Move 'Magic' to 'wizardry' submodule

src/movegen/wizardry/mod.rs

@@ -1,2 +1,25 @@
 pub(crate) mod generation;
 mod mask;
+
+use crate::board::Bitboard;
+
+/// A type representing the magic board indexing a given [crate::board::Square].
+pub struct Magic {
+    /// Magic number.
+    pub(crate) magic: u64,
+    /// Base offset into the magic square table.
+    pub(crate) offset: usize,
+    /// Mask to apply to the blocker board before applying the magic.
+    pub(crate) mask: Bitboard,
+    /// Length of the resulting mask after applying the magic.
+    pub(crate) shift: u8,
+}
+
+impl Magic {
+    /// Compute the index into the magics database for this set of `blockers`.
+    pub fn get_index(&self, blockers: Bitboard) -> usize {
+        let relevant_occupancy = (blockers & self.mask).0;
+        let base_index = ((relevant_occupancy.wrapping_mul(self.magic)) >> self.shift) as usize;
+        base_index + self.offset
+    }
+}