//
//  TravelAlbumAutoRetouchSettingSheetViewController.swift
//  suixinkan
//

import SnapKit
import UIKit

/// 自动 AI 修图设置 Sheet，先选修图方式，选择 AI 修图后再选带效果图的模板。
final class TravelAlbumAutoRetouchSettingSheetViewController: BaseViewController, UITableViewDelegate {
    private enum Step: Equatable {
        case mode
        case template
    }

    private enum Item: Hashable {
        case mode(TravelAlbumRetouchMode)
        case template(TravelAlbumEditPreset)
    }

    var onConfirm: ((TravelAlbumAutoRetouchConfiguration) -> Void)?
    var onCancelled: (() -> Void)?

    private let startsWithModeSelection: Bool
    private let backButton = UIButton(type: .system)
    private let titleLabel = UILabel()
    private let subtitleLabel = UILabel()
    private let tableView = UITableView(frame: .zero, style: .plain)
    private let cancelButton = UIButton(type: .system)
    private let confirmButton = UIButton(type: .system)
    private var dataSource: UITableViewDiffableDataSource<Int, Item>!
    private var step: Step
    private var pendingConfiguration: TravelAlbumAutoRetouchConfiguration
    private var selectedItem: Item?
    private var previewImages: [TravelAlbumEditPreset.Effect: UIImage] = [:]
    private var didConfirm = false

    /// 创建自动修图设置 Sheet。
    /// - Parameters:
    ///   - configuration: 当前配置，用于回显已选方式和模板。
    ///   - startsWithModeSelection: 是否先展示“不修图 / AI 修图”两个一级选项。
    init(
        configuration: TravelAlbumAutoRetouchConfiguration,
        startsWithModeSelection: Bool
    ) {
        self.startsWithModeSelection = startsWithModeSelection
        step = startsWithModeSelection ? .mode : .template
        pendingConfiguration = configuration
        if startsWithModeSelection {
            selectedItem = .mode(configuration.isEnabled ? .aiRetouch : .disabled)
        } else if let template = configuration.template {
            selectedItem = .template(template)
        }
        super.init(nibName: nil, bundle: nil)
        modalPresentationStyle = .pageSheet
        if let sheetPresentationController {
            let identifier = UISheetPresentationController.Detent.Identifier("travelAlbumAutoRetouchSetting")
            sheetPresentationController.detents = [
                .custom(identifier: identifier) { context in
                    min(660, context.maximumDetentValue)
                },
                .large(),
            ]
            sheetPresentationController.selectedDetentIdentifier = identifier
            sheetPresentationController.prefersGrabberVisible = false
            sheetPresentationController.preferredCornerRadius = AppRadius.xl
        }
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func setupNavigationBar() {}

    override func setupUI() {
        view.backgroundColor = .white

        backButton.setImage(UIImage(systemName: "chevron.left"), for: .normal)
        backButton.tintColor = AppColor.textPrimary
        backButton.accessibilityLabel = "返回修图方式"

        titleLabel.font = .systemFont(ofSize: 18, weight: .semibold)
        titleLabel.textColor = AppColor.textPrimary
        titleLabel.textAlignment = .center

        subtitleLabel.font = .app(.caption)
        subtitleLabel.textColor = AppColor.textSecondary
        subtitleLabel.textAlignment = .center
        subtitleLabel.numberOfLines = 0

        tableView.backgroundColor = .white
        tableView.separatorStyle = .none
        tableView.showsVerticalScrollIndicator = false
        tableView.delegate = self
        tableView.register(
            TravelAlbumAutoRetouchOptionCell.self,
            forCellReuseIdentifier: TravelAlbumAutoRetouchOptionCell.reuseIdentifier
        )

