move generation

.gitignore

@@ -0,0 +1,19 @@
+# will have compiled files and executables
+debug/
+target/
+.vscode/
+.zed/
+.helix/
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
+
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb
+
+# RustRover
+#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
+#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
+#  and can be added to the global gitignore or merged into this file.  For a more nuclear
+#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
+#.idea/

Cargo.lock

@@ -0,0 +1,47 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "diff"
+version = "0.1.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "56254986775e3233ffa9c4d7d3faaf6d36a2c09d30b20687e9f88bc8bafc16c8"
+
+[[package]]
+name = "pretty_assertions"
+version = "1.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3ae130e2f271fbc2ac3a40fb1d07180839cdbbe443c7a27e1e3c13c5cac0116d"
+dependencies = [
+ "diff",
+ "yansi",
+]
+
+[[package]]
+name = "tak_bot"
+version = "0.1.0"
+dependencies = [
+ "tak_lib",
+]
+
+[[package]]
+name = "tak_lib"
+version = "0.1.0"
+dependencies = [
+ "pretty_assertions",
+]
+
+[[package]]
+name = "tak_server"
+version = "0.1.0"
+
+[[package]]
+name = "tak_visualizer"
+version = "0.1.0"
+
+[[package]]
+name = "yansi"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cfe53a6657fd280eaa890a3bc59152892ffa3e30101319d168b781ed6529b049"

tak_bot/Cargo.toml

@@ -2,5 +2,7 @@
 name = "tak_bot"
 version = "0.1.0"
 edition = "2024"
+default-run = "tak_bot"
 
 [dependencies]
+tak_lib = { path = "../tak_lib" }

tak_bot/src/main.rs

@@ -1,3 +1,14 @@
+use std::time::Instant;
+
+use tak_lib::Board5x5;
+
 fn main() {
-    println!("Hello, world!");
+    let board = Board5x5::new();
+    // for b_move in board.moves_iter() {
+    // println!("{:?}", b_move);
+    // }
+    let before = Instant::now();
+    let moves: Vec<_> = board.moves_iter().collect();
+    let dur = before.elapsed();
+    println!("{:?}", dur);
 }

tak_lib/Cargo.toml

@@ -4,3 +4,7 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+
+[dev-dependencies]
+pretty_assertions = "1.4.1"
+

