1 files changed, 83 insertions, 0 deletions
diff --git a/src/construct/partial_mdx_expression.rs b/src/construct/partial_mdx_expression.rs
new file mode 100644
index 0000000..a949347
--- /dev/null
+++ b/src/construct/partial_mdx_expression.rs
@@ -0,0 +1,83 @@
+//! To do.
+
+use crate::construct::partial_space_or_tab::space_or_tab_min_max;
+use crate::event::Name;
+use crate::state::{Name as StateName, State};
+use crate::tokenizer::Tokenizer;
+use alloc::format;
+
+/// Start of MDX: expression.
+///
+/// ```markdown
+/// > | a {Math.PI} c
+///       ^
+/// ```
+pub fn start(tokenizer: &mut Tokenizer) -> State {
+    debug_assert_eq!(tokenizer.current, Some(b'{'));
+    tokenizer.enter(tokenizer.tokenize_state.token_1.clone());
+    tokenizer.enter(Name::MdxExpressionMarker);
+    tokenizer.consume();
+    tokenizer.exit(Name::MdxExpressionMarker);
+    State::Next(StateName::MdxExpressionBefore)
+}
+
+pub fn before(tokenizer: &mut Tokenizer) -> State {
+    match tokenizer.current {
+        None => {
+            State::Error(format!(
+                "{}:{}: Unexpected end of file in expression, expected a corresponding closing brace for `{{`",
+                tokenizer.point.line, tokenizer.point.column
+            ))
+        }
+        Some(b'\n') => {
+            tokenizer.enter(Name::LineEnding);
+            tokenizer.consume();
+            tokenizer.exit(Name::LineEnding);
+            State::Next(StateName::MdxExpressionEolAfter)
+        },
+        Some(b'}') if tokenizer.tokenize_state.size == 0 => {
+            tokenizer.enter(Name::MdxExpressionMarker);
+            tokenizer.consume();
+            tokenizer.exit(Name::MdxExpressionMarker);
+            tokenizer.exit(tokenizer.tokenize_state.token_1.clone());
+            State::Ok
+        },
+        Some(_) => {
+            tokenizer.enter(Name::MdxExpressionData);
+            State::Retry(StateName::MdxExpressionInside)
+        }
+    }
+}
+
+pub fn inside(tokenizer: &mut Tokenizer) -> State {
+    if matches!(tokenizer.current, None | Some(b'\n'))
+        || (tokenizer.current == Some(b'}') && tokenizer.tokenize_state.size == 0)
+    {
+        tokenizer.exit(Name::MdxExpressionData);
+        State::Retry(StateName::MdxExpressionBefore)
+    } else {
+        // To do: only count if agnostic.
+        if tokenizer.current == Some(b'{') {
+            tokenizer.tokenize_state.size += 1;
+        }
+
+        tokenizer.consume();
+        State::Next(StateName::MdxExpressionInside)
+    }
+}
+
+pub fn eol_after(tokenizer: &mut Tokenizer) -> State {
+    // Lazy continuation in a flow expression is a syntax error.
+    if tokenizer.tokenize_state.token_1 == Name::MdxFlowExpression && tokenizer.lazy {
+        State::Error(format!(
+            "{}:{}: Unexpected lazy line in expression in container, expected line to be prefixed with `>` when in a block quote, whitespace when in a list, etc",
+            tokenizer.point.line, tokenizer.point.column
+        ))
+    } else if matches!(tokenizer.current, Some(b'\t' | b' ')) {
+        tokenizer.attempt(State::Next(StateName::MdxExpressionBefore), State::Nok);
+        // To do: use `start_column` + constants.tabSize for max space to eat.
+        State::Next(space_or_tab_min_max(tokenizer, 0, usize::MAX))
+    } else {
+        State::Retry(StateName::MdxExpressionBefore)
+    }
+}