using AutoMapper;
using Marco.Pms.DataAccess.Data;
using Marco.Pms.Helpers.Utility;
using Marco.Pms.Model.Dtos.Tenant;
using Marco.Pms.Model.Employees;
using Marco.Pms.Model.Entitlements;
using Marco.Pms.Model.Filters;
using Marco.Pms.Model.MongoDBModels.Utility;
using Marco.Pms.Model.OrganizationModel;
using Marco.Pms.Model.Projects;
using Marco.Pms.Model.Roles;
using Marco.Pms.Model.TenantModels;
using Marco.Pms.Model.TenantModels.MongoDBModel;
using Marco.Pms.Model.Utilities;
using Marco.Pms.Model.ViewModels.Activities;
using Marco.Pms.Model.ViewModels.Tenant;
using Marco.Pms.Services.Helpers;
using Marco.Pms.Services.Service;
using Marco.Pms.Services.Service.ServiceInterfaces;
using MarcoBMS.Services.Helpers;
using MarcoBMS.Services.Service;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using System.Net;
using System.Text.Json;

// For more information on enabling Web API for empty projects, visit https://go.microsoft.com/fwlink/?LinkID=397860

namespace Marco.Pms.Services.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    [Authorize]
    public class TenantController : ControllerBase
    {
        private readonly IDbContextFactory<ApplicationDbContext> _dbContextFactory;
        private readonly IServiceScopeFactory _serviceScopeFactory;
        private readonly ILoggingService _logger;
        private readonly UserManager<ApplicationUser> _userManager;
        private readonly IMapper _mapper;
        private readonly UserHelper _userHelper;
        private readonly FeatureDetailsHelper _featureDetailsHelper;

        private readonly Guid tenantId;

        private readonly static Guid projectActiveStatus = Guid.Parse("b74da4c2-d07e-46f2-9919-e75e49b12731");
        private readonly static Guid projectInProgressStatus = Guid.Parse("cdad86aa-8a56-4ff4-b633-9c629057dfef");
        private readonly static Guid projectOnHoldStatus = Guid.Parse("603e994b-a27f-4e5d-a251-f3d69b0498ba");
        private readonly static Guid projectInActiveStatus = Guid.Parse("ef1c356e-0fe0-42df-a5d3-8daee355492d");
        private readonly static Guid projectCompletedStatus = Guid.Parse("33deaef9-9af1-4f2a-b443-681ea0d04f81");

        private readonly static Guid tenantActiveStatus = Guid.Parse("62b05792-5115-4f99-8ff5-e8374859b191");
        private readonly static Guid activePlanStatus = Guid.Parse("cd3a68ea-41fd-42f0-bd0c-c871c7337727");
        private readonly static Guid EmployeeFeatureId = Guid.Parse("81ab8a87-8ccd-4015-a917-0627cee6a100");
        private readonly static string AdminRoleName = "Admin";
        public TenantController(IDbContextFactory<ApplicationDbContext> dbContextFactory,
            IServiceScopeFactory serviceScopeFactory,
            ILoggingService logger,
            UserManager<ApplicationUser> userManager,
            IMapper mapper,
            UserHelper userHelper,
            FeatureDetailsHelper featureDetailsHelper)
        {
            _dbContextFactory = dbContextFactory ?? throw new ArgumentNullException(nameof(dbContextFactory));
            _serviceScopeFactory = serviceScopeFactory ?? throw new ArgumentNullException(nameof(serviceScopeFactory));
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
            _userManager = userManager ?? throw new ArgumentNullException(nameof(userManager));
            _mapper = mapper ?? throw new ArgumentNullException(nameof(mapper));
            _userHelper = userHelper ?? throw new ArgumentNullException(nameof(userHelper));
            _featureDetailsHelper = featureDetailsHelper ?? throw new ArgumentNullException(nameof(featureDetailsHelper));
            tenantId = userHelper.GetTenantId();
        }
        #region =================================================================== Tenant APIs ===================================================================

        /// <summary>
        /// Retrieves a paginated list of active tenants with optional filtering and searching.
        /// </summary>
        /// <param name="searchString">A string to search for across various tenant fields.</param>
        /// <param name="filter">A JSON serialized string containing advanced filter criteria.</param>
        /// <param name="pageSize">The number of records to return per page.</param>
        /// <param name="pageNumber">The page number to retrieve.</param>
        /// <returns>A paginated list of tenants matching the criteria.</returns>

        [HttpGet("list")]
        public async Task<IActionResult> GetTenantList([FromQuery] string? searchString, string? filter, int pageSize = 20, int pageNumber = 1)
        {

            using var scope = _serviceScopeFactory.CreateScope();

            var _permissionService = scope.ServiceProvider.GetRequiredService<PermissionServices>();
            _logger.LogInfo("Attempting to fetch tenant list with pageNumber: {PageNumber} and pageSize: {PageSize}", pageNumber, pageSize);

            try
            {
                // --- 1. PERMISSION CHECK ---
                var currentTenant = await _userHelper.GetCurrentTenant();
                if (currentTenant == null)
                {
                    _logger.LogWarning("Authentication failed: No logged-in tenant found.");
                    return StatusCode(403, ApiResponse<object>.ErrorResponse("Authentication required", "Tenant not found", 403));
                }
                var loggedInEmployee = await _userHelper.GetCurrentEmployeeAsync();
                if (loggedInEmployee == null)
                {
                    _logger.LogWarning("Authentication failed: No logged-in employee found.");
                    return StatusCode(403, ApiResponse<object>.ErrorResponse("Authentication required", "User is not logged in.", 403));
                }

                // A root user should have access regardless of the specific permission.
                var isSuperTenant = currentTenant.IsSuperTenant;
                var hasPermission = await _permissionService.HasPermission(PermissionsMaster.ManageTenants, loggedInEmployee.Id);

                if (!hasPermission && !isSuperTenant)
                {
                    _logger.LogWarning("Permission denied: User {EmployeeId} attempted to list tenants without 'ManageTenants' permission or root access.", loggedInEmployee.Id);
                    return StatusCode(403, ApiResponse<object>.ErrorResponse("Access denied", "User does not have the required permissions for this action.", 403));
                }

                // --- 2. QUERY CONSTRUCTION ---
                // Using a DbContext from the factory ensures a fresh context for this request.
                await using var _context = await _dbContextFactory.CreateDbContextAsync();

                // Start with a base IQueryable. Filters will be appended to this.
                var tenantQuery = _context.Tenants.Where(t => t.IsActive);

                if (hasPermission && !isSuperTenant)
                {
                    tenantQuery = tenantQuery.Where(t => t.Id == currentTenant.Id || t.CreatedById == loggedInEmployee.Id);
                }

                // Apply advanced filters from the JSON filter object.
                var tenantFilter = TryDeserializeFilter(filter);
                if (tenantFilter != null)
                {
                    // Date range filtering
                    if (tenantFilter.StartDate.HasValue && tenantFilter.EndDate.HasValue)
                    {
                        // OPTIMIZATION: Avoid using .Date on the database column, as it can prevent index usage.
                        // This structure (`>= start` and `< end.AddDays(1)`) is index-friendly and correctly inclusive.
                        var endDateExclusive = tenantFilter.EndDate.Value.AddDays(1);
                        tenantQuery = tenantQuery.Where(t => t.OnBoardingDate >= tenantFilter.StartDate.Value && t.OnBoardingDate < endDateExclusive);
                    }
                    // List-based filtering
                    if (tenantFilter.IndustryIds?.Any() == true)
                    {
                        tenantQuery = tenantQuery.Where(t => t.IndustryId.HasValue && tenantFilter.IndustryIds.Contains(t.IndustryId.Value));
                    }
                    if (tenantFilter.References?.Any() == true)
                    {
                        tenantQuery = tenantQuery.Where(t => tenantFilter.References.Contains(t.Reference));
                    }
                    if (tenantFilter.TenantStatusIds?.Any() == true)
                    {
                        tenantQuery = tenantQuery.Where(t => tenantFilter.TenantStatusIds.Contains(t.TenantStatusId));
                    }
                    if (tenantFilter.CreatedByIds?.Any() == true)
                    {
                        tenantQuery = tenantQuery.Where(t => t.CreatedById.HasValue && tenantFilter.CreatedByIds.Contains(t.CreatedById.Value));
                    }
                }

                // Apply free-text search string.
                if (!string.IsNullOrWhiteSpace(searchString))
                {
                    // OPTIMIZATION: Do not use .ToLower() on the database columns (e.g., `t.Name.ToLower()`).
                    // This makes the query non-SARGable and kills performance by preventing index usage.
                    // This implementation relies on the database collation being case-insensitive (e.g., `SQL_Latin1_General_CP1_CI_AS` in SQL Server).
                    tenantQuery = tenantQuery.Where(t =>
                        t.Name.Contains(searchString) ||
                        t.ContactName.Contains(searchString) ||
                        t.Email.Contains(searchString) ||
                        t.ContactNumber.Contains(searchString) ||
                        t.BillingAddress.Contains(searchString) ||
                        (t.TaxId != null && t.TaxId.Contains(searchString)) ||
                        (t.Description != null && t.Description.Contains(searchString)) ||
                        (t.DomainName != null && t.DomainName.Contains(searchString))
                    );
                }

                // --- 3. PAGINATION AND EXECUTION ---
                // First, get the total count of records for pagination metadata.
                // This executes a separate, efficient `COUNT(*)` query.
                int totalRecords = await tenantQuery.CountAsync();
                int totalPages = (int)Math.Ceiling((double)totalRecords / pageSize);

                _logger.LogInfo("Found {TotalRecords} total tenants matching the query.", totalRecords);

                // Now, apply ordering and pagination to fetch only the data for the current page.
                // This is efficient server-side pagination.
                var tenantList = await tenantQuery
                    .Include(t => t.Industry)       // Eager load related data to prevent N+1 queries.
                    .Include(t => t.TenantStatus)
                    .OrderByDescending(t => t.OnBoardingDate)
                    .Skip((pageNumber - 1) * pageSize)
                    .Take(pageSize)
                    .ToListAsync();

                // Map the entities to a ViewModel/DTO for the response.
                var vm = _mapper.Map<List<TenantListVM>>(tenantList);

                // --- 4. CONSTRUCT RESPONSE ---
                var response = new
                {
                    TotalCount = totalRecords,
                    TotalPages = totalPages,
                    CurrentPage = pageNumber,
                    PageSize = pageSize,
                    Filter = tenantFilter, // Return the applied filter for context on the client-side.
                    Data = vm
                };

                _logger.LogInfo("Successfully fetched {RecordCount} tenant records.", vm.Count);
                return Ok(ApiResponse<object>.SuccessResponse(response, $"{totalRecords} records of tenants fetched successfully", 200));
            }
            catch (Exception ex)
            {
                // CRITICAL SECURITY FIX: Do not expose the exception details to the client.
                // Log the full exception for debugging purposes.
                _logger.LogError(ex, "An unhandled exception occurred while fetching the tenant list.");

