From 0597b3b538515ce2f21be8f377ceca19f838f5bc Mon Sep 17 00:00:00 2001
From: tali <iitalics@gmail.com>
Date: Tue, 13 Dec 2022 14:11:09 -0500
Subject: [PATCH] Add Location, Orientation, Rotation types

---
 mino/src/lib.rs      |   2 +
 mino/src/location.rs | 110 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 112 insertions(+)
 create mode 100644 mino/src/location.rs

diff --git a/mino/src/lib.rs b/mino/src/lib.rs
index 61f13b5..fac5e43 100644
--- a/mino/src/lib.rs
+++ b/mino/src/lib.rs
@@ -1,7 +1,9 @@
 #![no_std]
 
+pub mod location;
 pub mod matrix;
 
+pub use location::Location;
 pub use matrix::Mat;
 
 /// Allows constructing a `Mat` constant with string literals:
diff --git a/mino/src/location.rs b/mino/src/location.rs
new file mode 100644
index 0000000..df03dd5
--- /dev/null
+++ b/mino/src/location.rs
@@ -0,0 +1,110 @@
+//! Data structures and operations for representing piece locations and rotations.
+
+/// Represents a location for a piece, including its orientation.
+#[derive(Copy, Clone, Eq, PartialEq, Debug)]
+pub struct Location {
+    /// Horizontal coordinate.
+    pub x: i16,
+    /// Vertical coordinate.
+    pub y: i16,
+    /// Orientation.
+    pub r: Orientation,
+}
+
+/// Represents an orientation state for a piece. The initial state is "north" (`N`), and
+/// there are 4 total orientations to represent each 90 degree turn possible.
+#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug, Default)]
+#[repr(i8)]
+pub enum Orientation {
+    /// North. The initial state.
+    #[default]
+    N = 0,
+    /// Clockwise ("cw") from north.
+    E = 1,
+    /// Two rotations in any direction from north.
+    S = 2,
+    /// Counterclockwise ("ccw") from north.
+    W = 3,
+}
+
+impl From<i8> for Orientation {
+    #[inline]
+    fn from(v: i8) -> Self {
+        unsafe { core::mem::transmute(v & 3) }
+    }
+}
+
+/// Represents a rotation operation. Includes 180 degree "flips", which are non-standard
+/// for tetris but exist in many unofficial iterations of the game.
+///
+/// Rotations may be combined with orientations using the [addition
+/// operator](core::ops::Add).
+///
+/// ```
+/// # use mino::location::{Orientation, Rotation};
+/// assert_eq!(Orientation::N + Rotation::Cw, Orientation::E);
+/// ```
+#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug)]
+#[repr(i8)]
+pub enum Rotation {
+    /// Clockwise.
+    Cw = 1,
+    /// 180 degrees.
+    Flip = 2,
+    /// Counterclockwise.
+    Ccw = 3,
+}
+
+impl core::ops::Add<Rotation> for Orientation {
+    type Output = Orientation;
+    fn add(self, r: Rotation) -> Orientation {
+        (self as i8).wrapping_add(r as i8).into()
+    }
+}
+
+impl core::ops::AddAssign<Rotation> for Orientation {
+    fn add_assign(&mut self, r: Rotation) {
+        *self = *self + r;
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_angle_rotate() {
+        use Orientation::*;
+        use Rotation::*;
+        assert_eq!(N + Cw, E);
+        assert_eq!(N + Ccw, W);
+        assert_eq!(N + Flip, S);
+        assert_eq!(E + Cw, S);
+        assert_eq!(E + Ccw, N);
+        assert_eq!(E + Flip, W);
+        assert_eq!(S + Cw, W);
+        assert_eq!(S + Ccw, E);
+        assert_eq!(S + Flip, N);
+        assert_eq!(W + Cw, N);
+        assert_eq!(W + Ccw, S);
+        assert_eq!(W + Flip, E);
+
+        let mut r = N;
+        r += Ccw;
+        assert_eq!(r, W);
+    }
+
+    #[test]
+    fn test_angle_from_i8() {
+        let mut r = Orientation::N;
+        for i in 0i8..=127 {
+            assert_eq!(r, i.into(), "i={i}");
+            r += Rotation::Cw;
+        }
+        r = Orientation::N;
+        for i in (-128i8..=-1).rev() {
+            r += Rotation::Ccw;
+            assert_eq!(r, i.into(), "i={i}");
+        }
+    }
+}