axum-api-template/src/middleware/auth.rs

//! Bearer-token authentication extractor.
//!
//! Use `AuthenticatedUser` as a handler parameter to require a valid JWT.
//! Unauthenticated requests are rejected with `401 Unauthorized` before the
//! handler body ever executes.
//!
//! # Example
//!
//! ```rust,ignore
//! async fn protected_handler(
//!     user: AuthenticatedUser,
//!     State(state): State<AppState>,
//! ) -> Result<impl IntoResponse, ApiError> {
//!     // user.id and user.roles are guaranteed valid here
//!     Ok(Json(json!({ "sub": user.id })))
//! }
//! ```

use axum::{
    async_trait,
    extract::FromRequestParts,
    http::request::Parts,
    RequestPartsExt,
};
use axum_extra::{
    headers::{authorization::Bearer, Authorization},
    TypedHeader,
};
use uuid::Uuid;

use crate::errors::ApiError;

// ── Authenticated user claim ──────────────────────────────────────────────────

/// Injected into handlers that require authentication.
#[derive(Debug, Clone)]
pub struct AuthenticatedUser {
    pub id: Uuid,
    pub roles: Vec<String>,
}

// ── FromRequestParts impl ─────────────────────────────────────────────────────

#[async_trait]
impl<S> FromRequestParts<S> for AuthenticatedUser
where
    S: Send + Sync,
{
    type Rejection = ApiError;

    async fn from_request_parts(parts: &mut Parts, _state: &S) -> Result<Self, Self::Rejection> {
        // Extract the Bearer token from the Authorization header.
        let TypedHeader(Authorization(bearer)) = parts
            .extract::<TypedHeader<Authorization<Bearer>>>()
            .await
            .map_err(|_| ApiError::Unauthorized("Missing or malformed Authorization header".to_string()))?;

        // TODO: replace this stub with real JWT validation.
        //
        // Example using `jsonwebtoken`:
        //   let secret = state.config().auth.jwt_secret.as_bytes();
        //   let token_data = decode::<Claims>(bearer.token(), &DecodingKey::from_secret(secret), &Validation::default())?;
        //   return Ok(AuthenticatedUser { id: token_data.claims.sub, roles: token_data.claims.roles });

        let _ = bearer.token(); // silence unused-variable lint on the stub

        Err(ApiError::Unauthorized("JWT validation not yet implemented".to_string()))
    }
}