        dataSource = UITableViewDiffableDataSource<Int, Item>(tableView: tableView) {
            [weak self] tableView, indexPath, item in
            let cell = tableView.dequeueReusableCell(
                withIdentifier: TravelAlbumAutoRetouchOptionCell.reuseIdentifier,
                for: indexPath
            ) as! TravelAlbumAutoRetouchOptionCell
            guard let self else { return cell }
            switch item {
            case .mode(let mode):
                let iconName = mode == .disabled ? "photo" : "wand.and.stars"
                let detail = mode == .disabled
                    ? "保留照片原效果"
                    : (self.pendingConfiguration.template.map { "当前模板：\($0.title)" } ?? "选择后需再选一个修图模板")
                cell.apply(
                    title: mode.title,
                    detail: detail,
                    previewImage: UIImage(systemName: iconName),
                    usesTemplateImage: true,
                    selected: self.selectedItem == item
                )
            case .template(let preset):
                cell.apply(
                    title: preset.title,
                    detail: preset.autoRetouchEffectDescription,
                    previewImage: self.previewImage(for: preset),
                    usesTemplateImage: false,
                    selected: self.selectedItem == item
                )
            }
            return cell
        }

        configureActionButton(cancelButton, title: "取消", isPrimary: false)
        configureActionButton(confirmButton, title: "确定", isPrimary: true)
        let buttonStack = UIStackView(arrangedSubviews: [cancelButton, confirmButton])
        buttonStack.axis = .horizontal
        buttonStack.spacing = AppSpacing.sm
        buttonStack.distribution = .fillEqually

        view.addSubview(backButton)
        view.addSubview(titleLabel)
        view.addSubview(subtitleLabel)
        view.addSubview(tableView)
        view.addSubview(buttonStack)

        backButton.snp.makeConstraints { make in
            make.leading.equalToSuperview().offset(AppSpacing.md)
            make.centerY.equalTo(titleLabel)
            make.size.equalTo(AppSpacing.minTouchTarget)
        }
        titleLabel.snp.makeConstraints { make in
            make.top.equalToSuperview().offset(AppSpacing.lg)
            make.leading.trailing.equalToSuperview().inset(60)
        }
        subtitleLabel.snp.makeConstraints { make in
            make.top.equalTo(titleLabel.snp.bottom).offset(AppSpacing.xs)
            make.leading.trailing.equalToSuperview().inset(AppSpacing.lg)
        }
        tableView.snp.makeConstraints { make in
            make.top.equalTo(subtitleLabel.snp.bottom).offset(AppSpacing.md)
            make.leading.trailing.equalToSuperview().inset(AppSpacing.md)
            make.bottom.equalTo(buttonStack.snp.top).offset(-AppSpacing.sm)
        }
        buttonStack.snp.makeConstraints { make in
            make.leading.trailing.equalToSuperview().inset(AppSpacing.md)
            make.bottom.equalTo(view.safeAreaLayoutGuide).offset(-AppSpacing.md)
            make.height.equalTo(AppSpacing.minTouchTarget)
        }

        refreshContent()
    }

    override func bindActions() {
        backButton.addTarget(self, action: #selector(backTapped), for: .touchUpInside)
        cancelButton.addTarget(self, action: #selector(cancelTapped), for: .touchUpInside)
        confirmButton.addTarget(self, action: #selector(confirmTapped), for: .touchUpInside)
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        if isBeingDismissed, !didConfirm {
            onCancelled?()
        }
    }

    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        step == .mode ? 80 : 108
    }

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)
        guard let item = dataSource.itemIdentifier(for: indexPath) else { return }
        switch item {
        case .mode(.disabled):
            pendingConfiguration = .disabled
            selectedItem = item
            applySnapshot()
            updateConfirmButton()
        case .mode(.aiRetouch):
            step = .template
            selectedItem = pendingConfiguration.template.map(Item.template)
            refreshContent()
        case .template(let preset):
            pendingConfiguration = .enabled(templateID: preset.id)
            selectedItem = item
            applySnapshot()
            updateConfirmButton()
        }
    }

