import Kingfisher
import SnapKit
import UIKit

/// 相册自动 AI 修图设置 Sheet，使用服务端精修模板并保持单选。
final class TravelAlbumAutoRetouchSettingSheetViewController: BaseViewController {
    private enum Item: Hashable {
        case mode(Bool)
        case template(TravelAlbumAIRetouchTemplate)
    }

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

    private let viewModel: TravelAlbumAutoRetouchSettingViewModel
    private let api: any TravelAlbumServing
    private let titleLabel = UILabel()
    private let subtitleLabel = UILabel()
    private let backButton = UIButton(type: .system)
    private let tableView = UITableView(frame: .zero, style: .plain)
    private var dataSource: UITableViewDiffableDataSource<Int, Item>!
    private let statusContainer = UIView()
    private let activityIndicator = UIActivityIndicatorView(style: .medium)
    private let statusLabel = UILabel()
    private let retryButton = UIButton(type: .system)
    private let cancelButton = UIButton(type: .system)
    private let confirmButton = UIButton(type: .system)

    /// 创建设置 Sheet。
    init(
        viewModel: TravelAlbumAutoRetouchSettingViewModel,
        api: any TravelAlbumServing
    ) {
        self.viewModel = viewModel
        self.api = api
        super.init(nibName: nil, bundle: nil)
        modalPresentationStyle = .pageSheet
        if let sheetPresentationController {
            sheetPresentationController.detents = [.large()]
            sheetPresentationController.selectedDetentIdentifier = .large
            sheetPresentationController.prefersGrabberVisible = true
            sheetPresentationController.preferredCornerRadius = 22
        }
    }

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

    override func setupUI() {
        view.backgroundColor = .white
        titleLabel.font = .systemFont(ofSize: 20, weight: .semibold)
        titleLabel.textColor = AppColor.textPrimary
        titleLabel.textAlignment = .center
        subtitleLabel.font = .systemFont(ofSize: 13)
        subtitleLabel.textColor = AppColor.textSecondary
        subtitleLabel.textAlignment = .center
        subtitleLabel.numberOfLines = 0

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

        tableView.backgroundColor = .white
        tableView.separatorStyle = .none
        tableView.rowHeight = 116
        tableView.delegate = self
        tableView.register(AutoRetouchOptionCell.self, forCellReuseIdentifier: AutoRetouchOptionCell.reuseIdentifier)
        configureDataSource()

        statusLabel.font = .systemFont(ofSize: 14)
        statusLabel.textColor = AppColor.textSecondary
        statusLabel.textAlignment = .center
        statusLabel.numberOfLines = 0
        retryButton.setTitle("重试", for: .normal)
        retryButton.titleLabel?.font = .systemFont(ofSize: 15, weight: .semibold)
        activityIndicator.color = AppColor.primary

        configureAction(cancelButton, title: "取消", filled: false)
        configureAction(confirmButton, title: "确定", filled: true)
        confirmButton.accessibilityIdentifier = "travelAlbum.autoRetouchConfirmButton"

        view.addSubview(titleLabel)
        view.addSubview(subtitleLabel)
        view.addSubview(backButton)
        view.addSubview(tableView)
        view.addSubview(statusContainer)
        statusContainer.addSubview(activityIndicator)
        statusContainer.addSubview(statusLabel)
        statusContainer.addSubview(retryButton)
        view.addSubview(cancelButton)
        view.addSubview(confirmButton)
    }

