Replace error_status() method by several response types

src/handlers/customers.rs

@@ -3,14 +3,11 @@
 //! Handlers for viewing a list of existing customers or creating a new one.
 
 use diesel::prelude::*;
-use rocket::http::Status;
-use rocket::response::status::Created;
-use rocket::uri;
-use rocket::{delete, get, post, put};
+use rocket::{delete, get, post, put, uri};
 use rocket_contrib::json::Json;
 
 use crate::models::{Customer, NewCustomer};
-use crate::rest_helpers::error_status;
+use crate::rest_helpers::*;
 use crate::DbConn;
 
 pub mod invoices;
@@ -18,56 +15,42 @@ pub mod tasks;
 
 /// Shows the list of customers.
 #[get("/")]
-pub fn index(conn: DbConn) -> Result<Json<Vec<Customer>>, Status> {
-    all!(Customer, *conn)
-        .map(|customers| Json(customers))
-        .map_err(|e| error_status(e))
+pub fn index(conn: DbConn) -> JsonResponse<Vec<Customer>> {
+    all!(Customer, *conn).into_json_response()
 }
 
 /// Creates a customer from the new customer
 #[post("/", format = "json", data = "<new_customer>")]
-pub fn create(
-    new_customer: Json<NewCustomer>,
-    conn: DbConn,
-) -> Result<Created<Json<Customer>>, Status> {
-    create!(Customer, new_customer.into_inner(), *conn)
-        .map(|customer: Customer| {
-            Created(
-                uri!("/customers", show: customer.id).to_string(),
-                Some(Json(customer)),
-            )
-        })
-        .map_err(|e| error_status(e))
+pub fn create(new_customer: Json<NewCustomer>, conn: DbConn) -> CreatedJsonResponse<Customer> {
+    let new_customer = new_customer.into_inner();
+    create!(Customer, new_customer, *conn).into_created_json_response(|customer: &Customer| {
+        uri!("/customers", show: customer.id).to_string()
+    })
 }
 
 /// Provides the form for the data required to create a new customer.
 #[get("/new")]
-pub fn new() -> Json<NewCustomer> {
-    Json(NewCustomer::default())
+pub fn new() -> JsonResponse<NewCustomer> {
+    NewCustomer::default().into_json_response()
 }
 
 /// Shows a form for viewing and updating information of the customer with the given ID.
 #[get("/<id>")]
-pub fn show(id: i32, conn: DbConn) -> Result<Json<Customer>, Status> {
-    get!(Customer, id, *conn)
-        .map(|customer| Json(customer))
-        .map_err(|e| error_status(e))
+pub fn show(id: i32, conn: DbConn) -> JsonResponse<Customer> {
+    get!(Customer, id, *conn).into_json_response()
 }
 
 /// Updates the customer with the given ID.
 #[put("/<id>", format = "json", data = "<customer>")]
-pub fn update(id: i32, customer: Json<Customer>, conn: DbConn) -> Result<Json<Customer>, Status> {
-    update!(Customer, id, customer.into_inner(), *conn)
-        .map(|customer| Json(customer))
-        .map_err(|e| error_status(e))
+pub fn update(id: i32, customer: Json<Customer>, conn: DbConn) -> JsonResponse<Customer> {
+    let customer = customer.into_inner();
+    update!(Customer, id, customer, *conn).into_json_response()
 }
 
 /// Destroys the customer with the given ID and redirects to the index handler.
 #[delete("/<id>")]
-pub fn destroy(id: i32, conn: DbConn) -> Result<Status, Status> {
-    delete!(Customer, id, *conn)
-        .map(|_| Status::NoContent)
-        .map_err(|e| error_status(e))
+pub fn destroy(id: i32, conn: DbConn) -> NoContentResponse {
+    destroy!(Customer, id, *conn).into_no_content_response()
 }
 
 #[cfg(test)]

src/rest_helpers.rs

@@ -1,12 +1,99 @@
-use diesel::result::Error as QueryError;
-use rocket::http::Status;
+//! Some REST API herlpers
+//!
+//! The macros, types and traits in this module are used to create a simple REST API on top of
+//! models that are in the database.
 
