using GB5Shared.DTO.Framework.Criteria;
using GB5Shared.DTO.Framework.Login;
using TMSDAL.DTO.TrainingEnrollment;

namespace TMSDAL.CustomCode.TrainingEnrollment
{
    public interface ITrainingEnrollmentDAL
    {
        // ════════════════════════════════════════════════════════════════════
        // READ
        // ════════════════════════════════════════════════════════════════════

        /// <summary>Fetch full enrollment record by primary key.</summary>
        Task<TrainingEnrollmentDTO?> GetTrainingEnrollment(int enrollmentId, LoginDTO loginDTO);

        /// <summary>
        /// Fetch ACTIVE enrollment by (InstanceId + EmployeeId + TenantId).
        /// Returns null if no active enrollment exists.
        /// Withdrawn / Rejected rows excluded — re-enrollment after those states is allowed.
        /// </summary>
        Task<TrainingEnrollmentDTO?> GetEnrollment(int instanceId, int employeeId, LoginDTO loginDTO);

        /// <summary>All enrollments for a training instance (JSON).</summary>
        Task<string> GetEnrollmentsByInstance(int instanceId, LoginDTO loginDTO);

        /// <summary>All enrollments for an employee (JSON).</summary>
        Task<string> GetEnrollmentsByEmployee(int employeeId, LoginDTO loginDTO);

        /// <summary>Full tenant enrollment list (JSON).</summary>
        Task<string> GetEnrollmentList(LoginDTO loginDTO);

        /// <summary>Paged / filtered dropdown select-list (JSON).</summary>
        Task<string> GetSelectList(CriteriaDTO criteriaDTO, LoginDTO loginDTO, CancellationToken ct);

        /// <summary>
        /// Next available waitlist position for an instance.
        /// Returns MAX(WaitlistPosition) + 1, or 1 if none waitlisted.
        /// </summary>
        Task<int> GetNextWaitlistPosition(int instanceId, LoginDTO loginDTO);

        // ════════════════════════════════════════════════════════════════════
        // WRITE
        // ════════════════════════════════════════════════════════════════════

        /// <summary>
        /// Insert a new enrollment. Returns Task — rows-affected not meaningful here.
        /// </summary>
        Task SaveTrainingEnrollment(TrainingEnrollmentDTO dto, LoginDTO loginDTO);

        /// <summary>
        /// Unified Manager + HR approval / rejection.
        /// ApprovalType on the DTO routes to the correct query and column set.
        /// </summary>
        Task<int> UpdateApproval(ApprovalUpdateDTO approvalDto, LoginDTO loginDTO);

        /// <summary>
        /// Withdraw an enrollment.
        /// Status must always be EnrollmentStatus.Withdrawn — enforced by BLL.
        /// </summary>
        Task<int> WithdrawEnrollment(int enrollmentId, byte status, string? reason, LoginDTO loginDTO);

        /// <summary>
        /// Soft-delete: sets STATUS = 0.
        /// Hard delete not permitted — history must be preserved.
        /// </summary>
        Task<int> DeleteTrainingEnrollment(int enrollmentId, LoginDTO loginDTO);
    }
}