    override func setupConstraints() {
        titleLabel.snp.makeConstraints { make in
            make.top.equalTo(view.safeAreaLayoutGuide).offset(12)
            make.leading.trailing.equalToSuperview().inset(56)
        }
        subtitleLabel.snp.makeConstraints { make in
            make.top.equalTo(titleLabel.snp.bottom).offset(8)
            make.leading.trailing.equalToSuperview().inset(28)
        }
        backButton.snp.makeConstraints { make in
            make.leading.equalToSuperview().offset(18)
            make.centerY.equalTo(titleLabel)
            make.size.equalTo(36)
        }
        cancelButton.snp.makeConstraints { make in
            make.leading.equalToSuperview().offset(16)
            make.bottom.equalTo(view.safeAreaLayoutGuide).offset(-12)
            make.height.equalTo(52)
            make.width.equalTo(confirmButton)
        }
        confirmButton.snp.makeConstraints { make in
            make.leading.equalTo(cancelButton.snp.trailing).offset(12)
            make.trailing.equalToSuperview().offset(-16)
            make.top.bottom.width.equalTo(cancelButton)
        }
        tableView.snp.makeConstraints { make in
            make.top.equalTo(subtitleLabel.snp.bottom).offset(14)
            make.leading.trailing.equalToSuperview()
            make.bottom.equalTo(cancelButton.snp.top).offset(-12)
        }
        statusContainer.snp.makeConstraints { $0.edges.equalTo(tableView) }
        activityIndicator.snp.makeConstraints { make in
            make.centerX.equalToSuperview()
            make.centerY.equalToSuperview().offset(-30)
        }
        statusLabel.snp.makeConstraints { make in
            make.top.equalTo(activityIndicator.snp.bottom).offset(12)
            make.leading.trailing.equalToSuperview().inset(36)
        }
        retryButton.snp.makeConstraints { make in
            make.top.equalTo(statusLabel.snp.bottom).offset(10)
            make.centerX.equalToSuperview()
            make.height.equalTo(36)
        }
    }

    override func bindActions() {
        cancelButton.addTarget(self, action: #selector(cancelTapped), for: .touchUpInside)
        confirmButton.addTarget(self, action: #selector(confirmTapped), for: .touchUpInside)
        backButton.addTarget(self, action: #selector(backTapped), 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() {
        dataSource = UITableViewDiffableDataSource<Int, Item>(tableView: tableView) { [weak self] tableView, indexPath, item in
            guard let self else { return nil }
            let cell = tableView.dequeueReusableCell(
                withIdentifier: AutoRetouchOptionCell.reuseIdentifier,
                for: indexPath
            ) as! AutoRetouchOptionCell
            switch item {
            case .mode(let enabled):
                cell.apply(
                    title: enabled ? "AI 修图" : "不修图",
                    detail: enabled ? "选择后需再选一个修图模板" : "保留原图",
                    imageURL: nil,
                    systemImage: enabled ? "wand.and.stars" : "photo",
                    selected: self.viewModel.isEnabled == enabled
                )
            case .template(let template):
                cell.apply(
                    title: template.name,
                    detail: "",
                    imageURL: template.previewURL,
                    systemImage: nil,
                    selected: self.viewModel.selectedTemplateId == template.id
                )
            }
            return cell
        }
    }

    @MainActor
    private func applyViewModel() {
        let isMode = viewModel.stage == .mode
        titleLabel.text = isMode ? "选择修图方式" : "选择修图模板"
        subtitleLabel.text = isMode
            ? "照片上传前可选择保留原图，或使用 AI 自动修图"
            : "缩略图为模板实际效果，后续上传的照片将自动套用"
        backButton.isHidden = isMode || !viewModel.startsWithModeSelection
        confirmButton.isEnabled = viewModel.pendingConfiguration != nil && !viewModel.isLoading
        confirmButton.alpha = confirmButton.isEnabled ? 1 : 0.45

        statusContainer.isHidden = !viewModel.isLoading && viewModel.errorMessage == nil
        if viewModel.isLoading {
            activityIndicator.startAnimating()
            statusLabel.text = "正在加载修图模板…"
            retryButton.isHidden = true
        } else {
            activityIndicator.stopAnimating()
            statusLabel.text = viewModel.errorMessage
            retryButton.isHidden = viewModel.errorMessage == nil
        }

        let previousItems = Set(dataSource.snapshot().itemIdentifiers)
        var snapshot = NSDiffableDataSourceSnapshot<Int, Item>()
        snapshot.appendSections([0])
        let items: [Item]
        if isMode {
            items = [.mode(false), .mode(true)]
        } else {
            items = viewModel.templates.map(Item.template)
        }
        snapshot.appendItems(items)
        snapshot.reconfigureItems(items.filter(previousItems.contains))
        dataSource.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 = 12
        if filled {
            button.backgroundColor = AppColor.primary
            button.setTitleColor(.white, for: .normal)
        } else {
            button.backgroundColor = UIColor(hex: 0xF4F5F7)
            button.setTitleColor(AppColor.textSecondary, for: .normal)
        }
    }

    @objc private func cancelTapped() { dismiss(animated: true) }
    @objc private func backTapped() { viewModel.returnToModeSelection() }
    @objc private func retryTapped() { Task { await viewModel.loadTemplates(api: api) } }

