use crate::{extract::rejection::*, response::IntoResponseParts};

use axum_core::extract::OptionalFromRequestParts;

use axum_core::{

    extract::FromRequestParts,

    response::{IntoResponse, Response, ResponseParts},

};

use http::{request::Parts, Extensions, Request};

use std::{

    convert::Infallible,

    task::{Context, Poll},

};

use tower_service::Service;

/// Extractor and response for extensions.

///

/// # As extractor

///

/// This is commonly used to share state across handlers.

///

/// ```rust,no_run

/// use axum::{

///     Router,

///     Extension,

///     routing::get,

/// };

/// use std::sync::Arc;

///

/// // Some shared state used throughout our application

/// struct State {

///     // ...

/// }

///

/// async fn handler(state: Extension<Arc<State>>) {

///     // ...

/// }

///

/// let state = Arc::new(State { /* ... */ });

///

/// let app = Router::new().route("/", get(handler))

///     // Add middleware that inserts the state into all incoming request's

///     // extensions.

///     .layer(Extension(state));

/// # let _: Router = app;

/// ```

///

/// If the extension is missing it will reject the request with a `500 Internal

/// Server Error` response. Alternatively, you can use `Option<Extension<T>>` to

/// make the extension extractor optional.

///

/// # As response

///

/// Response extensions can be used to share state with middleware.

///

/// ```rust

/// use axum::{

///     Extension,

///     response::IntoResponse,

/// };

///

/// async fn handler() -> (Extension<Foo>, &'static str) {

///     (

///         Extension(Foo("foo")),

///         "Hello, World!"

///     )

/// }

///

/// #[derive(Clone)]

/// struct Foo(&'static str);

/// ```

#[derive(Debug, Clone, Copy, Default)]

#[must_use]

pub struct Extension<T>(pub T);

impl<T> Extension<T>

where

    T: Clone + Send + Sync + 'static,

{

    fn from_extensions(extensions: &Extensions) -> Option<Self> {

        extensions.get::<T>().cloned().map(Extension)

    }

}

impl<T, S> FromRequestParts<S> for Extension<T>

where

    T: Clone + Send + Sync + 'static,

    S: Send + Sync,

{

    type Rejection = ExtensionRejection;

    async fn from_request_parts(req: &mut Parts, _state: &S) -> Result<Self, Self::Rejection> {

        Ok(Self::from_extensions(&req.extensions).ok_or_else(|| {

            MissingExtension::from_err(format!(

                "Extension of type `{}` was not found. Perhaps you forgot to add it? See `axum::Extension`.",

                std::any::type_name::<T>()

            ))

        })?)

    }

}

impl<T, S> OptionalFromRequestParts<S> for Extension<T>

where

    T: Clone + Send + Sync + 'static,

    S: Send + Sync,

{

    type Rejection = Infallible;

    async fn from_request_parts(

        req: &mut Parts,

        _state: &S,

    ) -> Result<Option<Self>, Self::Rejection> {

        Ok(Self::from_extensions(&req.extensions))

    }

}

axum_core::__impl_deref!(Extension);

impl<T> IntoResponseParts for Extension<T>

where

    T: Clone + Send + Sync + 'static,

{

    type Error = Infallible;

    fn into_response_parts(self, mut res: ResponseParts) -> Result<ResponseParts, Self::Error> {

        res.extensions_mut().insert(self.0);

        Ok(res)

    }

}

impl<T> IntoResponse for Extension<T>

where

    T: Clone + Send + Sync + 'static,

{

    fn into_response(self) -> Response {

        let mut res = ().into_response();

        res.extensions_mut().insert(self.0);

        res

    }

}

impl<S, T> tower_layer::Layer<S> for Extension<T>

where

    T: Clone + Send + Sync + 'static,

{

    type Service = AddExtension<S, T>;

    fn layer(&self, inner: S) -> Self::Service {

        AddExtension {

            inner,

            value: self.0.clone(),

        }

    }

}

/// Middleware for adding some shareable value to [request extensions].

///

/// See [Passing state from middleware to handlers](index.html#passing-state-from-middleware-to-handlers)

/// for more details.

///

/// [request extensions]: https://docs.rs/http/latest/http/struct.Extensions.html

///

/// If you need a layer to add an extension to every request,

/// use the [Layer](tower::Layer) implementation of [Extension].

#[derive(Clone, Copy, Debug)]

pub struct AddExtension<S, T> {

    pub(crate) inner: S,

    pub(crate) value: T,

}

impl<ResBody, S, T> Service<Request<ResBody>> for AddExtension<S, T>

where

    S: Service<Request<ResBody>>,

    T: Clone + Send + Sync + 'static,

{

    type Response = S::Response;

    type Error = S::Error;

    type Future = S::Future;

    #[inline]

    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {

        self.inner.poll_ready(cx)

    }

    fn call(&mut self, mut req: Request<ResBody>) -> Self::Future {

        req.extensions_mut().insert(self.value.clone());

        self.inner.call(req)

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    use crate::routing::get;

    use crate::test_helpers::TestClient;

    use crate::Router;

    use http::StatusCode;

    #[derive(Clone)]

    struct Foo(String);

    #[derive(Clone)]

    struct Bar(String);

    #[crate::test]

    async fn extension_extractor() {

        async fn requires_foo(Extension(foo): Extension<Foo>) -> String {

            foo.0

        }

        async fn optional_foo(extension: Option<Extension<Foo>>) -> String {

            extension.map(|foo| foo.0 .0).unwrap_or("none".to_owned())

        }

        async fn requires_bar(Extension(bar): Extension<Bar>) -> String {

            bar.0

        }

        async fn optional_bar(extension: Option<Extension<Bar>>) -> String {

            extension.map(|bar| bar.0 .0).unwrap_or("none".to_owned())

        }

        let app = Router::new()

            .route("/requires_foo", get(requires_foo))

            .route("/optional_foo", get(optional_foo))

            .route("/requires_bar", get(requires_bar))

            .route("/optional_bar", get(optional_bar))

            .layer(Extension(Foo("foo".to_owned())));

        let client = TestClient::new(app);

        let response = client.get("/requires_foo").await;

        assert_eq!(response.status(), StatusCode::OK);

        assert_eq!(response.text().await, "foo");

        let response = client.get("/optional_foo").await;

        assert_eq!(response.status(), StatusCode::OK);

        assert_eq!(response.text().await, "foo");

        let response = client.get("/requires_bar").await;

        assert_eq!(response.status(), StatusCode::INTERNAL_SERVER_ERROR);

        assert_eq!(response.text().await, "Missing request extension: Extension of type `axum::extension::tests::Bar` was not found. Perhaps you forgot to add it? See `axum::Extension`.");

        let response = client.get("/optional_bar").await;

        assert_eq!(response.status(), StatusCode::OK);

        assert_eq!(response.text().await, "none");

    }

}