Initial pass for AcceptLanguage header

Author: vodik

src/content/accept_language.rs

@@ -0,0 +1,88 @@
+//! Client header advertising which languages the client is able to understand.
+
+use crate::content::LanguageProposal;
+use crate::headers::{Header, HeaderValue, Headers, ACCEPT_LANGUAGE};
+
+use std::fmt::{self, Debug, Write};
+
+/// Client header advertising which languages the client is able to understand.
+pub struct AcceptLanguage {
+    wildcard: bool,
+    entries: Vec<LanguageProposal>,
+}
+
+impl AcceptLanguage {
+    /// Create a new instance of `AcceptLanguage`.
+    pub fn new() -> Self {
+        Self {
+            entries: vec![],
+            wildcard: false,
+        }
+    }
+
+    /// Create an instance of `AcceptLanguage` from a `Headers` instance.
+    pub fn from_headers(headers: impl AsRef<Headers>) -> crate::Result<Option<Self>> {
+        let mut entries = vec![];
+        let headers = match headers.as_ref().get(ACCEPT_LANGUAGE) {
+            Some(headers) => headers,
+            None => return Ok(None),
+        };
+
+        let mut wildcard = false;
+
+        for value in headers {
+            for part in value.as_str().trim().split(',') {
+                let part = part.trim();
+
+                if part.is_empty() {
+                    continue;
+                } else if part == "*" {
+                    wildcard = true;
+                    continue;
+                }
+
+                let entry = LanguageProposal::from_str(part)?;
+                entries.push(entry);
+            }
+        }
+
+        Ok(Some(Self { wildcard, entries }))
+    }
+}
+
+impl Header for AcceptLanguage {
+    fn header_name(&self) -> crate::headers::HeaderName {
+        ACCEPT_LANGUAGE
+    }
+
+    fn header_value(&self) -> crate::headers::HeaderValue {
+        let mut output = String::new();
+        for (n, directive) in self.entries.iter().enumerate() {
+            let directive: HeaderValue = directive.clone().into();
+            match n {
+                0 => write!(output, "{}", directive).unwrap(),
+                _ => write!(output, ", {}", directive).unwrap(),
+            };
+        }
+
+        if self.wildcard {
+            match output.len() {
+                0 => write!(output, "*").unwrap(),
+                _ => write!(output, ", *").unwrap(),
+            };
+        }
+
+        // SAFETY: the internal string is validated to be ASCII.
+        unsafe { HeaderValue::from_bytes_unchecked(output.into()) }
+    }
+}
+
+impl Debug for AcceptLanguage {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut list = f.debug_list();
+        for directive in &self.entries {
+            list.entry(directive);
+        }
+        list.finish()
+    }
+}