    @objc private func confirmTapped() {
        guard let configuration = viewModel.pendingConfiguration else { return }
        let completion = onConfirm
        dismiss(animated: true) { completion?(configuration) }
    }
}

extension TravelAlbumAutoRetouchSettingSheetViewController: UITableViewDelegate {
    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(let enabled): viewModel.selectMode(enabled: enabled)
        case .template(let template): viewModel.selectTemplate(id: template.id)
        }
    }
}

/// 自动修图方式或模板列表单元，提供效果图、说明和明确单选状态。
private final class AutoRetouchOptionCell: UITableViewCell {
    static let reuseIdentifier = "AutoRetouchOptionCell"
    private let card = 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
        card.layer.cornerRadius = 12
        card.layer.borderWidth = 1
        previewImageView.contentMode = .scaleAspectFill
        previewImageView.clipsToBounds = true
        previewImageView.layer.cornerRadius = 8
        titleLabel.font = .systemFont(ofSize: 16, weight: .semibold)
        titleLabel.textColor = AppColor.textPrimary
        detailLabel.font = .systemFont(ofSize: 13)
        detailLabel.textColor = AppColor.textSecondary
        detailLabel.numberOfLines = 2
        selectionImageView.contentMode = .scaleAspectFit

        contentView.addSubview(card)
        card.addSubview(previewImageView)
        card.addSubview(titleLabel)
        card.addSubview(detailLabel)
        card.addSubview(selectionImageView)
        card.snp.makeConstraints { make in
            make.top.bottom.equalToSuperview().inset(6)
            make.leading.trailing.equalToSuperview().inset(16)
        }
        previewImageView.snp.makeConstraints { make in
            make.leading.equalToSuperview().offset(12)
            make.top.bottom.equalToSuperview().inset(10)
            make.width.equalTo(previewImageView.snp.height)
        }
        selectionImageView.snp.makeConstraints { make in
            make.trailing.equalToSuperview().offset(-16)
            make.centerY.equalToSuperview()
            make.size.equalTo(24)
        }
        titleLabel.snp.makeConstraints { make in
            make.leading.equalTo(previewImageView.snp.trailing).offset(14)
            make.trailing.lessThanOrEqualTo(selectionImageView.snp.leading).offset(-12)
            make.bottom.equalTo(card.snp.centerY).offset(-2)
        }
        detailLabel.snp.makeConstraints { make in
            make.leading.trailing.equalTo(titleLabel)
            make.top.equalTo(card.snp.centerY).offset(4)
        }
    }

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

    override func prepareForReuse() {
        super.prepareForReuse()
        previewImageView.kf.cancelDownloadTask()
        previewImageView.image = nil
    }

    func apply(
        title: String,
        detail: String,
        imageURL: String?,
        systemImage: String?,
        selected: Bool
    ) {
        titleLabel.text = title
        let normalizedDetail = detail.trimmingCharacters(in: .whitespacesAndNewlines)
        detailLabel.text = normalizedDetail
        detailLabel.isHidden = normalizedDetail.isEmpty
        titleLabel.snp.remakeConstraints { make in
            make.leading.equalTo(previewImageView.snp.trailing).offset(14)
            make.trailing.lessThanOrEqualTo(selectionImageView.snp.leading).offset(-12)
            if normalizedDetail.isEmpty {
                make.centerY.equalToSuperview()
            } else {
                make.bottom.equalTo(card.snp.centerY).offset(-2)
            }
        }
        if let imageURL, let url = URL(string: imageURL), !imageURL.isEmpty {
            previewImageView.contentMode = .scaleAspectFill
            previewImageView.backgroundColor = .clear
            previewImageView.kf.setImage(with: url, placeholder: UIImage(systemName: "photo"))
        } else {
            previewImageView.image = systemImage.flatMap(UIImage.init(systemName:))
            previewImageView.contentMode = .center
            previewImageView.tintColor = AppColor.primary
            previewImageView.backgroundColor = AppColor.primary.withAlphaComponent(0.08)
        }
        card.backgroundColor = selected ? AppColor.primary.withAlphaComponent(0.07) : .white
        card.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 = normalizedDetail.isEmpty ? title : "\(title)，\(normalizedDetail)"
        accessibilityValue = selected ? "已选择" : "未选择"
        isAccessibilityElement = true
    }
}