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    use std::{collections::HashSet, convert::TryInto, iter::FromIterator, rc::Rc};

    use actix_utils::future::{self, Ready};
    use actix_web::{
        body::{EitherBody, MessageBody},
        dev::{RequestHead, Service, ServiceRequest, ServiceResponse, Transform},
        error::HttpError,
        http::{
            header::{HeaderName, HeaderValue},
            Method, Uri,
        },
        Either, Error, Result,
    };
    use log::error;
    use once_cell::sync::Lazy;
    use smallvec::smallvec;

    use crate::{AllOrSome, CorsError, CorsMiddleware, Inner, OriginFn};

    /// Convenience for getting mut refs to inner. Cleaner than `Rc::get_mut`.
    /// Additionally, always causes first error (if any) to be reported during initialization.
    fn cors<'a>(
        inner: &'a mut Rc<Inner>,
        err: &Option<Either<HttpError, CorsError>>,
    ) -> Option<&'a mut Inner> {
        if err.is_some() {
            return None;
        }

        Rc::get_mut(inner)
    }

    static ALL_METHODS_SET: Lazy<HashSet<Method>> = Lazy::new(|| {
        HashSet::from_iter(vec![
            Method::GET,
            Method::POST,
            Method::PUT,
            Method::DELETE,
            Method::HEAD,
            Method::OPTIONS,
            Method::CONNECT,
            Method::PATCH,
            Method::TRACE,
        ])
    });

    /// Builder for CORS middleware.
    ///
    /// To construct a CORS middleware, call [`Cors::default()`] to create a blank, restrictive builder.
    /// Then use any of the builder methods to customize CORS behavior.
    ///
    /// The alternative [`Cors::permissive()`] constructor is available for local development, allowing
    /// all origins and headers, etc. **The permissive constructor should not be used in production.**
    ///
    /// # Behavior
    ///
    /// In all cases, behavior for this crate follows the [Fetch Standard CORS protocol]. See that
    /// document for information on exact semantics for configuration options and combinations.
    ///
    /// # Errors
    ///
    /// Errors surface in the middleware initialization phase. This means that, if you have logs enabled
    /// in Actix Web (using `env_logger` or other crate that exposes logs from the `log` crate), error
    /// messages will outline what is wrong with the CORS configuration in the server logs and the
    /// server will fail to start up or serve requests.
    ///
    /// # Example
    ///
    /// ```
    /// use actix_cors::Cors;
    /// use actix_web::http::header;
    ///
    /// let cors = Cors::default()
    ///     .allowed_origin("https://www.rust-lang.org")
    ///     .allowed_methods(vec!["GET", "POST"])
    ///     .allowed_headers(vec![header::AUTHORIZATION, header::ACCEPT])
    ///     .allowed_header(header::CONTENT_TYPE)
    ///     .max_age(3600);
    ///
    /// // `cors` can now be used in `App::wrap`.
    /// ```
    ///
    /// [Fetch Standard CORS protocol]: https://fetch.spec.whatwg.org/#http-cors-protocol
    #[derive(Debug)]
    pub struct Cors {
        inner: Rc<Inner>,
        error: Option<Either<HttpError, CorsError>>,
    }

    impl Cors {
        /// Constructs a very permissive set of defaults for quick development. (Not recommended for
        /// production use.)
        ///
        /// *All* origins, methods, request headers and exposed headers allowed. Credentials supported.
        /// Max age 1 hour. Does not send wildcard.
        pub fn permissive() -> Self {
            let inner = Inner {
                allowed_origins: AllOrSome::All,
                allowed_origins_fns: smallvec![],

                allowed_methods: ALL_METHODS_SET.clone(),
                allowed_methods_baked: None,

                allowed_headers: AllOrSome::All,
                allowed_headers_baked: None,

                expose_headers: AllOrSome::All,
                expose_headers_baked: None,

                max_age: Some(3600),
                preflight: true,
                send_wildcard: false,
                supports_credentials: true,
                #[cfg(feature = "draft-private-network-access")]
                allow_private_network_access: false,
                vary_header: true,
                block_on_origin_mismatch: true,
            };

