1 files changed, 59 insertions, 0 deletions
diff --git a/src/repl/validator.rs b/src/repl/validator.rs
new file mode 100644
index 0000000..e1f6e99
--- /dev/null
+++ b/src/repl/validator.rs
@@ -0,0 +1,59 @@
+use reedline::{ValidationResult, Validator};
+
+/// A default validator which checks for mismatched quotes and brackets
+pub struct ReplValidator;
+
+impl Validator for ReplValidator {
+    fn validate(&self, line: &str) -> ValidationResult {
+        if incomplete_brackets(line) {
+            ValidationResult::Incomplete
+        } else {
+            ValidationResult::Complete
+        }
+    }
+}
+
+fn incomplete_brackets(line: &str) -> bool {
+    let mut balance: Vec<char> = Vec::new();
+    let mut symbol = None;
+    for c in line.chars() {
+        match symbol {
+            Some(s) => match (s, c) {
+                ('{', '}') | ('(', ')') => {
+                    balance.pop();
+                }
+                _ if s == c => {
+                    balance.push(c);
+                }
+                _ => {}
+            },
+            None => match c {
+                '{' | '(' => {
+                    balance.push(c);
+                    symbol = Some(c)
+                }
+                _ => {}
+            },
+        }
+    }
+
+    !balance.is_empty()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_incomplete_brackets() {
+        assert!(incomplete_brackets("{"));
+        assert!(incomplete_brackets("("));
+        assert!(!incomplete_brackets("{}"));
+        assert!(!incomplete_brackets("()"));
+        assert!(!incomplete_brackets("{ab\nc}"));
+        assert!(!incomplete_brackets("(ab\nc)"));
+        assert!(!incomplete_brackets("{[}"));
+        assert!(!incomplete_brackets("{{{{{}}}}}"));
+        assert!(incomplete_brackets("{{}"));
+    }
+}