import UIKit

// MARK: - 设置面板

/// EPUB 阅读器的设置面板控制器
/// 提供亮度、字号、行距、翻页方式、主题的调节功能
/// 支持 iOS 13+ SF Symbols 和低版本文字回退
final class RDEPUBReaderSettingsViewController: UIViewController {
    // MARK: 回调闭包

    /// 亮度变化回调（0.0 ~ 1.0）
    var onBrightnessChange: ((CGFloat) -> Void)?
    /// 字号变化回调（pt 值）
    var onFontSizeChange: ((CGFloat) -> Void)?
    /// 字体变化回调
    var onFontChoiceChange: ((RDEPUBReaderFontChoice) -> Void)?
    /// 行距倍数变化回调
    var onLineHeightChange: ((CGFloat) -> Void)?
    /// 栏数变化回调
    var onColumnCountChange: ((Int) -> Void)?
    /// 翻页模式变化回调
    var onDisplayTypeChange: ((RDReaderView.DisplayType) -> Void)?
    /// 主题变化回调
    var onThemeChange: ((RDEPUBReaderTheme) -> Void)?
    /// 设置页面关闭回调
    var onDismiss: (() -> Void)?

    // MARK: 主题预设枚举

    /// 设置面板中的主题预设枚举，用于按钮显示和主题切换
    private enum ThemePreset: Int, CaseIterable {
        case light
        case yellow
        case green
        case pink
        case blue
        case dark

        var title: String {
            switch self {
            case .light: return "浅色"
            case .yellow: return "米黄"
            case .green: return "青绿"
            case .pink: return "粉色"
            case .blue: return "蓝灰"
            case .dark: return "夜间"
            }
        }

        var theme: RDEPUBReaderTheme {
            switch self {
            case .light: return .light
            case .yellow: return .yellow
            case .green: return .green
            case .pink: return .pink
            case .blue: return .blue
            case .dark: return .dark
            }
        }
    }

    private let scrollView = UIScrollView()
    private let contentStack: UIStackView = {
        let stackView = UIStackView()
        stackView.axis = .vertical
        stackView.spacing = 20
        return stackView
    }()
    private let brightnessSlider = UISlider()
    private let fontValueLabel = UILabel()
    private let decreaseFontButton = UIButton(type: .system)
    private let increaseFontButton = UIButton(type: .system)
    private let fontChoiceControl = UISegmentedControl(items: RDEPUBReaderFontChoice.allCases.map(\.displayName))
    private let lineHeightControl = UISegmentedControl(items: ["紧凑", "标准", "宽松"])
    private let columnCountControl = UISegmentedControl(items: ["单栏", "双栏"])
    private let displayTypeControl = UISegmentedControl(items: ["仿真", "横滑", "竖滑"])
    private let themeStackView: UIStackView = {
        let stackView = UIStackView()
        stackView.axis = .horizontal
        stackView.distribution = .fillEqually
        stackView.spacing = 12
        return stackView
    }()
    private var themeButtons: [UIButton] = []

    /// 行距选项对应的倍数值（紧凑 1.3、标准 1.6、宽松 1.9）
    private let lineHeightValues: [CGFloat] = [1.3, 1.6, 1.9]
    /// 当前配置的本地副本，修改后通过回调通知控制器
    private var currentConfiguration: RDEPUBReaderConfiguration

    init(configuration: RDEPUBReaderConfiguration, brightness: CGFloat) {
        self.currentConfiguration = configuration
        super.init(nibName: nil, bundle: nil)
        brightnessSlider.value = Float(brightness)
        title = "样式设置"
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        setupNavigationItems()
        setupViews()
        syncControls()
        applyTheme(currentConfiguration.theme)
    }

    private func setupNavigationItems() {
        let doneItem = UIBarButtonItem(title: "完成", style: .done, target: self, action: #selector(doneAction))
        doneItem.accessibilityIdentifier = "epub.reader.settings.done"
        navigationItem.rightBarButtonItem = doneItem
    }

    private func setupViews() {
        view.addSubview(scrollView)
        scrollView.accessibilityIdentifier = "epub.reader.settings.scroll"
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.addSubview(contentStack)
        contentStack.translatesAutoresizingMaskIntoConstraints = false

