Add cache::Expires header

Author: yoshuawuyts

src/cache/expires.rs

@@ -0,0 +1,130 @@
+use crate::headers::{HeaderName, HeaderValue, Headers, ToHeaderValues, EXPIRES};
+use crate::utils::{fmt_http_date, parse_http_date};
+
+use std::fmt::Debug;
+use std::option;
+use std::time::{Duration, SystemTime};
+
+/// HTTP `Expires` header
+///
+/// # Specifications
+///
+/// - [RFC 7234  Hypertext Transfer Protocol (HTTP/1.1): Caching](https://tools.ietf.org/html/rfc7234#section-5.3)
+///
+/// # Examples
+///
+/// ```
+/// # fn main() -> http_types::Result<()> {
+/// #
+/// use http_types::Response;
+/// use http_types::cache::Expires;
+/// use std::time::{SystemTime, Duration};
+///
+/// let time = SystemTime::now() + Duration::from_secs(5 * 60);
+/// let expires = Expires::new_at(time);
+///
+/// let mut res = Response::new(200);
+/// expires.apply(&mut res);
+///
+/// let expires = Expires::from_headers(res)?.unwrap();
+///
+/// // HTTP dates only have second-precision.
+/// let elapsed = time.duration_since(expires.at())?;
+/// assert_eq!(elapsed.as_secs(), 0);
+/// #
+/// # Ok(()) }
+/// ```
+#[derive(Debug, Ord, PartialOrd, Eq, PartialEq)]
+pub struct Expires {
+    instant: SystemTime,
+}
+
+impl Expires {
+    /// Create a new instance of `Expires`.
+    pub fn new(dur: Duration) -> Self {
+        let instant = SystemTime::now() + dur;
+        Self { instant }
+    }
+
+    /// Create a new instance of `Expires` from secs.
+    pub fn new_at(instant: SystemTime) -> Self {
+        Self { instant }
+    }
+
+    /// Get the expiration time.
+    pub fn at(&self) -> SystemTime {
+        self.instant
+    }
+
+    /// Create an instance of `Expires` from a `Headers` instance.
+    pub fn from_headers(headers: impl AsRef<Headers>) -> crate::Result<Option<Self>> {
+        let headers = match headers.as_ref().get(EXPIRES) {
+            Some(headers) => headers,
+            None => return Ok(None),
+        };
+
+        // If we successfully parsed the header then there's always at least one
+        // entry. We want the last entry.
+        let header = headers.iter().last().unwrap();
+
+        let instant = parse_http_date(header.as_str())?;
+        Ok(Some(Self { instant }))
+    }
+
+    /// Insert a `HeaderName` + `HeaderValue` pair into a `Headers` instance.
+    pub fn apply(&self, mut headers: impl AsMut<Headers>) {
+        headers.as_mut().insert(EXPIRES, self.value());
+    }
+
+    /// Get the `HeaderName`.
+    pub fn name(&self) -> HeaderName {
+        EXPIRES
+    }
+
+    /// Get the `HeaderValue`.
+    pub fn value(&self) -> HeaderValue {
+        let output = fmt_http_date(self.instant);
+
+        // SAFETY: the internal string is validated to be ASCII.
+        unsafe { HeaderValue::from_bytes_unchecked(output.into()) }
+    }
+}
+
+impl ToHeaderValues for Expires {
+    type Iter = option::IntoIter<HeaderValue>;
+    fn to_header_values(&self) -> crate::Result<Self::Iter> {
+        // A HeaderValue will always convert into itself.
+        Ok(self.value().to_header_values().unwrap())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::headers::Headers;
+
+    #[test]
+    fn smoke() -> crate::Result<()> {
+        let time = SystemTime::now() + Duration::from_secs(5 * 60);
+        let expires = Expires::new_at(time);
+
+        let mut headers = Headers::new();
+        expires.apply(&mut headers);
+
+        let expires = Expires::from_headers(headers)?.unwrap();
+
+        // HTTP dates only have second-precision
+        let elapsed = time.duration_since(expires.at())?;
+        assert_eq!(elapsed.as_secs(), 0);
+        Ok(())
+    }
+
+    #[test]
+    fn bad_request_on_parse_error() -> crate::Result<()> {
+        let mut headers = Headers::new();
+        headers.insert(EXPIRES, "<nori ate the tag. yum.>");
+        let err = Expires::from_headers(headers).unwrap_err();
+        assert_eq!(err.status(), 400);
+        Ok(())
+    }
+}

src/cache/mod.rs

@@ -10,7 +10,9 @@
 
 mod age;
 mod cache_control;
+mod expires;
 
 pub use age::Age;
 pub use cache_control::CacheControl;
 pub use cache_control::CacheDirective;
+pub use expires::Expires;

src/utils/date.rs

@@ -2,6 +2,7 @@ use std::fmt::{self, Display, Formatter};
 use std::str::{from_utf8, FromStr};
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
+use crate::StatusCode;
 use crate::{bail, ensure, format_err};
 
 const IMF_FIXDATE_LENGTH: usize = 29;
@@ -39,7 +40,10 @@ pub(crate) struct HttpDate {
 /// ascdate formats. Two digit years are mapped to dates between
 /// 1970 and 2069.
 pub(crate) fn parse_http_date(s: &str) -> crate::Result<SystemTime> {
-    s.parse::<HttpDate>().map(|d| d.into())
+    s.parse::<HttpDate>().map(|d| d.into()).map_err(|mut e| {
+        e.set_status(StatusCode::BadRequest);
+        e
+    })
 }
 
 /// Format a date to be used in a HTTP header field.

src/utils/mod.rs

@@ -1,6 +1,7 @@
 mod date;
 
-pub(crate) use date::{fmt_http_date, parse_http_date};
+pub(crate) use date::fmt_http_date;
+pub(crate) use date::parse_http_date;
 
 /// Declares unstable items.
 #[doc(hidden)]