# Module: Azaion.Common.BusinessException

## Purpose
Custom exception type for domain-level errors, paired with an `ExceptionEnum` catalog of all business error codes.

## Public Interface

### BusinessException
| Member | Signature | Description |
|--------|-----------|-------------|
| Constructor | `BusinessException(ExceptionEnum exEnum)` | Creates exception with message from `ExceptionEnum`'s `[Description]` attribute |
| `ExceptionEnum` | `ExceptionEnum ExceptionEnum { get; set; }` | The specific error code |
| `GetMessage` | `static string GetMessage(ExceptionEnum exEnum)` | Looks up human-readable message for an error code |

### ExceptionEnum
| Value | Code | Description |
|-------|------|-------------|
| `NoEmailFound` | 10 | No such email found |
| `EmailExists` | 20 | Email already exists |
| `WrongPassword` | 30 | Passwords do not match |
| `PasswordLengthIncorrect` | 32 | Password should be at least 8 characters |
| `EmailLengthIncorrect` | 35 | Email is empty or invalid |
| `WrongEmail` | 37 | (no description attribute) |
| `HardwareIdMismatch` | 40 | Hardware mismatch — unauthorized hardware |
| `BadHardware` | 45 | Hardware should be not empty |
| `WrongResourceName` | 50 | Wrong resource file name |
| `NoFileProvided` | 60 | No file provided |

## Internal Logic
Static constructor eagerly loads all `ExceptionEnum` descriptions into a dictionary via `EnumExtensions.GetDescriptions<ExceptionEnum>()`. Messages are retrieved by dictionary lookup with fallback to `ToString()`.

## Dependencies
- `EnumExtensions` — for `GetDescriptions<T>()`

## Consumers
- `BusinessExceptionHandler` — catches and serializes to HTTP 409 response
- `UserService` — throws for email/password/hardware validation failures
- `ResourcesService` — throws for missing file uploads
- FluentValidation validators — reference `ExceptionEnum` codes in `.WithErrorCode()`

## Data Models
None.

## Configuration
None.

## External Integrations
None.

## Security
Error codes are returned to the client via `BusinessExceptionHandler`. Codes are numeric and messages are user-facing.

## Tests
None.