import SnapKit
import UIKit

/// 相册自动修图设置：在同一页切换修图方式、展开模板并确认草稿。
final class TravelAlbumAutoRetouchSettingSheetViewController: BaseViewController {
    /// 确认草稿后通知调用方保存相册配置。
    var onConfirm: ((TravelAlbumAutoRetouchConfiguration) -> Void)?

    private let viewModel: TravelAlbumAutoRetouchSettingViewModel
    private let api: any TravelAlbumServing
    private let titleLabel = UILabel()
    private let subtitleLabel = UILabel()
    private let headerStack = UIStackView()
    private let modeStack = UIStackView()
    private let originalOption = AutoRetouchModeControl(title: "不修图", detail: "保留相机原始照片", symbol: "photo")
    private let aiOption = AutoRetouchModeControl(title: "AI 修图", detail: "上传后自动套用模板", symbol: "wand.and.stars")
    private let contentRegion = UIView()
    private let templateHeader = UIStackView()
    private lazy var templateCollectionView = UICollectionView(frame: .zero, collectionViewLayout: makeTemplateLayout())
    private var templateDataSource: UICollectionViewDiffableDataSource<Int, TravelAlbumAIRetouchTemplate>!
    private let originalHint = UIStackView()
    private let statusStack = UIStackView()
    private let activityIndicator = UIActivityIndicatorView(style: .medium)
    private let statusLabel = UILabel()
    private let retryButton = UIButton(type: .system)
    private let footer = UIView()
    private let selectionLabel = UILabel()
    private let cancelButton = UIButton(type: .system)
    private let confirmButton = UIButton(type: .system)
    private var lastTemplatesVisible: Bool?

    /// 创建设置 Sheet；方式选择与模板区域共用同一份配置草稿。
    init(viewModel: TravelAlbumAutoRetouchSettingViewModel, api: any TravelAlbumServing) {
        self.viewModel = viewModel
        self.api = api
        super.init(nibName: nil, bundle: nil)
        modalPresentationStyle = .pageSheet
        if let sheet = sheetPresentationController {
            sheet.detents = [.large()]
            sheet.selectedDetentIdentifier = .large
            sheet.prefersGrabberVisible = true
            sheet.preferredCornerRadius = 24
        }
    }

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

    override func setupUI() {
        view.backgroundColor = UIColor(hex: 0xF6F8FC)
        titleLabel.text = viewModel.allowsModeSelection ? "选择修图方式" : "选择修图模板"
        titleLabel.font = .systemFont(ofSize: 22, weight: .bold)
        titleLabel.textColor = AppColor.textPrimary
        titleLabel.accessibilityTraits = .header
        subtitleLabel.text = "设置仅对后续上传的照片生效"
        subtitleLabel.font = .systemFont(ofSize: 13)
        subtitleLabel.textColor = AppColor.textSecondary
        headerStack.axis = .vertical
        headerStack.spacing = 8
        headerStack.addArrangedSubview(titleLabel)
        headerStack.addArrangedSubview(subtitleLabel)
        headerStack.setCustomSpacing(20, after: subtitleLabel)
        modeStack.axis = .horizontal
        modeStack.distribution = .fillEqually
        modeStack.spacing = 12
        modeStack.accessibilityIdentifier = "travelAlbum.autoRetouchModeOptions"
        originalOption.accessibilityIdentifier = "travelAlbum.autoRetouchOriginalOption"
        aiOption.accessibilityIdentifier = "travelAlbum.autoRetouchAIOption"
        modeStack.addArrangedSubview(originalOption)
        modeStack.addArrangedSubview(aiOption)
        headerStack.addArrangedSubview(modeStack)
        modeStack.isHidden = !viewModel.allowsModeSelection

