import java.text.SimpleDateFormat;
import java.util.*;
import java.util.stream.Collectors;

/**
 * 滞留件管理服务类
 * 核心功能：滞留件检测、通知管理、超时处理、统计分析
 */
public class OverduePackageService {
    // 配置参数（可通过配置文件加载）
    private static final int MAX_FREE_DAYS = 7;          // 最大免费存放天数
    private static final double DAILY_STORAGE_FEE = 1.0; // 每日滞留费用(元)
    private static final int NOTICE_INTERVAL = 3;        // 提醒间隔天数

    // 依赖服务注入
    private final ExpressService expressService;
    private final NotificationService notificationService;

    // 内部状态管理
    private final Map<String, OverdueRecord> overdueRecords = new HashMap<>();
    private final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm");

    /**
     * 构造函数（依赖注入模式）
     */
    public OverduePackageService(ExpressService expressService,
                                 NotificationService notificationService) {
        this.expressService = expressService;
        this.notificationService = notificationService;
        initializeOverdueMonitoring();
    }

    /**
     * 初始化滞留件监控线程
     */
    private void initializeOverdueMonitoring() {
        // 创建定时任务（每24小时执行一次检测）
        Timer timer = new Timer(true);
        timer.scheduleAtFixedRate(new TimerTask() {
            @Override
            public void run() {
                detectAndProcessOverduePackages();
            }
        }, 0, 24 * 60 * 60 * 1000);
    }

    /**
     * 滞留件检测与处理主逻辑
     */
    public synchronized void detectAndProcessOverduePackages() {
        // 1. 获取所有待取件包裹
        List<ExpressItem> allPackages = expressService.getAllPackages()
                .stream()
                .filter(item -> "待取件".equals(item.getStatus()))
                .collect(Collectors.toList());

        // 2. 计算存放天数并识别滞留件
        List<ExpressItem> overduePackages = new ArrayList<>();
        for (ExpressItem item : allPackages) {
            int storageDays = calculateStorageDays(item.getArrivalTime());
            item.setStorageDays(storageDays);

            if (storageDays > MAX_FREE_DAYS) {
                overduePackages.add(item);
                recordOverdueHistory(item, storageDays);
            }
        }

        // 3. 执行滞留处理流程
        overduePackages.forEach(this::processOverduePackage);
    }

    /**
     * 计算包裹存放天数（精确到小时）
     */
    private int calculateStorageDays(Date arrivalTime) {
        long now = System.currentTimeMillis();
        long elapsed = now - arrivalTime.getTime();
        return (int) (elapsed / (24 * 3600 * 1000));
    }

    /**
     * 记录滞留历史（防重复处理）
     */
    private void recordOverdueHistory(ExpressItem item, int currentDays) {
        String trackingNumber = item.getTrackingNumber();
        overdueRecords.putIfAbsent(trackingNumber, new OverdueRecord());

        OverdueRecord record = overdueRecords.get(trackingNumber);
        if (record.getLastNoticeDay() == 0 ||
                (currentDays - record.getLastNoticeDay()) >= NOTICE_INTERVAL) {

            record.setLastNoticeDay(currentDays);
            record.incrementNoticeCount();
        }
    }

    /**
     * 单个滞留件处理流程
     */
    private void processOverduePackage(ExpressItem item) {
        // 1. 费用计算
        double overdueFee = calculateOverdueFee(item.getStorageDays());

        // 2. 生成通知内容
        String noticeContent = buildNoticeContent(item, overdueFee);

        // 3. 发送通知（支持多通道）
        sendMultiChannelNotice(item.getPhone(), noticeContent);

        // 4. 标记为滞留状态（可选扩展）
        if (item.getStorageDays() > MAX_FREE_DAYS * 2) {
            expressService.markAsOverdue(item.getTrackingNumber());
        }
    }