src/content/language_range_proposal.rs

@@ -0,0 +1,125 @@
+use crate::ensure;
+use crate::headers::HeaderValue;
+use crate::language::LanguageRange;
+use crate::utils::parse_weight;
+
+use std::cmp::{Ordering, PartialEq};
+use std::ops::{Deref, DerefMut};
+use std::str::FromStr;
+
+/// A proposed `LanguageRange` in `AcceptLanguage`.
+#[derive(Debug, Clone, PartialEq)]
+pub struct LanguageProposal {
+    /// The proposed language.
+    pub(crate) language: LanguageRange,
+
+    /// The weight of the proposal.
+    ///
+    /// This is a number between 0.0 and 1.0, and is max 3 decimal points.
+    weight: Option<f32>,
+}
+
+impl LanguageProposal {
+    /// Create a new instance of `LanguageProposal`.
+    pub fn new(language: impl Into<LanguageRange>, weight: Option<f32>) -> crate::Result<Self> {
+        if let Some(weight) = weight {
+            ensure!(
+                weight.is_sign_positive() && weight <= 1.0,
+                "LanguageProposal should have a weight between 0.0 and 1.0"
+            )
+        }
+
+        Ok(Self {
+            language: language.into(),
+            weight,
+        })
+    }
+
+    /// Get the proposed language.
+    pub fn language_range(&self) -> &LanguageRange {
+        &self.language
+    }
+
+    /// Get the weight of the proposal.
+    pub fn weight(&self) -> Option<f32> {
+        self.weight
+    }
+
+    pub(crate) fn from_str(s: &str) -> crate::Result<Self> {
+        let mut parts = s.split(';');
+        let language = LanguageRange::from_str(parts.next().unwrap())?;
+        let weight = parts.next().map(parse_weight).transpose()?;
+        Ok(Self::new(language, weight)?)
+    }
+}
+
+impl From<LanguageRange> for LanguageProposal {
+    fn from(language: LanguageRange) -> Self {
+        Self {
+            language,
+            weight: None,
+        }
+    }
+}
+
+impl PartialEq<LanguageRange> for LanguageProposal {
+    fn eq(&self, other: &LanguageRange) -> bool {
+        self.language == *other
+    }
+}
+
+impl PartialEq<LanguageRange> for &LanguageProposal {
+    fn eq(&self, other: &LanguageRange) -> bool {
+        self.language == *other
+    }
+}
+
+impl Deref for LanguageProposal {
+    type Target = LanguageRange;
+    fn deref(&self) -> &Self::Target {
+        &self.language
+    }
+}
+
+impl DerefMut for LanguageProposal {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.language
+    }
+}
+
+impl PartialOrd for LanguageProposal {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        match (self.weight, other.weight) {
+            (Some(left), Some(right)) => left.partial_cmp(&right),
+            (Some(_), None) => Some(Ordering::Greater),
+            (None, Some(_)) => Some(Ordering::Less),
+            (None, None) => None,
+        }
+    }
+}
+
+impl From<LanguageProposal> for HeaderValue {
+    fn from(entry: LanguageProposal) -> HeaderValue {
+        let s = match entry.weight {
+            Some(weight) => format!("{};q={:.3}", entry.language, weight),
+            None => entry.language.to_string(),
+        };
+        unsafe { HeaderValue::from_bytes_unchecked(s.into_bytes()) }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn smoke() {
+        let _ = LanguageProposal::new("en", Some(1.0)).unwrap();
+    }
+
+    #[test]
+    fn error_code_500() {
+        let err = LanguageProposal::new("en", Some(1.1)).unwrap_err();
+        assert_eq!(err.status(), 500);
+    }
+}

src/content/mod.rs

@@ -33,24 +33,29 @@
 
 pub mod accept;
 pub mod accept_encoding;
+pub mod accept_language;
 pub mod content_encoding;
 
 mod content_length;
 mod content_location;
 mod content_type;
 mod encoding;
 mod encoding_proposal;
+mod language_range_proposal;
 mod media_type_proposal;
 
 #[doc(inline)]
 pub use accept::Accept;
 #[doc(inline)]
 pub use accept_encoding::AcceptEncoding;
 #[doc(inline)]
+pub use accept_language::AcceptLanguage;
+#[doc(inline)]
 pub use content_encoding::ContentEncoding;
 pub use content_length::ContentLength;
 pub use content_location::ContentLocation;
 pub use content_type::ContentType;
 pub use encoding::Encoding;
 pub use encoding_proposal::EncodingProposal;
+pub use language_range_proposal::LanguageProposal;
 pub use media_type_proposal::MediaTypeProposal;

src/language/mod.rs

@@ -7,7 +7,8 @@ mod parse;
 use crate::headers::HeaderValue;
 use std::{fmt::{self, Display}, borrow::Cow, str::FromStr};
 
-#[derive(Debug)]
+/// An RFC 4647 language range.
+#[derive(Debug, Clone, PartialEq)]
 pub struct LanguageRange {
     pub(crate) tags: Vec<Cow<'static, str>>
 }
@@ -40,3 +41,9 @@ impl FromStr for LanguageRange {
         parse::parse(s)
     }
 }
+
+impl<'a> From<&'a str> for LanguageRange {
+    fn from(value: &'a str) -> Self {
+        Self::from_str(value).unwrap()
+    }
+}