        let templateTitle = UILabel()
        templateTitle.text = viewModel.allowsModeSelection ? "选择修图模板" : "精修模板"
        templateTitle.font = .systemFont(ofSize: 17, weight: .semibold)
        templateTitle.textColor = AppColor.textPrimary
        templateTitle.accessibilityTraits = .header
        let templateTips = UILabel()
        templateTips.text = "单选模板 · 点击预览查看前后效果"
        templateTips.font = .systemFont(ofSize: 12)
        templateTips.textColor = AppColor.textSecondary
        templateHeader.axis = .vertical
        templateHeader.spacing = 5
        templateHeader.addArrangedSubview(templateTitle)
        templateHeader.addArrangedSubview(templateTips)

        templateCollectionView.backgroundColor = .clear
        templateCollectionView.alwaysBounceVertical = true
        templateCollectionView.accessibilityIdentifier = "travelAlbum.autoRetouchTemplateCollection"
        templateCollectionView.delegate = self
        templateCollectionView.register(TravelAlbumAIRetouchTemplateCell.self,
            forCellWithReuseIdentifier: TravelAlbumAIRetouchTemplateCell.reuseIdentifier)
        configureDataSource()

        let hintIcon = UIImageView(image: UIImage(systemName: "photo.on.rectangle.angled"))
        hintIcon.tintColor = AppColor.primary.withAlphaComponent(0.6)
        hintIcon.contentMode = .scaleAspectFit
        let hintTitle = UILabel()
        hintTitle.text = "保留原图，直接上传"
        hintTitle.font = .systemFont(ofSize: 17, weight: .semibold)
        hintTitle.textColor = AppColor.textPrimary
        let hintDetail = UILabel()
        hintDetail.text = "选择上方 AI 修图，即可在这里挑选模板"
        hintDetail.font = .systemFont(ofSize: 13)
        hintDetail.textColor = AppColor.textSecondary
        hintDetail.numberOfLines = 2
        hintDetail.textAlignment = .center
        originalHint.axis = .vertical
        originalHint.alignment = .center
        originalHint.spacing = 12
        originalHint.accessibilityIdentifier = "travelAlbum.autoRetouchOriginalHint"
        originalHint.addArrangedSubview(hintIcon)
        originalHint.addArrangedSubview(hintTitle)
        originalHint.addArrangedSubview(hintDetail)
        hintIcon.snp.makeConstraints { $0.size.equalTo(48) }

        statusStack.axis = .vertical
        statusStack.alignment = .center
        statusStack.spacing = 12
        statusStack.addArrangedSubview(activityIndicator)
        statusStack.addArrangedSubview(statusLabel)
        statusStack.addArrangedSubview(retryButton)
        activityIndicator.color = AppColor.primary
        statusLabel.font = .systemFont(ofSize: 14)
        statusLabel.textColor = AppColor.textSecondary
        statusLabel.textAlignment = .center
        statusLabel.numberOfLines = 0
        retryButton.setTitle("重新加载", for: .normal)
        retryButton.tintColor = AppColor.primary
        retryButton.titleLabel?.font = .systemFont(ofSize: 14, weight: .semibold)
        retryButton.snp.makeConstraints { $0.height.equalTo(44) }

        footer.backgroundColor = .white
        footer.layer.shadowColor = UIColor(hex: 0x182B49).cgColor
        footer.layer.shadowOpacity = 0.04
        footer.layer.shadowRadius = 12
        footer.layer.shadowOffset = CGSize(width: 0, height: -3)
        selectionLabel.font = .systemFont(ofSize: 13, weight: .medium)
        selectionLabel.textColor = AppColor.textSecondary
        selectionLabel.lineBreakMode = .byTruncatingTail
        selectionLabel.accessibilityIdentifier = "travelAlbum.autoRetouchSelectionSummary"
        configureAction(cancelButton, title: "取消", filled: false)
        configureAction(confirmButton, title: "确定", filled: true)
        confirmButton.accessibilityIdentifier = "travelAlbum.autoRetouchConfirmButton"