            Cors {
                inner: Rc::new(inner),
                error: None,
            }
        }

        /// Resets allowed origin list to a state where any origin is accepted.
        ///
        /// See [`Cors::allowed_origin`] for more info on allowed origins.
        pub fn allow_any_origin(mut self) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.allowed_origins = AllOrSome::All;
            }

            self
        }

        /// Adds an origin that is allowed to make requests.
        ///
        /// This method allows specifying a finite set of origins to verify the value of the `Origin`
        /// request header. These are `origin-or-null` types in the [Fetch Standard].
        ///
        /// By default, no origins are accepted.
        ///
        /// When this list is set, the client's `Origin` request header will be checked in a
        /// case-sensitive manner.
        ///
        /// When all origins are allowed and `send_wildcard` is set, `*` will be sent in the
        /// `Access-Control-Allow-Origin` response header. If `send_wildcard` is not set, the client's
        /// `Origin` request header will be echoed back in the `Access-Control-Allow-Origin`
        /// response header.
        ///
        /// If the origin of the request doesn't match any allowed origins and at least one
        /// `allowed_origin_fn` function is set, these functions will be used to determinate
        /// allowed origins.
        ///
        /// # Initialization Errors
        /// - If supplied origin is not valid uri
        /// - If supplied origin is a wildcard (`*`). [`Cors::send_wildcard`] should be used instead.
        ///
        /// [Fetch Standard]: https://fetch.spec.whatwg.org/#origin-header
        pub fn allowed_origin(mut self, origin: &str) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                match TryInto::<Uri>::try_into(origin) {
                    Ok(_) if origin == "*" => {
                        error!("Wildcard in `allowed_origin` is not allowed. Use `send_wildcard`.");
                        self.error = Some(Either::Right(CorsError::WildcardOrigin));
                    }

                    Ok(_) => {
                        if cors.allowed_origins.is_all() {
                            cors.allowed_origins = AllOrSome::Some(HashSet::with_capacity(8));
                        }

                        if let Some(origins) = cors.allowed_origins.as_mut() {
                            // any uri is a valid header value
                            let hv = origin.try_into().unwrap();
                            origins.insert(hv);
                        }
                    }

                    Err(err) => {
                        self.error = Some(Either::Left(err.into()));
                    }
                }
            }

            self
        }

        /// Determinates allowed origins by processing requests which didn't match any origins specified
        /// in the `allowed_origin`.
        ///
        /// The function will receive two parameters, the Origin header value, and the `RequestHead` of
        /// each request, which can be used to determine whether to allow the request or not.
        ///
        /// If the function returns `true`, the client's `Origin` request header will be echoed back
        /// into the `Access-Control-Allow-Origin` response header.
        pub fn allowed_origin_fn<F>(mut self, f: F) -> Cors
        where
            F: (Fn(&HeaderValue, &RequestHead) -> bool) + 'static,
        {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.allowed_origins_fns.push(OriginFn {
                    boxed_fn: Rc::new(f),
                });
            }

            self
        }

        /// Resets allowed methods list to all methods.
        ///
        /// See [`Cors::allowed_methods`] for more info on allowed methods.
        pub fn allow_any_method(mut self) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.allowed_methods = ALL_METHODS_SET.clone();
            }

            self
        }

        /// Sets a list of methods which allowed origins can perform.
        ///
        /// These will be sent in the `Access-Control-Allow-Methods` response header.
        ///
        /// This defaults to an empty set.
        pub fn allowed_methods<U, M>(mut self, methods: U) -> Cors
        where
            U: IntoIterator<Item = M>,
            M: TryInto<Method>,
            <M as TryInto<Method>>::Error: Into<HttpError>,
        {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                for m in methods {
                    match m.try_into() {
                        Ok(method) => {
                            cors.allowed_methods.insert(method);
                        }

