From f351f056a9f3a7655ddd9650c64fc2632822292e Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <bruno@belanyi.fr>
Date: Mon, 18 Jul 2022 13:22:04 +0200
Subject: [PATCH] Add 'Color' enum

---
 src/board/color.rs | 106 +++++++++++++++++++++++++++++++++++++++++++++
 src/board/mod.rs   |   3 ++
 2 files changed, 109 insertions(+)
 create mode 100644 src/board/color.rs

diff --git a/src/board/color.rs b/src/board/color.rs
new file mode 100644
index 0000000..ada896d
--- /dev/null
+++ b/src/board/color.rs
@@ -0,0 +1,106 @@
+use super::Rank;
+
+/// An enum representing the color of a player.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum Color {
+    White,
+    Black,
+}
+
+impl Color {
+    /// Convert from a file index into a [Color] type.
+    #[inline(always)]
+    pub fn from_index(index: usize) -> Self {
+        assert!(index < 2);
+        // SAFETY: we know the value is in-bounds
+        unsafe { Self::from_index_unchecked(index) }
+    }
+
+    /// Convert from a file index into a [Color] type, no bounds checking.
+    ///
+    /// # Safety
+    ///
+    /// Should only be called with values that can be output by [Color::index()].
+    #[inline(always)]
+    pub unsafe fn from_index_unchecked(index: usize) -> Self {
+        std::mem::transmute(index as u8)
+    }
+
+    /// Return the index of a given [Color].
+    #[inline(always)]
+    pub fn index(self) -> usize {
+        self as usize
+    }
+
+    /// Return the first [Rank] for pieces of the given [Color], where its pieces start.
+    #[inline(always)]
+    pub fn first_rank(self) -> Rank {
+        match self {
+            Self::White => Rank::First,
+            Self::Black => Rank::Eighth,
+        }
+    }
+
+    /// Return the second [Rank] for pieces of the given [Color], where its pawns start.
+    #[inline(always)]
+    pub fn second_rank(self) -> Rank {
+        match self {
+            Self::White => Rank::Second,
+            Self::Black => Rank::Seventh,
+        }
+    }
+
+    /// Return the fourth [Rank] for pieces of the given [Color], where its pawns move to after a
+    /// two-square move.
+    #[inline(always)]
+    pub fn fourth_rank(self) -> Rank {
+        match self {
+            Self::White => Rank::Fourth,
+            Self::Black => Rank::Fifth,
+        }
+    }
+
+    /// Return the seventh [Rank] for pieces of the given [Color], which is the rank before a pawn
+    /// gets promoted.
+    #[inline(always)]
+    pub fn seventh_rank(self) -> Rank {
+        match self {
+            Self::White => Rank::Seventh,
+            Self::Black => Rank::Second,
+        }
+    }
+}
+
+impl std::ops::Not for Color {
+    type Output = Color;
+
+    fn not(self) -> Self::Output {
+        match self {
+            Self::White => Self::Black,
+            Self::Black => Self::White,
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn from_index() {
+        assert_eq!(Color::from_index(0), Color::White);
+        assert_eq!(Color::from_index(1), Color::Black);
+    }
+
+    #[test]
+    fn index() {
+        assert_eq!(Color::White.index(), 0);
+        assert_eq!(Color::Black.index(), 1);
+    }
+
+    #[test]
+    fn not() {
+        assert_eq!(!Color::White, Color::Black);
+        assert_eq!(!Color::Black, Color::White);
+    }
+}
diff --git a/src/board/mod.rs b/src/board/mod.rs
index ea3c69e..6a29cbe 100644
--- a/src/board/mod.rs
+++ b/src/board/mod.rs
@@ -1,6 +1,9 @@
 pub mod bitboard;
 pub use bitboard::*;
 
+pub mod color;
+pub use color::*;
+
 pub mod direction;
 pub use direction::*;