                // Return a generic 500 Internal Server Error response.
                return StatusCode(500, ApiResponse<object>.ErrorResponse("An internal server error occurred.", "An unexpected error prevented the request from completing.", 500));
            }
        }

        // GET api/<TenantController>/5
        [HttpGet("details/{id}")]
        public async Task<IActionResult> GetTenantDetailsAsync(Guid id)
        {
            _logger.LogInfo("GetTenantDetails started for TenantId: {TenantId}", id);

            // Get currently logged-in employee info
            var loggedInEmployee = await _userHelper.GetCurrentEmployeeAsync();
            if (loggedInEmployee == null)
            {
                _logger.LogWarning("No logged-in employee found for the request.");
                return StatusCode(403, ApiResponse<object>.ErrorResponse("Unauthorized", "User must be logged in.", 403));
            }

            using var scope = _serviceScopeFactory.CreateScope();

            // Check permissions using a single service scope to avoid overhead
            bool hasManagePermission, hasModifyPermission, hasViewPermission;
            var manageTask = Task.Run(async () =>
            {
                var permissionService = scope.ServiceProvider.GetRequiredService<PermissionServices>();
                return await permissionService.HasPermission(PermissionsMaster.ManageTenants, loggedInEmployee.Id);
            });
            var modifyTask = Task.Run(async () =>
            {
                var permissionService = scope.ServiceProvider.GetRequiredService<PermissionServices>();
                return await permissionService.HasPermission(PermissionsMaster.ModifyTenant, loggedInEmployee.Id);
            });
            var viewTask = Task.Run(async () =>
            {
                var permissionService = scope.ServiceProvider.GetRequiredService<PermissionServices>();
                return await permissionService.HasPermission(PermissionsMaster.ViewTenant, loggedInEmployee.Id);
            });

            await Task.WhenAll(manageTask, modifyTask, viewTask);

            hasManagePermission = manageTask.Result;
            hasModifyPermission = modifyTask.Result;
            hasViewPermission = viewTask.Result;

            if (!hasManagePermission && !hasModifyPermission && !hasViewPermission)
            {
                _logger.LogWarning("Permission denied: User {EmployeeId} attempted to access tenant details without the required permissions.", loggedInEmployee.Id);
                return StatusCode(403,
                    ApiResponse<object>.ErrorResponse("Access denied", "User does not have the required permissions for this action.", 403));
            }

            // Create a single DbContext for main tenant fetch and related data requests
            await using var _context = await _dbContextFactory.CreateDbContextAsync();

            // Fetch tenant details with related Industry and TenantStatus in a single query
            var tenant = await _context.Tenants
                .Include(t => t.Industry)
                .Include(t => t.TenantStatus)
                .AsNoTracking()
                .FirstOrDefaultAsync(t => t.Id == id);

            if (tenant == null)
            {
                _logger.LogWarning("Tenant {TenantId} not found in database", id);
                return NotFound(ApiResponse<object>.ErrorResponse("Tenant not found", "Tenant not found", 404));
            }

            if (!hasManagePermission && (tenant.OrganizationId != loggedInEmployee.OrganizationId || (!hasModifyPermission && !hasViewPermission)))
            {
                _logger.LogWarning("Permission denied: User {EmployeeId} attempted to access tenant details of other tenant.", loggedInEmployee.Id);
                return StatusCode(403,
                    ApiResponse<object>.ErrorResponse("Access denied", "User does not have the required permissions for this action.", 403));
            }

            _logger.LogInfo("Tenant {TenantId} found.", tenant.Id);

            // Fetch dependent data in parallel to improve performance
            var employeesTask = Task.Run(async () =>
            {
                await using var dbContext = await _dbContextFactory.CreateDbContextAsync();
                return await dbContext.Employees
                    .Include(e => e.ApplicationUser)
                    .Where(e => e.TenantId == tenant.Id)
                    .AsNoTracking()
                    .ToListAsync();
            });

            var createdByTask = Task.Run(async () =>
            {
                await using var dbContext = await _dbContextFactory.CreateDbContextAsync();
                return await dbContext.Employees
                    .AsNoTracking()
                    .Where(e => e.Id == tenant.CreatedById)
                    .Select(e => _mapper.Map<BasicEmployeeVM>(e))
                    .FirstOrDefaultAsync();
            });

            var plansTask = Task.Run(async () =>
            {
                await using var dbContext = await _dbContextFactory.CreateDbContextAsync();
                return await dbContext.TenantSubscriptions
                    .Include(sp => sp.CreatedBy)
                        .ThenInclude(e => e!.JobRole)
                    .Include(sp => sp.UpdatedBy)
                       .ThenInclude(e => e!.JobRole)
                    .Include(sp => sp.Currency)
                    .Include(ts => ts.Plan).ThenInclude(sp => sp!.Plan)
                    .Where(ts => ts.TenantId == tenant.Id && ts.Plan != null)
                    .AsNoTracking()
                    .OrderBy(ts => ts.CreatedBy)
                    .ToListAsync();
            });

            var projectsTask = Task.Run(async () =>
            {
                await using var dbContext = await _dbContextFactory.CreateDbContextAsync();
                return await dbContext.Projects
                    .Include(p => p.ProjectStatus)
                    .Where(p => p.TenantId == tenant.Id)
                    .AsNoTracking()
                    .ToListAsync();
            });

            await Task.WhenAll(employeesTask, createdByTask, plansTask, projectsTask);

            var employees = employeesTask.Result;
            var createdBy = createdByTask.Result;
            var plans = plansTask.Result;
            var projects = projectsTask.Result;

            var _razorpayService = scope.ServiceProvider.GetRequiredService<IRazorpayService>();

            var paymentDetailIds = plans.Where(ts => ts.PaymentDetailId.HasValue).Select(ts => ts.PaymentDetailId!.Value).ToList();
            var paymentsDetails = await _razorpayService.GetPaymentDetailsListFromDataBase(paymentDetailIds);

            // Calculate active/inactive employees count
            var activeEmployeesCount = employees.Count(e => e.IsActive);
            var inActiveEmployeesCount = employees.Count - activeEmployeesCount;
            var activeUserCount = employees.Count(e => e.IsActive && e.ApplicationUserId != null && e.Email != null);


            // Filter current active (non-cancelled) subscription plan
            var currentPlan = plans.FirstOrDefault(ts => !ts.IsCancelled);
            var expiryDate = currentPlan?.EndDate;
            var nextBillingDate = currentPlan?.NextBillingDate;

            // Map Tenant entity to TenantDetailsVM response model
            var response = _mapper.Map<TenantDetailsVM>(tenant);
            response.ActiveEmployees = activeEmployeesCount;
            response.InActiveEmployees = inActiveEmployeesCount;

            // Count projects by status
            response.ActiveProjects = projects.Count(p => p.ProjectStatusId == projectActiveStatus);
            response.InProgressProjects = projects.Count(p => p.ProjectStatusId == projectInProgressStatus);
            response.OnHoldProjects = projects.Count(p => p.ProjectStatusId == projectOnHoldStatus);
            response.InActiveProjects = projects.Count(p => p.ProjectStatusId == projectInActiveStatus);
            response.CompletedProjects = projects.Count(p => p.ProjectStatusId == projectCompletedStatus);
            response.SeatsAvailable = (int)(currentPlan?.MaxUsers ?? 1) - activeUserCount;
            response.ExpiryDate = expiryDate;
            response.NextBillingDate = nextBillingDate;
            response.CreatedBy = createdBy;

            response.CurrentPlan = _mapper.Map<SubscriptionPlanDetailsVM>(currentPlan);
            response.CurrentPlan.PaymentDetail = paymentsDetails.FirstOrDefault(pd => currentPlan != null && pd.Id == currentPlan.PaymentDetailId);

            response.CurrentPlanFeatures = await _featureDetailsHelper.GetFeatureDetails(currentPlan?.Plan?.FeaturesId ?? Guid.Empty);
            // Map subscription history plans to DTO
            response.SubscriptionHistery = plans.Select(ts =>
            {
                var result = _mapper.Map<SubscriptionPlanDetailsVM>(ts);
                result.PaymentDetail = paymentsDetails.FirstOrDefault(pd => ts != null && pd.Id == ts.PaymentDetailId);
                return result;
            }).ToList();

            _logger.LogInfo("Tenant details fetched successfully for TenantId: {TenantId}", tenant.Id);

            return Ok(ApiResponse<object>.SuccessResponse(response, "Tenant profile fetched successfully", 200));
        }

        // POST api/<TenantController>
        [HttpPost("create")]
        public async Task<IActionResult> CreateTenant([FromBody] CreateTenantDto model)
        {
            using var scope = _serviceScopeFactory.CreateScope();
            await using var _context = await _dbContextFactory.CreateDbContextAsync();

            var _configuration = scope.ServiceProvider.GetRequiredService<IConfiguration>();
            var _emailSender = scope.ServiceProvider.GetRequiredService<IEmailSender>();
            var _permissionService = scope.ServiceProvider.GetRequiredService<PermissionServices>();

            _logger.LogInfo("Attempting to create a new tenant with organization name: {OrganizationName}", model.OrganizationName);

            // 1. --- PERMISSION CHECK ---
            var loggedInEmployee = await _userHelper.GetCurrentEmployeeAsync();
            if (loggedInEmployee == null)
            {
                // This case should ideally be handled by an [Authorize] attribute, but it's good practice to double-check.
                return StatusCode(403, ApiResponse<object>.ErrorResponse("Authentication required", "User is not logged in.", 403));
            }

            var hasPermission = await _permissionService.HasPermission(PermissionsMaster.ManageTenants, loggedInEmployee.Id);
            if (!hasPermission || !(loggedInEmployee.ApplicationUser?.IsRootUser ?? false))
            {
                _logger.LogWarning("Permission denied: User {EmployeeId} attempted to create a tenant without sufficient rights.", loggedInEmployee.Id);
                return StatusCode(403, ApiResponse<object>.ErrorResponse("Access denied", "User does not have the required permissions for this action.", 403));
            }

            // 2. --- VALIDATION ---
            // Check if a user with the same email already exists.
            var existingUser = await _userManager.FindByEmailAsync(model.Email);
            if (existingUser != null)
            {
                _logger.LogWarning("Tenant creation failed for email {Email}: an application user with this email already exists.", model.Email);
                return StatusCode(409, ApiResponse<object>.ErrorResponse("Tenant cannot be created", "A user with the specified email already exists.", 409));
            }

            // Check if a tenant with the same Tax ID and Domain Name already exists.
            var taxTask = Task.Run(async () =>
            {
                if (!string.IsNullOrWhiteSpace(model.TaxId))
                {
                    await using var context = await _dbContextFactory.CreateDbContextAsync();
                    return await context.Tenants.AnyAsync(t => t.TaxId == model.TaxId);