tak_lib/src/engine.rs

@@ -0,0 +1,244 @@
+use crate::{
+    Board, Direction, Move,
+    piece::{ColoredPiece, Piece},
+    tile::Tile,
+};
+
+pub struct BoardIter<'b, const N: usize> {
+    /// The board we're iterating over.
+    board: &'b Board<N>,
+    /// The most recent coordinate that we have finished with.
+    coord: (u8, u8),
+    /// The remaining move buffer.
+    ///
+    /// This contains all the moves that havent been returned yet,
+    /// and are in the tiles <= `coord`.
+    residual: Vec<Move<N>>,
+}
+
+impl<const N: usize> Board<N> {
+    /// Gets the possible moves for the given tile
+    pub fn get_moves_for_tile(&self, x: u8, y: u8, buf: &mut Vec<Move<N>>) {
+        let to_move = self.to_move();
+        let can_place_caps = self.caps_left[to_move as usize] != 0;
+        let top_piece = self.tiles[x as usize][y as usize].top_piece();
+        if top_piece == ColoredPiece::None {
+            // possible moves are place moves
+            get_placement_moves(x, y, can_place_caps, buf)
+        } else if top_piece.color() == to_move {
+            get_movement_moves(x, y, &self.tiles, buf)
+        }
+    }
+
+    pub fn moves_iter<'b>(&'b self) -> BoardIter<'b, N> {
+        let mut residual = Vec::new();
+        self.get_moves_for_tile(0, 0, &mut residual);
+        BoardIter {
+            board: self,
+            coord: (0, 0),
+            residual,
+        }
+    }
+
+    // TODO: update result
+    pub fn check_move(&self, m: Move<N>) -> Result<(), ()> {
+        let _ = m;
+        todo!()
+    }
+
+    pub fn unchecked_apply_move(mut self, m: Move<N>) -> Self {
+        match m {
+            Move::Place { piece, at } => {
+                self.tiles[at.0 as usize][at.1 as usize]
+                    .set_top_piece(ColoredPiece::new(self.to_move(), piece));
+                self
+            }
+            Move::Move {
+                from,
+                count,
+                dir,
+                drop,
+            } => {
+                let from_tile = self.tiles[from.0 as usize][from.1 as usize];
+                self
+            }
+        }
+    }
+}
+
+impl<'b, const N: usize> Iterator for BoardIter<'b, N> {
+    type Item = Move<N>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Some(v) = self.residual.pop() {
+            return Some(v);
+        }
+
+        if self.coord == (N as u8 - 1, N as u8 - 1) {
+            return None;
+        }
+
+        // increment the coord
+        self.coord.1 += 1;
+        self.coord.0 += self.coord.1 / N as u8;
+        self.coord.1 %= N as u8;
+
+        self.board
+            .get_moves_for_tile(self.coord.0, self.coord.1, &mut self.residual);
+
+        self.next()
+    }
+}
+
+/// Gets the possible placement moves on (`x`, `y`).
+///
+/// This does no checks on the tile, it just adds the moves.
+fn get_placement_moves<const N: usize>(x: u8, y: u8, can_place_caps: bool, buf: &mut Vec<Move<N>>) {
+    buf.push(Move::Place {
+        piece: Piece::Flat,
+        at: (x, y),
+    });
+    buf.push(Move::Place {
+        piece: Piece::Wall,
+        at: (x, y),
+    });
+    if can_place_caps {
+        buf.push(Move::Place {
+            piece: Piece::Caps,
+            at: (x, y),
+        });
+    }
+}
+
+/// Gets the possible moves by moving from (`x`, `y`).
+///
+/// This function does not check the colors of anything, so the caller must make sure
+/// the active player owns the piece on this tile, if you want to get only valid moves
+/// for the active player.
+pub(crate) fn get_movement_moves<const N: usize>(
+    x: u8,
+    y: u8,
+    tiles: &[[Tile; N]; N],
+    buf: &mut Vec<Move<N>>,
+) {
+    let tile = tiles[x as usize][y as usize];
+    let is_caps = tile.top_piece().piece() == Piece::Caps;
+    let max_grab = u8::min(N as u8, tile.stack_len() + 1);
+
+    for dir in Direction::ALL {
+        get_moves_in_dir(x, y, dir, tiles, buf, is_caps, max_grab);
+    }
+}
+
+/// Gets the possible moves moving from (`x`, `y`) in the given direction `dir`.
+///
+/// This function does not check the colors of anything, so the caller must make sure
+/// the active player owns the piece on this tile, if you want to get only valid moves
+/// for the active player.
+fn get_moves_in_dir<const N: usize>(
+    x: u8,
+    y: u8,
+    dir: Direction,
+    tiles: &[[Tile; N]; N],
+    moves: &mut Vec<Move<N>>,
+    is_caps: bool,
+    max_grab: u8,
+) {
+    // first, get the max distance we can go
+    let mut max_dist = max_grab.min(dir.dist_to_edge::<N>(x, y));
+    let mut end_w_capstone = false;
+    let (dx, dy) = dir.delta();
+
+    // step through the tiles to see if out movement gets blocked
+    for i in 1..=max_dist {
+        let xi = x as isize + (dx * i as isize);
+        let yi = y as isize + (dy * i as isize);
+        // we already clamp `max_distance` to the board edge, so indexing should be safe
+        let next_piece = tiles[xi as usize][yi as usize].top_piece().piece();
+
+        // check for pieces that will block us
+        if next_piece == Piece::Caps {
+            max_dist = i - 1;
+            break;
+        } else if next_piece == Piece::Wall {
+            // if we have a capstone, we can smash the wall
+            if is_caps {
+                end_w_capstone = true;
+                max_dist = i;
+            } else {
+                max_dist = i - 1;
+            }
+            break;
+        }
+    }
+    if max_dist == 0 {
+        return;
+    }
+
+    // now that we have our max distance, get all the possible moves
+    let mut insert_fn = |drops: [u8; N]| {
+        moves.push(Move::Move {
+            from: (x, y),
+            count: drops.iter().copied().sum::<u8>(),
+            dir,
+            drop: drops,
+        });
+    };
+    for grab in 1..=max_grab {
+        let mut buf = [0; N];
+        get_drop_amounts(&mut buf, 0, &mut insert_fn, grab, max_dist, end_w_capstone);
+    }
+}
+
+/// Gets the possible amounts of pieces to drop at each tile.
+///
+/// `pieces` is the number of pieces that are picked up.
+/// `len` is the max length that the stack can be moved.
+///
+/// If the top piece of the stack is a capstone, and the end of the line
+/// is a wall, `end_w_capstone` should be `true` and `len` should include
+/// that tile.
+pub(crate) fn get_drop_amounts<const N: usize>(
+    // shared state
+    buf: &mut [u8; N],
+    i: usize,
+    insert_fn: &mut impl FnMut([u8; N]),
+    // recursive parameters
+    pieces: u8,
+    len: u8,
+    end_w_capstone: bool,
+) {
+    debug_assert!(len > 0 || pieces == 0);
+    // base cases
+    if pieces == 0 {
+        insert_fn(buf.clone());
+        return;
+    }
+    if pieces == 1 {
+        buf[i] = 1;
+        insert_fn(buf.clone());
+        buf[i] = 0;
+        return;
+    }
+    if len == 1 {
+        if end_w_capstone {
+            if pieces == 1 {
+                buf[i] = 1;
+                insert_fn(buf.clone());
+                buf[i] = 0;
+            }
+        } else {
+            buf[i] = pieces;
+            insert_fn(buf.clone());
+            buf[i] = 0;
+        }
+        return;
+    }
+
+    // recursive case
+    for n in 1..=pieces {
+        buf[i] = n;
+        get_drop_amounts(buf, i + 1, insert_fn, pieces - n, len - 1, end_w_capstone);
+    }
+    buf[i] = 0;
+}

