// FAQViewController.swift
// Emoney Info
//
// Halaman Pusat Bantuan / FAQ
// - Search bar berfungsi (filter pertanyaan real-time)
// - Filter chip per kategori berfungsi
// - Accordion: tap pertanyaan untuk expand/collapse jawaban

import UIKit

final class FAQViewController: UIViewController {

    // MARK: - State

    private var allCategories: [FAQCategory] = FAQData.all
    private var activeFilter: String? = nil          // nil = semua kategori
    private var searchText: String = ""
    private var expandedItems: Set<String> = []      // key = "catID|qIndex"

    // Computed: filtered categories based on search + filter chip
    private var displayedCategories: [FAQCategory] {
        var source = allCategories

        // 1. Filter by category chip
        if let filter = activeFilter {
            source = source.filter { $0.id == filter }
        }

        // 2. Filter by search text
        if !searchText.isEmpty {
            let q = searchText.lowercased()
            source = source.compactMap { cat in
                let filtered = cat.items.filter {
                    $0.question.lowercased().contains(q) || $0.answer.lowercased().contains(q)
                }
                if filtered.isEmpty { return nil }
                return FAQCategory(id: cat.id, icon: cat.icon, title: cat.title, items: filtered)
            }
        }

        return source
    }

    // MARK: - UI

    private let scrollView   = UIScrollView()
    private let contentView  = UIView()

    private let headerView   = UIView()
    private let backButton   = UIButton(type: .system)
    private let titleLabel   = UILabel()
    private let subtitleLabel = UILabel()
    private let searchBar    = UISearchBar()

    // Category filter chips (horizontal scroll)
    private let chipScrollView = UIScrollView()
    private let chipStack      = UIStackView()

    // FAQ accordion container
    private let faqContainerStack = UIStackView()

    // "Still need help?" footer card
    private let helpCard = UIView()

    // MARK: - Lifecycle

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = Theme.Color.background
        setupScrollView()
        setupHeader()
        setupChips()
        setupFAQSection()
        setupHelpCard()
        reloadFAQ()
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        navigationController?.setNavigationBarHidden(true, animated: animated)
        (tabBarController as? MainTabBarController)?.setTabBarHidden(true, animated: animated)
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        (tabBarController as? MainTabBarController)?.setTabBarHidden(false, animated: animated)
    }

    // MARK: - Setup: ScrollView

    private func setupScrollView() {
        scrollView.showsVerticalScrollIndicator = false
        scrollView.keyboardDismissMode = .onDrag
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        contentView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(scrollView)
        scrollView.addSubview(contentView)

        NSLayoutConstraint.activate([
            scrollView.topAnchor.constraint(equalTo: view.topAnchor),
            scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor),

            contentView.topAnchor.constraint(equalTo: scrollView.topAnchor),
            contentView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor),
            contentView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor),
            contentView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor),
            contentView.widthAnchor.constraint(equalTo: scrollView.widthAnchor),
        ])
    }

    // MARK: - Setup: Header

    private func setupHeader() {
        // Teal rounded-bottom header card
        headerView.backgroundColor   = Theme.Color.primary
        headerView.layer.cornerRadius = 24
        headerView.layer.maskedCorners = [.layerMinXMaxYCorner, .layerMaxXMaxYCorner]
        headerView.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(headerView)

        // Back button
        let chevron = UIImage(systemName: "chevron.left",
                              withConfiguration: UIImage.SymbolConfiguration(pointSize: 16, weight: .semibold))
        backButton.setImage(chevron, for: .normal)
        backButton.tintColor = .white
        backButton.addTarget(self, action: #selector(backTapped), for: .touchUpInside)
        backButton.translatesAutoresizingMaskIntoConstraints = false

        // Header nav label "Help Center"
        let navLabel = UILabel()
        navLabel.text = L10n.helpCenterTitle
        navLabel.font = Theme.Font.caption(weight: .semibold)
        navLabel.textColor = UIColor.white.withAlphaComponent(0.85)
        navLabel.translatesAutoresizingMaskIntoConstraints = false

        // Title
        titleLabel.text = L10n.faqHeaderTitle
        titleLabel.font = Theme.Font.title(weight: .bold)
        titleLabel.textColor = .white
        titleLabel.numberOfLines = 0
        titleLabel.translatesAutoresizingMaskIntoConstraints = false

