Implement the export snippet parser.

src/parser/export_snippet.rs

@@ -1,6 +1,19 @@
+use nom::branch::alt;
+use nom::bytes::complete::tag;
+use nom::character::complete::anychar;
+use nom::combinator::opt;
+use nom::combinator::peek;
+use nom::combinator::recognize;
+use nom::combinator::verify;
+use nom::multi::many1;
+use nom::multi::many_till;
+use nom::sequence::tuple;
+
 use super::Context;
 use crate::error::Res;
-use crate::parser::util::not_yet_implemented;
+use crate::parser::parser_with_context::parser_with_context;
+use crate::parser::util::exit_matcher_parser;
+use crate::parser::util::get_consumed;
 use crate::parser::ExportSnippet;
 
 #[tracing::instrument(ret, level = "debug")]
@@ -8,6 +21,41 @@ pub fn export_snippet<'r, 's>(
     context: Context<'r, 's>,
     input: &'s str,
 ) -> Res<&'s str, ExportSnippet<'s>> {
-    not_yet_implemented()?;
-    todo!()
+    let (remaining, _) = tag("@@")(input)?;
+    let (remaining, backend_name) = backend(context, remaining)?;
+    let (remaining, backend_contents) =
+        opt(tuple((tag(":"), parser_with_context!(contents)(context))))(remaining)?;
+    let (remaining, _) = tag("@@")(remaining)?;
+    let source = get_consumed(input, remaining);
+    Ok((
+        remaining,
+        ExportSnippet {
+            source,
+            backend: backend_name,
+            contents: backend_contents.map(|(_colon, backend_contents)| backend_contents),
+        },
+    ))
+}
+
+#[tracing::instrument(ret, level = "debug")]
+fn backend<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
+    let (remaining, backend_name) =
+        recognize(many1(verify(anychar, |c| c.is_alphanumeric() || *c == '-')))(input)?;
+
+    Ok((remaining, backend_name))
+}
+
+#[tracing::instrument(ret, level = "debug")]
+fn contents<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, &'s str> {
+    let (remaining, source) = recognize(verify(
+        many_till(
+            anychar,
+            peek(alt((
+                parser_with_context!(exit_matcher_parser)(context),
+                tag("@@"),
+            ))),
+        ),
+        |(children, _exit_contents)| !children.is_empty(),
+    ))(input)?;
+    Ok((remaining, source))
 }