    private func refreshContent() {
        switch step {
        case .mode:
            titleLabel.text = "选择修图方式"
            subtitleLabel.text = "照片上传前可选择保留原图，或使用 AI 自动修图"
            backButton.isHidden = true
        case .template:
            titleLabel.text = "选择修图模板"
            subtitleLabel.text = "缩略图为模板实际效果，后续上传的照片将自动套用"
            backButton.isHidden = !startsWithModeSelection
        }
        applySnapshot()
        updateConfirmButton()
    }

    private func applySnapshot() {
        var snapshot = NSDiffableDataSourceSnapshot<Int, Item>()
        snapshot.appendSections([0])
        switch step {
        case .mode:
            snapshot.appendItems(TravelAlbumRetouchMode.allCases.map(Item.mode))
        case .template:
            snapshot.appendItems(TravelAlbumEditPreset.autoRetouchOptions.map(Item.template))
        }

        // 选中状态存放在页面状态中，item 本身的标识不会变化。
        // Diffable Data Source 不会主动重新配置相同 item，因此需显式刷新仍在当前列表中的选项。
        let currentItems = Set(dataSource.snapshot().itemIdentifiers)
        let retainedItems = snapshot.itemIdentifiers.filter(currentItems.contains)
        snapshot.reconfigureItems(retainedItems)
        dataSource.apply(snapshot, animatingDifferences: false)
    }

    private func updateConfirmButton() {
        let isEnabled: Bool
        switch selectedItem {
        case .mode(.disabled):
            isEnabled = step == .mode
        case .mode(.aiRetouch):
            isEnabled = step == .mode && pendingConfiguration.isEnabled && pendingConfiguration.isValid
        case .template:
            isEnabled = step == .template && pendingConfiguration.isEnabled && pendingConfiguration.isValid
        case nil:
            isEnabled = false
        }
        confirmButton.isEnabled = isEnabled
        confirmButton.alpha = isEnabled ? 1 : 0.45
    }

    private func configureActionButton(_ button: UIButton, title: String, isPrimary: Bool) {
        button.setTitle(title, for: .normal)
        button.setTitleColor(isPrimary ? .white : AppColor.textSecondary, for: .normal)
        button.titleLabel?.font = .app(.subtitle)
        button.backgroundColor = isPrimary ? AppColor.primary : AppColor.inputBackground
        button.layer.cornerRadius = AppRadius.md
    }

    private func previewImage(for preset: TravelAlbumEditPreset) -> UIImage? {
        if let image = previewImages[preset.effect] {
            return image
        }
        guard let source = makePreviewSourceImage() else { return nil }
        let image = TravelAlbumAIEditImageProcessor.render(effect: preset.effect, source: source)
        previewImages[preset.effect] = image
        return image
    }

    private func makePreviewSourceImage() -> UIImage? {
        guard let source = UIImage(named: "purchased_lakeside_flowers") else { return nil }
        let size = CGSize(width: 176, height: 176)
        return UIGraphicsImageRenderer(size: size).image { _ in
            let scale = max(size.width / source.size.width, size.height / source.size.height)
            let drawSize = CGSize(width: source.size.width * scale, height: source.size.height * scale)
            let origin = CGPoint(x: (size.width - drawSize.width) / 2, y: (size.height - drawSize.height) / 2)
            source.draw(in: CGRect(origin: origin, size: drawSize))
        }
    }

    @objc private func backTapped() {
        guard startsWithModeSelection else { return }
        step = .mode
        selectedItem = .mode(pendingConfiguration.isEnabled ? .aiRetouch : .disabled)
        refreshContent()
    }

    @objc private func cancelTapped() {
        dismiss(animated: true)
    }

    @objc private func confirmTapped() {
        guard confirmButton.isEnabled else { return }
        didConfirm = true
        onConfirm?(pendingConfiguration)
        dismiss(animated: true)
    }
}

/// 自动修图选项行，一级方式显示图标，模板显示本地生成的真实效果缩略图。
private final class TravelAlbumAutoRetouchOptionCell: UITableViewCell {
    static let reuseIdentifier = "TravelAlbumAutoRetouchOptionCell"

    private let cardView = UIView()
    private let previewImageView = UIImageView()
    private let titleLabel = UILabel()
    private let detailLabel = UILabel()
    private let selectionImageView = UIImageView()

