Implement entity parser.

src/parser/entity.rs

@@ -0,0 +1,50 @@
+use nom::branch::alt;
+use nom::bytes::complete::tag;
+use nom::bytes::complete::tag_no_case;
+use nom::character::complete::satisfy;
+use nom::character::complete::space0;
+use nom::combinator::eof;
+use nom::combinator::peek;
+use nom::combinator::recognize;
+
+use super::Context;
+use crate::error::Res;
+use crate::parser::object::Entity;
+use crate::parser::parser_with_context::parser_with_context;
+use crate::parser::util::get_consumed;
+
+#[tracing::instrument(ret, level = "debug")]
+pub fn entity<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Entity<'s>> {
+    let (remaining, _) = tag("\\")(input)?;
+    let (remaining, entity_name) = name(context, remaining)?;
+    let (remaining, _) = alt((
+        tag("{}"),
+        peek(recognize(parser_with_context!(entity_end)(context))),
+    ))(remaining)?;
+    let (remaining, _) = space0(remaining)?;
+
+    let source = get_consumed(input, remaining);
+    Ok((
+        remaining,
+        Entity {
+            source,
+            entity_name,
+        },
+    ))
+}
+
+#[tracing::instrument(ret, level = "debug")]
+fn name<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
+    // TODO: This should be defined by org-entities and optionally org-entities-user
+
+    // TODO: Add the rest of the entities, this is a very incomplete list
+    let (remaining, proto) = alt((alt((tag_no_case("delta"), tag_no_case("pi"))),))(input)?;
+    Ok((remaining, proto))
+}
+
+#[tracing::instrument(ret, level = "debug")]
+fn entity_end<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, ()> {
+    let (remaining, _) = alt((eof, recognize(satisfy(|c| !c.is_alphabetic()))))(input)?;
+
+    Ok((remaining, ()))
+}

toy_language.txt

@@ -1 +1,3 @@
-foo <<<*bar* baz>>> lorem ipsum *bar* baz dolar.
+foo \Delta bar
+foo \pibar
+foo \pi{}bar