    /**
     * 计算滞留费用（简单线性计费）
     */
    private double calculateOverdueFee(int storageDays) {
        int overdueDays = storageDays - MAX_FREE_DAYS;
        return overdueDays > 0 ? overdueDays * DAILY_STORAGE_FEE : 0;
    }

    /**
     * 构建多格式通知内容
     */
    private String buildNoticeContent(ExpressItem item, double fee) {
        return String.format("""
            【快递滞留提醒】
            运单号：%s
            收件人：%s
            滞留天数：%d天
            当前费用：%.2f元
            请尽快取件避免额外费用！
            """,
                item.getTrackingNumber(),
                item.getRecipient(),
                item.getStorageDays(),
                fee);
    }

    /**
     * 多通道通知发送（短信+邮件+系统消息）
     */
    private void sendMultiChannelNotice(String phone, String content) {
        // 短信通知
        notificationService.sendSMS(phone, content);

        // 邮件通知（需实现邮件服务）
        // notificationService.sendEmail(recipientEmail, "快递滞留提醒", content);

        // 系统内消息（需集成消息中心）
        // messageCenter.pushSystemNotice(userId, content);
    }

    /**
     * 滞留件统计报表生成
     */
    public String generateOverdueReport() {
        Map<Integer, Long> dailyCount = overdueRecords.values().stream()
                .collect(Collectors.groupingBy(
                        OverdueRecord::getNoticeCount,
                        Collectors.counting()
                ));

        StringBuilder report = new StringBuilder();
        report.append("===== 滞留件统计报表 =====\n");
        report.append("统计时间：").append(dateFormat.format(new Date())).append("\n");
        report.append("-------------------------\n");
        report.append("总滞留包裹数：").append(overdueRecords.size()).append("\n");

        dailyCount.forEach((times, count) ->
                report.append(String.format("被提醒%d次包裹数：%d\n", times, count)));

        return report.toString();
    }

    /**
     * 滞留记录实体类
     */
    private static class OverdueRecord {
        private int lastNoticeDay;     // 最后一次通知时的存放天数
        private int noticeCount;       // 通知发送次数

        // Getter/Setter
        public int getLastNoticeDay() { return lastNoticeDay; }
        public void setLastNoticeDay(int day) { this.lastNoticeDay = day; }
        public int getNoticeCount() { return noticeCount; }
        public void incrementNoticeCount() { this.noticeCount++; }
    }

    /**
     * 通知服务接口（需具体实现）
     */
    public interface NotificationService {
        void sendSMS(String phone, String message);
        // void sendEmail(String to, String subject, String content);
    }

    /**
     * 滞留件查询服务
     */
    public List<ExpressItem> queryOverduePackages(int minDays, int maxDays) {
        return expressService.getAllPackages().stream()
                .filter(item -> {
                    int days = item.getStorageDays();
                    return days >= minDays && days <= maxDays;
                })
                .sorted(Comparator.comparingInt(ExpressItem::getStorageDays).reversed())
                .collect(Collectors.toList());
    }

    /**
     * 批量处理滞留件（自动退回）
     */
    public int batchReturnOverduePackages(int maxDays) {
        List<ExpressItem> toReturn = queryOverduePackages(maxDays, Integer.MAX_VALUE);
        toReturn.forEach(item -> expressService.markAsReturned(item.getTrackingNumber()));
        return toReturn.size();
    }

    /**
     * 滞留费用明细查询
     */
    public Map<String, Double> getOverdueFees(String trackingNumber) {
        OverdueRecord record = overdueRecords.get(trackingNumber);
        if (record == null) return Collections.emptyMap();

        Map<String, Double> feeDetail = new HashMap<>();
        feeDetail.put("baseFee", (double) (record.getNoticeCount() * NOTICE_INTERVAL));
        feeDetail.put("totalFee", calculateOverdueFee(record.getNoticeCount() * NOTICE_INTERVAL));
        return feeDetail;
    }
}