UIApplication.shared.sendAction(#selector(UIResponder.resignFirstResponder), to: nil, from: nil, for: nil)
#endif
    }
}

private extension FeedbackView {
    enum Field: Hashable {
        case suggestion
        case email
    }

    struct SubmittedFeedback {
        let suggestion: String
        let category: FeedbackCategory
        let rating: Int
        let email: String?
    }

    enum FeedbackCategory: String, CaseIterable, Identifiable {
        case idea
        case bug
        case praise
        case content

        var id: String { rawValue }

        var title: String {
            switch self {
            case .idea:
                return NSLocalizedString("Идея", comment: "feedback category: idea")
            case .bug:
                return NSLocalizedString("Проблема", comment: "feedback category: bug")
            case .praise:
                return NSLocalizedString("Похвала", comment: "feedback category: praise")
            case .content:
                return NSLocalizedString("Контент", comment: "feedback category: content")
            }
        }

        var subtitle: String {
            switch self {
            case .idea:
                return NSLocalizedString("Предложите, что добавить", comment: "feedback category subtitle: idea")
            case .bug:
                return NSLocalizedString("Расскажите, что не работает", comment: "feedback category subtitle: bug")
            case .praise:
                return NSLocalizedString("Поделитесь, что понравилось", comment: "feedback category subtitle: praise")
            case .content:
                return NSLocalizedString("Сообщите о материалах", comment: "feedback category subtitle: content")
            }
        }

        var iconName: String {
            switch self {
            case .idea:
                return "lightbulb"
            case .bug:
                return "ant"
            case .praise:
                return "heart.fill"
            case .content:
                return "doc.richtext"
            }
        }

        var promptTitle: String {
            switch self {
            case .idea:
                return NSLocalizedString("Опишите идею", comment: "feedback prompt: idea")
            case .bug:
                return NSLocalizedString("Что случилось?", comment: "feedback prompt: bug")
            case .praise:
                return NSLocalizedString("Что вам понравилось?", comment: "feedback prompt: praise")
            case .content:
                return NSLocalizedString("О каком контенте идёт речь?", comment: "feedback prompt: content")
            }
        }

        var placeholder: String {
            switch self {
            case .idea:
                return NSLocalizedString("Например: хотелось бы видеть подборку по интересам...", comment: "feedback placeholder: idea")
            case .bug:
                return NSLocalizedString("Например: приложение вылетает, когда я открываю профиль...", comment: "feedback placeholder: bug")
            case .praise:
                return NSLocalizedString("Например: понравилась новая лента, потому что...", comment: "feedback placeholder: praise")
            case .content:
                return NSLocalizedString("Например: заметил неточную информацию в статье...", comment: "feedback placeholder: content")
            }
        }
    }
}

struct FeedbackView_Previews: PreviewProvider {
    static var previews: some View {
        NavigationView {
            FeedbackView()
                .environmentObject(ThemeManager())
        }
    }
}