        // Search bar
        searchBar.placeholder = L10n.faqSearchPlaceholder
        searchBar.searchBarStyle = .minimal
        searchBar.backgroundColor = .white
        searchBar.layer.cornerRadius = 12
        searchBar.clipsToBounds = true
        searchBar.delegate = self
        searchBar.translatesAutoresizingMaskIntoConstraints = false
        if let tf = searchBar.value(forKey: "searchField") as? UITextField {
            tf.backgroundColor = .white
            tf.font = Theme.Font.body(weight: .regular)
        }

        [backButton, navLabel, titleLabel, searchBar].forEach { headerView.addSubview($0) }

        NSLayoutConstraint.activate([
            headerView.topAnchor.constraint(equalTo: contentView.topAnchor),
            headerView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
            headerView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),

            backButton.topAnchor.constraint(equalTo: headerView.safeAreaLayoutGuide.topAnchor, constant: 16),
            backButton.leadingAnchor.constraint(equalTo: headerView.leadingAnchor, constant: 20),
            backButton.widthAnchor.constraint(equalToConstant: 32),
            backButton.heightAnchor.constraint(equalToConstant: 32),

            navLabel.centerYAnchor.constraint(equalTo: backButton.centerYAnchor),
            navLabel.leadingAnchor.constraint(equalTo: backButton.trailingAnchor, constant: 8),

            titleLabel.topAnchor.constraint(equalTo: backButton.bottomAnchor, constant: 20),
            titleLabel.leadingAnchor.constraint(equalTo: headerView.leadingAnchor, constant: 24),
            titleLabel.trailingAnchor.constraint(equalTo: headerView.trailingAnchor, constant: -24),

            searchBar.topAnchor.constraint(equalTo: titleLabel.bottomAnchor, constant: 16),
            searchBar.leadingAnchor.constraint(equalTo: headerView.leadingAnchor, constant: 16),
            searchBar.trailingAnchor.constraint(equalTo: headerView.trailingAnchor, constant: -16),
            searchBar.bottomAnchor.constraint(equalTo: headerView.bottomAnchor, constant: -20),
            searchBar.heightAnchor.constraint(equalToConstant: 44),
        ])
    }

    // MARK: - Setup: Category Chips

    private func setupChips() {
        chipScrollView.showsHorizontalScrollIndicator = false
        chipScrollView.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(chipScrollView)

        chipStack.axis      = .horizontal
        chipStack.spacing   = 10
        chipStack.alignment = .center
        chipStack.translatesAutoresizingMaskIntoConstraints = false
        chipScrollView.addSubview(chipStack)

        NSLayoutConstraint.activate([
            chipScrollView.topAnchor.constraint(equalTo: headerView.bottomAnchor, constant: 20),
            chipScrollView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
            chipScrollView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
            chipScrollView.heightAnchor.constraint(equalToConstant: 44),

            chipStack.centerYAnchor.constraint(equalTo: chipScrollView.centerYAnchor),
            chipStack.leadingAnchor.constraint(equalTo: chipScrollView.leadingAnchor, constant: 20),
            chipStack.trailingAnchor.constraint(equalTo: chipScrollView.trailingAnchor, constant: -20),
        ])

        // "All" chip + one per category
        buildChips()
    }

    private func buildChips() {
        chipStack.arrangedSubviews.forEach { $0.removeFromSuperview() }

        let allChip = makeChip(id: nil, icon: "square.grid.2x2", title: L10n.faqFilterAll)
        chipStack.addArrangedSubview(allChip)

        for cat in allCategories {
            let chip = makeChip(id: cat.id, icon: cat.icon, title: cat.title)
            chipStack.addArrangedSubview(chip)
        }
    }

    private func makeChip(id: String?, icon: String, title: String) -> UIView {
        let isActive = (id == activeFilter)

        let container = UIControl()
        container.backgroundColor = isActive ? Theme.Color.primary : .white
        container.layer.cornerRadius = 18
        container.layer.borderWidth = isActive ? 0 : 1
        container.layer.borderColor = UIColor.systemGray5.cgColor
        container.layer.shadowColor   = UIColor.black.cgColor
        container.layer.shadowOpacity = isActive ? 0.08 : 0.04
        container.layer.shadowOffset  = CGSize(width: 0, height: 2)
        container.layer.shadowRadius  = 4

