using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using FrameworkDAL.CustomCode.SessionStore;
using FrameworkDAL.DTO.SessionStore;
using GB5Shared.DTO.Framework.Login;
using Microsoft.Extensions.Logging;

namespace FrameworkBLL.SessionStore
{
    /// <summary>
    /// Session-management service for MSESSIONSTORE in the GB5 system database.
    ///
    /// Mirrors the role of BaseEntityAppService for the session lifecycle:
    ///   Insert  → called at login (upsert to handle re-login safely)
    ///   Update  → called on activity heartbeat
    ///   Delete  → called on logout or force-logout
    ///   Queries → consumed by the auto-logout background job
    ///
    /// All writes target the GB5 system DB — never the tenant DB —
    /// regardless of which client connection is active at call time.
    /// </summary>
    public class SessionStoreBLL : ISessionStoreBLL
    {
        private readonly ISessionStoreDAL _dal;
        private readonly ILogger<SessionStoreBLL> _logger;

        public SessionStoreBLL(ISessionStoreDAL dal, ILogger<SessionStoreBLL> logger)
        {
            _dal = dal;
            _logger = logger;
        }

        /// <inheritdoc/>
        public async Task InsertSessionAsync(SessionStoreDTO dto, LoginDTO login, CancellationToken ct = default)
        {
            if (dto is null) throw new ArgumentNullException(nameof(dto));
            
            // Ensure MachineIp is never null (NVARCHAR column, nullable in DB but cleaner to default)
            if (string.IsNullOrEmpty(dto.MachineIp))
                dto.MachineIp = string.Empty;

            await _dal.UpsertSessionAsync(dto, ct).ConfigureAwait(false);

            _logger.LogInformation(
                "Session inserted | ServerconfigId={ServerconfigId} LoginEventLogId={LoginEventLogId} UserId={UserId}",
                dto.ServerconfigId, dto.LoginEventLogId, dto.UserId);
        }

        /// <inheritdoc/>
        public async Task UpdateSessionAsync(
            int serverConfigId, int loginEventLogId, DateTime lastUsedTime,
            LoginDTO login, CancellationToken ct = default)
        {
            await _dal.UpdateSessionAsync(serverConfigId, loginEventLogId, lastUsedTime, ct).ConfigureAwait(false);
        }

        /// <inheritdoc/>
        public async Task DeleteSessionAsync(
            int serverConfigId, int loginEventLogId,
            LoginDTO login, CancellationToken ct = default)
        {
            if (loginEventLogId <= 0)
            {
                _logger.LogWarning("DeleteSession skipped — LoginEventLogId={LoginEventLogId} is invalid.", loginEventLogId);
                return;
            }

            await _dal.DeleteSessionAsync(serverConfigId, loginEventLogId, ct).ConfigureAwait(false);

            _logger.LogInformation(
                "Session deleted | ServerconfigId={ServerconfigId} LoginEventLogId={LoginEventLogId}",
                serverConfigId, loginEventLogId);
        }

        /// <inheritdoc/>
        public async Task<bool> LogOutIfPresentAsync(
            int serverConfigId, int loginEventLogId,
            LoginDTO login, CancellationToken ct = default)
        {
            if (loginEventLogId <= 0)
            {
                _logger.LogWarning("LogOutIfPresent skipped — LoginEventLogId={LoginEventLogId} is invalid.", loginEventLogId);
                return false;
            }

            int count = await _dal.GetSessionCountAsync(serverConfigId, loginEventLogId, ct).ConfigureAwait(false);
            if (count == 0)
            {
                _logger.LogInformation(
                    "LogOutIfPresent — no active session | ServerconfigId={ServerconfigId} LoginEventLogId={LoginEventLogId}.",
                    serverConfigId, loginEventLogId);
                return false;
            }

            await _dal.DeleteSessionAsync(serverConfigId, loginEventLogId, ct).ConfigureAwait(false);

            _logger.LogInformation(
                "LogOutIfPresent — session removed | ServerconfigId={ServerconfigId} LoginEventLogId={LoginEventLogId}.",
                serverConfigId, loginEventLogId);

            return true;
        }

        /// <inheritdoc/>
        public async Task<IEnumerable<UnusedSessionDTO>> GetUnusedSessionsAsync(
            int serverConfigId, int expiryMinutes,
            LoginDTO login, CancellationToken ct = default)
        {
            return await _dal.GetUnusedSessionsAsync(serverConfigId, expiryMinutes, ct).ConfigureAwait(false);
        }

        /// <inheritdoc/>
        public async Task DeleteOldSessionsAsync(DateTime todayDate, LoginDTO login, CancellationToken ct = default)
        {
            await _dal.DeleteOldSessionsAsync(todayDate, ct).ConfigureAwait(false);
        }
    }
}