From 1ae6d5df4887a4b9979be0cab41eeba0a23d913c Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Tue, 24 Jun 2025 20:00:04 -0700
Subject: [PATCH] =?UTF-8?q?[core,=20position]=20Rename=20the=20type=20of?=
 =?UTF-8?q?=20Score's=20inner=20value=20=E2=86=92=20Value?=
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---
 core/src/colors.rs         |  4 +--
 core/src/score.rs          | 65 ++++++++++++++++++++++++++++++--------
 position/src/evaluation.rs |  6 ++--
 3 files changed, 57 insertions(+), 18 deletions(-)

diff --git a/core/src/colors.rs b/core/src/colors.rs
index 53e2c1e..e1255b7 100644
--- a/core/src/colors.rs
+++ b/core/src/colors.rs
@@ -1,6 +1,6 @@
 // Eryn Wells <eryn@erynwells.me>
 
-use crate::{Direction, score::ScoreInner};
+use crate::{Direction, score};
 use std::fmt;
 use thiserror::Error;
 
@@ -59,7 +59,7 @@ impl Color {
     }
 
     #[must_use]
-    pub const fn score_factor(self) -> ScoreInner {
+    pub const fn score_factor(self) -> score::Value {
         match self {
             Color::White => 1,
             Color::Black => -1,
diff --git a/core/src/score.rs b/core/src/score.rs
index a7f24cd..2dfd7c9 100644
--- a/core/src/score.rs
+++ b/core/src/score.rs
@@ -5,22 +5,53 @@ use std::{
     ops::{Add, AddAssign, Mul, Neg, Sub, SubAssign},
 };
 
-pub(crate) type ScoreInner = i32;
+pub(crate) type Value = i32;
 
 /// A score for a position in centipawns.
 #[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
-pub struct Score(ScoreInner);
+pub struct Score(Value);
 
 impl Score {
-    #[must_use]
-    pub const fn zero() -> Self {
-        Self(0)
-    }
+    pub const ZERO: Score = Score(0);
+
+    /// The minimum possible value of a score. Notably, this is *not* the
+    /// minimum value for the inner integer value so negation works correctly.
+    /// This property is important during search, which relies on being able to
+    /// negate "infinity".
+    ///
+    /// ## Examples
+    ///
+    /// ```
+    /// use chessfriend_core::score::Score;
+    /// assert_eq!(!Score::MIN, Score::MAX);
+    /// ```
+    ///
+    pub const MIN: Score = Score(Value::MIN + 1);
+
+    /// The maximum possible value of a score.
+    pub const MAX: Score = Score(Value::MAX);
+
+    const CENTIPAWNS_PER_POINT: f32 = 100.0;
 
     #[must_use]
-    pub const fn new(value: ScoreInner) -> Self {
+    pub const fn new(value: Value) -> Self {
         Self(value)
     }
+
+    /// Returns `true` if this [`Score`] is zero.
+    ///
+    /// ## Examples
+    ///
+    /// ```
+    /// use chessfriend_core::score::Score;
+    /// assert!(Score::ZERO.is_zero());
+    /// assert!(Score::new(0).is_zero());
+    /// ```
+    ///
+    #[must_use]
+    pub const fn is_zero(&self) -> bool {
+        self.0 == 0
+    }
 }
 
 impl Add for Score {
@@ -51,15 +82,15 @@ impl SubAssign for Score {
     }
 }
 
-impl Mul<ScoreInner> for Score {
-    type Output = Score;
+impl Mul<Value> for Score {
+    type Output = Self;
 
-    fn mul(self, rhs: ScoreInner) -> Self::Output {
+    fn mul(self, rhs: Value) -> Self::Output {
         Score(self.0 * rhs)
     }
 }
 
-impl Mul<Score> for ScoreInner {
+impl Mul<Score> for Value {
     type Output = Score;
 
     fn mul(self, rhs: Score) -> Self::Output {
@@ -67,8 +98,16 @@ impl Mul<Score> for ScoreInner {
     }
 }
 
-impl From<ScoreInner> for Score {
-    fn from(value: ScoreInner) -> Self {
+impl Neg for Score {
+    type Output = Self;
+
+    fn neg(self) -> Self::Output {
+        Score(-self.0)
+    }
+}
+
+impl From<Value> for Score {
+    fn from(value: Value) -> Self {
         Score(value)
     }
 }
diff --git a/position/src/evaluation.rs b/position/src/evaluation.rs
index 883398b..b776777 100644
--- a/position/src/evaluation.rs
+++ b/position/src/evaluation.rs
@@ -19,10 +19,10 @@ impl Evaluator {
     fn material_balance(board: &Board, color: Color) -> Score {
         let other_color = color.other();
 
-        Shape::into_iter().fold(Score::zero(), |acc, shape| {
+        Shape::into_iter().fold(Score::ZERO, |acc, shape| {
             let (active_pieces, other_pieces) = (
-                board.count_piece(&Piece::new(color, shape)) as i32,
-                board.count_piece(&Piece::new(other_color, shape)) as i32,
+                i32::from(board.count_piece(&Piece::new(color, shape))),
+                i32::from(board.count_piece(&Piece::new(other_color, shape))),
             );
 
             let factor = shape.score() * (active_pieces - other_pieces);