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use std::sync::Arc;

use crate::{async_trait, Context, Endpoint, Middleware, Next, Result};

/// A set of method to chain middleware/endpoint to middleware
/// or make middleware shared.
pub trait MiddlewareExt<S>: Sized + for<'a> Middleware<'a, S> {
    /// Chain two middlewares.
    fn chain<M>(self, next: M) -> Chain<Self, M>
    where
        M: for<'a> Middleware<'a, S>,
    {
        Chain(self, next)
    }

    /// Chain an endpoint to a middleware.
    fn end<E>(self, next: E) -> Chain<Self, E>
    where
        E: for<'a> Endpoint<'a, S>,
    {
        Chain(self, next)
    }

    /// Make middleware shared.
    fn shared(self) -> Shared<S>
    where
        S: 'static,
    {
        Shared(Arc::new(self))
    }
}

/// Extra methods of endpoint.
pub trait EndpointExt<S>: Sized + for<'a> Endpoint<'a, S> {
    /// Box an endpoint.
    fn boxed(self) -> Boxed<S>
    where
        S: 'static,
    {
        Boxed(Box::new(self))
    }
}

impl<S, T> MiddlewareExt<S> for T where T: for<'a> Middleware<'a, S> {}
impl<S, T> EndpointExt<S> for T where T: for<'a> Endpoint<'a, S> {}

/// A middleware composing and executing other middlewares in a stack-like manner.
pub struct Chain<T, U>(T, U);

/// Shared middleware.
pub struct Shared<S>(Arc<dyn for<'a> Middleware<'a, S>>);

/// Boxed endpoint.
pub struct Boxed<S>(Box<dyn for<'a> Endpoint<'a, S>>);

#[async_trait(?Send)]
impl<'a, S, T, U> Middleware<'a, S> for Chain<T, U>
where
    U: Middleware<'a, S>,
    T: for<'b> Middleware<'b, S>,
{
    #[inline]
    async fn handle(&'a self, ctx: &'a mut Context<S>, next: Next<'a>) -> Result {
        let ptr = ctx as *mut Context<S>;
        let mut next = self.1.handle(unsafe { &mut *ptr }, next);
        self.0.handle(ctx, &mut next).await
    }
}

#[async_trait(?Send)]
impl<'a, S> Middleware<'a, S> for Shared<S>
where
    S: 'static,
{
    #[inline]
    async fn handle(&'a self, ctx: &'a mut Context<S>, next: Next<'a>) -> Result {
        self.0.handle(ctx, next).await
    }
}

impl<S> Clone for Shared<S> {
    #[inline]
    fn clone(&self) -> Self {
        Self(self.0.clone())
    }
}

#[async_trait(?Send)]
impl<'a, S> Endpoint<'a, S> for Boxed<S>
where
    S: 'static,
{
    #[inline]
    async fn call(&'a self, ctx: &'a mut Context<S>) -> Result {
        self.0.call(ctx).await
    }
}

#[async_trait(?Send)]
impl<'a, S, T, U> Endpoint<'a, S> for Chain<T, U>
where
    U: Endpoint<'a, S>,
    T: for<'b> Middleware<'b, S>,
{
    #[inline]
    async fn call(&'a self, ctx: &'a mut Context<S>) -> Result {
        let ptr = ctx as *mut Context<S>;
        let mut next = self.1.call(unsafe { &mut *ptr });
        self.0.handle(ctx, &mut next).await
    }
}

#[cfg(all(test, feature = "runtime"))]
mod tests {
    use std::sync::Arc;

    use futures::lock::Mutex;
    use http::StatusCode;

    use crate::{async_trait, App, Context, Middleware, Next, Request, Status};

    struct Pusher {
        data: usize,
        vector: Arc<Mutex<Vec<usize>>>,
    }

    impl Pusher {
        fn new(data: usize, vector: Arc<Mutex<Vec<usize>>>) -> Self {
            Self { data, vector }
        }
    }

    #[async_trait(?Send)]
    impl<'a> Middleware<'a, ()> for Pusher {
        async fn handle(&'a self, _ctx: &'a mut Context, next: Next<'a>) -> Result<(), Status> {
            self.vector.lock().await.push(self.data);
            next.await?;
            self.vector.lock().await.push(self.data);
            Ok(())
        }
    }

    #[async_std::test]
    async fn middleware_order() -> Result<(), Box<dyn std::error::Error>> {
        let vector = Arc::new(Mutex::new(Vec::new()));
        let service = App::new()
            .gate(Pusher::new(0, vector.clone()))
            .gate(Pusher::new(1, vector.clone()))
            .gate(Pusher::new(2, vector.clone()))
            .gate(Pusher::new(3, vector.clone()))
            .gate(Pusher::new(4, vector.clone()))
            .gate(Pusher::new(5, vector.clone()))
            .gate(Pusher::new(6, vector.clone()))
            .gate(Pusher::new(7, vector.clone()))
            .gate(Pusher::new(8, vector.clone()))
            .gate(Pusher::new(9, vector.clone()))
            .end(())
            .http_service();
        let resp = service.serve(Request::default()).await;
        assert_eq!(StatusCode::OK, resp.status);
        for i in 0..10 {
            assert_eq!(i, vector.lock().await[i]);
            assert_eq!(i, vector.lock().await[19 - i]);
        }
        Ok(())
    }
}