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: this iterator stops returning values before this
// can result in undefined behavior
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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