        let iconView = UIImageView(image: UIImage(systemName: icon,
            withConfiguration: UIImage.SymbolConfiguration(pointSize: 12, weight: .medium)))
        iconView.tintColor = isActive ? .white : Theme.Color.secondary
        iconView.contentMode = .scaleAspectFit
        iconView.translatesAutoresizingMaskIntoConstraints = false

        let label = UILabel()
        label.text = title
        label.font = Theme.Font.caption(weight: .semibold)
        label.textColor = isActive ? .white : Theme.Color.textPrimary
        label.translatesAutoresizingMaskIntoConstraints = false

        let stack = UIStackView(arrangedSubviews: [iconView, label])
        stack.axis    = .horizontal
        stack.spacing = 5
        stack.alignment = .center
        stack.isUserInteractionEnabled = false
        stack.translatesAutoresizingMaskIntoConstraints = false
        container.addSubview(stack)

        NSLayoutConstraint.activate([
            iconView.widthAnchor.constraint(equalToConstant: 14),
            iconView.heightAnchor.constraint(equalToConstant: 14),
            stack.leadingAnchor.constraint(equalTo: container.leadingAnchor, constant: 14),
            stack.trailingAnchor.constraint(equalTo: container.trailingAnchor, constant: -14),
            stack.centerYAnchor.constraint(equalTo: container.centerYAnchor),
            container.heightAnchor.constraint(equalToConstant: 36),
        ])

        // Store filter ID in accessibilityIdentifier for lookup
        container.accessibilityIdentifier = id ?? "__all__"
        container.addTarget(self, action: #selector(chipTapped(_:)), for: .touchUpInside)

        return container
    }

    // MARK: - Setup: FAQ Accordion Section

    private func setupFAQSection() {
        faqContainerStack.axis    = .vertical
        faqContainerStack.spacing = 12
        faqContainerStack.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(faqContainerStack)

        NSLayoutConstraint.activate([
            faqContainerStack.topAnchor.constraint(equalTo: chipScrollView.bottomAnchor, constant: 20),
            faqContainerStack.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 20),
            faqContainerStack.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -20),
        ])
    }

    // MARK: - Setup: Help Card Footer

    private func setupHelpCard() {
        helpCard.backgroundColor   = Theme.Color.primary
        helpCard.layer.cornerRadius = 20
        helpCard.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(helpCard)

        let iconView = UIImageView(image: UIImage(systemName: "questionmark.bubble.fill",
            withConfiguration: UIImage.SymbolConfiguration(pointSize: 28, weight: .medium)))
        iconView.tintColor = .white
        iconView.translatesAutoresizingMaskIntoConstraints = false

        let helpTitle = UILabel()
        helpTitle.text = L10n.faqHelpCardTitle
        helpTitle.font = Theme.Font.subtitle(weight: .bold)
        helpTitle.textColor = .white
        helpTitle.numberOfLines = 0
        helpTitle.translatesAutoresizingMaskIntoConstraints = false

        let helpDesc = UILabel()
        helpDesc.text = L10n.faqHelpCardDesc
        helpDesc.font = Theme.Font.caption(weight: .regular)
        helpDesc.textColor = UIColor.white.withAlphaComponent(0.85)
        helpDesc.numberOfLines = 0
        helpDesc.translatesAutoresizingMaskIntoConstraints = false

        let emailButton = UIButton(type: .system)
        emailButton.setTitle(L10n.faqEmailSupport, for: .normal)
        emailButton.setImage(UIImage(systemName: "envelope.fill",
            withConfiguration: UIImage.SymbolConfiguration(pointSize: 14, weight: .medium)), for: .normal)
        emailButton.tintColor = Theme.Color.primary
        emailButton.backgroundColor = .white
        emailButton.layer.cornerRadius = 14
        emailButton.titleLabel?.font = Theme.Font.body(weight: .semibold)
        emailButton.contentEdgeInsets = UIEdgeInsets(top: 12, left: 20, bottom: 12, right: 20)
        emailButton.imageEdgeInsets = UIEdgeInsets(top: 0, left: -6, bottom: 0, right: 0)
        emailButton.addTarget(self, action: #selector(emailTapped), for: .touchUpInside)
        emailButton.translatesAutoresizingMaskIntoConstraints = false

