//! Middleware types.


use std::sync::Arc;

use crate::endpoint::DynEndpoint;
use crate::{Request, Response};
use async_trait::async_trait;
use std::future::Future;
use std::pin::Pin;

/// Middleware that wraps around the remaining middleware chain.

#[async_trait]
pub trait Middleware<State>: Send + Sync + 'static {
    /// Asynchronously handle the request, and return a response.

    async fn handle(&self, request: Request<State>, next: Next<'_, State>) -> crate::Result;

    /// Set the middleware's name. By default it uses the type signature.

    fn name(&self) -> &str {
        std::any::type_name::<Self>()
    }
}

#[async_trait]
impl<State, F> Middleware<State> for F
where
    State: Clone + Send + Sync + 'static,
    F: Send
        + Sync
        + 'static
        + for<'a> Fn(
            Request<State>,
            Next<'a, State>,
        ) -> Pin<Box<dyn Future<Output = crate::Result> + 'a + Send>>,
{
    async fn handle(&self, req: Request<State>, next: Next<'_, State>) -> crate::Result {
        (self)(req, next).await
    }
}

/// The remainder of a middleware chain, including the endpoint.

#[allow(missing_debug_implementations)]
pub struct Next<'a, State> {
    pub(crate) endpoint: &'a DynEndpoint<State>,
    pub(crate) next_middleware: &'a [Arc<dyn Middleware<State>>],
}

impl<State: Clone + Send + Sync + 'static> Next<'_, State> {
    /// Asynchronously execute the remaining middleware chain.

    pub async fn run(mut self, req: Request<State>) -> Response {
        if let Some((current, next)) = self.next_middleware.split_first() {
            self.next_middleware = next;
            match current.handle(req, self).await {
                Ok(request) => request,
                Err(err) => err.into(),
            }
        } else {
            match self.endpoint.call(req).await {
                Ok(request) => request,
                Err(err) => err.into(),
            }
        }
    }
}