Initial implementation for citations.

This implementation definitely has bugs and is completely untested at this point. I'm just committing the initial "assume everything works" version before I did into debugging and fixing.

src/parser/citation_reference.rs

@@ -30,7 +30,7 @@ pub fn citation_reference<'r, 's>(
     input: &'s str,
 ) -> Res<&'s str, CitationReference<'s>> {
     let (remaining, _prefix) = parser_with_context!(key_prefix)(context)(input)?;
-    let (remaining, _key) = parser_with_context!(key)(context)(remaining)?;
+    let (remaining, _key) = parser_with_context!(citation_reference_key)(context)(remaining)?;
     let (remaining, _suffix) = parser_with_context!(key_suffix)(context)(remaining)?;
     let source = get_consumed(input, remaining);
 
@@ -38,7 +38,10 @@ pub fn citation_reference<'r, 's>(
 }
 
 #[tracing::instrument(ret, level = "debug")]
-fn key<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
+pub fn citation_reference_key<'r, 's>(
+    context: Context<'r, 's>,
+    input: &'s str,
+) -> Res<&'s str, &'s str> {
     let (remaining, source) = recognize(tuple((
         tag("@"),
         many1(verify(
@@ -99,7 +102,7 @@ fn key_suffix<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str,
 }
 
 #[tracing::instrument(ret, level = "debug")]
-fn get_bracket_depth<'r, 's>(context: Context<'r, 's>) -> Option<&'r CitationBracket<'s>> {
+pub fn get_bracket_depth<'r, 's>(context: Context<'r, 's>) -> Option<&'r CitationBracket<'s>> {
     for node in context.iter() {
         match node.get_data() {
             ContextElement::CitationBracket(depth) => return Some(depth),
@@ -135,7 +138,10 @@ fn key_prefix_end<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s s
             return close_bracket;
         }
     }
-    alt((tag(";"), recognize(parser_with_context!(key)(context))))(input)
+    alt((
+        tag(";"),
+        recognize(parser_with_context!(citation_reference_key)(context)),
+    ))(input)
 }
 
 #[tracing::instrument(ret, level = "debug")]