From e7a08775ebb6fc7fde9261c94a9874d2b7b55111 Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@fizz.buzz>
Date: Sat, 22 Apr 2023 17:12:49 -0400
Subject: [PATCH] First stab at latex environment parser.

---
 src/parser/latex_environment.rs | 66 ++++++++++++++++++++++++++++++++-
 1 file changed, 65 insertions(+), 1 deletion(-)

diff --git a/src/parser/latex_environment.rs b/src/parser/latex_environment.rs
index c6cbb426..78d02099 100644
--- a/src/parser/latex_environment.rs
+++ b/src/parser/latex_environment.rs
@@ -1,5 +1,22 @@
+use nom::branch::alt;
+use nom::bytes::complete::tag;
+use nom::bytes::complete::tag_no_case;
+use nom::bytes::complete::take_while1;
+use nom::character::complete::line_ending;
+use nom::character::complete::space0;
+use nom::combinator::eof;
+use nom::combinator::map;
+use nom::sequence::tuple;
+
+use super::util::get_consumed;
 use super::Context;
 use crate::error::Res;
+use crate::parser::exiting::ExitClass;
+use crate::parser::parser_context::ContextElement;
+use crate::parser::parser_context::ExitMatcherNode;
+use crate::parser::parser_with_context::parser_with_context;
+use crate::parser::plain_text::plain_text;
+use crate::parser::util::start_of_line;
 use crate::parser::LatexEnvironment;
 
 #[tracing::instrument(ret, level = "debug")]
@@ -7,5 +24,52 @@ pub fn latex_environment<'r, 's>(
     context: Context<'r, 's>,
     input: &'s str,
 ) -> Res<&'s str, LatexEnvironment<'s>> {
-    todo!()
+    start_of_line(context, input)?;
+    let (remaining, _leading_whitespace) = space0(input)?;
+    let (remaining, (_opening, name, _open_close_brace, _ws, _line_ending)) = tuple((
+        tag_no_case(r#"\begin{"#),
+        name,
+        tag("}"),
+        space0,
+        line_ending,
+    ))(remaining)?;
+
+    let latex_environment_end_specialized = latex_environment_end(name);
+    let parser_context =
+        context.with_additional_node(ContextElement::ExitMatcherNode(ExitMatcherNode {
+            class: ExitClass::Beta,
+            exit_matcher: &latex_environment_end_specialized,
+        }));
+
+    let (remaining, _contents) = map(parser_with_context!(plain_text)(&parser_context), |obj| {
+        obj.source
+    })(remaining)?;
+    let (remaining, _end) = latex_environment_end_specialized(&parser_context, remaining)?;
+
+    let source = get_consumed(input, remaining);
+    Ok((remaining, LatexEnvironment { source }))
+}
+
+#[tracing::instrument(ret, level = "debug")]
+fn name<'s>(input: &'s str) -> Res<&'s str, &'s str> {
+    take_while1(|c: char| c.is_alphanumeric() || c == '*')(input)
+}
+
+fn latex_environment_end(
+    current_name: &str,
+) -> impl for<'r, 's> Fn(Context<'r, 's>, &'s str) -> Res<&'s str, &'s str> {
+    let current_name_lower = current_name.to_lowercase();
+    move |context: Context, input: &str| {
+        start_of_line(context, input)?;
+        let (remaining, _leading_whitespace) = space0(input)?;
+        let (remaining, (_begin, _name, _close_brace, _ws, _line_ending)) = tuple((
+            tag_no_case(r#"\end{"#),
+            tag_no_case(current_name_lower.as_str()),
+            tag("}"),
+            space0,
+            alt((eof, line_ending)),
+        ))(remaining)?;
+        let source = get_consumed(input, remaining);
+        Ok((remaining, source))
+    }
 }