                }
                return false;
            });
            var domainTask = Task.Run(async () =>
            {
                if (!string.IsNullOrWhiteSpace(model.DomainName))
                {
                    await using var context = await _dbContextFactory.CreateDbContextAsync();
                    return await context.Tenants.AnyAsync(t => t.DomainName == model.DomainName);

                }
                return false;
            });

            await Task.WhenAll(taxTask, domainTask);

            if (taxTask.Result || domainTask.Result)
            {
                if (!string.IsNullOrWhiteSpace(model.TaxId))
                {
                    _logger.LogWarning("Tenant creation failed for Tax ID {TaxId}: a tenant with this Tax ID already exists.", model.TaxId);
                }
                if (!string.IsNullOrWhiteSpace(model.DomainName))
                {
                    _logger.LogWarning("Tenant creation failed for Domain Name {DomainName}: a tenant with this Domain Name already exists.", model.DomainName);
                }
                return StatusCode(409, ApiResponse<object>.ErrorResponse("Tenant cannot be created", "A tenant already exists.", 409));
            }

            // Check if the provided logo is a valid Base64 string.
            if (!string.IsNullOrWhiteSpace(model.logoImage) && !IsBase64String(model.logoImage))
            {
                _logger.LogWarning("Tenant creation failed for user {EmployeeId}: The provided logo image was not a valid Base64 string.", loggedInEmployee.Id);
                return StatusCode(400, ApiResponse<object>.ErrorResponse("Tenant cannot be created", "The provided logo image is invalid.", 400));
            }

            // 3. --- DATABASE TRANSACTION ---
            // Use a transaction to ensure all related entities are created successfully or none at all.
            await using var transaction = await _context.Database.BeginTransactionAsync();
            try
            {
                // Get last SPRID and increment for new organization
                var lastOrganization = await _context.Organizations.OrderByDescending(sp => sp.SPRID).FirstOrDefaultAsync();
                double lastSPRID = lastOrganization?.SPRID ?? 5400;

                // Map DTO to entity and set defaults
                Organization organization = new Organization
                {
                    Name = model.OrganizationName,
                    Email = model.Email,
                    ContactPerson = $"{model.FirstName} {model.LastName}",
                    Address = model.BillingAddress,
                    ContactNumber = model.ContactNumber,
                    SPRID = lastSPRID + 1,
                    logoImage = model.logoImage,
                    CreatedAt = DateTime.UtcNow,
                    CreatedById = loggedInEmployee.Id,
                    IsActive = true
                };

                _context.Organizations.Add(organization);

                // Create the primary Tenant entity

                var tenant = _mapper.Map<Tenant>(model);

                tenant.TenantStatusId = tenantActiveStatus;
                tenant.CreatedById = loggedInEmployee.Id;
                tenant.IsSuperTenant = false;
                tenant.OrganizationId = organization.Id;

                _context.Tenants.Add(tenant);

                // Create the root ApplicationUser for the new tenant
                var applicationUser = new ApplicationUser
                {
                    Email = model.Email,
                    UserName = model.Email, // Best practice to use email as username for simplicity
                    IsRootUser = true,
                    EmailConfirmed = true // Auto-confirming email as it's part of a trusted setup process
                };

                // SECURITY WARNING: Hardcoded passwords are a major vulnerability.
                // Replace "User@123" with a securely generated random password.
                var initialPassword = "User@123"; // TODO: Replace with password generation service.
                var result = await _userManager.CreateAsync(applicationUser, initialPassword);

                if (!result.Succeeded)
                {
                    // If user creation fails, roll back the transaction immediately and return the errors.
                    await transaction.RollbackAsync();
                    var errors = result.Errors.Select(e => e.Description).ToList();
                    _logger.LogWarning("Failed to create ApplicationUser for tenant {TenantName}. Errors: {Errors}", model.OrganizationName, string.Join(", ", errors));
                    return BadRequest(ApiResponse<object>.ErrorResponse("Failed to create user", errors, 400));
                }

                // Create the default "Admin" Job Role for the tenant
                var adminJobRole = new JobRole
                {
                    Name = AdminRoleName,
                    Description = "Default administrator role for the tenant.",
                    TenantId = tenant.Id
                };
                _context.JobRoles.Add(adminJobRole);

                // Create the primary Employee record and link it to the ApplicationUser and JobRole
                var employeeUser = new Employee
                {
                    FirstName = model.FirstName,
                    LastName = model.LastName,
                    Email = model.Email,
                    PhoneNumber = model.ContactNumber,
                    JoiningDate = model.OnBoardingDate,
                    ApplicationUserId = applicationUser.Id,
                    JobRole = adminJobRole, // Link to the newly created role
                    CurrentAddress = model.BillingAddress,
                    IsActive = true,
                    IsSystem = false,
                    IsPrimary = true,
                    OrganizationId = organization.Id,
                    HasApplicationAccess = true
                };
                _context.Employees.Add(employeeUser);

                var applicationRole = new ApplicationRole
                {
                    Role = "Super User",
                    Description = "Super User",
                    IsSystem = true,
                    TenantId = tenant.Id
                };
                _context.ApplicationRoles.Add(applicationRole);

                var rolePermissionMappigs = new List<RolePermissionMappings> {
                    new RolePermissionMappings
                    {
                        ApplicationRoleId = applicationRole.Id,
                        FeaturePermissionId = PermissionsMaster.ModifyTenant
                    },
                    new RolePermissionMappings
                    {
                        ApplicationRoleId = applicationRole.Id,
                        FeaturePermissionId = PermissionsMaster.ViewTenant
                    },
                    new RolePermissionMappings
                    {
                        ApplicationRoleId = applicationRole.Id,
                        FeaturePermissionId = PermissionsMaster.ManageMasters
                    },
                    new RolePermissionMappings
                    {
                        ApplicationRoleId = applicationRole.Id,
                        FeaturePermissionId = PermissionsMaster.ViewMasters
                    },
                    new RolePermissionMappings
                    {
                        ApplicationRoleId = applicationRole.Id,
                        FeaturePermissionId = PermissionsMaster.ViewOrganization
                    },
                    new RolePermissionMappings
                    {
                        ApplicationRoleId = applicationRole.Id,
                        FeaturePermissionId = PermissionsMaster.AddOrganization
                    },
                    new RolePermissionMappings
                    {
                        ApplicationRoleId = applicationRole.Id,
                        FeaturePermissionId = PermissionsMaster.EditOrganization
                    }
                };
                _context.RolePermissionMappings.AddRange(rolePermissionMappigs);

                _context.EmployeeRoleMappings.Add(new EmployeeRoleMapping
                {
                    EmployeeId = employeeUser.Id,
                    RoleId = applicationRole.Id,
                    IsEnabled = true,
                    TenantId = tenant.Id
                });

                // Create a default project for the new tenant
                var project = new Project
                {
                    Name = "Default Project",
                    ProjectStatusId = Guid.Parse("b74da4c2-d07e-46f2-9919-e75e49b12731"), // Consider using a constant for this GUID
                    ProjectAddress = model.BillingAddress,
                    StartDate = model.OnBoardingDate,
                    EndDate = DateTime.MaxValue,
                    PromoterId = organization.Id,
                    PMCId = organization.Id,
                    ContactPerson = tenant.ContactName,
                    TenantId = tenant.Id
                };
                _context.Projects.Add(project);

                var projectAllocation = new ProjectAllocation
                {
                    ProjectId = project.Id,
                    EmployeeId = employeeUser.Id,
                    AllocationDate = model.OnBoardingDate,
                    IsActive = true,
                    JobRoleId = adminJobRole.Id,
                    TenantId = tenant.Id
                };
                _context.ProjectAllocations.Add(projectAllocation);

                // Map organization services
                if (model.ServiceIds?.Any() ?? false)
                {
                    var serviceOrgMappings = model.ServiceIds.Select(s => new OrgServiceMapping
                    {
                        ServiceId = s,
                        OrganizationId = organization.Id
                    }).ToList();

                    _context.OrgServiceMappings.AddRange(serviceOrgMappings);
                }

                // All entities are now added to the context. Save them all in a single database operation.
                await _context.SaveChangesAsync();

                // 4. --- POST-CREATION ACTIONS ---
                // Generate a password reset token so the new user can set their own password.
                _logger.LogInfo("User {Email} created. Sending password setup email.", applicationUser.Email);
                var token = await _userManager.GeneratePasswordResetTokenAsync(applicationUser);
                var resetLink = $"{_configuration["AppSettings:WebFrontendUrl"]}/reset-password?token={WebUtility.UrlEncode(token)}&email={WebUtility.UrlEncode(applicationUser.Email)}";
                await _emailSender.SendResetPasswordEmailOnRegister(applicationUser.Email, employeeUser.FirstName, resetLink);

                // Map the result to a ViewModel for the API response.
                var tenantVM = _mapper.Map<TenantVM>(tenant);
                tenantVM.CreatedBy = _mapper.Map<BasicEmployeeVM>(loggedInEmployee);

                // Commit the transaction as all operations were successful.
                await transaction.CommitAsync();

                _logger.LogInfo("Successfully created tenant {TenantId} for organization {OrganizationName}.", tenant.Id, tenant.Name);
                return StatusCode(201, ApiResponse<TenantVM>.SuccessResponse(tenantVM, "Tenant created successfully.", 201));
            }
            catch (DbUpdateException dbEx)
            {
                await transaction.RollbackAsync();
                // Log the detailed database exception, including the inner exception if available.
                _logger.LogError(dbEx, "A database update exception occurred while creating tenant for email {Email}. Inner Exception: {InnerException}",
                    model.Email, dbEx.InnerException?.Message ?? string.Empty);
                return StatusCode(500, ApiResponse<object>.ErrorResponse("An internal database error occurred.", ExceptionMapper(dbEx), 500));
            }
            catch (Exception ex)
            {
                await transaction.RollbackAsync();
                // Log the general exception.
                _logger.LogError(ex, "An unexpected exception occurred while creating tenant for email {Email}.", model.Email);
                return StatusCode(500, ApiResponse<object>.ErrorResponse("An unexpected internal error occurred.", ExceptionMapper(ex), 500));
            }
        }

        /// <summary>
        /// Updates tenant and root employee details for a specified tenant ID.
        /// </summary>
        /// <param name="id">ID of the tenant to update</param>
        /// <param name="model">Details to update</param>
        /// <returns>Result of the operation</returns>

        [HttpPut("edit/{id}")]
        public async Task<IActionResult> UpdateTenant(Guid id, [FromBody] UpdateTenantDto model)
        {
            _logger.LogInfo("UpdateTenant called for TenantId: {TenantId} by user.", id);

            // 1. Retrieve the logged-in employee information
            var loggedInEmployee = await _userHelper.GetCurrentEmployeeAsync();
            if (loggedInEmployee == null)
            {
                _logger.LogWarning("Unauthorized access - User not logged in.");
                return StatusCode(403, ApiResponse<object>.ErrorResponse("Unauthorized", "User must be logged in.", 403));
            }