                        Err(err) => {
                            self.error = Some(Either::Left(err.into()));
                            break;
                        }
                    }
                }
            }

            self
        }

        /// Resets allowed request header list to a state where any header is accepted.
        ///
        /// See [`Cors::allowed_headers`] for more info on allowed request headers.
        pub fn allow_any_header(mut self) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.allowed_headers = AllOrSome::All;
            }

            self
        }

        /// Add an allowed request header.
        ///
        /// See [`Cors::allowed_headers`] for more info on allowed request headers.
        pub fn allowed_header<H>(mut self, header: H) -> Cors
        where
            H: TryInto<HeaderName>,
            <H as TryInto<HeaderName>>::Error: Into<HttpError>,
        {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                match header.try_into() {
                    Ok(method) => {
                        if cors.allowed_headers.is_all() {
                            cors.allowed_headers = AllOrSome::Some(HashSet::with_capacity(8));
                        }

                        if let AllOrSome::Some(ref mut headers) = cors.allowed_headers {
                            headers.insert(method);
                        }
                    }

                    Err(err) => self.error = Some(Either::Left(err.into())),
                }
            }

            self
        }

        /// Sets a list of request header field names which can be used when this resource is accessed
        /// by allowed origins.
        ///
        /// If `All` is set, whatever is requested by the client in `Access-Control-Request-Headers`
        /// will be echoed back in the `Access-Control-Allow-Headers` header.
        ///
        /// This defaults to an empty set.
        pub fn allowed_headers<U, H>(mut self, headers: U) -> Cors
        where
            U: IntoIterator<Item = H>,
            H: TryInto<HeaderName>,
            <H as TryInto<HeaderName>>::Error: Into<HttpError>,
        {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                for h in headers {
                    match h.try_into() {
                        Ok(method) => {
                            if cors.allowed_headers.is_all() {
                                cors.allowed_headers = AllOrSome::Some(HashSet::with_capacity(8));
                            }

                            if let AllOrSome::Some(ref mut headers) = cors.allowed_headers {
                                headers.insert(method);
                            }
                        }
                        Err(err) => {
                            self.error = Some(Either::Left(err.into()));
                            break;
                        }
                    }
                }
            }

            self
        }

        /// Resets exposed response header list to a state where all headers are exposed.
        ///
        /// See [`Cors::expose_headers`] for more info on exposed response headers.
        pub fn expose_any_header(mut self) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.expose_headers = AllOrSome::All;
            }

            self
        }

        /// Sets a list of headers which are safe to expose to the API of a CORS API specification.
        ///
        /// This corresponds to the `Access-Control-Expose-Headers` response header.
        ///
        /// This defaults to an empty set.
        pub fn expose_headers<U, H>(mut self, headers: U) -> Cors
        where
            U: IntoIterator<Item = H>,
            H: TryInto<HeaderName>,
            <H as TryInto<HeaderName>>::Error: Into<HttpError>,
        {
            for h in headers {
                match h.try_into() {
                    Ok(header) => {
                        if let Some(cors) = cors(&mut self.inner, &self.error) {
                            if cors.expose_headers.is_all() {
                                cors.expose_headers = AllOrSome::Some(HashSet::with_capacity(8));
                            }
                            if let AllOrSome::Some(ref mut headers) = cors.expose_headers {
                                headers.insert(header);
                            }
                        }
                    }
                    Err(err) => {
                        self.error = Some(Either::Left(err.into()));
                        break;
                    }
                }
            }

            self
        }

        /// Sets a maximum time (in seconds) for which this CORS request may be cached.
        ///
        /// This value is set as the `Access-Control-Max-Age` header.
        ///
        /// Pass a number (of seconds) or use None to disable sending max age header.
        pub fn max_age(mut self, max_age: impl Into<Option<usize>>) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.max_age = max_age.into();
            }

            self
        }

        /// Configures use of wildcard (`*`) origin in responses when appropriate.
        ///
        /// If send wildcard is set and the `allowed_origins` parameter is `All`, a wildcard
        /// `Access-Control-Allow-Origin` response header is sent, rather than the request’s
        /// `Origin` header.
        ///
        /// This option **CANNOT** be used in conjunction with a [credential
        /// supported](Self::supports_credentials()) configuration. Doing so will result in an error
        /// during server startup.
        ///
        /// Defaults to disabled.
        pub fn send_wildcard(mut self) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.send_wildcard = true;
            }