    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        selectionStyle = .none
        backgroundColor = .clear

        cardView.layer.cornerRadius = AppRadius.sm
        cardView.layer.borderWidth = 1
        previewImageView.clipsToBounds = true
        previewImageView.layer.cornerRadius = AppRadius.xs
        titleLabel.font = .app(.bodyMedium)
        titleLabel.textColor = AppColor.textPrimary
        detailLabel.font = .app(.caption)
        detailLabel.textColor = AppColor.textTertiary
        detailLabel.numberOfLines = 2
        selectionImageView.contentMode = .scaleAspectFit

        contentView.addSubview(cardView)
        cardView.addSubview(previewImageView)
        cardView.addSubview(titleLabel)
        cardView.addSubview(detailLabel)
        cardView.addSubview(selectionImageView)

        cardView.snp.makeConstraints { make in
            make.edges.equalToSuperview().inset(UIEdgeInsets(top: 4, left: 0, bottom: 4, right: 0))
        }
        previewImageView.snp.makeConstraints { make in
            make.top.bottom.leading.equalToSuperview().inset(8)
            make.width.equalTo(88)
        }
        titleLabel.snp.makeConstraints { make in
            make.leading.equalTo(previewImageView.snp.trailing).offset(AppSpacing.sm)
            make.trailing.lessThanOrEqualTo(selectionImageView.snp.leading).offset(-AppSpacing.sm)
            make.bottom.equalTo(cardView.snp.centerY).offset(-2)
        }
        detailLabel.snp.makeConstraints { make in
            make.top.equalTo(cardView.snp.centerY).offset(2)
            make.leading.trailing.equalTo(titleLabel)
        }
        selectionImageView.snp.makeConstraints { make in
            make.trailing.equalToSuperview().offset(-AppSpacing.md)
            make.centerY.equalToSuperview()
            make.size.equalTo(22)
        }
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    /// 刷新选项文案、效果图与单选外观。
    func apply(
        title: String,
        detail: String,
        previewImage: UIImage?,
        usesTemplateImage: Bool,
        selected: Bool
    ) {
        titleLabel.text = title
        detailLabel.text = detail
        previewImageView.image = usesTemplateImage
            ? previewImage?.withConfiguration(UIImage.SymbolConfiguration(pointSize: 28, weight: .medium))
            : previewImage
        previewImageView.contentMode = usesTemplateImage ? .center : .scaleAspectFill
        previewImageView.tintColor = AppColor.primary
        previewImageView.backgroundColor = usesTemplateImage ? AppColor.primaryLight : AppColor.pageBackground
        cardView.backgroundColor = selected ? AppColor.primaryLight : .white
        cardView.layer.borderColor = (selected ? AppColor.primary : AppColor.border).cgColor
        selectionImageView.image = UIImage(systemName: selected ? "checkmark.circle.fill" : "circle")
        selectionImageView.tintColor = selected ? AppColor.primary : AppColor.textTertiary
        accessibilityLabel = "\(title)，\(detail)"
        accessibilityValue = selected ? "已选择" : "未选择"
    }
}

private extension TravelAlbumEditPreset {
    /// 模板效果的简短说明，与缩略图一起帮助用户判断效果。
    var autoRetouchEffectDescription: String {
        switch effect {
        case .original:
            return "保留原图色彩"
        case .portrait:
            return "明亮柔和的人像质感"
        case .vintage:
            return "低饱和复古色调"
        case .brocade:
            return "鲜活通透的旅拍风格"
        case .distantMountain:
            return "自然淡雅的远山色调"
        case .mist:
            return "轻雾低对比氛围"
        case .summer:
            return "温暖明亮的油画色彩"
        case .rich:
            return "高饱和浓郁油画质感"
        }
    }
}