            // 2. Check permissions using a single service scope to avoid overhead
            bool hasManagePermission, hasModifyPermission;
            UtilityMongoDBHelper _updateLogHelper;
            using (var scope = _serviceScopeFactory.CreateScope())
            {
                var permissionService = scope.ServiceProvider.GetRequiredService<PermissionServices>();
                _updateLogHelper = scope.ServiceProvider.GetRequiredService<UtilityMongoDBHelper>();

                var manageTask = permissionService.HasPermission(PermissionsMaster.ManageTenants, loggedInEmployee.Id);
                var modifyTask = permissionService.HasPermission(PermissionsMaster.ModifyTenant, loggedInEmployee.Id);

                await Task.WhenAll(manageTask, modifyTask);

                hasManagePermission = manageTask.Result;
                hasModifyPermission = modifyTask.Result;
            }

            if (!hasManagePermission && !hasModifyPermission)
            {
                _logger.LogWarning("Access denied: User {EmployeeId} lacks required permissions for UpdateTenant on TenantId: {TenantId}.", loggedInEmployee.Id, id);
                return StatusCode(403, ApiResponse<object>.ErrorResponse("Access denied", "User does not have the required permissions for this action.", 403));
            }
            if (!hasManagePermission && hasModifyPermission && id != loggedInEmployee.TenantId)
            {
                _logger.LogWarning("Permission denied: User {EmployeeId} attempted to access tenant details of other tenant.", loggedInEmployee.Id);
                return StatusCode(403,
                    ApiResponse<object>.ErrorResponse("Access denied", "User does not have the required permissions for this action.", 403));
            }
            // 3. Use a single DbContext instance for data access
            await using var context = await _dbContextFactory.CreateDbContextAsync();

            // 4. Fetch tenant (with related Industry, TenantStatus), tracking enabled for updates
            var tenant = await context.Tenants
                .Include(t => t.Industry)
                .Include(t => t.TenantStatus)
                .AsNoTracking()
                .FirstOrDefaultAsync(t => t.Id == id);

            if (tenant == null)
            {
                _logger.LogWarning("Tenant not found: ID {TenantId}", id);
                return NotFound(ApiResponse<object>.ErrorResponse("Tenant not found", "Tenant not found", 404));
            }

            _logger.LogInfo("Tenant {TenantId} fetched for update.", tenant.Id);

            var tenantObject = _updateLogHelper.EntityToBsonDocument(tenant);
            // 5. Map update DTO properties to the tenant entity
            _mapper.Map(model, tenant);

            // 6. Fetch root employee for the tenant (includes ApplicationUser)
            var rootEmployee = await context.Employees
                .Include(e => e.ApplicationUser)
                .FirstOrDefaultAsync(e => e.TenantId == tenant.Id && e.ApplicationUser != null && (e.ApplicationUser.IsRootUser ?? false));

            if (rootEmployee == null)
            {
                _logger.LogWarning("Root employee not found for tenant {TenantId}", id);
                return NotFound(ApiResponse<object>.ErrorResponse("Root employee not found", "Root employee not found", 404));
            }
            var employeeobject = _updateLogHelper.EntityToBsonDocument(rootEmployee);
            // 7. Update root employee details
            rootEmployee.FirstName = model.FirstName;
            rootEmployee.LastName = model.LastName;
            rootEmployee.PhoneNumber = model.ContactNumber;
            rootEmployee.CurrentAddress = model.BillingAddress;

            // 8. Save changes to DB
            try
            {
                context.Tenants.Update(tenant);
                await context.SaveChangesAsync();
                _logger.LogInfo("Tenant {TenantId} and root employee updated successfully.", tenant.Id);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error updating Tenant {TenantId} or root employee.", tenant.Id);
                return StatusCode(500, ApiResponse<object>.ErrorResponse("Error updating tenant", "Unexpected error occurred while updating tenant.", 500));
            }

            var tenantTaks = Task.Run(async () =>
            {
                await _updateLogHelper.PushToUpdateLogsAsync(new UpdateLogsObject
                {
                    EntityId = tenant.Id.ToString(),
                    UpdatedById = loggedInEmployee.Id.ToString(),
                    OldObject = tenantObject,
                    UpdatedAt = DateTime.UtcNow
                }, "TenantModificationLog");
            });
            var employeeTaks = Task.Run(async () =>
            {
                await _updateLogHelper.PushToUpdateLogsAsync(new UpdateLogsObject
                {
                    EntityId = rootEmployee.Id.ToString(),
                    UpdatedById = loggedInEmployee.Id.ToString(),
                    OldObject = employeeobject,
                    UpdatedAt = DateTime.UtcNow
                }, "EmployeeModificationLog");
            });

            await Task.WhenAll(tenantTaks, employeeTaks);

            // 9. Map updated tenant to ViewModel for response
            var response = _mapper.Map<TenantVM>(tenant);

            return Ok(ApiResponse<object>.SuccessResponse(response, "Tenant updated successfully", 200));
        }

        // DELETE api/<TenantController>/5
        [HttpDelete("delete/{id}")]
        public async Task<IActionResult> DeleteTenant(Guid id, [FromQuery] bool isActive = false)
        {
            var action = isActive ? "activation" : "deactivation";
            _logger.LogInfo("Attempting tenant {Action} for ID: {TenantId}", action, id);

            // --- 1. Authentication & Authorization ---
            var loggedInEmployee = await _userHelper.GetCurrentEmployeeAsync();
            if (loggedInEmployee == null)
            {
                _logger.LogWarning("Unauthorized tenant status update attempt. User is not logged in.");
                return StatusCode(403, ApiResponse<object>.ErrorResponse("Unauthorized", "User must be logged in to perform this action.", 403));
            }

            using var scope = _serviceScopeFactory.CreateScope();
            var _permissionService = scope.ServiceProvider.GetRequiredService<PermissionServices>();
            var _updateLogHelper = scope.ServiceProvider.GetRequiredService<UtilityMongoDBHelper>();

            var hasPermission = await _permissionService.HasPermission(PermissionsMaster.ManageTenants, loggedInEmployee.Id);
            if (!hasPermission && !(loggedInEmployee.ApplicationUser?.IsRootUser ?? false))
            {
                _logger.LogWarning(
                    "Permission Denied: User {EmployeeId} attempted tenant status update for Tenant {TenantId} without 'ManageTenants' permission.",
                    loggedInEmployee.Id, id);
                return StatusCode(403, ApiResponse<object>.ErrorResponse("Access Denied", "User does not have the required permissions for this action.", 403));
            }

            // --- 2. Data Retrieval ---
            await using var context = await _dbContextFactory.CreateDbContextAsync();
            var tenant = await context.Tenants
                // Include related data only if it's required by the TenantVM mapping.
                // If not, removing these improves performance.
                .Include(t => t.Industry)
                .Include(t => t.TenantStatus)
                .FirstOrDefaultAsync(t => t.Id == id);

            if (tenant == null)
            {
                _logger.LogWarning("Tenant status update failed: Tenant with ID {TenantId} not found.", id);
                return NotFound(ApiResponse<object>.ErrorResponse("Not Found", $"Tenant with ID '{id}' was not found.", 404));
            }

            // --- 3. Logic & State Change ---
            // Efficiency: If the state is already what is being requested, do nothing.
            if (tenant.IsActive == isActive)
            {
                var currentStatus = isActive ? "already active" : "already inactive";
                _logger.LogInfo("No action needed. Tenant {TenantId} is {Status}.", tenant.Id, currentStatus);
                var noChangeMessage = $"Tenant was {currentStatus}. No changes were made.";
                return Ok(ApiResponse<object>.SuccessResponse(_mapper.Map<TenantVM>(tenant), noChangeMessage, 200));
            }

            // Capture the state *before* modification for the audit log.
            var tenantOldStateBson = _updateLogHelper.EntityToBsonDocument(tenant);
            tenant.IsActive = isActive;

            // --- 4. Database Persistence ---
            try
            {
                await context.SaveChangesAsync();
                _logger.LogInfo("Successfully updated Tenant {TenantId} IsActive status to {IsActive}.", tenant.Id, isActive);
            }
            catch (DbUpdateException ex) // Be more specific with exceptions if possible.
            {
                _logger.LogError(ex, "Database error occurred while updating status for Tenant {TenantId}.", tenant.Id);
                return StatusCode(500, ApiResponse<object>.ErrorResponse("Database Error", "An error occurred while saving changes to the database.", 500));
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "An unexpected error occurred while updating status for Tenant {TenantId}.", tenant.Id);
                return StatusCode(500, ApiResponse<object>.ErrorResponse("Server Error", "An unexpected error occurred.", 500));
            }

            // --- 5. Audit Logging ---
            // This runs after the DB save is confirmed.
            // Note: If this call fails, the audit log will be missing for a successful DB change.
            // For critical systems, consider a more robust outbox pattern.
            await _updateLogHelper.PushToUpdateLogsAsync(new UpdateLogsObject
            {
                EntityId = tenant.Id.ToString(),
                UpdatedById = loggedInEmployee.Id.ToString(),
                OldObject = tenantOldStateBson,
                UpdatedAt = DateTime.UtcNow
            }, "TenantModificationLog");
            _logger.LogInfo("Audit log created for status change of Tenant {TenantId} by User {EmployeeId}.", tenant.Id, loggedInEmployee.Id);


            // --- 6. Prepare and Return Response ---
            var responseData = _mapper.Map<TenantVM>(tenant);
            var successMessage = $"Tenant successfully {(isActive ? "activated" : "deactivated")}.";

            return Ok(ApiResponse<object>.SuccessResponse(responseData, successMessage, 200));
        }

        [AllowAnonymous]
        [HttpPost("self/create")]
        public async Task<IActionResult> SelfRegistrationTenant([FromBody] TenantEnquireDto model)
        {
            // Log the start of the registration attempt
            _logger.LogInfo("Self-registration request received at {Timestamp}.", DateTime.UtcNow);
            try
            {
                // Create db context asynchronously for optimized resource use
                await using var context = await _dbContextFactory.CreateDbContextAsync();

                // 2. --- VALIDATION ---
                // Check if a user with the same email already exists.
                var existingUser = await _userManager.FindByEmailAsync(model.Email);
                if (existingUser != null)
                {
                    _logger.LogWarning("Tenant creation failed for email {Email}: an application user with this email already exists.", model.Email);
                    return StatusCode(409, ApiResponse<object>.ErrorResponse("Tenant cannot be created", "A user with the specified email already exists.", 409));
                }

                var industry = await context.Industries.FirstOrDefaultAsync(i => i.Id == model.IndustryId);
                if (industry == null)
                {
                    _logger.LogWarning("Industry not found while creating the tenant enquire");
                    return NotFound(ApiResponse<object>.ErrorResponse("Industry not found", "Industry not found", 404));
                }