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

            contentStack.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor, constant: 16),
            contentStack.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor, constant: -16),
            contentStack.topAnchor.constraint(equalTo: scrollView.topAnchor, constant: 20),
            contentStack.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor, constant: -24),
            contentStack.widthAnchor.constraint(equalTo: scrollView.widthAnchor, constant: -32)
        ])

        brightnessSlider.minimumValue = 0
        brightnessSlider.maximumValue = 1
        brightnessSlider.accessibilityIdentifier = "epub.reader.settings.brightness"
        brightnessSlider.addTarget(self, action: #selector(brightnessChanged(_:)), for: .valueChanged)

        fontValueLabel.font = UIFont.monospacedDigitSystemFont(ofSize: 16, weight: .semibold)
        fontValueLabel.textAlignment = .center
        fontValueLabel.accessibilityIdentifier = "epub.reader.settings.font.value"
        fontValueLabel.setContentHuggingPriority(.required, for: .horizontal)

        configureFontButton(decreaseFontButton, title: "A-")
        configureFontButton(increaseFontButton, title: "A+")
        decreaseFontButton.accessibilityIdentifier = "epub.reader.settings.font.decrease"
        increaseFontButton.accessibilityIdentifier = "epub.reader.settings.font.increase"
        decreaseFontButton.addTarget(self, action: #selector(decreaseFontAction), for: .touchUpInside)
        increaseFontButton.addTarget(self, action: #selector(increaseFontAction), for: .touchUpInside)

        lineHeightControl.accessibilityIdentifier = "epub.reader.settings.lineHeight"
        fontChoiceControl.accessibilityIdentifier = "epub.reader.settings.font.choice"
        columnCountControl.accessibilityIdentifier = "epub.reader.settings.columns"
        displayTypeControl.accessibilityIdentifier = "epub.reader.settings.displayType"
        fontChoiceControl.addTarget(self, action: #selector(fontChoiceChanged(_:)), for: .valueChanged)
        lineHeightControl.addTarget(self, action: #selector(lineHeightChanged(_:)), for: .valueChanged)
        columnCountControl.addTarget(self, action: #selector(columnCountChanged(_:)), for: .valueChanged)
        displayTypeControl.addTarget(self, action: #selector(displayTypeChanged(_:)), for: .valueChanged)

        ThemePreset.allCases.forEach { preset in
            let button = UIButton(type: .system)
            button.tag = preset.rawValue
            button.layer.cornerRadius = 18
            button.layer.borderWidth = 1.5
            button.backgroundColor = preset.theme.contentBackgroundColor
            button.accessibilityLabel = preset.title
            button.accessibilityIdentifier = "epub.reader.settings.theme.\(preset.rawValue)"
            button.addTarget(self, action: #selector(themeButtonAction(_:)), for: .touchUpInside)
            themeButtons.append(button)
            themeStackView.addArrangedSubview(button)
            NSLayoutConstraint.activate([
                button.heightAnchor.constraint(equalToConstant: 36)
            ])
        }

        contentStack.addArrangedSubview(makeSection(title: "亮度", content: brightnessSlider))
        contentStack.addArrangedSubview(makeSection(title: "字号", content: makeFontSizeRow()))
        contentStack.addArrangedSubview(makeSection(title: "字体", content: fontChoiceControl))
        contentStack.addArrangedSubview(makeSection(title: "行距", content: lineHeightControl))
        contentStack.addArrangedSubview(makeSection(title: "分栏", content: columnCountControl))
        contentStack.addArrangedSubview(makeSection(title: "翻页方式", content: displayTypeControl))
        contentStack.addArrangedSubview(makeSection(title: "主题", content: themeStackView))
    }

    private func makeSection(title: String, content: UIView) -> UIView {
        let container = UIStackView()
        container.axis = .vertical
        container.spacing = 10

        let titleLabel = UILabel()
        titleLabel.text = title
        titleLabel.font = UIFont.systemFont(ofSize: 14, weight: .semibold)

        content.translatesAutoresizingMaskIntoConstraints = false
        container.addArrangedSubview(titleLabel)
        container.addArrangedSubview(content)
        return container
    }

    private func makeFontSizeRow() -> UIView {
        let stackView = UIStackView(arrangedSubviews: [decreaseFontButton, fontValueLabel, increaseFontButton])
        stackView.axis = .horizontal
        stackView.alignment = .center
        stackView.distribution = .fill
        stackView.spacing = 12

