1 files changed, 44 insertions, 0 deletions
diff --git a/src/util/skip.rs b/src/util/skip.rs
new file mode 100644
index 0000000..2c4198a
--- /dev/null
+++ b/src/util/skip.rs
@@ -0,0 +1,44 @@
+use crate::tokenizer::{Event, TokenType};
+
+/// To do.
+pub fn opt(events: &[Event], index: usize, token_types: &[TokenType]) -> usize {
+    skip_opt_with_direction(events, index, token_types, true)
+}
+
+/// To do.
+pub fn opt_back(events: &[Event], index: usize, token_types: &[TokenType]) -> usize {
+    skip_opt_with_direction(events, index, token_types, false)
+}
+
+/// To do.
+fn skip_opt_with_direction(
+    events: &[Event],
+    index: usize,
+    token_types: &[TokenType],
+    forward: bool,
+) -> usize {
+    let mut index = index;
+
+    while index < events.len() {
+        let current = &events[index].token_type;
+
+        if !token_types.contains(current) {
+            break;
+        }
+
+        // assert_eq!(events[index].event_type, EventType::Enter);
+        index = if forward { index + 1 } else { index - 1 };
+
+        loop {
+            if events[index].token_type == *current {
+                // assert_eq!(events[index].event_type, EventType::Exit);
+                index = if forward { index + 1 } else { index - 1 };
+                break;
+            }
+
+            index = if forward { index + 1 } else { index - 1 };
+        }
+    }
+
+    index
+}