                // Map DTO to domain model and assign new Guid
                var tenantEnquire = _mapper.Map<TenantEnquire>(model);
                tenantEnquire.Id = Guid.NewGuid();

                // Add new tenant enquiry to the database
                await context.TenantEnquires.AddAsync(tenantEnquire);
                await context.SaveChangesAsync();

                // Log successful registration
                _logger.LogInfo("Tenant enquiry created successfully. ID: {TenantEnquireId}", tenantEnquire.Id);

                // Return success response with proper status code and user information
                return Ok(ApiResponse<object>.SuccessResponse(tenantEnquire, "Tenant enquiry added successfully.", 201));
            }
            catch (Exception ex)
            {
                // Log error with detailed exception information at Error level
                _logger.LogError(ex, "Error occurred during self-registration: {Message}", ex.Message);

                // Return standardized error response to the client
                var errorResponse = ApiResponse<object>.ErrorResponse("Failed to add tenant enquiry, please try again later.", "Failed to add tenant enquiry, please try again later.", 500);

                return StatusCode(500, errorResponse);
            }
        }


        #endregion

        #region =================================================================== Subscription APIs ===================================================================

        [HttpPost("add-subscription")]
        public async Task<IActionResult> AddSubscriptionAsync(AddSubscriptionDto model)
        {
            var loggedInEmployee = await _userHelper.GetCurrentEmployeeAsync();

            _logger.LogInfo("AddSubscription called by employee {EmployeeId} for Tenant {TenantId} and Plan {PlanId}",
                loggedInEmployee.Id, model.TenantId, model.PlanId);
            if (loggedInEmployee == null)
            {
                _logger.LogWarning("No logged-in employee found.");
                return StatusCode(403, ApiResponse<object>.ErrorResponse("Unauthorized", "User must be logged in.", 403));
            }

            await using var _context = await _dbContextFactory.CreateDbContextAsync();
            using var scope = _serviceScopeFactory.CreateScope();

            var _permissionService = scope.ServiceProvider.GetRequiredService<PermissionServices>();

            var isRootUser = loggedInEmployee.ApplicationUser?.IsRootUser ?? false;
            var hasPermission = await _permissionService.HasPermission(PermissionsMaster.ManageTenants, loggedInEmployee.Id);

            if (!hasPermission || !isRootUser)
            {
                _logger.LogWarning("Permission denied: User {EmployeeId} attempted to add subscription without permission or root access.",
                    loggedInEmployee.Id);

                return StatusCode(403,
                    ApiResponse<object>.ErrorResponse("Access denied",
                    "User does not have the required permissions for this action.", 403));
            }

            var subscriptionPlan = await _context.SubscriptionPlanDetails.Include(sp => sp.Plan).FirstOrDefaultAsync(sp => sp.Id == model.PlanId);

            var tenant = await _context.Tenants.FirstOrDefaultAsync(t => t.Id == model.TenantId);
            if (tenant == null)
            {
                _logger.LogWarning("Tenant {TenantId} not found in database", model.TenantId);
                return NotFound(ApiResponse<object>.ErrorResponse("Tenant not found", "Tenant not found", 404));
            }
            if (subscriptionPlan == null)
            {
                _logger.LogWarning("Subscription plan {PlanId} not found in database", model.PlanId);
                return NotFound(ApiResponse<object>.ErrorResponse("Subscription plan not found", "Subscription plan not found", 404));
            }
            var activeUsers = await _context.Employees.CountAsync(e => e.Email != null && e.ApplicationUserId != null && e.TenantId == tenant.Id && e.IsActive);
            if (activeUsers > model.MaxUsers)
            {
                _logger.LogWarning("Employee {EmployeeId} add less max user than the active user in the tenant {TenantId}", loggedInEmployee.Id, tenant.Id);
                return BadRequest(ApiResponse<object>.ErrorResponse("Invalid Max user count", "Max User count must be higher than active user count", 400));
            }
            await using var transaction = await _context.Database.BeginTransactionAsync();
            var utcNow = DateTime.UtcNow;

            // Prepare subscription dates based on frequency
            var endDate = subscriptionPlan.Frequency switch
            {
                PLAN_FREQUENCY.MONTHLY => utcNow.AddDays(30),
                PLAN_FREQUENCY.QUARTERLY => utcNow.AddDays(90),
                PLAN_FREQUENCY.HALF_YEARLY => utcNow.AddDays(120),
                PLAN_FREQUENCY.YEARLY => utcNow.AddDays(360),
                _ => utcNow // default if unknown
            };

            var tenantSubscription = new TenantSubscriptions
            {
                TenantId = model.TenantId,
                PlanId = model.PlanId,
                StatusId = activePlanStatus,
                CreatedAt = utcNow,
                MaxUsers = model.MaxUsers,
                CreatedById = loggedInEmployee.Id,
                CurrencyId = model.CurrencyId,
                IsTrial = model.IsTrial,
                StartDate = utcNow,
                EndDate = endDate,
                NextBillingDate = endDate,
                AutoRenew = model.AutoRenew
            };

            _context.TenantSubscriptions.Add(tenantSubscription);

            try
            {
                await _context.SaveChangesAsync();
                _logger.LogInfo("Tenant subscription added successfully for Tenant {TenantId}, Plan {PlanId}",
                    model.TenantId, model.PlanId);
            }
            catch (DbUpdateException dbEx)
            {
                _logger.LogError(dbEx, "Database exception while adding subscription plan to tenant {TenantId}", model.TenantId);
                return StatusCode(500, ApiResponse<object>.ErrorResponse("Internal error occured", ExceptionMapper(dbEx), 500));
            }

            try
            {
                var features = await _featureDetailsHelper.GetFeatureDetails(subscriptionPlan.FeaturesId);
                if (features == null)
                {
                    _logger.LogInfo("No features found for subscription plan {PlanId}", model.PlanId);
                    await transaction.CommitAsync();
                    return Ok(ApiResponse<object>.SuccessResponse(tenantSubscription, "Tenant subscription successfully added", 200));
                }

                // Helper to get permissions for a module asynchronously
                async Task<List<Guid>> GetPermissionsForModuleAsync(List<Guid>? featureIds)
                {
                    if (featureIds == null || featureIds.Count == 0) return new List<Guid>();

                    await using var ctx = await _dbContextFactory.CreateDbContextAsync();
                    return await ctx.FeaturePermissions.AsNoTracking()
                        .Where(fp => featureIds.Contains(fp.FeatureId))
                        .Select(fp => fp.Id)
                        .ToListAsync();
                }

                // Fetch permission tasks for all modules in parallel
                var projectPermissionTask = GetPermissionsForModuleAsync(features.Modules?.ProjectManagement?.FeatureId);
                var attendancePermissionTask = GetPermissionsForModuleAsync(features.Modules?.Attendance?.FeatureId);
                var directoryPermissionTask = GetPermissionsForModuleAsync(features.Modules?.Directory?.FeatureId);
                var expensePermissionTask = GetPermissionsForModuleAsync(features.Modules?.Expense?.FeatureId);
                var employeePermissionTask = GetPermissionsForModuleAsync(new List<Guid> { EmployeeFeatureId });

                await Task.WhenAll(projectPermissionTask, attendancePermissionTask, directoryPermissionTask, expensePermissionTask, employeePermissionTask);

                var newPermissionIds = new List<Guid>();
                var deletePermissionIds = new List<Guid>();

                // Add or remove permissions based on modules enabled status
                void ProcessPermissions(bool? enabled, List<Guid> permissions)
                {
                    if (enabled == true)
                        newPermissionIds.AddRange(permissions);
                    else
                        deletePermissionIds.AddRange(permissions);
                }

                ProcessPermissions(features.Modules?.ProjectManagement?.Enabled, projectPermissionTask.Result);
                ProcessPermissions(features.Modules?.Attendance?.Enabled, attendancePermissionTask.Result);
                ProcessPermissions(features.Modules?.Directory?.Enabled, directoryPermissionTask.Result);
                ProcessPermissions(features.Modules?.Expense?.Enabled, expensePermissionTask.Result);

                newPermissionIds = newPermissionIds.Distinct().ToList();
                deletePermissionIds = deletePermissionIds.Distinct().ToList();

                // Get root employee and role for this tenant
                var rootEmployee = await _context.Employees
                    .Include(e => e.ApplicationUser)
                    .FirstOrDefaultAsync(e => e.ApplicationUser != null && (e.ApplicationUser.IsRootUser ?? false) && e.OrganizationId == tenant.OrganizationId);

                if (rootEmployee == null)
                {
                    _logger.LogWarning("Root employee not found for tenant {TenantId}", model.TenantId);
                    await transaction.CommitAsync();
                    return Ok(ApiResponse<object>.SuccessResponse(tenantSubscription, "Tenant subscription successfully added", 200));
                }

                var roleId = await _context.EmployeeRoleMappings
                    .AsNoTracking()
                    .Where(er => er.EmployeeId == rootEmployee.Id && er.TenantId == model.TenantId)
                    .Select(er => er.RoleId)
                    .FirstOrDefaultAsync();

                if (roleId == Guid.Empty)
                {
                    _logger.LogWarning("RoleId for root employee {EmployeeId} in tenant {TenantId} not found", rootEmployee.Id, model.TenantId);
                    await transaction.CommitAsync();
                    return Ok(ApiResponse<object>.SuccessResponse(tenantSubscription, "Tenant subscription successfully added", 200));
                }

                var oldRolePermissionMappings = await _context.RolePermissionMappings
                    .Where(rp => rp.ApplicationRoleId == roleId)
                    .ToListAsync();

                var oldPermissionIds = oldRolePermissionMappings.Select(rp => rp.FeaturePermissionId).ToList();

                // Prevent accidentally deleting essential employee permissions
                var permissionIdCount = oldPermissionIds.Count - deletePermissionIds.Count;
                if (permissionIdCount <= 4 && deletePermissionIds.Any())
                {
                    var employeePermissionIds = employeePermissionTask.Result;
                    deletePermissionIds = deletePermissionIds.Where(p => !employeePermissionIds.Contains(p)).ToList();
                }

                // Prepare mappings to delete and add
                var deleteMappings = oldRolePermissionMappings.Where(rp => deletePermissionIds.Contains(rp.FeaturePermissionId)).ToList();
                var addRolePermissionMappings = newPermissionIds
                    .Where(p => !oldPermissionIds.Contains(p))
                    .Select(p => new RolePermissionMappings
                    {
                        ApplicationRoleId = roleId,
                        FeaturePermissionId = p
                    })
                    .ToList();

                if (addRolePermissionMappings.Any())
                {
                    _context.RolePermissionMappings.AddRange(addRolePermissionMappings);
                    _logger.LogInfo("Added {Count} new role permission mappings for role {RoleId}", addRolePermissionMappings.Count, roleId);
                }
                if (deleteMappings.Any())
                {
                    _context.RolePermissionMappings.RemoveRange(deleteMappings);
                    _logger.LogInfo("Removed {Count} role permission mappings for role {RoleId}", deleteMappings.Count, roleId);
                }

                var _cache = scope.ServiceProvider.GetRequiredService<CacheUpdateHelper>();
                await _cache.ClearAllEmployeesFromCacheByTenantId(tenant.Id);

                var _masteData = scope.ServiceProvider.GetRequiredService<MasterDataService>();

                if (features.Modules?.ProjectManagement?.Enabled ?? false)
                {
                    var workCategoryMaster = _masteData.GetWorkCategoriesData(tenant.Id);
                    var workStatusMaster = _masteData.GetWorkStatusesData(tenant.Id);