            self
        }

        /// Allows users to make authenticated requests.
        ///
        /// If true, injects the `Access-Control-Allow-Credentials` header in responses. This allows
        /// cookies and credentials to be submitted across domains.
        ///
        /// This option **CANNOT** be used in conjunction with option cannot be used in conjunction
        /// with [wildcard origins](Self::send_wildcard()) configured. Doing so will result in an error
        /// during server startup.
        ///
        /// Defaults to disabled.
        pub fn supports_credentials(mut self) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.supports_credentials = true;
            }

            self
        }

        /// Allow private network access.
        ///
        /// If true, injects the `Access-Control-Allow-Private-Network: true` header in responses if the
        /// request contained the `Access-Control-Request-Private-Network: true` header.
        ///
        /// For more information on this behavior, see the draft [Private Network Access] spec.
        ///
        /// Defaults to `false`.
        ///
        /// [Private Network Access]: https://wicg.github.io/private-network-access
        #[cfg(feature = "draft-private-network-access")]
        pub fn allow_private_network_access(mut self) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.allow_private_network_access = true;
            }

            self
        }

        /// Disables `Vary` header support.
        ///
        /// When enabled the header `Vary: Origin` will be returned as per the Fetch Standard
        /// implementation guidelines.
        ///
        /// Setting this header when the `Access-Control-Allow-Origin` is dynamically generated
        /// (eg. when there is more than one allowed origin, and an Origin other than '*' is returned)
        /// informs CDNs and other caches that the CORS headers are dynamic, and cannot be cached.
        ///
        /// By default, `Vary` header support is enabled.
        pub fn disable_vary_header(mut self) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.vary_header = false;
            }

            self
        }

        /// Disables preflight request handling.
        ///
        /// When enabled CORS middleware automatically handles `OPTIONS` requests. This is useful for
        /// application level middleware.
        ///
        /// By default, preflight support is enabled.
        pub fn disable_preflight(mut self) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.preflight = false;
            }

            self
        }

        /// Configures whether requests should be pre-emptively blocked on mismatched origin.
        ///
        /// If `true`, a 400 Bad Request is returned immediately when a request fails origin validation.
        ///
        /// If `false`, the request will be processed as normal but relevant CORS headers will not be
        /// appended to the response. In this case, the browser is trusted to validate CORS headers and
        /// and block requests based on pre-flight requests. Use this setting to allow cURL and other
        /// non-browser HTTP clients to function as normal, no matter what `Origin` the request has.
        ///
        /// Defaults to true.
        pub fn block_on_origin_mismatch(mut self, block: bool) -> Cors {
            if let Some(cors) = cors(&mut self.inner, &self.error) {
                cors.block_on_origin_mismatch = block;
            }

            self
        }
    }

    impl Default for Cors {
        /// A restrictive (security paranoid) set of defaults.
        ///
        /// *No* allowed origins, methods, request headers or exposed headers. Credentials
        /// not supported. No max age (will use browser's default).
        fn default() -> Cors {
            let inner = Inner {
                allowed_origins: AllOrSome::Some(HashSet::with_capacity(8)),
                allowed_origins_fns: smallvec![],

                allowed_methods: HashSet::with_capacity(8),
                allowed_methods_baked: None,

                allowed_headers: AllOrSome::Some(HashSet::with_capacity(8)),
                allowed_headers_baked: None,

                expose_headers: AllOrSome::Some(HashSet::with_capacity(8)),
                expose_headers_baked: None,

                max_age: None,
                preflight: true,
                send_wildcard: false,
                supports_credentials: false,
                #[cfg(feature = "draft-private-network-access")]
                allow_private_network_access: false,
                vary_header: true,
                block_on_origin_mismatch: true,
            };

            Cors {
                inner: Rc::new(inner),
                error: None,
            }
        }
    }

    impl<S, B> Transform<S, ServiceRequest> for Cors
    where
        S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
        S::Future: 'static,

