Add region code

Distribution/Features/Region/IRegionRepository.cs

@@ -4,6 +4,8 @@ public interface IRegionRepository
 {
     Task<Models.Region?> GetByIdAsync(Guid id);
     Task<List<Models.Region>> GetAllAsync();
+    Task<List<string>> GetAllCodesAsync();
+    Task<bool> CodeExistsAsync(string code, Guid? excludeId = null);
     Task AddAsync(Models.Region entity);
     void Update(Models.Region entity);
     void Remove(Models.Region entity);

Distribution/Features/Region/RegionController.cs

@@ -10,6 +10,11 @@ public class RegionController(RegionService service) : ControllerBase
     public async Task<IActionResult> GetAll() =>
         Ok(await service.GetAllAsync());
 
+    // Suggested code for the Add Region form; the user may override it.
+    [HttpGet("next-code")]
+    public async Task<IActionResult> GetNextCode() =>
+        Ok(await service.GetNextCodeAsync());
+
     [HttpGet("{id:guid}")]
     public async Task<IActionResult> GetById(Guid id)
     {

Distribution/Features/Region/RegionDTOs.cs

@@ -1,10 +1,14 @@
 namespace Distribution.Features.Region;
 
-public record CreateRegionRequest(string Name);
+// Code is optional: blank/null auto-generates the next REG-#### code; otherwise stored as entered (trimmed).
+public record CreateRegionRequest(string Name, string? Code = null);
 
-public record UpdateRegionRequest(string Name);
+public record NextRegionCodeResponse(string Code);
 
-public record RegionResponse(Guid Id, string Name, bool IsActive, DateTime CreatedAt);
+// Code is auto-generated on create; on update it is optional (null/blank keeps the current code).
+public record UpdateRegionRequest(string Name, string? Code = null);
+
+public record RegionResponse(Guid Id, string Code, string Name, bool IsActive, DateTime CreatedAt);
 
 public record RegionalTargetResponse(Guid RegionId, string Period, decimal TargetValue);
 

Distribution/Features/Region/RegionRepository.cs

@@ -11,6 +11,13 @@ public class RegionRepository(AppDBContext context) : IRegionRepository
     public async Task<List<Models.Region>> GetAllAsync() =>
         await context.Regions.ToListAsync();
 
+    // Includes soft-deleted regions: the unique index on Code doesn't know about IsActive.
+    public async Task<List<string>> GetAllCodesAsync() =>
+        await context.Regions.Select(r => r.Code).ToListAsync();
+
+    public async Task<bool> CodeExistsAsync(string code, Guid? excludeId = null) =>
+        await context.Regions.AnyAsync(r => r.Code == code && (excludeId == null || r.Id != excludeId));
+
     public async Task AddAsync(Models.Region entity) =>
         await context.Regions.AddAsync(entity);
 

Distribution/Features/Region/RegionService.cs

@@ -6,6 +6,7 @@ namespace Distribution.Features.Region;
 public class RegionService(IRegionRepository repo, IUnitOfWork uow, ICurrentUserService currentUser, IScopeAccessService scopeAccess)
 {
     private const int RegionalAgencyRoleLevel = 60;
+    private const string CodePrefix = "REG-";
 
     // TODO: re-enable the RegionalManager+scope / RegionalAgency role gate on ManageAsync once
     // the role model for this endpoint is finalized. Left open (allow-all) for now on purpose.
@@ -14,19 +15,42 @@ public class RegionService(IRegionRepository repo, IUnitOfWork uow, ICurrentUser
     public async Task<List<RegionResponse>> GetAllAsync() =>
         (await repo.GetAllAsync())
             .Where(r => r.IsActive)
-            .Select(r => new RegionResponse(r.Id, r.Name, r.IsActive, r.CreatedAt))
+            .Select(r => new RegionResponse(r.Id, r.Code, r.Name, r.IsActive, r.CreatedAt))
             .ToList();
 
     public async Task<RegionResponse?> GetByIdAsync(Guid id)
     {
         var region = await repo.GetByIdAsync(id);
         if (region is null || !region.IsActive) return null;
-        return new RegionResponse(region.Id, region.Name, region.IsActive, region.CreatedAt);
+        return new RegionResponse(region.Id, region.Code, region.Name, region.IsActive, region.CreatedAt);
+    }
+
+    // Next code = highest existing REG-#### number + 1 (soft-deleted regions included so codes are never reused).
+    public async Task<NextRegionCodeResponse> GetNextCodeAsync() => new(await GenerateCodeAsync());
+
+    private async Task<string> GenerateCodeAsync()
+    {
+        var max = (await repo.GetAllCodesAsync())
+            .Where(c => c.StartsWith(CodePrefix, StringComparison.OrdinalIgnoreCase)
+                        && int.TryParse(c[CodePrefix.Length..], out _))
+            .Select(c => int.Parse(c[CodePrefix.Length..]))
+            .DefaultIfEmpty(0)
+            .Max();
+        return $"{CodePrefix}{max + 1:D4}";
     }
 
     public async Task<RegionResponse> CreateAsync(CreateRegionRequest request, CancellationToken ct = default)
     {
-        var region = new Models.Region { Name = request.Name };
+        string code;
+        if (string.IsNullOrWhiteSpace(request.Code))
+            code = await GenerateCodeAsync();
+        else
+        {
+            code = request.Code.Trim();
+            if (await repo.CodeExistsAsync(code))
+                throw new InvalidOperationException($"Region code '{code}' is already in use.");
+        }
+        var region = new Models.Region { Name = request.Name, Code = code };
         await uow.BeginAsync(ct);
         try
         {
@@ -38,7 +62,7 @@ public class RegionService(IRegionRepository repo, IUnitOfWork uow, ICurrentUser
             await uow.RollbackAsync(ct);
             throw;
         }
-        return new RegionResponse(region.Id, region.Name, region.IsActive, region.CreatedAt);
+        return new RegionResponse(region.Id, region.Code, region.Name, region.IsActive, region.CreatedAt);
     }
 
     public async Task<RegionResponse?> UpdateAsync(Guid id, UpdateRegionRequest request, CancellationToken ct = default)
@@ -46,6 +70,13 @@ public class RegionService(IRegionRepository repo, IUnitOfWork uow, ICurrentUser
         var region = await repo.GetByIdAsync(id);
         if (region is null || !region.IsActive) return null;
         region.Name = request.Name;
+        if (!string.IsNullOrWhiteSpace(request.Code))
+        {
+            var code = request.Code.Trim();
+            if (code != region.Code && await repo.CodeExistsAsync(code, id))
+                throw new InvalidOperationException($"Region code '{code}' is already in use.");
+            region.Code = code;
+        }
         await uow.BeginAsync(ct);
         try
         {
@@ -57,7 +88,7 @@ public class RegionService(IRegionRepository repo, IUnitOfWork uow, ICurrentUser
             await uow.RollbackAsync(ct);
             throw;
         }
-        return new RegionResponse(region.Id, region.Name, region.IsActive, region.CreatedAt);
+        return new RegionResponse(region.Id, region.Code, region.Name, region.IsActive, region.CreatedAt);
     }
 
     public async Task<bool> DeleteAsync(Guid id, CancellationToken ct = default)