                    _context.WorkCategoryMasters.AddRange(workCategoryMaster);
                    _context.WorkStatusMasters.AddRange(workStatusMaster);
                }
                if (features.Modules?.Expense?.Enabled ?? false)
                {
                    var expenseCategoryMaster = _masteData.GetExpenseCategoryData(tenant.Id);

                    _context.ExpenseCategoryMasters.AddRange(expenseCategoryMaster);
                }

                await _context.SaveChangesAsync();

                await transaction.CommitAsync();

                _logger.LogInfo("Permissions updated successfully for tenant {TenantId} subscription", model.TenantId);

                return Ok(ApiResponse<object>.SuccessResponse(tenantSubscription, "Tenant Subscription Successfully", 200));
            }
            catch (Exception ex)
            {
                await transaction.RollbackAsync();
                _logger.LogError(ex, "Exception occurred while updating permissions for tenant {TenantId}", model.TenantId);
                return StatusCode(500, ApiResponse<object>.ErrorResponse("Internal error occured", ExceptionMapper(ex), 500));
            }
        }

        [HttpPut("update-subscription")]
        public async Task<IActionResult> UpdateSubscriptionAsync(UpdateSubscriptionDto model)
        {
            // 1. Get the logged-in user's employee record.
            var loggedInEmployee = await _userHelper.GetCurrentEmployeeAsync();

            // 2. Create a new DbContext instance for this request.
            await using var context = await _dbContextFactory.CreateDbContextAsync();

            // 3. Get PermissionServices from DI inside a fresh scope (rarely needed, but retained for your design).
            using var scope = _serviceScopeFactory.CreateScope();
            var permissionService = scope.ServiceProvider.GetRequiredService<PermissionServices>();
            var _updateLogHelper = scope.ServiceProvider.GetRequiredService<UtilityMongoDBHelper>();

            // 4. Check user permissions: must be both Root user and have ManageTenants permission.
            var isRootUser = loggedInEmployee.ApplicationUser?.IsRootUser ?? false;
            var hasPermission = await permissionService.HasPermission(PermissionsMaster.ManageTenants, loggedInEmployee.Id);

            if (!isRootUser || !hasPermission)
            {
                _logger.LogWarning("Permission denied for EmployeeId={EmployeeId}. Root: {IsRoot}, HasPermission: {HasPermission}",
                    loggedInEmployee.Id, isRootUser, hasPermission);
                return StatusCode(403, ApiResponse<object>.ErrorResponse("Access denied",
                    "User does not have the required permissions.", 403));
            }

            // 5. Fetch Tenant, SubscriptionPlan, and TenantSubscription in parallel (efficiently).
            var tenantTask = _dbContextFactory.CreateDbContextAsync().ContinueWith(ctx =>
                ctx.Result.Tenants.AsNoTracking().FirstOrDefaultAsync(t => t.Id == model.TenantId)).Unwrap();

            var planDetailsTask = _dbContextFactory.CreateDbContextAsync().ContinueWith(ctx =>
                ctx.Result.SubscriptionPlanDetails.Include(sp => sp.Plan).AsNoTracking().FirstOrDefaultAsync(sp => sp.Id == model.PlanId)).Unwrap();

            var currentSubscriptionTask = _dbContextFactory.CreateDbContextAsync().ContinueWith(ctx =>
                ctx.Result.TenantSubscriptions.Include(ts => ts.Currency).AsNoTracking().FirstOrDefaultAsync(ts => ts.TenantId == model.TenantId && !ts.IsCancelled)).Unwrap();

            await Task.WhenAll(tenantTask, planDetailsTask, currentSubscriptionTask);

            var tenant = tenantTask.Result;
            if (tenant == null)
            {
                _logger.LogWarning("Tenant {TenantId} not found.", model.TenantId);
                return NotFound(ApiResponse<object>.ErrorResponse("Tenant not found", "Tenant not found", 404));
            }

            var subscriptionPlan = planDetailsTask.Result;
            if (subscriptionPlan == null)
            {
                _logger.LogWarning("Subscription plan {PlanId} not found.", model.PlanId);
                return NotFound(ApiResponse<object>.ErrorResponse("Subscription plan not found", "Subscription plan not found", 404));
            }

            var currentSubscription = currentSubscriptionTask.Result;
            var utcNow = DateTime.UtcNow;

            var activeUsers = await context.Employees.CountAsync(e => e.Email != null && e.ApplicationUserId != null && e.TenantId == tenant.Id && e.IsActive);
            if (activeUsers > model.MaxUsers)
            {
                _logger.LogWarning("Employee {EmployeeId} add less max user than the active user in the tenant {TenantId}", loggedInEmployee.Id, tenant.Id);
                return BadRequest(ApiResponse<object>.ErrorResponse("Invalid Max user count", "Max User count must be higher than active user count", 400));
            }

            // 6. If the tenant already has this plan, extend/renew it.
            if (currentSubscription != null && currentSubscription.PlanId == subscriptionPlan.Id)
            {
                var existingEntityBson = _updateLogHelper.EntityToBsonDocument(currentSubscription);
                DateTime newEndDate;
                // 6a. If the subscription is still active, extend from current EndDate; else start from now.
                if (currentSubscription.EndDate.Date >= utcNow.Date)
                {
                    newEndDate = subscriptionPlan.Frequency switch
                    {
                        PLAN_FREQUENCY.MONTHLY => currentSubscription.EndDate.AddDays(30),
                        PLAN_FREQUENCY.QUARTERLY => currentSubscription.EndDate.AddDays(90),
                        PLAN_FREQUENCY.HALF_YEARLY => currentSubscription.EndDate.AddDays(120),
                        PLAN_FREQUENCY.YEARLY => currentSubscription.EndDate.AddDays(360),
                        _ => currentSubscription.EndDate
                    };
                }
                else
                {
                    newEndDate = subscriptionPlan.Frequency switch
                    {
                        PLAN_FREQUENCY.MONTHLY => utcNow.AddDays(30),
                        PLAN_FREQUENCY.QUARTERLY => utcNow.AddDays(90),
                        PLAN_FREQUENCY.HALF_YEARLY => utcNow.AddDays(120),
                        PLAN_FREQUENCY.YEARLY => utcNow.AddDays(360),
                        _ => utcNow // default if unknown
                    };
                }

                // 6b. Update subscription details
                if (model.MaxUsers != null && model.MaxUsers > 0)
                {
                    currentSubscription.MaxUsers = model.MaxUsers.Value;
                }
                currentSubscription.StartDate = utcNow;
                currentSubscription.EndDate = newEndDate;
                currentSubscription.NextBillingDate = newEndDate;
                currentSubscription.UpdateAt = utcNow;
                currentSubscription.UpdatedById = loggedInEmployee.Id;

                context.TenantSubscriptions.Update(currentSubscription);
                await context.SaveChangesAsync();

                _logger.LogInfo("Subscription renewed: Tenant={TenantId}, Plan={PlanId}, NewEnd={EndDate}",
                    model.TenantId, model.PlanId, newEndDate);

                await _updateLogHelper.PushToUpdateLogsAsync(new UpdateLogsObject
                {
                    EntityId = currentSubscription.Id.ToString(),
                    UpdatedById = loggedInEmployee.Id.ToString(),
                    OldObject = existingEntityBson,
                    UpdatedAt = DateTime.UtcNow
                }, "SubscriptionPlanModificationLog");

                return Ok(ApiResponse<object>.SuccessResponse(currentSubscription, "Subscription renewed/extended", 200));
            }

            // 7. Else, change plan: new subscription record, close the old if exists.
            await using var transaction = await context.Database.BeginTransactionAsync();
            try
            {
                // 7a. Compute new plan dates
                var endDate = subscriptionPlan.Frequency switch
                {
                    PLAN_FREQUENCY.MONTHLY => utcNow.AddDays(30),
                    PLAN_FREQUENCY.QUARTERLY => utcNow.AddDays(90),
                    PLAN_FREQUENCY.HALF_YEARLY => utcNow.AddDays(120),
                    PLAN_FREQUENCY.YEARLY => utcNow.AddDays(360),
                    _ => utcNow // default if unknown
                };

                var newSubscription = new TenantSubscriptions
                {
                    TenantId = model.TenantId,
                    PlanId = model.PlanId,
                    StatusId = activePlanStatus,
                    CreatedAt = utcNow,
                    MaxUsers = model.MaxUsers ?? (currentSubscription?.MaxUsers ?? subscriptionPlan.MaxUser),
                    CreatedById = loggedInEmployee.Id,
                    CurrencyId = model.CurrencyId,
                    StartDate = utcNow,
                    EndDate = endDate,
                    NextBillingDate = endDate,
                    IsTrial = currentSubscription?.IsTrial ?? false,
                    AutoRenew = currentSubscription?.AutoRenew ?? false
                };
                context.TenantSubscriptions.Add(newSubscription);

                // 7b. If an old subscription exists, cancel it.
                if (currentSubscription != null)
                {
                    currentSubscription.IsCancelled = true;
                    currentSubscription.CancellationDate = utcNow;
                    currentSubscription.UpdateAt = utcNow;
                    currentSubscription.UpdatedById = loggedInEmployee.Id;
                    context.TenantSubscriptions.Update(currentSubscription);
                }
                await context.SaveChangesAsync();
                _logger.LogInfo("Subscription plan changed: Tenant={TenantId}, NewPlan={PlanId}",
                    model.TenantId, model.PlanId);


                // 8. Update tenant permissions based on subscription features.
                var features = await _featureDetailsHelper.GetFeatureDetails(subscriptionPlan.FeaturesId);
                if (features == null)
                {
                    _logger.LogInfo("No features for Plan={PlanId}.", model.PlanId);
                    await transaction.CommitAsync();
                    return Ok(ApiResponse<object>.SuccessResponse(newSubscription, "Tenant subscription updated (no features)", 200));
                }

                // 8a. Async helper to get all permission IDs for a given module.
                async Task<List<Guid>> GetPermissionsForFeaturesAsync(List<Guid>? featureIds)
                {
                    if (featureIds == null || featureIds.Count == 0) return new List<Guid>();

                    await using var ctx = await _dbContextFactory.CreateDbContextAsync();
                    return await ctx.FeaturePermissions.AsNoTracking()
                        .Where(fp => featureIds.Contains(fp.FeatureId))
                        .Select(fp => fp.Id)
                        .ToListAsync();
                }