-/// Returns a Rocket status for the provided Diesel (query) error.
-pub fn error_status(error: QueryError) -> Status {
-    dbg!(&error);
-    match error {
-        QueryError::NotFound => Status::NotFound,
-        _ => Status::InternalServerError,
+#![allow(unused_macros)]
+
+use diesel::result::{DatabaseErrorKind, Error as QueryError};
+use rocket::http::Status;
+use rocket::response::status::Created;
+use rocket_contrib::json::Json;
+use serde::Serialize;
+
+/// Conversion into a Rocket [`Status`].
+trait IntoStatus {
+    fn into_status(self) -> Status;
+}
+
+impl IntoStatus for QueryError {
+    fn into_status(self) -> Status {
+        match self {
+            QueryError::NotFound => Status::NotFound,
+            QueryError::DatabaseError(kind, _info) => match kind {
+                DatabaseErrorKind::UniqueViolation => Status::Conflict,
+                DatabaseErrorKind::ForeignKeyViolation => Status::BadRequest,
+                _ => Status::InternalServerError,
+            },
+            _ => Status::InternalServerError,
+        }
+    }
+}
+
+/// A specialized `Result` type for Rocket JSON reponses.
+///
+/// It contains either a JSON serialization or an (error) Rocket [`Status`].
+pub type JsonResponse<T> = Result<Json<T>, Status>;
+
+/// Conversion into a [`JsonResponse`].
+pub trait IntoJsonResponse<T> {
+    fn into_json_response(self) -> JsonResponse<T>;
+}
+
+impl<T> IntoJsonResponse<T> for Result<T, QueryError> {
+    fn into_json_response(self) -> JsonResponse<T> {
+        self.map(|item| Json(item))
+            .map_err(|error| error.into_status())
+    }
+}
+
+impl<T> IntoJsonResponse<T> for T
+where
+    T: Serialize,
+{
+    fn into_json_response(self) -> JsonResponse<T> {
+        Ok(Json(self))
+    }
+}
+
+/// A specialized `Result` type for Rocket Created (with JSON) reponses.
+///
+/// It contains either a JSON serialization with URI in a [`Created`] struct or an (error) Rocket
+/// [`Status`].
+pub type CreatedJsonResponse<T> = Result<Created<Json<T>>, Status>;
+
+/// Conversion into a [`CreatedJsonResponse`].
+pub trait IntoCreatedJsonResponse<T> {
+    fn into_created_json_response<F>(self, uri_func: F) -> CreatedJsonResponse<T>
+    where
+        F: Fn(&T) -> String;
+}
+
+impl<T> IntoCreatedJsonResponse<T> for Result<T, QueryError> {
+    fn into_created_json_response<F>(self, uri_func: F) -> CreatedJsonResponse<T>
+    where
+        F: Fn(&T) -> String,
+    {
+        self.map(|item| Created(uri_func(&item), Some(Json(item))))
+            .map_err(|error| error.into_status())
+    }
+}
+
+/// A specialized `Result` type for Rocket `Status::NoContent` reponses.
+///
+/// It contains either a [`Status::NoContent`] in the Ok case, or an (error) Rocket [`Status`]
+/// in the Err case.
+pub type NoContentResponse = Result<Status, Status>;
+
+/// Conversion into a [`NoContentResponse`].
+pub trait IntoNoContentResponse {
+    fn into_no_content_response(self) -> NoContentResponse;
+}
+
+impl<T> IntoNoContentResponse for Result<T, QueryError> {
+    fn into_no_content_response(self) -> NoContentResponse {
+        self.map(|_item| Status::NoContent)
+            .map_err(|error| error.into_status())
     }
 }
 
@@ -51,7 +138,7 @@ macro_rules! update {
     }};
 }
 
-macro_rules! delete {
+macro_rules! destroy {
     ($model_name:ident, $primary_key:expr, $conn:expr) => {{
         use diesel::associations::HasTable;
         let table = $crate::models::$model_name::table();