/// <summary>
/// Log table — append-only. No UPDATE or DELETE operations.
/// </summary>
namespace TMSDAL.DTO.CertRenewalAlert
{
    /// <summary>
    /// Maps to DBO.LCERTRENEWALALERT
    /// LOG table — append-only. Records each certificate renewal or expiry alert that was fired.
    /// Never updated. Never deleted. Never FK-referenced by other tables.
    /// PK is IDENTITY — do NOT set LCertRenewalAlertId manually on insert.
    /// One row per alert fired. Multiple rows per certificate are expected.
    /// </summary>
    public class CertRenewalAlertDTO
    {
        // =====================================================
        // PRIMARY KEY — IDENTITY
        // =====================================================

        /// <summary>
        /// Auto-generated IDENTITY PK — set by SQL Server, not AutoNumber.
        /// Do NOT pass this on insert. Read-only after creation.
        /// </summary>
        public int LCertRenewalAlertId { get; set; }


        // =====================================================
        // BUSINESS COLUMNS — FOREIGN KEY
        // =====================================================

        /// <summary>
        /// FK → TTRAININGCERTIFICATE.TRAININGCERTIFICATEID
        /// The certificate that triggered this alert.
        /// Required on every insert.
        /// </summary>
        public int TrainingCertificateId { get; set; }

        /// <summary>
        /// Joined from TTRAININGCERTIFICATE — display reference only.
        /// The unique certificate number e.g. "CERT-2026-00142".
        /// </summary>
        public string? CertificateNumber { get; set; }

        /// <summary>
        /// Joined from TTRAININGCERTIFICATE — display reference only.
        /// The human-readable title of the certificate e.g. "Fire Safety Level 2".
        /// </summary>
        public string? CertificateTitle { get; set; }


        // =====================================================
        // BUSINESS COLUMNS — ALERT CLASSIFICATION
        // =====================================================

        /// <summary>
        /// Type of alert fired.
        /// 0 = RenewalReminder — certificate approaching renewal window.
        /// 1 = ExpiryWarning   — certificate close to expiry date.
        /// 2 = ExpiredNotice   — certificate has already expired.
        /// </summary>
        public byte AlertType { get; set; }

        /// <summary>
        /// Number of days before expiry when this alert was scheduled.
        /// 0 = fired on expiry date itself.
        /// Positive values = days before expiry (e.g. 30, 14, 7, 1).
        /// </summary>
        public int DaysBeforeExpiry { get; set; } = 0;


        // =====================================================
        // BUSINESS COLUMNS — SCHEDULING & DELIVERY
        // =====================================================

        /// <summary>
        /// When this alert was scheduled to be sent.
        /// Set at creation time by the scheduling engine.
        /// </summary>
        public DateTime ScheduledAt { get; set; }

        /// <summary>
        /// Actual timestamp when the alert was dispatched to recipients.
        /// Null until AlertStatus transitions to 1 (Sent).
        /// </summary>
        public DateTime? SentAt { get; set; }

        /// <summary>
        /// Who receives this alert.
        /// 0 = Employee only.
        /// 1 = Supervisor only.
        /// 2 = HR only.
        /// 3 = All (Employee + Supervisor + HR).
        /// </summary>
        public byte RecipientType { get; set; } = 3;

        /// <summary>
        /// Channel through which the alert is delivered.
        /// 0 = Email.
        /// 1 = InApp notification.
        /// 2 = SMS.
        /// 3 = All channels.
        /// </summary>
        public byte AlertChannel { get; set; } = 0;


        // =====================================================
        // BUSINESS COLUMNS — STATUS
        // =====================================================

        /// <summary>
        /// Current delivery status of this alert.
        /// 0 = Scheduled — queued, not yet sent.
        /// 1 = Sent      — successfully dispatched to recipients.
        /// 2 = Failed    — dispatch attempted but failed (retry may occur).
        /// 3 = Cancelled — manually cancelled before dispatch.
        /// </summary>
        public byte AlertStatus { get; set; } = 0;

        /// <summary>
        /// Timestamp when the recipient acknowledged or dismissed the alert.
        /// Null if not yet acknowledged or channel does not support acknowledgement.
        /// </summary>
        public DateTime? AcknowledgedAt { get; set; }


        // =====================================================
        // LOG STANDARD FIELDS
        // =====================================================

        /// <summary>
        /// FK → MUSER.USERID
        /// The system user or service account that created this log entry.
        /// Set by BLL from LoginDTO.UserId on insert.
        /// </summary>
        public int CreatedById { get; set; }

        /// <summary>
        /// Timestamp when this log entry was created.
        /// Set by SQL Server DEFAULT GETDATE() — do not set manually.
        /// </summary>
        public DateTime CreatedOn { get; set; }
    }
}