using GB5Shared.DTO.Framework.Login;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;
using System.Threading;
using System.Threading.Tasks;

namespace FrameworkBLL.SchedulerTaskGenerator
{
    /// <summary>
    /// Background service that polls for ready scheduler tasks on a fixed interval.
    /// Scoped services (BLL, DAL) are resolved per cycle via IServiceScopeFactory.
    ///
    /// Use this when Quartz is NOT available (simple deployments, Docker, etc.)
    /// Use SchedulerQuartzJob instead when precise cron-based triggering of the
    /// poll cycle itself is required.
    /// </summary>
    public sealed class SchedulerBackgroundService : BackgroundService
    {
        private readonly IServiceProvider _services;
        private readonly IConfiguration _config;
        private readonly ILogger<SchedulerBackgroundService> _logger;
        private readonly TimeSpan _pollingInterval;

        public SchedulerBackgroundService(
            IServiceProvider services,
            IConfiguration config,
            ILogger<SchedulerBackgroundService> logger,
            TimeSpan? pollingInterval = null)
        {
            _services = services ?? throw new ArgumentNullException(nameof(services));
            _config = config ?? throw new ArgumentNullException(nameof(config));
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
            _pollingInterval = pollingInterval ?? TimeSpan.FromSeconds(30);
        }

        // ─────────────────────────────────────────────────────────────────
        // Main execution loop
        // ─────────────────────────────────────────────────────────────────

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            _logger.LogInformation(
                "SchedulerBackgroundService started. PollingIntervalSeconds={Interval}",
                _pollingInterval.TotalSeconds);

            while (!stoppingToken.IsCancellationRequested)
            {
                try
                {
                    using var scope = _services.CreateScope();
                    var taskManager = scope.ServiceProvider
                                               .GetRequiredService<ISchedulerTaskManager>();

                    // ✅ Build LoginDTO from config — includes ClientId for tenant isolation
                    var login = BuildLoginFromConfig();

                    // ✅ Pass stoppingToken so cycle respects graceful shutdown
                    var summary = await taskManager.ExecuteReadyTasksAsync(login, stoppingToken)
                        .ConfigureAwait(false);

                    _logger.LogInformation(
                        "SchedulerBackgroundService cycle complete | " +
                        "Total={Total} Published={Published} Skipped={Skipped} At={Time:HH:mm:ss}",
                        summary.Total, summary.Published, summary.Skipped, DateTime.UtcNow);
                }
                catch (OperationCanceledException)
                {
                    // Graceful shutdown — exit loop cleanly
                    break;
                }
                catch (Exception ex)
                {
                    // Log but do not crash the service — next cycle will retry
                    _logger.LogError(ex,
                        "SchedulerBackgroundService cycle failed at {Time:HH:mm:ss}",
                        DateTime.UtcNow);
                }

                try
                {
                    await Task.Delay(_pollingInterval, stoppingToken).ConfigureAwait(false);
                }
                catch (TaskCanceledException)
                {
                    break;
                }
            }

            _logger.LogInformation("SchedulerBackgroundService stopped.");
        }

        // ─────────────────────────────────────────────────────────────────
        // LoginDTO resolution
        // ─────────────────────────────────────────────────────────────────

        /// <summary>
        /// Builds LoginDTO from appsettings.json SchedulerRun section.
        /// ✅ ClientId is now set — all DAL queries use login.ClientId for @TenantId.
        ///
        /// Required config keys:
        ///   SchedulerRun:DatabaseName  — e.g. "GB5_PROD"
        ///   SchedulerRun:ClientId      — e.g. "-1399999958"  (TenantId in DB)
        ///   SchedulerRun:UserId        — e.g. "-1"           (system user)
        /// </summary>
        private LoginDTO BuildLoginFromConfig()
        {
            var dbName = _config["SchedulerRun:DatabaseName"];
            var clientId = _config["SchedulerRun:ClientId"];
            var userId = _config["SchedulerRun:UserId"];

            if (string.IsNullOrWhiteSpace(dbName))
                throw new InvalidOperationException(
                    "SchedulerRun:DatabaseName is not configured in appsettings.");

            if (string.IsNullOrWhiteSpace(clientId))
                throw new InvalidOperationException(
                    "SchedulerRun:ClientId is not configured in appsettings. " +
                    "This is required for tenant isolation in all DAL queries.");

            return new LoginDTO
            {
                DatabaseName = dbName,
                ClientId = int.Parse(clientId),
                UserId = string.IsNullOrWhiteSpace(userId) ? -1 : int.Parse(userId),
                UserName = "SchedulerService"
            };
        }
    }
}