        NSLayoutConstraint.activate([
            decreaseFontButton.widthAnchor.constraint(equalToConstant: 64),
            increaseFontButton.widthAnchor.constraint(equalToConstant: 64),
            decreaseFontButton.heightAnchor.constraint(equalToConstant: 36),
            increaseFontButton.heightAnchor.constraint(equalToConstant: 36)
        ])
        return stackView
    }

    private func configureFontButton(_ button: UIButton, title: String) {
        button.setTitle(title, for: .normal)
        button.titleLabel?.font = UIFont.systemFont(ofSize: 16, weight: .semibold)
        button.layer.cornerRadius = 18
        button.layer.borderWidth = 1
    }

    private func syncControls() {
        fontValueLabel.text = String(Int(currentConfiguration.fontSize.rounded()))
        fontChoiceControl.selectedSegmentIndex = RDEPUBReaderFontChoice.allCases.firstIndex(of: currentConfiguration.fontChoice) ?? 0

        let lineHeightIndex = lineHeightValues.enumerated().min { abs($0.element - currentConfiguration.lineHeightMultiple) < abs($1.element - currentConfiguration.lineHeightMultiple) }?.offset ?? 1
        lineHeightControl.selectedSegmentIndex = lineHeightIndex
        columnCountControl.selectedSegmentIndex = currentConfiguration.numberOfColumns > 1 ? 1 : 0

        switch currentConfiguration.displayType {
        case .pageCurl:
            displayTypeControl.selectedSegmentIndex = 0
        case .horizontalScroll:
            displayTypeControl.selectedSegmentIndex = 1
        case .verticalScroll:
            displayTypeControl.selectedSegmentIndex = 2
        }

        let selectedPreset = ThemePreset.allCases.first(where: { $0.theme == currentConfiguration.theme }) ?? .light
        updateThemeSelection(selectedPreset)
        updateControlAccessibilityValues()
    }

    private func applyTheme(_ theme: RDEPUBReaderTheme) {
        view.backgroundColor = theme.contentBackgroundColor
        scrollView.backgroundColor = theme.contentBackgroundColor
        contentStack.arrangedSubviews
            .compactMap { $0 as? UIStackView }
            .flatMap { $0.arrangedSubviews }
            .compactMap { $0 as? UILabel }
            .forEach { $0.textColor = theme.contentTextColor }

        fontValueLabel.textColor = theme.contentTextColor
        [decreaseFontButton, increaseFontButton].forEach { button in
            button.setTitleColor(theme.toolControlTextColor, for: .normal)
            button.layer.borderColor = theme.toolControlBorderUnselectColor.cgColor
            button.backgroundColor = theme.toolBackgroundColor
        }

        [fontChoiceControl, lineHeightControl, columnCountControl, displayTypeControl].forEach { control in
            control.backgroundColor = theme.toolBackgroundColor
            if #available(iOS 13.0, *) {
                control.selectedSegmentTintColor = theme.toolControlTextColor.withAlphaComponent(0.14)
            } else {
                control.tintColor = theme.toolControlTextColor
            }
            control.setTitleTextAttributes([.foregroundColor: theme.contentTextColor], for: .normal)
            control.setTitleTextAttributes([.foregroundColor: theme.toolControlTextColor], for: .selected)
        }

