hyper::header!

macro_rules! header {
    // $a:meta: Attributes associated with the header item (usually docs)
    // $id:ident: Identifier of the header
    // $n:expr: Lowercase name of the header
    // $nn:expr: Nice name of the header

    // List header, zero or more items
    ($(#[$a:meta])*($id:ident, $n:expr) => ($item:ty)*) => {
        $(#[$a])*
        #[derive(Clone, Debug, PartialEq)]
        pub struct $id(pub Vec<$item>);
        __hyper__deref!($id => Vec<$item>);
        impl $crate::header::Header for $id {
            fn header_name() -> &'static str {
                $n
            }
            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
                $crate::header::parsing::from_comma_delimited(raw).map($id)
            }
        }
        impl $crate::header::HeaderFormat for $id {
            fn fmt_header(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                $crate::header::parsing::fmt_comma_delimited(f, &self.0[..])
            }
        }
        impl ::std::fmt::Display for $id {
            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                use $crate::header::HeaderFormat;
                self.fmt_header(f)
            }
        }
    };
    // List header, one or more items
    ($(#[$a:meta])*($id:ident, $n:expr) => ($item:ty)+) => {
        $(#[$a])*
        #[derive(Clone, Debug, PartialEq)]
        pub struct $id(pub Vec<$item>);
        __hyper__deref!($id => Vec<$item>);
        impl $crate::header::Header for $id {
            fn header_name() -> &'static str {
                $n
            }
            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
                $crate::header::parsing::from_comma_delimited(raw).map($id)
            }
        }
        impl $crate::header::HeaderFormat for $id {
            fn fmt_header(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                $crate::header::parsing::fmt_comma_delimited(f, &self.0[..])
            }
        }
        impl ::std::fmt::Display for $id {
            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                use $crate::header::HeaderFormat;
                self.fmt_header(f)
            }
        }
    };
    // Single value header
    ($(#[$a:meta])*($id:ident, $n:expr) => [$value:ty]) => {
        $(#[$a])*
        #[derive(Clone, Debug, PartialEq)]
        pub struct $id(pub $value);
        __hyper__deref!($id => $value);
        impl $crate::header::Header for $id {
            fn header_name() -> &'static str {
                $n
            }
            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
                $crate::header::parsing::from_one_raw_str(raw).map($id)
            }
        }
        impl $crate::header::HeaderFormat for $id {
            fn fmt_header(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                ::std::fmt::Display::fmt(&**self, f)
            }
        }
        impl ::std::fmt::Display for $id {
            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                ::std::fmt::Display::fmt(&**self, f)
            }
        }
    };
    // List header, one or more items with "*" option
    ($(#[$a:meta])*($id:ident, $n:expr) => {Any / ($item:ty)+}) => {
        $(#[$a])*
        #[derive(Clone, Debug, PartialEq)]
        pub enum $id {
            /// Any value is a match
            Any,
            /// Only the listed items are a match
            Items(Vec<$item>),
        }
        impl $crate::header::Header for $id {
            fn header_name() -> &'static str {
                $n
            }
            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
                // FIXME: Return None if no item is in $id::Only
                if raw.len() == 1 {
                    if raw[0] == b"*" {
                        return Some($id::Any)
                    }
                }
                $crate::header::parsing::from_comma_delimited(raw).map(|vec| $id::Items(vec))
            }
        }
        impl $crate::header::HeaderFormat for $id {
            fn fmt_header(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                match *self {
                    $id::Any => f.write_str("*"),
                    $id::Items(ref fields) => $crate::header::parsing::fmt_comma_delimited(
                        f, &fields[..])
                }
            }
        }
        impl ::std::fmt::Display for $id {
            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                use $crate::header::HeaderFormat;
                self.fmt_header(f)
            }
        }
    };

    // optional test module
    ($(#[$a:meta])*($id:ident, $n:expr) => ($item:ty)* $tm:ident{$($tf:item)*}) => {
        header! {
            $(#[$a])*
            ($id, $n) => ($item)*
        }

        __hyper__tm! { $id, $tm { $($tf)* }}
    };
    ($(#[$a:meta])*($id:ident, $n:expr) => ($item:ty)+ $tm:ident{$($tf:item)*}) => {
        header! {
            $(#[$a])*
            ($id, $n) => ($item)+
        }

        __hyper__tm! { $id, $tm { $($tf)* }}
    };
    ($(#[$a:meta])*($id:ident, $n:expr) => [$item:ty] $tm:ident{$($tf:item)*}) => {
        header! {
            $(#[$a])*
            ($id, $n) => [$item]
        }

        __hyper__tm! { $id, $tm { $($tf)* }}
    };
    ($(#[$a:meta])*($id:ident, $n:expr) => {Any / ($item:ty)+} $tm:ident{$($tf:item)*}) => {
        header! {
            $(#[$a])*
            ($id, $n) => {Any / ($item)+}
        }

        __hyper__tm! { $id, $tm { $($tf)* }}
    };
}