| 1 | use std::fmt; |
| 2 | |
| 3 | /// Every way a domain rule can be violated. |
| 4 | /// |
| 5 | /// Deliberately coarse: a variant earns its place when a caller needs to react to it |
| 6 | /// differently, not merely to describe a failure more precisely. |
| 7 | #[derive(Debug, Clone, PartialEq, Eq)] |
| 8 | pub enum DomainError { |
| 9 | /// A value failed validation. Carries the field and the reason. |
| 10 | Validation { field: String, reason: String }, |
| 11 | /// The requested entity does not exist. |
| 12 | NotFound { entity: &'static str }, |
| 13 | /// The entity already exists and the operation requires it not to. |
| 14 | AlreadyExists { entity: &'static str }, |
| 15 | /// Credentials did not match. Deliberately says nothing about which part failed. |
| 16 | InvalidCredentials, |
| 17 | /// The actor is known but not permitted to do this. |
| 18 | /// |
| 19 | /// Distinct from [`NotFound`](Self::NotFound): used where the resource is public |
| 20 | /// anyway, so pretending it does not exist would be theatre rather than privacy. |
| 21 | Forbidden, |
| 22 | } |
| 23 | |
| 24 | impl DomainError { |
| 25 | pub fn validation(field: impl Into<String>, reason: impl Into<String>) -> Self { |
| 26 | Self::Validation { |
| 27 | field: field.into(), |
| 28 | reason: reason.into(), |
| 29 | } |
| 30 | } |
| 31 | } |
| 32 | |
| 33 | impl fmt::Display for DomainError { |
| 34 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| 35 | match self { |
| 36 | Self::Validation { field, reason } => write!(f, "invalid {field}: {reason}"), |
| 37 | Self::NotFound { entity } => write!(f, "{entity} not found"), |
| 38 | Self::AlreadyExists { entity } => write!(f, "{entity} already exists"), |
| 39 | Self::InvalidCredentials => f.write_str("invalid credentials"), |
| 40 | Self::Forbidden => f.write_str("not permitted"), |
| 41 | } |
| 42 | } |
| 43 | } |
| 44 | |
| 45 | impl std::error::Error for DomainError {} |