From 7e73782a7d51b40a558b74793c1d6c1abdea857d Mon Sep 17 00:00:00 2001
From: Botahamec <botahamec@outlook.com>
Date: Thu, 8 Jul 2021 20:32:44 -0400
Subject: here's what i have so far

---
 model/src/moves_iter.rs | 143 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 model/src/moves_iter.rs

(limited to 'model/src/moves_iter.rs')

diff --git a/model/src/moves_iter.rs b/model/src/moves_iter.rs
new file mode 100644
index 0000000..307ee96
--- /dev/null
+++ b/model/src/moves_iter.rs
@@ -0,0 +1,143 @@
+use crate::moves::{Move, MoveDirection};
+use crate::possible_moves::PossibleMoves;
+
+const FORWARD_LEFT_SLIDE_SQUARES: [usize; 33] = [
+	1, 3, 3, 4, 6, 6, 7, 8, 9, 12, 12, 12, 13, 14, 15, 16, 17, 19, 19, 20, 21, 22, 23, 24, 27, 27,
+	27, 28, 29, 30, 32, 32, 32,
+];
+const FORWARD_RIGHT_SLIDE_SQUARES: [usize; 33] = [
+	2, 2, 3, 4, 6, 6, 7, 8, 10, 10, 12, 12, 13, 14, 15, 16, 18, 18, 19, 20, 21, 22, 23, 24, 26, 26,
+	27, 28, 29, 30, 32, 32, 32,
+];
+const BACKWARD_LEFT_SLIDE_SQUARES: [usize; 33] = [
+	1, 3, 3, 4, 5, 7, 7, 8, 9, 11, 11, 13, 13, 14, 15, 16, 17, 19, 19, 20, 21, 22, 23, 24, 25, 27,
+	27, 28, 29, 30, 31, 32, 32,
+];
+const BACKWARD_RIGHT_SLIDE_SQUARES: [usize; 33] = [
+	2, 2, 3, 4, 5, 7, 7, 8, 10, 10, 11, 13, 13, 14, 15, 16, 19, 19, 19, 20, 21, 22, 23, 24, 26, 26,
+	27, 28, 29, 30, 31, 32, 32,
+];
+
+const FORWARD_LEFT_JUMP_SQUARES: [usize; 33] = [
+	1, 6, 6, 6, 6, 6, 7, 8, 9, 12, 12, 12, 13, 14, 15, 16, 17, 20, 20, 20, 21, 22, 23, 28, 28, 28,
+	28, 28, 29, 32, 32, 32, 32,
+];
+const FORWARD_RIGHT_JUMP_SQUARES: [usize; 33] = [
+	2, 2, 3, 6, 6, 6, 7, 12, 12, 12, 12, 12, 13, 14, 15, 18, 18, 18, 19, 20, 21, 22, 23, 26, 26,
+	26, 27, 28, 29, 32, 32, 32, 32,
+];
+const BACKWARD_LEFT_JUMP_SQUARES: [usize; 33] = [
+	4, 4, 4, 4, 5, 8, 8, 8, 9, 14, 14, 14, 14, 14, 15, 16, 17, 20, 20, 20, 21, 22, 23, 24, 25, 28,
+	28, 28, 29, 30, 31, 32, 32,
+];
+const BACKWARD_RIGHT_JUMP_SQUARES: [usize; 33] = [
+	2, 2, 3, 4, 5, 10, 10, 10, 10, 10, 11, 14, 14, 14, 15, 20, 20, 20, 20, 20, 21, 22, 23, 26, 26,
+	26, 27, 28, 29, 30, 31, 32, 32,
+];
+
+static SLIDE_ARRAYS: [[usize; 33]; 4] = [
+	FORWARD_LEFT_SLIDE_SQUARES,
+	FORWARD_RIGHT_SLIDE_SQUARES,
+	BACKWARD_LEFT_SLIDE_SQUARES,
+	BACKWARD_RIGHT_SLIDE_SQUARES,
+];
+
+static JUMP_ARRAYS: [[usize; 33]; 4] = [
+	FORWARD_LEFT_JUMP_SQUARES,
+	FORWARD_RIGHT_JUMP_SQUARES,
+	BACKWARD_LEFT_JUMP_SQUARES,
+	BACKWARD_RIGHT_JUMP_SQUARES,
+];
+
+pub struct PossibleMovesIter {
+	possible_moves: PossibleMoves,
+	current_square: usize,
+	current_direction: MoveDirection,
+	movers: u32,
+	squares: &'static [usize; 33],
+}
+
+impl From<PossibleMoves> for PossibleMovesIter {
+	fn from(possible_moves: PossibleMoves) -> Self {
+		Self {
+			possible_moves,
+			current_square: 0,
+			current_direction: MoveDirection::ForwardLeft,
+			movers: possible_moves.forward_left_bits(),
+			squares: unsafe {
+				if possible_moves.can_jump() {
+					JUMP_ARRAYS.get_unchecked(0)
+				} else {
+					SLIDE_ARRAYS.get_unchecked(0)
+				}
+			},
+		}
+	}
+}
+
+impl Iterator for PossibleMovesIter {
+	type Item = Move;
+
+	fn next(&mut self) -> Option<Self::Item> {
+		loop {
+			if self.current_square == 32 {
+				if self.current_direction != MoveDirection::BackwardRight {
+					self.current_square = 0;
+					// safety: only results in undefined variant if equal to backward right
+					// this has already been checked for
+					self.current_direction =
+						unsafe { std::mem::transmute((self.current_direction as u8) + 1) };
+					self.movers = self
+						.possible_moves
+						.get_direction_bits(self.current_direction);
+
+					// safety: the max value of the enum is 3
+					unsafe {
+						self.squares = &*(self.squares as *const [usize; 33]).add(1);
+					}
+				} else {
+					return None;
+				}
+			}
+
+			if (self.movers >> self.current_square) & 1 != 0 {
+				let next_move = Move::new(
+					self.current_square,
+					self.current_direction,
+					self.possible_moves.can_jump(),
+				);
+
+				// safety: self.current_square will never be > 32
+				// squares does not contain such a value
+				unsafe {
+					self.current_square = *self.squares.get_unchecked(self.current_square);
+				}
+
+				return Some(next_move);
+			}
+
+			if self.current_square != 32 {
+				// safety: self.current_square will never be > 32
+				// squares does not contain such a value
+				unsafe {
+					self.current_square = *self.squares.get_unchecked(self.current_square);
+				}
+			}
+		}
+	}
+
+	fn size_hint(&self) -> (usize, Option<usize>) {
+		(
+			0,
+			Some(
+				(32 - self.current_square)
+					+ 32 * match self.current_direction {
+						MoveDirection::ForwardLeft => 3,
+						MoveDirection::ForwardRight => 2,
+						MoveDirection::BackwardLeft => 1,
+						MoveDirection::BackwardRight => 0,
+					},
+			),
+		)
+	}
+}
-- 
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