using System;
using System.Collections.Generic;
using Quartz;

namespace CRMBLL.Task
{
    // GB4 parity: CommonFunctionFrameDAL.GetNextOccurrence — walks a CRON expression
    // forward from startDate, collecting each fire time up to (and excluding) endDate.
    // Used by TaskBLL.GenerateTask to compute which dates need a recurring task generated.
    public static class CronOccurrenceCalculator
    {
        private const int MaxIterations = 10000;

        public static List<DateTime> GetNextOccurrences(string cronExpression, DateTime startDate, DateTime endDate)
        {
            var occurrences = new List<DateTime>();
            var schedule = new CronExpression(cronExpression);
            var cursor = new DateTimeOffset(startDate);

            for (int i = 0; i < MaxIterations; i++)
            {
                DateTimeOffset? nextFire = schedule.GetNextValidTimeAfter(cursor);
                if (nextFire == null) break;

                DateTime nextDate = nextFire.Value.LocalDateTime;
                if (nextDate > endDate) break;

                occurrences.Add(nextDate);
                cursor = nextFire.Value;
            }

            return occurrences;
        }
    }
}