feat(headers): add AcceptLanguage header

Adds header support for Accept-Language, using a struct for the primary
and sub components of the language.

src/header/common/accept_language.rs

@@ -0,0 +1,86 @@
+use header::{self, QualityItem};
+use std::str::FromStr;
+use std::fmt;
+
+/// A language tag.
+/// See http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.10
+#[derive(Clone, PartialEq, Debug)]
+pub struct Language{
+    primary: String,
+    sub: Option<String>
+}
+
+impl FromStr for Language {
+    type Err = ();
+    fn from_str(s: &str) -> Result<Language, ()> {
+        let mut i = s.split_str("-");
+        let p = i.next();
+        let s = i.next();
+        match (p, s) {
+            (Some(p),Some(s)) => Ok(Language{primary: p.to_string(),
+                                             sub: Some(s.to_string())}),
+            (Some(p),_) => Ok(Language{primary: p.to_string(), sub: None}),
+            _ => Err(())
+        }
+    }
+}
+
+impl fmt::Display for Language {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        try!(write!(f, "{}", self.primary));
+        match self.sub {
+            Some(ref s) => write!(f, "-{}", s),
+            None => Ok(())
+        }
+    }
+}
+
+/// The `Accept-Language` header
+///
+/// The `Accept-Language` header can be used by clients to indicate what
+/// response languages they accept.
+#[derive(Clone, PartialEq, Debug)]
+pub struct AcceptLanguage(pub Vec<QualityItem<Language>>);
+
+impl_list_header!(AcceptLanguage,
+                  "Accept-Language",
+                  Vec<QualityItem<Language>>);
+
+bench_header!(bench, AcceptLanguage,
+              { vec![b"en-us;q=1.0, en;q=0.5, fr".to_vec()] });
+
+#[test]
+fn test_parse_header() {
+    let a: AcceptLanguage = header::Header::parse_header(
+        [b"en-us;q=1.0, en;q=0.5, fr".to_vec()].as_slice()).unwrap();
+    let b = AcceptLanguage(vec![
+        QualityItem { item: Language{primary: "en".to_string(),
+                                   sub: Some("us".to_string())},
+                      quality: 1f32 },
+        QualityItem { item: Language{primary: "en".to_string(), sub: None},
+                      quality: 0.5f32 },
+        QualityItem { item: Language{primary: "fr".to_string(), sub: None},
+                      quality: 1f32 },
+    ]);
+    assert_eq!(format!("{}", a), format!("{}", b));
+    assert_eq!(a, b);
+}
+
+#[test]
+fn test_display() {
+    assert_eq!("en".to_string(),
+               format!("{}", Language{primary: "en".to_string(),
+                                      sub: None}));
+    assert_eq!("en-us".to_string(),
+               format!("{}", Language{primary: "en".to_string(),
+                                      sub: Some("us".to_string())}));
+}
+
+#[test]
+fn test_from_str() {
+    assert_eq!(Language { primary: "en".to_string(), sub: None },
+               "en".parse().unwrap());
+    assert_eq!(Language { primary: "en".to_string(),
+                          sub: Some("us".to_string()) },
+               "en-us".parse().unwrap());
+}

src/header/common/mod.rs

@@ -9,6 +9,7 @@
 pub use self::access_control::*;
 pub use self::accept::Accept;
 pub use self::accept_encoding::AcceptEncoding;
+pub use self::accept_language::AcceptLanguage;
 pub use self::allow::Allow;
 pub use self::authorization::{Authorization, Scheme, Basic};
 pub use self::cache_control::{CacheControl, CacheDirective};
@@ -147,6 +148,7 @@ macro_rules! impl_header(
 mod access_control;
 mod accept;
 mod accept_encoding;
+mod accept_language;
 mod allow;
 mod authorization;
 mod cache_control;