        B: MessageBody + 'static,
    {
        type Response = ServiceResponse<EitherBody<B>>;
        type Error = Error;
        type InitError = ();
        type Transform = CorsMiddleware<S>;
        type Future = Ready<Result<Self::Transform, Self::InitError>>;

        fn new_transform(&self, service: S) -> Self::Future {
            if let Some(ref err) = self.error {
                match err {
                    Either::Left(err) => error!("{}", err),
                    Either::Right(err) => error!("{}", err),
                }

                return future::err(());
            }

            let mut inner = Rc::clone(&self.inner);

            if inner.supports_credentials && inner.send_wildcard && inner.allowed_origins.is_all() {
                error!(
                    "Illegal combination of CORS options: credentials can not be supported when all \
                        origins are allowed and `send_wildcard` is enabled."
                );
                return future::err(());
            }

            // bake allowed headers value if Some and not empty
            match inner.allowed_headers.as_ref() {
                Some(header_set) if !header_set.is_empty() => {
                    let allowed_headers_str = intersperse_header_values(header_set);
                    Rc::make_mut(&mut inner).allowed_headers_baked = Some(allowed_headers_str);
                }
                _ => {}
            }

            // bake allowed methods value if not empty
            if !inner.allowed_methods.is_empty() {
                let allowed_methods_str = intersperse_header_values(&inner.allowed_methods);
                Rc::make_mut(&mut inner).allowed_methods_baked = Some(allowed_methods_str);
            }

            // bake exposed headers value if Some and not empty
            match inner.expose_headers.as_ref() {
                Some(header_set) if !header_set.is_empty() => {
                    let expose_headers_str = intersperse_header_values(header_set);
                    Rc::make_mut(&mut inner).expose_headers_baked = Some(expose_headers_str);
                }
                _ => {}
            }

            future::ok(CorsMiddleware { service, inner })
        }
    }

    /// Only call when values are guaranteed to be valid header values and set is not empty.
    pub(crate) fn intersperse_header_values<T>(val_set: &HashSet<T>) -> HeaderValue
    where
        T: AsRef<str>,
    {
        debug_assert!(
            !val_set.is_empty(),
            "only call `intersperse_header_values` when set is not empty"
        );

        val_set
            .iter()
            .fold(String::with_capacity(64), |mut acc, val| {
                acc.push_str(", ");
                acc.push_str(val.as_ref());
                acc
            })
            // set is not empty so string will always have leading ", " to trim
            [2..]
            .try_into()
            // all method names are valid header values
            .unwrap()
    }

    #[cfg(test)]
    mod test {
        use std::convert::{Infallible, TryInto};

        use actix_web::{
            body,
            dev::{fn_service, Transform},
            http::{header::HeaderName, StatusCode},
            test::{self, TestRequest},
            HttpResponse,
        };

        use super::*;

        #[test]
        fn illegal_allow_credentials() {
            // using the permissive defaults (all origins allowed) and adding send_wildcard
            // and supports_credentials should error on construction

            assert!(Cors::permissive()
                .supports_credentials()
                .send_wildcard()
                .new_transform(test::ok_service())
                .into_inner()
                .is_err());
        }

        #[actix_web::test]
        async fn restrictive_defaults() {
            let cors = Cors::default()
                .new_transform(test::ok_service())
                .await
                .unwrap();

            let req = TestRequest::default()
                .insert_header(("Origin", "https://www.example.com"))
                .to_srv_request();

            let resp = test::call_service(&cors, req).await;
            assert_eq!(resp.status(), StatusCode::BAD_REQUEST);
        }

        #[actix_web::test]
        async fn allowed_header_try_from() {
            let _cors = Cors::default().allowed_header("Content-Type");
        }

        #[actix_web::test]
        async fn allowed_header_try_into() {
            struct ContentType;

            impl TryInto<HeaderName> for ContentType {
                type Error = Infallible;

                fn try_into(self) -> Result<HeaderName, Self::Error> {
                    Ok(HeaderName::from_static("content-type"))
                }
            }

            let _cors = Cors::default().allowed_header(ContentType);
        }

        #[actix_web::test]
        async fn middleware_generic_over_body_type() {
            let srv = fn_service(|req: ServiceRequest| async move {
                Ok(req.into_response(HttpResponse::with_body(StatusCode::OK, body::None::new())))
            });

            Cors::default().new_transform(srv).await.unwrap();
        }
    }