        [iconView, helpTitle, helpDesc, emailButton].forEach { helpCard.addSubview($0) }

        NSLayoutConstraint.activate([
            helpCard.topAnchor.constraint(equalTo: faqContainerStack.bottomAnchor, constant: 28),
            helpCard.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 20),
            helpCard.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -20),
            helpCard.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -140),

            iconView.topAnchor.constraint(equalTo: helpCard.topAnchor, constant: 24),
            iconView.leadingAnchor.constraint(equalTo: helpCard.leadingAnchor, constant: 24),
            iconView.widthAnchor.constraint(equalToConstant: 36),
            iconView.heightAnchor.constraint(equalToConstant: 36),

            helpTitle.topAnchor.constraint(equalTo: iconView.bottomAnchor, constant: 12),
            helpTitle.leadingAnchor.constraint(equalTo: helpCard.leadingAnchor, constant: 24),
            helpTitle.trailingAnchor.constraint(equalTo: helpCard.trailingAnchor, constant: -24),

            helpDesc.topAnchor.constraint(equalTo: helpTitle.bottomAnchor, constant: 8),
            helpDesc.leadingAnchor.constraint(equalTo: helpCard.leadingAnchor, constant: 24),
            helpDesc.trailingAnchor.constraint(equalTo: helpCard.trailingAnchor, constant: -24),

            emailButton.topAnchor.constraint(equalTo: helpDesc.bottomAnchor, constant: 20),
            emailButton.leadingAnchor.constraint(equalTo: helpCard.leadingAnchor, constant: 24),
            emailButton.bottomAnchor.constraint(equalTo: helpCard.bottomAnchor, constant: -24),
        ])
    }

    // MARK: - Reload FAQ Accordion

    private func reloadFAQ() {
        faqContainerStack.arrangedSubviews.forEach { $0.removeFromSuperview() }

        let categories = displayedCategories

        if categories.isEmpty {
            let emptyLabel = UILabel()
            emptyLabel.text = L10n.faqNoResults
            emptyLabel.font = Theme.Font.body(weight: .regular)
            emptyLabel.textColor = Theme.Color.textSecondary
            emptyLabel.textAlignment = .center
            emptyLabel.numberOfLines = 0
            faqContainerStack.addArrangedSubview(emptyLabel)
            return
        }

        for cat in categories {
            // Category header label
            let catLabel = UILabel()
            catLabel.text = cat.title.uppercased()
            catLabel.font = Theme.Font.caption(weight: .semibold)
            catLabel.textColor = Theme.Color.textSecondary
            faqContainerStack.addArrangedSubview(catLabel)
            faqContainerStack.setCustomSpacing(8, after: catLabel)

            // White card holding all items for this category
            let card = UIView()
            card.backgroundColor = Theme.Color.card
            card.layer.cornerRadius = 16
            card.layer.shadowColor   = UIColor.black.cgColor
            card.layer.shadowOpacity = 0.06
            card.layer.shadowOffset  = CGSize(width: 0, height: 2)
            card.layer.shadowRadius  = 8
            card.translatesAutoresizingMaskIntoConstraints = false

            let itemStack = UIStackView()
            itemStack.axis    = .vertical
            itemStack.spacing = 0
            itemStack.translatesAutoresizingMaskIntoConstraints = false
            card.addSubview(itemStack)

            NSLayoutConstraint.activate([
                itemStack.topAnchor.constraint(equalTo: card.topAnchor, constant: 4),
                itemStack.leadingAnchor.constraint(equalTo: card.leadingAnchor),
                itemStack.trailingAnchor.constraint(equalTo: card.trailingAnchor),
                itemStack.bottomAnchor.constraint(equalTo: card.bottomAnchor, constant: -4),
            ])

            for (qIndex, item) in cat.items.enumerated() {
                let key = "\(cat.id)|\(qIndex)"
                let isExpanded = expandedItems.contains(key)

                let row = FAQItemRow(
                    item: item,
                    isExpanded: isExpanded,
                    onToggle: { [weak self] in
                        self?.toggleItem(key: key)
                    }
                )
                itemStack.addArrangedSubview(row)

                if qIndex < cat.items.count - 1 {
                    let sep = UIView()
                    sep.backgroundColor = Theme.Color.background
                    sep.translatesAutoresizingMaskIntoConstraints = false
                    sep.heightAnchor.constraint(equalToConstant: 1).isActive = true
                    itemStack.addArrangedSubview(sep)
                }
            }

            faqContainerStack.addArrangedSubview(card)
            faqContainerStack.setCustomSpacing(20, after: card)
        }
    }