        view.addSubview(headerStack)
        view.addSubview(contentRegion)
        contentRegion.addSubview(templateHeader)
        contentRegion.addSubview(templateCollectionView)
        contentRegion.addSubview(originalHint)
        contentRegion.addSubview(statusStack)
        view.addSubview(footer)
        footer.addSubview(selectionLabel)
        footer.addSubview(cancelButton)
        footer.addSubview(confirmButton)
    }

    override func setupConstraints() {
        headerStack.snp.makeConstraints { make in
            make.top.equalTo(view.safeAreaLayoutGuide).offset(16)
            make.leading.trailing.equalToSuperview().inset(16)
        }
        contentRegion.snp.makeConstraints { make in
            make.top.equalTo(headerStack.snp.bottom).offset(22)
            make.leading.trailing.equalToSuperview()
            make.bottom.equalTo(footer.snp.top).offset(-8)
        }
        templateHeader.snp.makeConstraints { make in
            make.top.equalToSuperview()
            make.leading.trailing.equalToSuperview().inset(16)
        }
        templateCollectionView.snp.makeConstraints { make in
            make.top.equalTo(templateHeader.snp.bottom).offset(12)
            make.leading.trailing.bottom.equalToSuperview()
        }
        originalHint.snp.makeConstraints { make in
            make.centerY.equalToSuperview().offset(-12)
            make.leading.trailing.equalToSuperview().inset(24)
        }
        statusStack.snp.makeConstraints { make in
            make.center.equalTo(templateCollectionView)
            make.leading.trailing.equalToSuperview().inset(32)
        }
        footer.snp.makeConstraints { make in
            make.leading.trailing.bottom.equalToSuperview()
        }
        selectionLabel.snp.makeConstraints { make in
            make.top.equalToSuperview().offset(14)
            make.leading.trailing.equalToSuperview().inset(16)
        }
        cancelButton.snp.makeConstraints { make in
            make.top.equalTo(selectionLabel.snp.bottom).offset(12)
            make.leading.equalToSuperview().offset(16)
            make.height.equalTo(50)
            make.width.equalTo(96)
            make.bottom.equalTo(view.safeAreaLayoutGuide).offset(-12)
        }
        confirmButton.snp.makeConstraints { make in
            make.leading.equalTo(cancelButton.snp.trailing).offset(12)
            make.trailing.equalToSuperview().offset(-16)
            make.top.bottom.equalTo(cancelButton)
        }
    }

    override func bindActions() {
        originalOption.addTarget(self, action: #selector(originalTapped), for: .touchUpInside)
        aiOption.addTarget(self, action: #selector(aiTapped), for: .touchUpInside)
        cancelButton.addTarget(self, action: #selector(cancelTapped), for: .touchUpInside)
        confirmButton.addTarget(self, action: #selector(confirmTapped), for: .touchUpInside)
        retryButton.addTarget(self, action: #selector(retryTapped), for: .touchUpInside)
        viewModel.onStateChange = { [weak self] in
            Task { @MainActor in self?.applyViewModel() }
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        applyViewModel()
        Task { await viewModel.loadTemplates(api: api) }
    }

    private func configureDataSource() {
        templateDataSource = UICollectionViewDiffableDataSource<Int, TravelAlbumAIRetouchTemplate>(
            collectionView: templateCollectionView
        ) { [weak self] collectionView, indexPath, template in
            guard let self else { return nil }
            let cell = collectionView.dequeueReusableCell(
                withReuseIdentifier: TravelAlbumAIRetouchTemplateCell.reuseIdentifier, for: indexPath
            ) as! TravelAlbumAIRetouchTemplateCell
            cell.apply(template: template, selected: self.viewModel.selectedTemplateId == template.id)
            cell.onPreviewTapped = { [weak self] in self?.showPreview(for: template) }
            return cell
        }
    }

