//! HTTP extensions.

use bytes::Bytes;
use http::header::HeaderName;
#[cfg(feature = "http1")]
use http::header::{IntoHeaderName, ValueIter};
use http::HeaderMap;
#[cfg(feature = "ffi")]
use std::collections::HashMap;
#[cfg(feature = "http2")]
use std::fmt;

#[cfg(feature = "http2")]
/// Represents the `:protocol` pseudo-header used by
/// the [Extended CONNECT Protocol].
///
/// [Extended CONNECT Protocol]: https://datatracker.ietf.org/doc/html/rfc8441#section-4
#[derive(Clone, Eq, PartialEq)]
pub struct Protocol {
    inner: h2::ext::Protocol,
}

#[cfg(feature = "http2")]
impl Protocol {
    /// Converts a static string to a protocol name.
    pub const fn from_static(value: &'static str) -> Self {
        Self {
            inner: h2::ext::Protocol::from_static(value),
        }
    }

    /// Returns a str representation of the header.
    pub fn as_str(&self) -> &str {
        self.inner.as_str()
    }

    pub(crate) fn from_inner(inner: h2::ext::Protocol) -> Self {
        Self { inner }
    }

    pub(crate) fn into_inner(self) -> h2::ext::Protocol {
        self.inner
    }
}

#[cfg(feature = "http2")]
impl<'a> From<&'a str> for Protocol {
    fn from(value: &'a str) -> Self {
        Self {
            inner: h2::ext::Protocol::from(value),
        }
    }
}

#[cfg(feature = "http2")]
impl AsRef<[u8]> for Protocol {
    fn as_ref(&self) -> &[u8] {
        self.inner.as_ref()
    }
}

#[cfg(feature = "http2")]
impl fmt::Debug for Protocol {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.inner.fmt(f)
    }
}

/// A map from header names to their original casing as received in an HTTP message.
///
/// If an HTTP/1 response `res` is parsed on a connection whose option
/// [`http1_preserve_header_case`] was set to true and the response included
/// the following headers:
///
/// ```ignore
/// x-Bread: Baguette
/// X-BREAD: Pain
/// x-bread: Ficelle
/// ```
///
/// Then `res.extensions().get::<HeaderCaseMap>()` will return a map with:
///
/// ```ignore
/// HeaderCaseMap({
///     "x-bread": ["x-Bread", "X-BREAD", "x-bread"],
/// })
/// ```
///
/// [`http1_preserve_header_case`]: /client/struct.Client.html#method.http1_preserve_header_case
#[derive(Clone, Debug)]
pub(crate) struct HeaderCaseMap(HeaderMap<Bytes>);

#[cfg(feature = "http1")]
impl HeaderCaseMap {
    /// Returns a view of all spellings associated with that header name,
    /// in the order they were found.
    pub(crate) fn get_all<'a>(
        &'a self,
        name: &HeaderName,
    ) -> impl Iterator<Item = impl AsRef<[u8]> + 'a> + 'a {
        self.get_all_internal(name).into_iter()
    }

    /// Returns a view of all spellings associated with that header name,
    /// in the order they were found.
    pub(crate) fn get_all_internal<'a>(&'a self, name: &HeaderName) -> ValueIter<'_, Bytes> {
        self.0.get_all(name).into_iter()
    }

    pub(crate) fn default() -> Self {
        Self(Default::default())
    }

    #[cfg(any(test, feature = "ffi"))]
    pub(crate) fn insert(&mut self, name: HeaderName, orig: Bytes) {
        self.0.insert(name, orig);
    }

    pub(crate) fn append<N>(&mut self, name: N, orig: Bytes)
    where
        N: IntoHeaderName,
    {
        self.0.append(name, orig);
    }
}

#[cfg(feature = "ffi")]
#[derive(Clone, Debug)]
/// Hashmap<Headername, numheaders with that name>
pub(crate) struct OriginalHeaderOrder {
    /// Stores how many entries a Headername maps to. This is used
    /// for accounting.
    num_entries: HashMap<HeaderName, usize>,
    /// Stores the ordering of the headers. ex: `vec[i] = (headerName, idx)`,
    /// The vector is ordered such that the ith element
    /// represents the ith header that came in off the line.
    /// The `HeaderName` and `idx` are then used elsewhere to index into
    /// the multi map that stores the header values.
    entry_order: Vec<(HeaderName, usize)>,
}

#[cfg(all(feature = "http1", feature = "ffi"))]
impl OriginalHeaderOrder {
    pub(crate) fn default() -> Self {
        OriginalHeaderOrder {
            num_entries: HashMap::new(),
            entry_order: Vec::new(),
        }
    }

    pub(crate) fn insert(&mut self, name: HeaderName) {
        if !self.num_entries.contains_key(&name) {
            let idx = 0;
            self.num_entries.insert(name.clone(), 1);
            self.entry_order.push((name, idx));
        }
        // Replacing an already existing element does not
        // change ordering, so we only care if its the first
        // header name encountered
    }

    pub(crate) fn append<N>(&mut self, name: N)
    where
        N: IntoHeaderName + Into<HeaderName> + Clone,
    {
        let name: HeaderName = name.into();
        let idx;
        if self.num_entries.contains_key(&name) {
            idx = self.num_entries[&name];
            *self.num_entries.get_mut(&name).unwrap() += 1;
        } else {
            idx = 0;
            self.num_entries.insert(name.clone(), 1);
        }
        self.entry_order.push((name, idx));
    }

    // No doc test is run here because `RUSTFLAGS='--cfg hyper_unstable_ffi'`
    // is needed to compile. Once ffi is stablized `no_run` should be removed
    // here.
    /// This returns an iterator that provides header names and indexes
    /// in the original order received.
    ///
    /// # Examples
    /// ```no_run
    /// use hyper::ext::OriginalHeaderOrder;
    /// use hyper::header::{HeaderName, HeaderValue, HeaderMap};
    ///
    /// let mut h_order = OriginalHeaderOrder::default();
    /// let mut h_map = Headermap::new();
    ///
    /// let name1 = b"Set-CookiE";
    /// let value1 = b"a=b";
    /// h_map.append(name1);
    /// h_order.append(name1);
    ///
    /// let name2 = b"Content-Encoding";
    /// let value2 = b"gzip";
    /// h_map.append(name2, value2);
    /// h_order.append(name2);
    ///
    /// let name3 = b"SET-COOKIE";
    /// let value3 = b"c=d";
    /// h_map.append(name3, value3);
    /// h_order.append(name3)
    ///
    /// let mut iter = h_order.get_in_order()
    ///
    /// let (name, idx) = iter.next();
    /// assert_eq!(b"a=b", h_map.get_all(name).nth(idx).unwrap());
    ///
    /// let (name, idx) = iter.next();
    /// assert_eq!(b"gzip", h_map.get_all(name).nth(idx).unwrap());
    ///
    /// let (name, idx) = iter.next();
    /// assert_eq!(b"c=d", h_map.get_all(name).nth(idx).unwrap());
    /// ```
    pub(crate) fn get_in_order(&self) -> impl Iterator<Item = &(HeaderName, usize)> {
        self.entry_order.iter()
    }
}