//
//  StatisticsViewController.swift
//  suixinkan
//

import SnapKit
import UIKit

/// 数据 Tab 根页面，展示订单统计汇总和每日明细。
final class StatisticsViewController: UIViewController {

    private let viewModel = StatisticsViewModel()

    private lazy var tableView: UITableView = {
        let table = UITableView(frame: .zero, style: .grouped)
        table.backgroundColor = AppDesignUIKit.pageBackground
        table.dataSource = self
        table.delegate = self
        table.register(StatisticsSummaryCell.self, forCellReuseIdentifier: StatisticsSummaryCell.reuseID)
        table.register(StatisticsDailyCell.self, forCellReuseIdentifier: StatisticsDailyCell.reuseID)
        table.register(StatisticsPeriodCell.self, forCellReuseIdentifier: StatisticsPeriodCell.reuseID)
        return table
    }()

    private lazy var refreshControl = UIRefreshControl()

    override func viewDidLoad() {
        super.viewDidLoad()
        title = "数据"
        view.backgroundColor = AppDesignUIKit.pageBackground
        view.addSubview(tableView)
        tableView.snp.makeConstraints { make in make.edges.equalToSuperview() }
        refreshControl.addTarget(self, action: #selector(refreshPulled), for: .valueChanged)
        tableView.refreshControl = refreshControl

        viewModel.onChange = { [weak self] in self?.tableView.reloadData() }
        appServices.accountContext.onChange = { [weak self] in Task { await self?.reload(showLoading: true) } }
        appServices.permissionContext.onChange = { [weak self] in Task { await self?.reload(showLoading: true) } }
        Task { await reload(showLoading: true) }
    }

    @objc private func refreshPulled() {
        Task {
            await reload(showLoading: false)
            refreshControl.endRefreshing()
        }
    }

    private var currentScenicId: Int? { appServices.accountContext.currentScenic?.id }
    private var currentRoleId: Int? { appServices.permissionContext.currentRole?.id }

    private func reload(showLoading: Bool) async {
        guard currentScenicId != nil else {
            tableView.reloadData()
            return
        }
        do {
            try await appServices.globalLoading.withOptionalLoading(showLoading, message: "加载数据...") {
                try await self.viewModel.reload(
                    api: self.appServices.statisticsAPI,
                    scenicId: self.currentScenicId,
                    roleId: self.currentRoleId,
                    showLoading: false
                )
            }
        } catch {
            showToast(error.localizedDescription)
        }
    }

    private func selectPeriod(_ period: StatisticsPeriod) {
        Task {
            do {
                try await appServices.globalLoading.withLoading(message: "加载数据...") {
                    try await viewModel.selectPeriod(
                        period,
                        api: appServices.statisticsAPI,
                        scenicId: currentScenicId,
                        roleId: currentRoleId
                    )
                }
            } catch {
                showToast(error.localizedDescription)
            }
        }
    }

    private func loadMore() async {
        do {
            try await viewModel.loadMore(
                api: appServices.statisticsAPI,
                scenicId: currentScenicId,
                roleId: currentRoleId
            )
        } catch {
            showToast(error.localizedDescription)
        }
    }

    private func amountText(_ value: Double) -> String {
        "¥\(String(format: "%.2f", value))"
    }
}

extension StatisticsViewController: UITableViewDataSource, UITableViewDelegate {
    func numberOfSections(in tableView: UITableView) -> Int {
        currentScenicId == nil ? 1 : 3
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        if currentScenicId == nil { return 1 }
        switch section {
        case 0: return 1
        case 1: return 1
        default:
            if viewModel.loading && viewModel.dailyItems.isEmpty { return 0 }
            return max(viewModel.dailyItems.count, 1)
        }
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        if currentScenicId == nil {
            let cell = UITableViewCell()
            cell.selectionStyle = .none
            cell.backgroundColor = .clear
            cell.contentView.subviews.forEach { $0.removeFromSuperview() }
            let empty = makeEmptyStateView(title: "缺少经营上下文", message: "请先在首页选择景区后查看数据看板。", systemImage: "chart.bar.doc.horizontal")
            cell.contentView.addSubview(empty)
            empty.snp.makeConstraints { make in make.edges.equalToSuperview(); make.height.equalTo(360) }
            return cell
        }

        switch indexPath.section {
        case 0:
            let cell = tableView.dequeueReusableCell(withIdentifier: StatisticsPeriodCell.reuseID, for: indexPath) as! StatisticsPeriodCell
            cell.configure(selectedPeriod: viewModel.selectedPeriod) { [weak self] period in
                self?.selectPeriod(period)
            }
            return cell
        case 1:
            let cell = tableView.dequeueReusableCell(withIdentifier: StatisticsSummaryCell.reuseID, for: indexPath) as! StatisticsSummaryCell
            cell.configure(
                periodText: viewModel.selectedPeriod.selectedTimeText,
                summary: viewModel.summary,
                amountText: amountText
            )
            return cell
        default:
            if viewModel.dailyItems.isEmpty {
                let cell = UITableViewCell()
                cell.textLabel?.text = "暂无数据"
                cell.selectionStyle = .none
                return cell
            }
            let cell = tableView.dequeueReusableCell(withIdentifier: StatisticsDailyCell.reuseID, for: indexPath) as! StatisticsDailyCell
            cell.configure(item: viewModel.dailyItems[indexPath.row], amountText: amountText)
            return cell
        }
    }

    func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        section == 2 ? "每日明细" : nil
    }

    func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        guard indexPath.section == 2, indexPath.row == viewModel.dailyItems.count - 1 else { return }
        Task { await loadMore() }
    }
}

private final class StatisticsPeriodCell: UITableViewCell {
    static let reuseID = "StatisticsPeriodCell"
    private var onSelect: ((StatisticsPeriod) -> Void)?
    private let stack = UIStackView()

