Distribution_GL/Services/CostCenterService.cs

using General_Ledger_Service.DTOs.Common;
using General_Ledger_Service.DTOs.CostCenters;
using General_Ledger_Service.Enums;
using General_Ledger_Service.Exceptions;
using General_Ledger_Service.Infra.UoW;
using General_Ledger_Service.Interfaces.Repositories;
using General_Ledger_Service.Interfaces.Services;
using General_Ledger_Service.Models;

namespace General_Ledger_Service.Services
{
    public class CostCenterService(
        ICostCenterRepository costCenterRepository,
        ISystemConfigRepository systemConfigRepository,
        IAuditLogRepository auditLogRepository,
        IUnitOfWork unitOfWork) : ICostCenterService
    {
        private readonly ICostCenterRepository _costCenterRepository = costCenterRepository;
        private readonly ISystemConfigRepository _systemConfigRepository = systemConfigRepository;
        private readonly IAuditLogRepository _auditLogRepository = auditLogRepository;
        private readonly IUnitOfWork _unitOfWork = unitOfWork;

        public async Task<ApiResponse> CreateCostCenterAsync(CreateCostCenterRequest request)
        {
            CostCenter? parent = null;

            if (request.ParentCostCenterId.HasValue)
            {
                parent = await _costCenterRepository.GetByIdAsync(request.ParentCostCenterId.Value)
                    ?? throw new NotFoundException("Parent cost center not found");

                var resultingDepth = await _costCenterRepository.GetAncestorDepthAsync(parent.CostCenterId);
                await DepthGuard.EnsureWithinMaxDepthAsync(
                    _systemConfigRepository, "COST_CENTER_MAX_DEPTH", null, resultingDepth, "Maximum Cost Center depth exceeded");
            }

            var code = await GenerateCostCenterCodeAsync(parent);

            var costCenter = new CostCenter
            {
                Code = code,
                Name = request.Name,
                ParentCostCenterId = request.ParentCostCenterId,
                IsActive = request.IsActive
            };

            await _unitOfWork.BeginAsync();
            try
            {
                await _costCenterRepository.AddAsync(costCenter);
                await _unitOfWork.SaveChangesAsync();

                await _auditLogRepository.AddAsync(new AuditLog
                {
                    Category = AuditCategory.Administrative,
                    EntityName = "CostCenter",
                    EntityId = costCenter.CostCenterId.ToString(),
                    Action = AuditAction.Create,
                    Description = $"Cost center {costCenter.Code} created",
                    PerformedBy = null
                });
                await _unitOfWork.SaveChangesAsync();

                await _unitOfWork.CommitAsync();
            }
            catch
            {
                await _unitOfWork.RollbackAsync();
                throw;
            }

            return ResponseHelpers.Created("Cost center created successfully", costCenter);
        }

        private async Task<string> GenerateCostCenterCodeAsync(CostCenter? parent)
        {
            if (parent != null)
            {
                for (var suffix = 1; suffix <= 99; suffix++)
                {
                    var code = $"{parent.Code}-{suffix:D2}";
                    if (await _costCenterRepository.GetByCodeAsync(code) is null)
                    {
                        return code;
                    }
                }

                throw new BadRequestException("Maximum number of child cost centers under this parent has been reached.");
            }

            // Probes each candidate slot directly (same fix as AccountService.GenerateAccountCodeAsync)
            // rather than trusting a root count, so a pre-existing, manually-coded cost center can
            // never collide with a generated one.
            for (var slot = 1; slot <= 999; slot++)
            {
                var code = $"CC-{slot:D3}";
                if (await _costCenterRepository.GetByCodeAsync(code) is null)
                {
                    return code;
                }
            }

            throw new BadRequestException("Maximum number of root-level cost centers has been reached.");
        }

        public async Task<ApiResponse> GetCostCenterByCodeAsync(string costCenterCode, string? expand)
        {
            var costCenter = await _costCenterRepository.GetByCodeAsync(costCenterCode)
                ?? throw new NotFoundException("Cost center not found");

            var breadcrumb = await _costCenterRepository.GetAncestorBreadcrumbAsync(costCenter.CostCenterId);

            List<CostCenterTreeNode>? descendantTree = null;
            if (string.Equals(expand, "tree", StringComparison.OrdinalIgnoreCase))
            {
                descendantTree = await _costCenterRepository.GetDescendantTreeAsync(costCenter.CostCenterId);
            }

            var data = new CostCenterDetailResponse
            {
                CostCenter = costCenter,
                AncestorBreadcrumb = breadcrumb,
                DescendantTree = descendantTree
            };

            return ResponseHelpers.Ok("Cost center retrieved successfully", data);
        }
    }
}