tak_lib/src/lib.rs

@@ -1,14 +1,140 @@
-pub fn add(left: u64, right: u64) -> u64 {
+pub mod engine;
-    left + right
+pub mod piece;
-}
-
 #[cfg(test)]
-mod tests {
+mod test_engine;
-    use super::*;
+pub mod tile;
 
-    #[test]
+use crate::{
-    fn it_works() {
+    piece::{Color, Piece},
-        let result = add(2, 2);
+    tile::Tile,
-        assert_eq!(result, 4);
+};
+use std::fmt::Display;
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub enum Direction {
+    East,
+    North,
+    West,
+    South,
+}
+impl Display for Direction {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Direction::East => write!(f, "e"),
+            Direction::North => write!(f, "n"),
+            Direction::West => write!(f, "w"),
+            Direction::South => write!(f, "s"),
+        }
     }
 }
+impl Direction {
+    pub const ALL: [Direction; 4] = [
+        Direction::East,
+        Direction::North,
+        Direction::West,
+        Direction::South,
+    ];
+
+    pub fn delta(&self) -> (isize, isize) {
+        match self {
+            Direction::East => (1, 0),
+            Direction::North => (0, 1),
+            Direction::West => (-1, 0),
+            Direction::South => (0, -1),
+        }
+    }
+
+    #[inline]
+    pub fn dist_to_edge<const N: usize>(&self, x: u8, y: u8) -> u8 {
+        match self {
+            Direction::East => N as u8 - x - 1,
+            Direction::North => N as u8 - y - 1,
+            Direction::West => x,
+            Direction::South => y,
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+pub struct Board<const N: usize> {
+    half_moves: u32,
+    /// The amount of stones that white and black have left.
+    stones_left: [u8; 2],
+    /// The amount of capstones that white and black have left.
+    caps_left: [u8; 2],
+    play_state: PlayState,
+    tiles: [[Tile; N]; N],
+}
+pub type Board3x3 = Board<3>;
+pub type Board4x4 = Board<4>;
+pub type Board5x5 = Board<5>;
+pub type Board6x6 = Board<6>;
+pub type Board8x8 = Board<8>;
+
+impl<const N: usize> Board<N> {
+    /// The number of capstones in each players' pouches.
+    pub const N_STONES: u8 = match N {
+        3 => 10,
+        4 => 15,
+        5 => 21,
+        6 => 30,
+        8 => 50,
+        _ => panic!("N must be 3, 4, 5, 6, or 8"),
+    };
+    /// The number of capstones in the players' pouches.
+    pub const N_CAPS: u8 = match N {
+        3 => 0,
+        4 => 0,
+        5 => 1,
+        6 => 1,
+        8 => 2,
+        _ => panic!("N must be 3, 4, 5, 6, or 8"),
+    };
+
+    /// Constructs a new `Board` in the starting state.
+    pub fn new() -> Self {
+        Board {
+            half_moves: 0,
+            stones_left: [Self::N_STONES, Self::N_STONES],
+            caps_left: [Self::N_CAPS, Self::N_CAPS],
+            play_state: PlayState::WhitePlaceBlack,
+            tiles: [[Tile::EMPTY; N]; N],
+        }
+    }
+
+    /// Gets the player who is to move
+    #[inline]
+    pub fn to_move(&self) -> Color {
+        if self.half_moves % 2 == 0 {
+            Color::White
+        } else {
+            Color::Black
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+pub enum Move<const N: usize> {
+    Place {
+        piece: Piece,
+        at: (u8, u8),
+    },
+    Move {
+        from: (u8, u8),
+        count: u8,
+        dir: Direction,
+        drop: [u8; N],
+    },
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub enum PlayState {
+    Normal,
+    WhitePlaceBlack,
+    BlackPlaceWhite,
+    WhiteWinRoad,
+    WhiteWinFlat,
+    BlackWinRoad,
+    BlackWinFlat,
+    Tie,
+}