    private func makeTemplateLayout() -> UICollectionViewCompositionalLayout {
        let item = NSCollectionLayoutItem(layoutSize: NSCollectionLayoutSize(
            widthDimension: .fractionalWidth(1), heightDimension: .fractionalHeight(1)
        ))
        let group = NSCollectionLayoutGroup.horizontal(
            layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .absolute(156)),
            subitem: item, count: 3
        )
        group.interItemSpacing = .fixed(12)
        let section = NSCollectionLayoutSection(group: group)
        section.interGroupSpacing = 12
        section.contentInsets = NSDirectionalEdgeInsets(top: 4, leading: 16, bottom: 12, trailing: 16)
        return UICollectionViewCompositionalLayout(section: section)
    }

    private func showPreview(for template: TravelAlbumAIRetouchTemplate) {
        guard presentedViewController == nil else { return }
        guard let content = template.comparisonContent else { showToast("暂无对比预览"); return }
        present(BeforeAfterComparisonViewController(viewModel: BeforeAfterComparisonViewModel(content: content)), animated: true)
    }

    @MainActor
    private func applyViewModel() {
        let showsTemplates = viewModel.isEnabled
        originalOption.apply(selected: !showsTemplates)
        aiOption.apply(selected: showsTemplates)
        confirmButton.isEnabled = viewModel.canConfirm
        confirmButton.alpha = viewModel.canConfirm ? 1 : 0.4
        selectionLabel.text = !showsTemplates ? "将保留原图，不进行 AI 修图"
            : viewModel.selectedTemplateName.map { "已选择：\($0)" } ?? "请选择一个修图模板"
        selectionLabel.textColor = showsTemplates && viewModel.selectedTemplateName != nil ? AppColor.primary : AppColor.textSecondary
        let updateVisibility = {
            self.originalHint.isHidden = showsTemplates
            self.templateHeader.isHidden = !showsTemplates
            self.templateCollectionView.isHidden = !showsTemplates || self.viewModel.isLoading || self.viewModel.errorMessage != nil
            self.statusStack.isHidden = !showsTemplates || (!self.viewModel.isLoading && self.viewModel.errorMessage == nil)
        }
        if let previous = lastTemplatesVisible, previous != showsTemplates,
           view.window != nil, !UIAccessibility.isReduceMotionEnabled {
            UIView.transition(with: contentRegion, duration: 0.2, options: [.transitionCrossDissolve, .beginFromCurrentState], animations: updateVisibility)
        } else {
            updateVisibility()
        }
        lastTemplatesVisible = showsTemplates
        if viewModel.isLoading {
            activityIndicator.startAnimating()
        } else {
            activityIndicator.stopAnimating()
        }
        activityIndicator.isHidden = !viewModel.isLoading
        statusLabel.text = viewModel.isLoading ? "正在加载修图模板…" : viewModel.errorMessage
        retryButton.isHidden = viewModel.isLoading
        let previousTemplates = Set(templateDataSource.snapshot().itemIdentifiers)
        var snapshot = NSDiffableDataSourceSnapshot<Int, TravelAlbumAIRetouchTemplate>()
        snapshot.appendSections([0])
        snapshot.appendItems(viewModel.templates)
        snapshot.reconfigureItems(viewModel.templates.filter(previousTemplates.contains))
        templateDataSource.apply(snapshot, animatingDifferences: true)
    }

    private func configureAction(_ button: UIButton, title: String, filled: Bool) {
        button.setTitle(title, for: .normal)
        button.titleLabel?.font = .systemFont(ofSize: 16, weight: .semibold)
        button.layer.cornerRadius = 14
        button.backgroundColor = filled ? AppColor.primary : .white
        button.setTitleColor(filled ? .white : AppColor.textSecondary, for: .normal)
        button.layer.borderWidth = filled ? 0 : 1
        button.layer.borderColor = UIColor(hex: 0xDFE5EF).cgColor
    }