                // 8b. Fetch all module permissions concurrently.
                var projectPermTask = GetPermissionsForFeaturesAsync(features.Modules?.ProjectManagement?.FeatureId);
                var attendancePermTask = GetPermissionsForFeaturesAsync(features.Modules?.Attendance?.FeatureId);
                var directoryPermTask = GetPermissionsForFeaturesAsync(features.Modules?.Directory?.FeatureId);
                var expensePermTask = GetPermissionsForFeaturesAsync(features.Modules?.Expense?.FeatureId);
                var employeePermTask = GetPermissionsForFeaturesAsync(new List<Guid> { EmployeeFeatureId }); // assumed defined

                await Task.WhenAll(projectPermTask, attendancePermTask, directoryPermTask, expensePermTask, employeePermTask);

                // 8c. Find root employee & role for this tenant.
                var rootEmployee = await context.Employees
                    .Include(e => e.ApplicationUser)
                    .FirstOrDefaultAsync(e => e.ApplicationUser != null && (e.ApplicationUser.IsRootUser ?? false) && e.OrganizationId == tenant.OrganizationId);

                if (rootEmployee == null)
                {
                    _logger.LogWarning("No root employee for Tenant={TenantId}.", model.TenantId);
                    await transaction.CommitAsync();
                    return Ok(ApiResponse<object>.SuccessResponse(newSubscription, "Tenant subscription updated (no root employee)", 200));
                }

                var rootRoleId = await context.EmployeeRoleMappings
                    .AsNoTracking()
                    .Include(er => er.Role)
                    .Where(er => er.EmployeeId == rootEmployee.Id && er.TenantId == model.TenantId && er.Role != null && er.Role.Role == "Super User")
                    .Select(er => er.RoleId)
                    .FirstOrDefaultAsync();

                if (rootRoleId == Guid.Empty)
                {
                    _logger.LogWarning("No root role for Employee={EmployeeId}, Tenant={TenantId}.", rootEmployee.Id, model.TenantId);
                    await transaction.CommitAsync();
                    return Ok(ApiResponse<object>.SuccessResponse(newSubscription, "Tenant subscription updated (no root role)", 200));
                }

                var dbOldRolePerms = await context.RolePermissionMappings.Where(x => x.ApplicationRoleId == rootRoleId).ToListAsync();
                var oldPermIds = dbOldRolePerms.Select(rp => rp.FeaturePermissionId).ToList();

                // 8d. Prepare add and remove permission lists.
                var newPermissionIds = new List<Guid>();
                var revokePermissionIds = new List<Guid>();
                var employeePerms = employeePermTask.Result;
                var isOldEmployeePermissionIdExist = oldPermIds.Any(fp => employeePerms.Contains(fp));

                void ProcessPerms(bool? enabled, List<Guid> ids)
                {
                    var isOldPermissionIdExist = oldPermIds.Any(fp => ids.Contains(fp) && !employeePerms.Contains(fp));

                    if (enabled == true && !isOldPermissionIdExist) newPermissionIds.AddRange(ids);
                    if (enabled == true && !isOldEmployeePermissionIdExist) newPermissionIds.AddRange(ids);
                    if (enabled == false && isOldPermissionIdExist)
                        revokePermissionIds.AddRange(ids);
                }
                ProcessPerms(features.Modules?.ProjectManagement?.Enabled, projectPermTask.Result);
                ProcessPerms(features.Modules?.Attendance?.Enabled, attendancePermTask.Result);
                ProcessPerms(features.Modules?.Directory?.Enabled, directoryPermTask.Result);
                ProcessPerms(features.Modules?.Expense?.Enabled, expensePermTask.Result);

                newPermissionIds = newPermissionIds.Distinct().ToList();
                revokePermissionIds = revokePermissionIds.Distinct().ToList();


                // 8e. Prevent accidental loss of basic employee permissions.
                if ((features.Modules?.ProjectManagement?.Enabled == true ||
                    features.Modules?.Attendance?.Enabled == true ||
                    features.Modules?.Directory?.Enabled == true ||
                    features.Modules?.Expense?.Enabled == true) && isOldEmployeePermissionIdExist)
                {
                    revokePermissionIds = revokePermissionIds.Where(pid => !employeePerms.Contains(pid)).ToList();
                }

                // 8f. Prepare permission-mapping records to add/remove.
                var mappingsToRemove = dbOldRolePerms.Where(rp => revokePermissionIds.Contains(rp.FeaturePermissionId)).ToList();
                var mappingsToAdd = newPermissionIds
                    .Where(pid => !oldPermIds.Contains(pid))
                    .Select(pid => new RolePermissionMappings { ApplicationRoleId = rootRoleId, FeaturePermissionId = pid })
                    .ToList();

                if (mappingsToAdd.Any())
                {
                    context.RolePermissionMappings.AddRange(mappingsToAdd);
                    _logger.LogInfo("Permissions granted: {Count} for Role={RoleId}", mappingsToAdd.Count, rootRoleId);
                }
                if (mappingsToRemove.Any())
                {
                    context.RolePermissionMappings.RemoveRange(mappingsToRemove);
                    _logger.LogInfo("Permissions revoked: {Count} for Role={RoleId}", mappingsToRemove.Count, rootRoleId);
                }

                var _cache = scope.ServiceProvider.GetRequiredService<CacheUpdateHelper>();
                await _cache.ClearAllEmployeesFromCacheByTenantId(tenant.Id);

                var _masteData = scope.ServiceProvider.GetRequiredService<MasterDataService>();

                if (features.Modules?.ProjectManagement?.Enabled ?? false)
                {
                    var workCategoryMaster = _masteData.GetWorkCategoriesData(tenant.Id);
                    var workStatusMaster = _masteData.GetWorkStatusesData(tenant.Id);

                    var workCategoryTask = Task.Run(async () =>
                    {
                        await using var _context = await _dbContextFactory.CreateDbContextAsync();
                        return await _context.WorkCategoryMasters.AnyAsync(wc => wc.IsSystem && wc.TenantId == tenant.Id);
                    });
                    var workStatusTask = Task.Run(async () =>
                    {
                        await using var _context = await _dbContextFactory.CreateDbContextAsync();
                        return await _context.WorkStatusMasters.AnyAsync(ws => ws.IsSystem && ws.TenantId == tenant.Id);
                    });

                    await Task.WhenAll(workCategoryTask, workStatusTask);

                    var workCategoryExist = workCategoryTask.Result;
                    var workStatusExist = workStatusTask.Result;
                    if (!workCategoryExist)
                    {
                        context.WorkCategoryMasters.AddRange(workCategoryMaster);
                    }
                    if (!workStatusExist)
                    {
                        context.WorkStatusMasters.AddRange(workStatusMaster);
                    }
                }
                if (features.Modules?.Expense?.Enabled ?? false)
                {
                    var expenseCategoryMaster = _masteData.GetExpenseCategoryData(tenant.Id);

                    var expenseCategoryNames = expenseCategoryMaster.Select(et => et.Name).ToList();
                    var expenseCategoryExist = await context.ExpensesTypeMaster.AnyAsync(et => expenseCategoryNames.Contains(et.Name) && et.TenantId == tenant.Id);

                    if (!expenseCategoryExist)
                    {
                        context.ExpenseCategoryMasters.AddRange(expenseCategoryMaster);
                    }
                }

                await context.SaveChangesAsync();
                await transaction.CommitAsync();

                _logger.LogInfo("Tenant subscription and permissions updated: Tenant={TenantId}", model.TenantId);

                return Ok(ApiResponse<object>.SuccessResponse(newSubscription, "Tenant subscription successfully updated", 200));
            }
            catch (DbUpdateException dbEx)
            {
                await transaction.RollbackAsync();
                _logger.LogError(dbEx, "Database exception updating subscription for TenantId={TenantId}", model.TenantId);
                return StatusCode(500, ApiResponse<object>.ErrorResponse("Internal database error", ExceptionMapper(dbEx), 500));
            }
            catch (Exception ex)
            {
                await transaction.RollbackAsync();
                _logger.LogError(ex, "General exception for TenantId={TenantId}", model.TenantId);
                return StatusCode(500, ApiResponse<object>.ErrorResponse("Internal error occurred", ExceptionMapper(ex), 500));
            }
        }

        [AllowAnonymous]
        [HttpPost("self/subscription")]
        public async Task<IActionResult> SelfSubscriptionAsync(SelfSubscriptionDto model)
        {
            try
            {
                using var scope = _serviceScopeFactory.CreateScope();
                var _tenantService = scope.ServiceProvider.GetRequiredService<ITenantService>();
                var response = await _tenantService.CreateTenantAsync(model.TenantEnquireId, model.PaymentDetailId, model.PlanId);
                return StatusCode(response.StatusCode, response);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error occured while add self subscription");
                return StatusCode(500, ApiResponse<object>.ErrorResponse("Error Occured while self subscription", "Error Occured while self subscription", 500));
            }
        }

        [HttpPut("renew/subscription")]
        public async Task<IActionResult> RenewSubscriptionAsync(RenewSubscriptionDto model)
        {
            try
            {
                var loggedInEmployee = await _userHelper.GetCurrentEmployeeAsync();

                using var scope = _serviceScopeFactory.CreateScope();
                var _tenantService = scope.ServiceProvider.GetRequiredService<ITenantService>();
                var response = await _tenantService.RenewSubscriptionAsync(tenantId, loggedInEmployee.Id, model.PaymentDetailId, model.PlanId);
                return StatusCode(response.StatusCode, response);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error occured while add renewing subscription");
                return StatusCode(500, ApiResponse<object>.ErrorResponse("Error Occured while renewing subscription", "Error Occured while renewing subscription", 500));
            }
        }

        #endregion

        #region =================================================================== Subscription Plan APIs ===================================================================

        [HttpGet("list/subscription-plan")]
        public async Task<IActionResult> GetSubscriptionPlanList([FromQuery] PLAN_FREQUENCY? frequency)
        {
            _logger.LogInfo("GetSubscriptionPlanList called with frequency: {Frequency}", frequency ?? PLAN_FREQUENCY.MONTHLY);

            // Initialize the list to store subscription plan view models
            List<SubscriptionPlanVM> detailsVM = new List<SubscriptionPlanVM>();

            try
            {
                // Create DbContext
                await using var _context = await _dbContextFactory.CreateDbContextAsync();

                // Load subscription plans with optional frequency filtering
                IQueryable<SubscriptionPlanDetails> query = _context.SubscriptionPlanDetails.Include(sp => sp.Plan).Include(sp => sp.Currency);

                if (frequency.HasValue)
                {
                    query = query.Where(sp => sp.Frequency == frequency.Value);
                    _logger.LogInfo("Filtering subscription plans by frequency: {Frequency}", frequency);
                }
                else
                {
                    _logger.LogInfo("Fetching all subscription plans without frequency filter");
                }

                var subscriptionPlans = await query.ToListAsync();

