Add TT cutoffs

src/search/transposition_table.rs

@@ -15,12 +15,10 @@ impl TranspositionTable {
     }
 
     pub fn lookup(&self, zobrist_hash: ZobristHash) -> Option<&TTEntry> {
-        let entry = self
+        self
             .positions
             .get((zobrist_hash.0 % self.size) as usize)
-            .and_then(|entry| entry.as_ref());
-
-        entry
+            .and_then(|entry| entry.as_ref())
     }
 
     pub fn insert(&mut self, tt_entry: TTEntry) {
@@ -33,14 +31,36 @@ impl TranspositionTable {
 pub struct TTEntry {
     pub hash: ZobristHash,
     pub mv: Option<Move>,
+    pub depth: u8,
+    pub score: i32,
+    pub node_type: NodeType,
 }
 
 impl TTEntry {
-    pub const fn new(hash: ZobristHash, mv: Option<Move>) -> Self {
-        Self { hash, mv }
+    pub const fn new(
+        hash: ZobristHash,
+        mv: Option<Move>,
+        depth: u8,
+        score: i32,
+        node_type: NodeType,
+    ) -> Self {
+        Self {
+            hash,
+            mv,
+            depth,
+            score,
+            node_type,
+        }
     }
 }
 
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub enum NodeType {
+    Exact,
+    LowerBound,
+    UpperBound,
+}
+
 #[cfg(test)]
 mod tests {
     use crate::{