feat: implemented the frontier-based scheduling for the graph executor with simplified state management (gotta love .clone)

src/graph/staging.rs

@@ -1,38 +1,6 @@
 use serde_json::Value;
 use std::collections::HashMap;
 
-#[derive(Debug, Default, Clone)]
-pub struct StagingArea {
-    writes: HashMap<String, Value>,
-}
-
-#[allow(dead_code)]
-impl StagingArea {
-    pub fn new() -> Self {
-        Self::default()
-    }
-
-    pub fn write(&mut self, key: impl Into<String>, value: Value) {
-        self.writes.insert(key.into(), value);
-    }
-
-    pub fn get(&self, key: &str) -> Option<&Value> {
-        self.writes.get(key)
-    }
-
-    pub fn is_empty(&self) -> bool {
-        self.writes.is_empty()
-    }
-
-    pub fn len(&self) -> usize {
-        self.writes.len()
-    }
-
-    pub fn into_writes(self) -> HashMap<String, Value> {
-        self.writes
-    }
-}
-
 /// Published form of one branch's writes for the super-step merge phase.
 /// Callers assemble these into a deterministically-ordered `Vec` keyed by
 /// `(node_id, invocation_index)` before passing to
@@ -40,58 +8,8 @@ impl StagingArea {
 /// branches and the input-list position for map sub-branches — so multiple
 /// invocations of the same `branch:` node by a `map` are still totally ordered.
 #[derive(Debug, Clone)]
-#[allow(dead_code)]
 pub struct BranchWrites {
     pub node_id: String,
     pub invocation_index: usize,
     pub writes: HashMap<String, Value>,
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use serde_json::json;
-
-    #[test]
-    fn new_staging_area_is_empty() {
-        let s = StagingArea::new();
-
-        assert!(s.is_empty());
-        assert_eq!(s.len(), 0);
-    }
-
-    #[test]
-    fn write_stores_value_under_key() {
-        let mut s = StagingArea::new();
-
-        s.write("key", json!("value"));
-
-        assert_eq!(s.get("key"), Some(&json!("value")));
-        assert_eq!(s.len(), 1);
-        assert!(!s.is_empty());
-    }
-
-    #[test]
-    fn write_overwrites_existing_key() {
-        let mut s = StagingArea::new();
-
-        s.write("k", json!(1));
-        s.write("k", json!(2));
-
-        assert_eq!(s.get("k"), Some(&json!(2)));
-        assert_eq!(s.len(), 1);
-    }
-
-    #[test]
-    fn into_writes_consumes_and_yields_map() {
-        let mut s = StagingArea::new();
-        s.write("a", json!(1));
-        s.write("b", json!(2));
-
-        let writes = s.into_writes();
-
-        assert_eq!(writes.len(), 2);
-        assert_eq!(writes.get("a"), Some(&json!(1)));
-        assert_eq!(writes.get("b"), Some(&json!(2)));
-    }
-}