use futures::future::BoxFuture;

use http::{
    header::{HeaderValue, IntoHeaderName},
    HeaderMap, HttpTryFrom,
};

use crate::{
    middleware::{Middleware, Next},
    Context, Response,
};

/// Middleware for providing a set of default headers for all responses.
#[derive(Clone, Default)]
pub struct DefaultHeaders {
    headers: HeaderMap,
}

impl DefaultHeaders {
    /// Construct a new instance with an empty list of headers.
    pub fn new() -> DefaultHeaders {
        DefaultHeaders::default()
    }

    #[inline]
    /// Add a header to the default header list.
    pub fn header<K, V>(mut self, key: K, value: V) -> Self
    where
        K: IntoHeaderName,
        HeaderValue: HttpTryFrom<V>,
    {
        let value = HeaderValue::try_from(value)
            .map_err(Into::into)
            .expect("Cannot create default header");

        self.headers.append(key, value);

        self
    }
}

impl<Data: Send + Sync + 'static> Middleware<Data> for DefaultHeaders {
    fn handle<'a>(&'a self, cx: Context<Data>, next: Next<'a, Data>) -> BoxFuture<'a, Response> {
        box_async! {
            let mut res = await!(next.run(cx));

            let headers = res.headers_mut();
            for (key, value) in self.headers.iter() {
                headers.entry(key).unwrap().or_insert_with(|| value.clone());
            }
            res
        }
    }
}