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//! # API standard and JSON responses.
//!
//! This module provides useful traits and methods to craft API replies from an existing type.
#[cfg(feature = "pgsql")]
use diesel::result::{DatabaseErrorInformation, DatabaseErrorKind, QueryResult};
#[cfg(feature = "pgsql")]
use diesel::result::Error as ResultError;
use rocket::http::Status;
use rocket_contrib::json::Json;
#[cfg(feature = "serialization")]
use serde::Serialize;
/* -------------------------------------------------------------
Custom types
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
pub type ApiJsonResponse<T> = Result<Json<T>, Status>;
/* -------------------------------------------------------------
API Response
:: Implementation for QueryResult (Diesel ORM)
:: Implementation for Json (Rocket contrib)
:: Implementation for Serialize (Serde)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/// This trait allows to consume an object into an HTTP response.
pub trait ApiResponse<T> {
/// Consumes the value and creates a JSON or a Status result response.
fn into_json_response(self) -> ApiJsonResponse<T>;
}
#[cfg(feature = "pgsql")]
impl<T> ApiResponse<T> for QueryResult<T> {
/// Prepares an API response from a query result.
///
/// The result is the data structure prepared by the Diesel ORM after a SELECT query
/// with one result, for example using `first` method. You can also you use it to
/// parse the returning result (... RETURNING *), which is a default for Diesel after
/// an INSERT query.
///
/// So result can be:
/// - Ok(T)
/// - Err(E) where E is a Status containing an HTTP error code according the situation
///
/// # Examples
///
/// To offer a /player/foo route to serve player information from the players table:
///
/// ```
/// use limiting_factor::api::ApiResponse;
/// use limiting_factor::api::ApiJsonResponse;
///
/// #[get("/player/<name>")]
/// pub fn get_player(connection: DatabaseConnection, name: String) -> ApiJsonResponse<Player> {
/// players
/// .filter(username.eq(&name))
/// .first::<Player>(&*connection)
/// .into_json_response()
/// }
/// ```
///
/// This will produce a JSON representation when the result is found,
/// a 404 error when no result is found, a 500 error if there is a database issue.
///
/// To insert a new player in the same table:
///
/// ```
/// use limiting_factor::api::ApiResponse;
/// use limiting_factor::api::ApiJsonResponse;
///
/// #[post("/register", format="application/json", data="<user>")]
/// pub fn register(connection: DatabaseConnection, user: Json<UserToRegister>) -> ApiJsonResponse<Player> {
/// let user: UserToRegister = user.into_inner();
/// let player_to_create = user.to_new_player();
///
/// diesel::insert_into(players)
/// .values(&player_to_create)
/// .get_result::<Player>(&*connection)
/// .into_json_response()
/// }
/// ```
///
/// This will produce a JSON representation of the newly inserted player if successful.
/// If the insert fails because of an unique constraint violation (e.g. an username already
/// taken), it returns a 409 Conflict.
/// If the failure is from a foreign key integrity constraint, it returns a 400.
/// If there is any other database issue, it returns a 500.
fn into_json_response(self) -> ApiJsonResponse<T> {
self
// CASE I - The query returns one value, we return a JSON representation fo the item
.map(|item| Json(item))
.map_err(|error| match error {
// Case II - The query returns no result, we return a 404 Not found response
ResultError::NotFound => Status::NotFound,
// Case III - We need to handle a database error, which could be a 400/409/500
ResultError::DatabaseError(kind, details) => {
build_database_error_response(kind, details)
}
// Case IV - The error is probably server responsibility, log it and throw a 500
_ => error.into_failure_response(),
})
}
}
/// Prepares an API response from a JSON.
impl<T> ApiResponse<T> for Json<T> {
fn into_json_response(self) -> ApiJsonResponse<T> {
Ok(self)
}
}
/// Prepares an API response from a Serde-serializable result.
///
/// This is probably the easiest way to convert most struct
/// into API responders.
///
/// # Examples
///
#[cfg(feature = "serialization")]
impl<T> ApiResponse<T> for T
where T: Serialize
{
fn into_json_response(self) -> ApiJsonResponse<T> {
Ok(Json(self))
}
}
/* -------------------------------------------------------------
API Delete Response
:: Implementation for QueryResult (Diesel ORM)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
#[cfg(feature = "pgsql")]
/// This trait allows to consume an object into an HTTP response.
///
/// This response is a odd case for DELETE queries, which return
/// a scalar with the rows deleted count value, or an error.
pub trait ApiDeleteResponse<T> {
/// Consumes the value and creates a JSON or a Status result response.
fn into_delete_json_response(self) -> ApiJsonResponse<()>;
}
#[cfg(feature = "pgsql")]
impl ApiDeleteResponse<usize> for QueryResult<usize> {
fn into_delete_json_response(self) -> ApiJsonResponse<()> {
match self {
Ok(0) => Err(Status::NotFound),
Ok(1) => Ok(Json(())),
_ => Err(Status::BadRequest),
}
}
}
/* -------------------------------------------------------------
Failure response
:: Implementation for diesel::result::Error
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/// This trait allows to consume an object into an HTTP failure response.
pub trait FailureResponse {
/// Consumes the variable and creates a Failure response .
fn into_failure_response(self) -> Status;
}
#[cfg(feature = "pgsql")]
impl FailureResponse for ResultError {
/// Consumes the error and creates a 500 Internal server error Status response.
fn into_failure_response(self) -> Status {
build_internal_server_error_response(&self.to_string())
}
}
/* -------------------------------------------------------------
Helper methods to prepare API responses
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
#[deprecated(since="0.6.0", note="Use directly Status::NotFound instead.")]
pub fn build_not_found_response() -> Status {
Status::NotFound
}
#[deprecated(since="0.6.0", note="Use directly Status::BadRequest instead.")]
pub fn build_bad_request_response() -> Status {
Status::BadRequest
}
pub fn build_internal_server_error_response(message: &str) -> Status {
warn!(target:"api", "{}", message);
Status::InternalServerError
}
#[cfg(feature = "pgsql")]
fn build_database_error_response(error_kind: DatabaseErrorKind, info: Box<dyn DatabaseErrorInformation>) -> Status {
match error_kind {
// Case IIIa - The query tries to do an INSERT violating an unique constraint
// e.g. two INSERT with the same unique value
// We return a 409 Conflict
DatabaseErrorKind::UniqueViolation => Status::Conflict,
// Case IIIb - The query violated a foreign key constraint
// e.g. an INSERT referring to a non existing user 1004
// when there is no id 1004 in users table
// We return a 400 Bad request
DatabaseErrorKind::ForeignKeyViolation => Status::BadRequest,
// Case IIIc - For other databases errors, the client responsibility isn't involved.
_ => build_internal_server_error_response(info.message()),
}
}

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