                // Map and fetch feature details for each subscription plan
                foreach (var subscriptionPlan in subscriptionPlans)
                {
                    var response = _mapper.Map<SubscriptionPlanVM>(subscriptionPlan);

                    try
                    {
                        response.Features = await _featureDetailsHelper.GetFeatureDetails(subscriptionPlan.FeaturesId);
                    }
                    catch (Exception exFeature)
                    {
                        _logger.LogError(exFeature, "Failed to fetch features for FeaturesId: {FeaturesId}", subscriptionPlan.FeaturesId);
                        response.Features = null; // or set to a default/fallback value
                    }

                    detailsVM.Add(response);
                }

                _logger.LogInfo("Successfully fetched {Count} subscription plans", detailsVM.Count);

                return Ok(ApiResponse<object>.SuccessResponse(detailsVM, "List of plans fetched successfully", 200));
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error occurred while fetching subscription plans");
                return StatusCode(500, ApiResponse<object>.ErrorResponse("An error occurred while fetching subscription plans."));
            }
        }

        /// <summary>
        /// Creates a new subscription plan with details for each frequency (monthly, quarterly, half-yearly, yearly).
        /// Only employees with root status and 'ManageTenants' permission can create plans.
        /// </summary>
        [HttpPost("create/subscription-plan")]
        public async Task<IActionResult> CreateSubscriptionPlan([FromBody] SubscriptionPlanDto model)
        {
            // Step 1: Authenticate and check permissions
            var loggedInEmployee = await _userHelper.GetCurrentEmployeeAsync();
            await using var _context = await _dbContextFactory.CreateDbContextAsync();
            using var scope = _serviceScopeFactory.CreateScope();
            var _permissionService = scope.ServiceProvider.GetRequiredService<PermissionServices>();

            // Permission check: root user or explicit ManageTenants permission
            var isRootUser = loggedInEmployee.ApplicationUser?.IsRootUser ?? false;
            var hasPermission = await _permissionService.HasPermission(PermissionsMaster.ManageTenants, loggedInEmployee.Id);
            if (!(hasPermission && isRootUser))
            {
                _logger.LogWarning("Permission denied: User {EmployeeId} attempted to create a subscription plan.", loggedInEmployee.Id);
                return StatusCode(403, ApiResponse<object>.ErrorResponse("Access denied", "User does not have the required permissions for this action.", 403));
            }

            _logger.LogInfo("User {EmployeeId} authorized to create subscription plan.", loggedInEmployee.Id);

            // Step 2: Map DTO to entity and persist the base SubscriptionPlan
            var plan = _mapper.Map<SubscriptionPlan>(model);
            _context.SubscriptionPlans.Add(plan);

            try
            {
                await _context.SaveChangesAsync();
                _logger.LogInfo("Base subscription plan {PlanId} saved by user {EmployeeId}.", plan.Id, loggedInEmployee.Id);
            }
            catch (DbUpdateException dbEx)
            {
                _logger.LogError(dbEx, "Database exception occurred while saving the base subscription plan.");
                return StatusCode(500, ApiResponse<object>.ErrorResponse("Internal error occurred", ExceptionMapper(dbEx), 500));
            }

            // Step 3: Prepare tasks for each plan frequency
            var frequencies = new[]
            {
                (model.MonthlyPlan, PLAN_FREQUENCY.MONTHLY),
                (model.QuarterlyPlan, PLAN_FREQUENCY.QUARTERLY),
                (model.HalfYearlyPlan, PLAN_FREQUENCY.HALF_YEARLY),
                (model.YearlyPlan, PLAN_FREQUENCY.YEARLY)
            };

            var tasks = frequencies
                .Select(f => CreateSubscriptionPlanDetails(f.Item1, plan, loggedInEmployee, f.Item2))
                .ToArray();

            // Await all frequency tasks
            await Task.WhenAll(tasks);

            // Step 4: Collect successful plan details or return errors if any
            var responseList = new List<SubscriptionPlanVM>();
            for (int i = 0; i < tasks.Length; i++)
            {
                var result = tasks[i].Result;
                if (result.StatusCode == 200 && result.Data != null)
                {
                    responseList.Add(result.Data);
                }
                // status code 400 - skip, e.g. missing data for this frequency
                else if (result.StatusCode != 400)
                {
                    _logger.LogWarning("Failed to create plan details for {Frequency}: {Error}", frequencies[i].Item2, result.Message);
                    return StatusCode(result.StatusCode, result);
                }
            }

            _logger.LogInfo("Subscription plan {PlanId} created successfully with {DetailCount} details.", plan.Id, responseList.Count);
            return StatusCode(201, ApiResponse<object>.SuccessResponse(responseList, "Plan Created Successfully", 201));
        }

        #endregion

        #region =================================================================== Helper Functions ===================================================================

        private static object ExceptionMapper(Exception ex)
        {
            return new
            {
                Message = ex.Message,
                StackTrace = ex.StackTrace,
                Source = ex.Source,
                InnerException = new
                {
                    Message = ex.InnerException?.Message,
                    StackTrace = ex.InnerException?.StackTrace,
                    Source = ex.InnerException?.Source,
                }
            };
        }
        private bool IsBase64String(string? input)
        {
            if (string.IsNullOrWhiteSpace(input))
            {
                return false;
            }

            string base64Data = input;
            const string dataUriMarker = "base64,";
            int markerIndex = input.IndexOf(dataUriMarker, StringComparison.Ordinal);

            // If the marker is found, extract the actual Base64 data
            if (markerIndex >= 0)
            {
                base64Data = input.Substring(markerIndex + dataUriMarker.Length);
            }

            // Now, validate the extracted payload
            base64Data = base64Data.Trim();

            // Check for valid length (must be a multiple of 4) and non-empty
            if (base64Data.Length == 0 || base64Data.Length % 4 != 0)
            {
                return false;
            }

            // The most reliable test is to simply try to convert it.
            // The .NET converter is strict and will throw a FormatException
            // for invalid characters or incorrect padding.
            try
            {
                Convert.FromBase64String(base64Data);
                return true;
            }
            catch (FormatException)
            {
                // The string is not a valid Base64 payload.
                return false;
            }
        }
        private TenantFilter? TryDeserializeFilter(string? filter)
        {
            if (string.IsNullOrWhiteSpace(filter))
            {
                return null;
            }

            var options = new JsonSerializerOptions { PropertyNameCaseInsensitive = true };
            TenantFilter? expenseFilter = null;

            try
            {
                // First, try to deserialize directly. This is the expected case (e.g., from a web client).
                expenseFilter = JsonSerializer.Deserialize<TenantFilter>(filter, options);
            }
            catch (JsonException ex)
            {
                _logger.LogError(ex, "[{MethodName}] Failed to directly deserialize filter. Attempting to unescape and re-parse. Filter: {Filter}", nameof(TryDeserializeFilter), filter);

                // If direct deserialization fails, it might be an escaped string (common with tools like Postman or some mobile clients).
                try
                {
                    // Unescape the string first, then deserialize the result.
                    string unescapedJsonString = JsonSerializer.Deserialize<string>(filter, options) ?? "";
                    if (!string.IsNullOrWhiteSpace(unescapedJsonString))
                    {
                        expenseFilter = JsonSerializer.Deserialize<TenantFilter>(unescapedJsonString, options);
                    }
                }
                catch (JsonException ex1)
                {
                    // If both attempts fail, log the final error and return null.
                    _logger.LogError(ex1, "[{MethodName}] All attempts to deserialize the filter failed. Filter will be ignored. Filter: {Filter}", nameof(TryDeserializeFilter), filter);
                    return null;
                }
            }
            return expenseFilter;
        }

        /// <summary>
        /// Handles the creation and persistence of SubscriptionPlanDetails for a particular frequency.
        /// </summary>
        private async Task<ApiResponse<SubscriptionPlanVM>> CreateSubscriptionPlanDetails(SubscriptionPlanDetailsDto? model, SubscriptionPlan plan, Employee loggedInEmployee, PLAN_FREQUENCY frequency)
        {
            if (model == null)
            {
                _logger.LogInfo("No plan detail provided for {Frequency} - skipping.", frequency);
                return ApiResponse<SubscriptionPlanVM>.ErrorResponse("Invalid", "No data provided for this frequency", 400);
            }

            await using var _dbContext = await _dbContextFactory.CreateDbContextAsync();

            // Fetch currency master record
            var currencyMaster = await _dbContext.CurrencyMaster.AsNoTracking().FirstOrDefaultAsync(c => c.Id == model.CurrencyId);
            if (currencyMaster == null)
            {
                _logger.LogWarning("Currency with Id {CurrencyId} not found for plan {PlanId}/{Frequency}.", model.CurrencyId, plan.Id, frequency);
                return ApiResponse<SubscriptionPlanVM>.ErrorResponse("Currency not found", "Specified currency not found", 404);
            }

            // Map to entity and create related feature details
            var planDetails = _mapper.Map<SubscriptionPlanDetails>(model);
            var features = _mapper.Map<FeatureDetails>(model.Features);

            try
            {
                await _featureDetailsHelper.AddFeatureDetails(features);
                _logger.LogInfo("FeatureDetails for plan {PlanId}/{Frequency} saved in MongoDB.", plan.Id, frequency);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Exception occurred while saving features in MongoDB for {PlanId}/{Frequency}.", plan.Id, frequency);
                return ApiResponse<SubscriptionPlanVM>.ErrorResponse("Internal error occurred", ExceptionMapper(ex), 500);
            }

            planDetails.PlanId = plan.Id;
            planDetails.Frequency = frequency;
            planDetails.FeaturesId = features.Id;
            planDetails.CreatedById = loggedInEmployee.Id;
            planDetails.CreateAt = DateTime.UtcNow;

            _dbContext.SubscriptionPlanDetails.Add(planDetails);

            // Prepare view model
            var VM = _mapper.Map<SubscriptionPlanVM>(planDetails);
            VM.PlanName = plan.PlanName;
            VM.Description = plan.Description;
            VM.Features = features;
            VM.Currency = currencyMaster;

            try
            {
                await _dbContext.SaveChangesAsync();
                _logger.LogInfo("Subscription plan details for {PlanId}/{Frequency} saved to SQL.", plan.Id, frequency);
            }
            catch (DbUpdateException dbEx)
            {
                _logger.LogError(dbEx, "Database exception occurred while saving plan details for {PlanId}/{Frequency}.", plan.Id, frequency);
                return ApiResponse<SubscriptionPlanVM>.ErrorResponse("Internal error occurred", ExceptionMapper(dbEx), 500);
            }

            return ApiResponse<SubscriptionPlanVM>.SuccessResponse(VM, "Success", 200);
        }

        #endregion
    }
}
