1 files changed, 28 insertions, 0 deletions

diff --git a/src/lisp/eval.rs b/src/lisp/eval.rs
index b39730b..784cba0 100644
--- a/src/lisp/eval.rs
+++ b/src/lisp/eval.rs
@@ -20,6 +20,15 @@ pub struct Evaluator<'ctx, 'global> {
     pub context: Context,
 }
 
+impl<'ctx, 'global> Evaluator<'ctx, 'global> {
+    pub fn new(app: &'global mut AppState<'ctx>) -> Self {
+        Self {
+            app,
+            context: Vec::new(),
+        }
+    }
+}
+
 impl<'ctx, 'global> Evaluator<'ctx, 'global>
 where
     'ctx: 'global,
@@ -337,6 +346,25 @@ pub fn lookup(env_list: &[Environment], key: &str) -> Result<LispExpr, LispError
     }
 }
 
+pub fn completions<'a>(env_list: &'a [Environment], prefix: &str) -> Vec<&'a str> {
+    fn helper<'h>(env_list: &'h [Environment], prefix: &str, completions: &mut Vec<Vec<&'h str>>) {
+        if !env_list.is_empty() {
+            let nearest_env = env_list.last().unwrap();
+            completions.push(
+                nearest_env
+                    .keys()
+                    .filter(|k| k.starts_with(prefix))
+                    .map(|s| &s[prefix.len()..])
+                    .collect::<Vec<_>>(),
+            );
+            helper(&env_list[..env_list.len() - 1], prefix, completions);
+        }
+    }
+    let mut completions = Vec::new();
+    helper(env_list, prefix, &mut completions);
+    completions.into_iter().flatten().collect()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;