Building the plain list item context.

src/parser/util.rs

@@ -1,5 +1,6 @@
 use nom::branch::alt;
 use nom::character::complete::line_ending;
+use nom::character::complete::none_of;
 use nom::character::complete::space0;
 use nom::combinator::eof;
 use nom::combinator::not;
@@ -7,6 +8,8 @@ use nom::combinator::recognize;
 use nom::multi::many0;
 use nom::sequence::tuple;
 
+use super::error::CustomError;
+use super::error::MyError;
 use super::error::Res;
 use super::parser_context::ContextElement;
 use super::Context;
@@ -76,6 +79,33 @@ pub fn trailing_whitespace(input: &str) -> Res<&str, &str> {
     alt((eof, recognize(tuple((line_ending, many0(blank_line))))))(input)
 }
 
+/// Check that we are at the start of a line
+pub fn start_of_line<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, ()> {
+    let document_root = context.get_document_root().unwrap();
+    let preceding_character = get_one_before(document_root, input)
+        .map(|slice| slice.chars().next())
+        .flatten();
+    match preceding_character {
+        Some('\n') => {}
+        Some(_) => {
+            // Not at start of line, cannot be a heading
+            return Err(nom::Err::Error(CustomError::MyError(MyError(
+                "Not at start of line",
+            ))));
+        }
+        // If None, we are at the start of the file which allows for headings
+        None => {}
+    };
+    Ok((input, ()))
+}
+
+/// Pull one non-whitespace character.
+///
+/// This function only operates on spaces, tabs, carriage returns, and line feeds. It does not handle fancy unicode whitespace.
+pub fn non_whitespace_character(input: &str) -> Res<&str, char> {
+    none_of(" \t\r\n")(input)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;