    @objc private func originalTapped() { viewModel.selectMode(enabled: false) }
    @objc private func aiTapped() { viewModel.selectMode(enabled: true) }
    @objc private func cancelTapped() { dismiss(animated: true) }
    @objc private func retryTapped() { Task { await viewModel.loadTemplates(api: api) } }
    @objc private func confirmTapped() {
        guard viewModel.canConfirm, let configuration = viewModel.pendingConfiguration else { return }
        let completion = onConfirm
        dismiss(animated: true) { completion?(configuration) }
    }
}

extension TravelAlbumAutoRetouchSettingSheetViewController: UICollectionViewDelegate {
    /// 点击模板更新草稿；预览按钮独立处理，不改变选择。
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        guard let template = templateDataSource.itemIdentifier(for: indexPath) else { return }
        viewModel.selectTemplate(id: template.id)
    }
}

/// 修图方式单选卡片，使用图标、边框和勾选共同传达当前选择。
private final class AutoRetouchModeControl: UIControl {
    private let iconContainer = UIView()
    private let iconView = UIImageView()
    private let checkView = UIImageView()
    private let titleLabel = UILabel()

    /// 创建可点击的方式卡片；所有内容由整个控件统一响应触摸。
    init(title: String, detail: String, symbol: String) {
        super.init(frame: .zero)
        layer.cornerRadius = 16
        layer.borderWidth = 1
        iconContainer.layer.cornerRadius = 10
        iconView.image = UIImage(systemName: symbol)
        iconView.contentMode = .scaleAspectFit
        titleLabel.text = title
        titleLabel.font = .systemFont(ofSize: 16, weight: .semibold)
        let detailLabel = UILabel()
        detailLabel.text = detail
        detailLabel.font = .systemFont(ofSize: 12)
        detailLabel.textColor = AppColor.textSecondary
        detailLabel.numberOfLines = 2
        checkView.contentMode = .scaleAspectFit
        [iconContainer, iconView, checkView, titleLabel, detailLabel].forEach {
            $0.isUserInteractionEnabled = false
            addSubview($0)
        }
        iconContainer.snp.makeConstraints { make in
            make.top.leading.equalToSuperview().offset(12)
            make.size.equalTo(32)
        }
        iconView.snp.makeConstraints { $0.edges.equalTo(iconContainer).inset(7) }
        checkView.snp.makeConstraints { make in
            make.top.trailing.equalToSuperview().inset(12)
            make.size.equalTo(22)
        }
        titleLabel.snp.makeConstraints { make in
            make.top.equalTo(iconContainer.snp.bottom).offset(10)
            make.leading.trailing.equalToSuperview().inset(12)
        }
        detailLabel.snp.makeConstraints { make in
            make.top.equalTo(titleLabel.snp.bottom).offset(4)
            make.leading.trailing.equalTo(titleLabel)
            make.bottom.equalToSuperview().inset(12)
        }
        isAccessibilityElement = true
        accessibilityLabel = "\(title)，\(detail)"
    }

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

    /// 更新卡片背景与单选语义。
    func apply(selected: Bool) {
        isSelected = selected
        backgroundColor = selected ? AppColor.primaryLight : .white
        layer.borderColor = (selected ? AppColor.primary : UIColor(hex: 0xDFE5EF)).cgColor
        layer.borderWidth = selected ? 1.5 : 1
        iconContainer.backgroundColor = selected ? AppColor.primary : UIColor(hex: 0xEFF2F7)
        iconView.tintColor = selected ? .white : AppColor.textSecondary
        titleLabel.textColor = selected ? AppColor.primary : AppColor.textPrimary
        checkView.image = UIImage(systemName: selected ? "checkmark.circle.fill" : "circle")
        checkView.tintColor = selected ? AppColor.primary : UIColor(hex: 0xC7CFDC)
        accessibilityValue = selected ? "已选择" : "未选择"
        accessibilityTraits = selected ? [.button, .selected] : [.button]
    }
}