Return early if king is under check and small refactorings

src/evaluation/evaluation.rs

@@ -6,9 +6,6 @@ use crate::{
     evaluation::psqt::{mirror_index, piece_square_score},
 };
 
-pub const MAX_EVAL: i32 = 100000;
-pub const MIN_EVAL: i32 = -100000;
-
 const fn piece_score(piece_type: PieceType) -> i32 {
     match piece_type {
         PieceType::Pawn => 100,

src/evaluation/mod.rs

@@ -1,2 +1,6 @@
 pub mod evaluation;
 pub mod psqt;
+
+pub const MAX_SCORE: i32 = 100000;
+pub const MIN_SCORE: i32 = -100000;
+pub const MATE_SCORE: i32 = 50000;