use http::HeaderValue;

/// `Upgrade` header, defined in [RFC7230](https://datatracker.ietf.org/doc/html/rfc7230#section-6.7)

///

/// The `Upgrade` header field is intended to provide a simple mechanism

/// for transitioning from HTTP/1.1 to some other protocol on the same

/// connection.  A client MAY send a list of protocols in the Upgrade

/// header field of a request to invite the server to switch to one or

/// more of those protocols, in order of descending preference, before

/// sending the final response.  A server MAY ignore a received Upgrade

/// header field if it wishes to continue using the current protocol on

/// that connection.  Upgrade cannot be used to insist on a protocol

/// change.

///

/// ## ABNF

///

/// ```text

/// Upgrade          = 1#protocol

///

/// protocol         = protocol-name ["/" protocol-version]

/// protocol-name    = token

/// protocol-version = token

/// ```

///

/// ## Example values

///

/// * `HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11`

///

/// # Note

///

/// In practice, the `Upgrade` header is never that complicated. In most cases,

/// it is only ever a single value, such as `"websocket"`.

///

/// # Examples

///

/// ```

/// use headers::Upgrade;

///

/// let ws = Upgrade::websocket();

/// ```

#[derive(Clone, Debug, PartialEq)]

pub struct Upgrade(HeaderValue);

derive_header! {

    Upgrade(_),

    name: UPGRADE

}

impl Upgrade {

    /// Constructs an `Upgrade: websocket` header.

    pub fn websocket() -> Upgrade {

        Upgrade(HeaderValue::from_static("websocket"))

    }

}