using w4c_workflows.Models;

namespace w4c_workflows.Services.Triggers;

/// <summary>
/// Pure due-check for scheduled triggers. Extracted from the scheduler so the
/// cron/interval timing rules are unit-testable without Redis/Postgres.
/// </summary>
public static class TriggerDue
{
    /// <summary>
    /// Whether a cron/interval trigger should fire now. A workflow with no
    /// recorded last fire fires once on first discovery (the scheduler's initial
    /// pass), then again when its schedule next elapses.
    /// </summary>
    public static bool IsDue(TriggerSpec spec, DateTimeOffset? lastFire, DateTimeOffset now)
    {
        if (lastFire == null)
            return true;

        if (spec.Type == TriggerType.Interval)
        {
            var interval = spec.Interval ?? TimeSpan.Zero;
            return interval > TimeSpan.Zero && lastFire.Value + interval <= now;
        }

        if (spec.Type == TriggerType.Cron
            && CronExpression.TryParse(spec.Cron, out var cron, out _))
        {
            var next = cron!.GetNextOccurrence(lastFire.Value);
            return next.HasValue && next.Value <= now;
        }

        return false;
    }
}