    // MARK: - Toggle accordion item

    private func toggleItem(key: String) {
        if expandedItems.contains(key) {
            expandedItems.remove(key)
        } else {
            expandedItems.insert(key)
        }
        UIView.animate(withDuration: 0.25, delay: 0,
                       usingSpringWithDamping: 0.85, initialSpringVelocity: 0) {
            self.reloadFAQ()
            self.view.layoutIfNeeded()
        }
    }

    // MARK: - Actions

    @objc private func backTapped() {
        navigationController?.popViewController(animated: true)
    }

    @objc private func chipTapped(_ sender: UIControl) {
        let rawID = sender.accessibilityIdentifier
        activeFilter = (rawID == "__all__") ? nil : rawID
        expandedItems.removeAll()
        buildChips()
        reloadFAQ()
    }

    @objc private func emailTapped() {
        let address = "apps@indonesiainyourhand.com"
        let subject = "Ask Support"
        let encoded = subject.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) ?? subject
        if let url = URL(string: "mailto:\(address)?subject=\(encoded)") {
            UIApplication.shared.open(url)
        }
    }
}

// MARK: - UISearchBarDelegate

extension FAQViewController: UISearchBarDelegate {
    func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
        self.searchText = searchText
        expandedItems.removeAll()
        reloadFAQ()
    }

    func searchBarSearchButtonClicked(_ searchBar: UISearchBar) {
        searchBar.resignFirstResponder()
    }
}

// MARK: - FAQItemRow (Accordion Row)

private final class FAQItemRow: UIView {

    private let questionLabel = UILabel()
    private let answerLabel   = UILabel()
    private let chevron       = UIImageView()

    var onToggle: (() -> Void)?

    init(item: FAQItem, isExpanded: Bool, onToggle: @escaping () -> Void) {
        self.onToggle = onToggle
        super.init(frame: .zero)
        setup(item: item, isExpanded: isExpanded)
    }

    required init?(coder: NSCoder) { fatalError() }

    private func setup(item: FAQItem, isExpanded: Bool) {
        // Chevron icon
        let chevronConfig = UIImage.SymbolConfiguration(pointSize: 12, weight: .semibold)
        chevron.image = UIImage(systemName: "chevron.down", withConfiguration: chevronConfig)
        chevron.tintColor = Theme.Color.textSecondary
        chevron.contentMode = .scaleAspectFit
        chevron.transform = isExpanded
            ? CGAffineTransform(rotationAngle: .pi)
            : .identity
        chevron.translatesAutoresizingMaskIntoConstraints = false

        // Question
        questionLabel.text = item.question
        questionLabel.font = Theme.Font.body(weight: .medium)
        questionLabel.textColor = Theme.Color.textPrimary
        questionLabel.numberOfLines = 0

        // Answer
        answerLabel.text = item.answer
        answerLabel.font = Theme.Font.caption(weight: .regular)
        answerLabel.textColor = Theme.Color.textSecondary
        answerLabel.numberOfLines = 0
        answerLabel.isHidden = !isExpanded

        let questionStack = UIStackView(arrangedSubviews: [questionLabel, chevron])
        questionStack.axis      = .horizontal
        questionStack.spacing   = 12
        questionStack.alignment = .top
        questionStack.translatesAutoresizingMaskIntoConstraints = false

        let mainStack = UIStackView(arrangedSubviews: [questionStack, answerLabel])
        mainStack.axis    = .vertical
        mainStack.spacing = 10
        mainStack.translatesAutoresizingMaskIntoConstraints = false
        addSubview(mainStack)

        NSLayoutConstraint.activate([
            chevron.widthAnchor.constraint(equalToConstant: 16),
            chevron.heightAnchor.constraint(equalToConstant: 16),

            mainStack.topAnchor.constraint(equalTo: topAnchor, constant: 16),
            mainStack.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 16),
            mainStack.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -16),
            mainStack.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -16),
        ])

        let tap = UITapGestureRecognizer(target: self, action: #selector(rowTapped))
        addGestureRecognizer(tap)
        isUserInteractionEnabled = true
    }

    @objc private func rowTapped() { onToggle?() }
}