Add `other::Referer` header

src/other/mod.rs

@@ -2,8 +2,10 @@
 
 mod date;
 mod expect;
+mod referer;
 mod source_map;
 
 pub use date::Date;
 pub use expect::Expect;
+pub use referer::Referer;
 pub use source_map::SourceMap;

src/other/referer.rs

@@ -0,0 +1,162 @@
+use crate::headers::{HeaderName, HeaderValue, Headers, REFERER};
+use crate::{bail_status as bail, Status, Url};
+
+use std::convert::TryInto;
+
+/// Contains the address of the page making the request.
+///
+/// __Important__: Although this header has many innocent uses it can have
+/// undesirable consequences for user security and privacy.
+///
+/// [MDN Documentation](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referer)
+///
+/// # Specifications
+///
+/// - [RFC 7231, section 5.5.2: Referer](https://tools.ietf.org/html/rfc7231#section-5.5.2)
+///
+/// # Examples
+///
+/// ```
+/// # fn main() -> http_types::Result<()> {
+/// #
+/// use http_types::{Response, Url};
+/// use http_types::other::Referer;
+///
+/// let referer = Referer::new(Url::parse("https://example.net/")?);
+///
+/// let mut res = Response::new(200);
+/// referer.apply(&mut res);
+///
+/// let base_url = Url::parse("https://example.net/")?;
+/// let referer = Referer::from_headers(base_url, res)?.unwrap();
+/// assert_eq!(referer.location(), &Url::parse("https://example.net/")?);
+/// #
+/// # Ok(()) }
+/// ```
+#[derive(Debug)]
+pub struct Referer {
+    location: Url,
+}
+
+impl Referer {
+    /// Create a new instance of `Referer` header.
+    pub fn new(location: Url) -> Self {
+        Self { location }
+    }
+
+    /// Create a new instance from headers.
+    pub fn from_headers<U>(base_url: U, headers: impl AsRef<Headers>) -> crate::Result<Option<Self>>
+    where
+        U: TryInto<Url>,
+        U::Error: std::fmt::Debug,
+    {
+        let headers = match headers.as_ref().get(REFERER) {
+            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_value = headers.iter().last().unwrap();
+
+        let url = match Url::parse(header_value.as_str()) {
+            Ok(url) => url,
+            Err(_) => match base_url.try_into() {
+                Ok(base_url) => base_url.join(header_value.as_str().trim()).status(400)?,
+                Err(_) => bail!(400, "Invalid base url provided"),
+            },
+        };
+
+        Ok(Some(Self { location: url }))
+    }
+
+    /// Sets the header.
+    pub fn apply(&self, mut headers: impl AsMut<Headers>) {
+        headers.as_mut().insert(self.name(), self.value());
+    }
+
+    /// Get the `HeaderName`.
+    pub fn name(&self) -> HeaderName {
+        REFERER
+    }
+
+    /// Get the `HeaderValue`.
+    pub fn value(&self) -> HeaderValue {
+        let output = self.location.to_string();
+
+        // SAFETY: the internal string is validated to be ASCII.
+        unsafe { HeaderValue::from_bytes_unchecked(output.into()) }
+    }
+
+    /// Get the url.
+    pub fn location(&self) -> &Url {
+        &self.location
+    }
+
+    /// Set the url.
+    pub fn set_location<U>(&mut self, location: U)
+    where
+        U: TryInto<Url>,
+        U::Error: std::fmt::Debug,
+    {
+        self.location = location
+            .try_into()
+            .expect("Could not convert into valid URL")
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::headers::Headers;
+
+    #[test]
+    fn smoke() -> crate::Result<()> {
+        let referer = Referer::new(Url::parse("https://example.net/test.json")?);
+
+        let mut headers = Headers::new();
+        referer.apply(&mut headers);
+
+        let base_url = Url::parse("https://example.net/")?;
+        let referer = Referer::from_headers(base_url, headers)?.unwrap();
+        assert_eq!(
+            referer.location(),
+            &Url::parse("https://example.net/test.json")?
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn bad_request_on_parse_error() -> crate::Result<()> {
+        let mut headers = Headers::new();
+        headers.insert(REFERER, "htt://<nori ate the tag. yum.>");
+        let err =
+            Referer::from_headers(Url::parse("https://example.net").unwrap(), headers).unwrap_err();
+        assert_eq!(err.status(), 400);
+        Ok(())
+    }
+
+    #[test]
+    fn fallback_works() -> crate::Result<()> {
+        let mut headers = Headers::new();
+        headers.insert(REFERER, "/test.json");
+
+        let base_url = Url::parse("https://fallback.net/")?;
+        let referer = Referer::from_headers(base_url, headers)?.unwrap();
+        assert_eq!(
+            referer.location(),
+            &Url::parse("https://fallback.net/test.json")?
+        );
+
+        let mut headers = Headers::new();
+        headers.insert(REFERER, "https://example.com/test.json");
+
+        let base_url = Url::parse("https://fallback.net/")?;
+        let referer = Referer::from_headers(base_url, headers)?.unwrap();
+        assert_eq!(
+            referer.location(),
+            &Url::parse("https://example.com/test.json")?
+        );
+        Ok(())
+    }
+}