Allow deletion of admins

src/backend/src/Randall.Api/Admin/AdminController.cs

@@ -19,8 +19,9 @@ public class AdminController(
     DeleteUserHandler deleteUserHandler,
     MakeAdminHandler makeAdminHandler) : ControllerBase
 {
-    private bool IsAdmin =>
-        User.FindFirstValue("isAdmin") == "true";
+    private bool IsAdmin => User.FindFirstValue("isAdmin") == "true";
+    private Guid RequesterId => Guid.Parse(User.FindFirstValue(System.Security.Claims.ClaimTypes.NameIdentifier)
+        ?? User.FindFirstValue("sub")!);
 
     [HttpGet("users")]
     public async Task<IActionResult> GetAllUsers(CancellationToken ct)
@@ -62,7 +63,7 @@ public class AdminController(
     public async Task<IActionResult> DeleteUser(Guid id, CancellationToken ct)
     {
         if (!IsAdmin) return Forbid();
-        var result = await deleteUserHandler.HandleAsync(new DeleteUserCommand(id), ct);
+        var result = await deleteUserHandler.HandleAsync(new DeleteUserCommand(RequesterId, id), ct);
         if (!result.IsSuccess)
             return BadRequest(new ProblemDetails { Detail = result.Error });
         return NoContent();

src/backend/src/Randall.Application/Admin/DeleteUser/DeleteUserCommand.cs

@@ -1,3 +1,3 @@
 namespace Randall.Application.Admin.DeleteUser;
 
-public record DeleteUserCommand(Guid UserId);
+public record DeleteUserCommand(Guid RequesterId, Guid UserId);

src/backend/src/Randall.Application/Admin/DeleteUser/DeleteUserHandler.cs

@@ -11,8 +11,15 @@ public class DeleteUserHandler(IUserRepository userRepository)
         if (user is null)
             return Result.Failure("User not found.");
 
+        if (user.Id == command.RequesterId)
+            return Result.Failure("You cannot delete your own account.");
+
         if (user.IsAdmin)
-            return Result.Failure("Admin users cannot be deleted.");
+        {
+            var adminCount = await userRepository.CountAdminsAsync(ct);
+            if (adminCount <= 1)
+                return Result.Failure("Cannot delete the last admin account.");
+        }
 
         userRepository.Delete(user);
         await userRepository.SaveChangesAsync(ct);

src/backend/src/Randall.Domain/Users/IUserRepository.cs

@@ -7,6 +7,7 @@ public interface IUserRepository
     Task<bool> ExistsByEmailAsync(string email, CancellationToken ct = default);
     Task<List<User>> GetPendingAsync(CancellationToken ct = default);
     Task<List<User>> GetAllAsync(CancellationToken ct = default);
+    Task<int> CountAdminsAsync(CancellationToken ct = default);
     Task<List<User>> GetAllNonAdminAsync(CancellationToken ct = default);
     Task AddAsync(User user, CancellationToken ct = default);
     void Delete(User user);

src/backend/src/Randall.Infrastructure/Persistence/Users/UserRepository.cs

@@ -20,6 +20,9 @@ public class UserRepository(AppDbContext context) : IUserRepository
     public Task<List<User>> GetAllAsync(CancellationToken ct = default) =>
         context.Users.OrderBy(u => u.Name).ToListAsync(ct);
 
+    public Task<int> CountAdminsAsync(CancellationToken ct = default) =>
+        context.Users.CountAsync(u => u.IsAdmin);
+
     public Task<List<User>> GetAllNonAdminAsync(CancellationToken ct = default) =>
         context.Users.Where(u => !u.IsAdmin).OrderBy(u => u.Name).ToListAsync(ct);