        navigationController?.navigationBar.tintColor = theme.toolControlTextColor
        navigationController?.navigationBar.barTintColor = theme.toolBackgroundColor
        navigationController?.navigationBar.titleTextAttributes = [.foregroundColor: theme.toolControlTextColor]
        updateThemeSelection(ThemePreset.allCases.first(where: { $0.theme == theme }) ?? .light)
    }

    private func updateThemeSelection(_ preset: ThemePreset) {
        themeButtons.forEach { button in
            let isSelected = button.tag == preset.rawValue
            button.layer.borderWidth = isSelected ? 2 : 1
            button.layer.borderColor = isSelected ? currentConfiguration.theme.toolControlTextColor.cgColor : currentConfiguration.theme.toolControlBorderUnselectColor.cgColor
            button.accessibilityValue = isSelected ? "selected" : "unselected"
        }
    }

    private func updateControlAccessibilityValues() {
        fontChoiceControl.accessibilityValue = fontChoiceControl.titleForSegment(at: fontChoiceControl.selectedSegmentIndex)
        lineHeightControl.accessibilityValue = lineHeightControl.titleForSegment(at: lineHeightControl.selectedSegmentIndex)
        columnCountControl.accessibilityValue = columnCountControl.titleForSegment(at: columnCountControl.selectedSegmentIndex)
        displayTypeControl.accessibilityValue = displayTypeControl.titleForSegment(at: displayTypeControl.selectedSegmentIndex)
    }

    @objc private func doneAction() {
        dismiss(animated: true) { [weak self] in
            self?.onDismiss?()
        }
    }

    @objc private func brightnessChanged(_ slider: UISlider) {
        onBrightnessChange?(CGFloat(slider.value))
    }

    @objc private func decreaseFontAction() {
        let nextValue = max(12, currentConfiguration.fontSize - 1)
        guard nextValue != currentConfiguration.fontSize else { return }
        currentConfiguration.fontSize = nextValue
        fontValueLabel.text = String(Int(nextValue.rounded()))
        onFontSizeChange?(nextValue)
    }

    @objc private func increaseFontAction() {
        let nextValue = min(36, currentConfiguration.fontSize + 1)
        guard nextValue != currentConfiguration.fontSize else { return }
        currentConfiguration.fontSize = nextValue
        fontValueLabel.text = String(Int(nextValue.rounded()))
        onFontSizeChange?(nextValue)
    }

    @objc private func fontChoiceChanged(_ control: UISegmentedControl) {
        let choices = RDEPUBReaderFontChoice.allCases
        let index = max(0, min(control.selectedSegmentIndex, choices.count - 1))
        let choice = choices[index]
        guard choice != currentConfiguration.fontChoice else { return }
        currentConfiguration.fontChoice = choice
        updateControlAccessibilityValues()
        onFontChoiceChange?(choice)
    }

    @objc private func lineHeightChanged(_ control: UISegmentedControl) {
        let index = max(0, min(control.selectedSegmentIndex, lineHeightValues.count - 1))
        let value = lineHeightValues[index]
        currentConfiguration.lineHeightMultiple = value
        updateControlAccessibilityValues()
        onLineHeightChange?(value)
    }

    @objc private func columnCountChanged(_ control: UISegmentedControl) {
        let numberOfColumns = control.selectedSegmentIndex == 1 ? 2 : 1
        currentConfiguration.numberOfColumns = numberOfColumns
        updateControlAccessibilityValues()
        onColumnCountChange?(numberOfColumns)
    }

    @objc private func displayTypeChanged(_ control: UISegmentedControl) {
        let displayType: RDReaderView.DisplayType
        switch control.selectedSegmentIndex {
        case 1:
            displayType = .horizontalScroll
        case 2:
            displayType = .verticalScroll
        default:
            displayType = .pageCurl
        }
        currentConfiguration.displayType = displayType
        updateControlAccessibilityValues()
        onDisplayTypeChange?(displayType)
    }

    @objc private func themeButtonAction(_ sender: UIButton) {
        guard let preset = ThemePreset(rawValue: sender.tag) else { return }
        currentConfiguration.theme = preset.theme
        applyTheme(preset.theme)
        onThemeChange?(preset.theme)
    }
}