    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        selectionStyle = .none
        stack.axis = .horizontal
        stack.spacing = 8
        stack.distribution = .fillEqually
        contentView.addSubview(stack)
        stack.snp.makeConstraints { make in make.edges.equalToSuperview().inset(12) }
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) { fatalError() }

    func configure(selectedPeriod: StatisticsPeriod, onSelect: @escaping (StatisticsPeriod) -> Void) {
        self.onSelect = onSelect
        stack.arrangedSubviews.forEach { $0.removeFromSuperview() }
        for period in StatisticsPeriod.allCases {
            let button = UIButton(type: .system)
            button.setTitle(period.rawValue, for: .normal)
            button.titleLabel?.font = .systemFont(ofSize: AppMetrics.FontSize.subheadline, weight: period == selectedPeriod ? .semibold : .regular)
            button.setTitleColor(period == selectedPeriod ? AppDesignUIKit.primary : AppDesignUIKit.textSecondary, for: .normal)
            button.backgroundColor = period == selectedPeriod ? AppDesignUIKit.primarySoft : UIColor(hex: 0xF4F4F4)
            button.layer.cornerRadius = 6
            button.tag = StatisticsPeriod.allCases.firstIndex(of: period) ?? 0
            button.addTarget(self, action: #selector(periodTapped(_:)), for: .touchUpInside)
            stack.addArrangedSubview(button)
        }
    }

    @objc private func periodTapped(_ sender: UIButton) {
        let period = StatisticsPeriod.allCases[sender.tag]
        onSelect?(period)
    }
}

private final class StatisticsSummaryCell: UITableViewCell {
    static let reuseID = "StatisticsSummaryCell"
    private let stack = UIStackView()

    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        selectionStyle = .none
        stack.axis = .vertical
        stack.spacing = 8
        contentView.addSubview(stack)
        stack.snp.makeConstraints { make in make.edges.equalToSuperview().inset(12) }
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) { fatalError() }

    func configure(periodText: String, summary: StatisticsSummaryResponse, amountText: (Double) -> String) {
        stack.arrangedSubviews.forEach { $0.removeFromSuperview() }
        let dateLabel = UILabel()
        dateLabel.text = "已选日期：\(periodText)"
        dateLabel.font = .systemFont(ofSize: AppMetrics.FontSize.subheadline)
        stack.addArrangedSubview(dateLabel)

        stack.addArrangedSubview(summaryCard("订单总金额", amountText(summary.orderAmountValue), UIColor(hex: 0x22C55E)))
        let row = UIStackView()
        row.axis = .horizontal
        row.spacing = 8
        row.distribution = .fillEqually
        row.addArrangedSubview(summaryCard("订单总数", "\(summary.orderCount)单", UIColor(hex: 0x7F00FF)))
        row.addArrangedSubview(summaryCard("实收金额", amountText(summary.receivedAmountValue), UIColor(hex: 0x22C55E)))
        stack.addArrangedSubview(row)

        let row2 = UIStackView()
        row2.axis = .horizontal
        row2.spacing = 8
        row2.distribution = .fillEqually
        row2.addArrangedSubview(summaryCard("客单价", amountText(summary.orderPriceAverageValue), AppDesignUIKit.primary))
        row2.addArrangedSubview(summaryCard("退款金额", amountText(summary.refundAmountValue), UIColor(hex: 0xEF4444)))
        stack.addArrangedSubview(row2)
    }

    private func summaryCard(_ title: String, _ value: String, _ color: UIColor) -> UIView {
        let card = UIView()
        card.backgroundColor = color.withAlphaComponent(0.08)
        card.layer.cornerRadius = 8
        let titleLabel = UILabel()
        titleLabel.text = title
        titleLabel.font = .systemFont(ofSize: AppMetrics.FontSize.caption)
        let valueLabel = UILabel()
        valueLabel.text = value
        valueLabel.font = .systemFont(ofSize: AppMetrics.FontSize.title3, weight: .bold)
        valueLabel.textColor = color
        let inner = UIStackView(arrangedSubviews: [titleLabel, valueLabel])
        inner.axis = .vertical
        inner.spacing = 4
        card.addSubview(inner)
        inner.snp.makeConstraints { make in make.edges.equalToSuperview().inset(12) }
        card.snp.makeConstraints { make in make.height.greaterThanOrEqualTo(72) }
        return card
    }
}

private final class StatisticsDailyCell: UITableViewCell {
    static let reuseID = "StatisticsDailyCell"

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

    @available(*, unavailable)
    required init?(coder: NSCoder) { fatalError() }

    func configure(item: StatisticsDailyItem, amountText: (Double) -> String) {
        textLabel?.font = .systemFont(ofSize: AppMetrics.FontSize.subheadline, weight: .semibold)
        detailTextLabel?.font = .systemFont(ofSize: AppMetrics.FontSize.caption)
        textLabel?.text = item.date
        detailTextLabel?.text = "\(item.orderCount)单 · 实收 \(amountText(item.receivedValue))"
    }
}