using System;

namespace XP.ReportEngine.Services
{
    /// <summary>
    /// 报告编号生成器 | Report ID generator
    /// 生成格式为 RPT-yyyyMMdd-NNN 的唯一报告编号
    /// Generates unique report IDs in format: RPT-yyyyMMdd-NNN
    /// 线程安全，每日自动重置计数器
    /// Thread-safe with daily counter reset
    /// </summary>
    public class ReportIdGenerator
    {
        private readonly object _lock = new();
        private int _dailyCounter;
        private string _currentDate;

        /// <summary>
        /// 构造函数 | Constructor
        /// </summary>
        public ReportIdGenerator()
        {
            _currentDate = DateTime.Now.ToString("yyyyMMdd");
            _dailyCounter = 0;
        }

        /// <summary>
        /// 生成下一个唯一报告编号 | Generate next unique report ID
        /// 格式：RPT-yyyyMMdd-NNN（如 RPT-20250101-001）
        /// Format: RPT-yyyyMMdd-NNN (e.g., RPT-20250101-001)
        /// </summary>
        /// <returns>唯一报告编号 | Unique report ID</returns>
        public string GenerateNext()
        {
            lock (_lock)
            {
                var today = DateTime.Now.ToString("yyyyMMdd");

                // 日期变更时重置计数器 | Reset counter when date changes
                if (today != _currentDate)
                {
                    _currentDate = today;
                    _dailyCounter = 0;
                }

                _dailyCounter++;
                return $"RPT-{_currentDate}-{_dailyCounter:D3}";
            }
        }

        /// <summary>
        /// 根据指定时间戳生成报告编号 | Generate report ID with specified timestamp
        /// 用于需要指定日期的场景（如补录报告）
        /// Used for scenarios requiring specific dates (e.g., backfilling reports)
        /// </summary>
        /// <param name="timestamp">指定的时间戳 | Specified timestamp</param>
        /// <returns>唯一报告编号 | Unique report ID</returns>
        public string GenerateForDate(DateTime timestamp)
        {
            lock (_lock)
            {
                var dateStr = timestamp.ToString("yyyyMMdd");

                // 如果指定日期与当前日期相同，使用当前计数器
                // If specified date matches current date, use current counter
                if (dateStr == _currentDate)
                {
                    _dailyCounter++;
                    return $"RPT-{_currentDate}-{_dailyCounter:D3}";
                }

                // 如果指定日期与当前日期不同，更新日期并重置计数器
                // If specified date differs from current date, update date and reset counter
                _currentDate = dateStr;
                _dailyCounter = 1;
                return $"RPT-{_currentDate}-{_dailyCounter:D3}";
            }
        }
    }
}