tak_lib/src/piece.rs

@@ -0,0 +1,105 @@
+use std::fmt::Debug;
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+#[repr(u8)]
+pub enum Color {
+    White = 0,
+    Black = 1,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[repr(u8)]
+pub enum Piece {
+    None = 0,
+    Flat = 1,
+    Wall = 2,
+    Caps = 3,
+}
+impl Debug for Piece {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Piece::None => write!(f, "----"),
+            Piece::Flat => write!(f, "Flat"),
+            Piece::Wall => write!(f, "Wall"),
+            Piece::Caps => write!(f, "Caps"),
+        }
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+#[repr(u8)]
+pub enum ColoredPiece {
+    None = 0,
+    WhiteFlat = 1,
+    WhiteWall = 2,
+    WhiteCaps = 3,
+
+    BlackFlat = 5,
+    BlackWall = 6,
+    BlackCaps = 7,
+}
+
+impl ColoredPiece {
+    /// Constructs a new `ColoredPiece`.
+    pub fn new(color: Color, piece: Piece) -> Self {
+        let mut piece_val = (piece as u8) | ((color as u8) << 2);
+        if piece_val == 4 {
+            piece_val = 0;
+        }
+        // safety: value will always be in range
+        unsafe { std::mem::transmute(piece_val) }
+    }
+
+    /// Constructs a new `ColoredPiece` from the given raw value.
+    pub fn from_u8_opt(val: u8) -> Option<Self> {
+        if val <= 7 && val != 4 {
+            // safety: value is checked to be in range
+            Some(unsafe { std::mem::transmute(val) })
+        } else {
+            None
+        }
+    }
+
+    /// Constructs a new `ColoredPiece` from the given raw value.
+    ///
+    /// ## Panics
+    /// This panics if `val` is outside the range `0..=7` or is `4`.
+    pub fn from_u8(val: u8) -> Self {
+        if val <= 7 && val != 4 {
+            // safety: value is checked to be in range
+            unsafe { std::mem::transmute(val) }
+        } else {
+            panic!("`val` ({}) was not in range for `ColoredPiece`!", val);
+        }
+    }
+
+    /// Gets the color of the piece,
+    /// returning `Color::White` if `self` is `None`.
+    pub fn color(&self) -> Color {
+        if (*self as u8 >> 2) == 1 {
+            Color::Black
+        } else {
+            Color::White
+        }
+    }
+
+    /// Gets the color of the piece,
+    /// returning `None` if `self` is `None`.
+    pub fn color_opt(&self) -> Option<Color> {
+        let val = *self as u8;
+        if val == 0 {
+            return None;
+        } else if (val >> 2) == 1 {
+            Some(Color::Black)
+        } else {
+            Some(Color::White)
+        }
+    }
+
+    /// Gets the piece type of this piece.
+    pub fn piece(&self) -> Piece {
+        let piece_val = *self as u8 & 0b11;
+        // safety: value will always be in range
+        unsafe { std::mem::transmute(piece_val) }
+    }
+}

tak_lib/src/test_engine.rs

@@ -0,0 +1,568 @@
+use crate::{Direction, Move, engine::get_movement_moves, piece::ColoredPiece, tile::Tile};
+
+#[cfg(test)]
+fn expect_get_drop_ammounts<const N: usize>(
+    pieces: u8,
+    len: u8,
+    end_w_capstone: bool,
+    expected_drop_list: Vec<[u8; N]>,
+) {
+    use crate::engine::get_drop_amounts;
+
+    let mut buf = [0; N];
+    let mut drop_list = Vec::new();
+    let mut insert_fn = |drops: [u8; N]| {
+        drop_list.push(drops);
+    };
+    get_drop_amounts(&mut buf, 0, &mut insert_fn, pieces, len, end_w_capstone);
+
+    if let Err(err) = assert_uo_list_eq(expected_drop_list, drop_list) {
+        panic!(
+            "incorrect drop list! (pieces={}, len={}, end_w_capstone={})\n{}",
+            pieces, len, end_w_capstone, err
+        );
+    }
+}
+
+#[test]
+fn test_full_len_drop_amounts() {
+    expect_get_drop_ammounts(1, 1, false, vec![[1]]);
+    expect_get_drop_ammounts(1, 1, false, vec![[1, 0]]);
+    expect_get_drop_ammounts(1, 1, false, vec![[1, 0, 0]]);
+    expect_get_drop_ammounts(2, 2, false, vec![[1, 1, 0, 0, 0], [2, 0, 0, 0, 0]]);
+    expect_get_drop_ammounts(
+        3,
+        3,
+        false,
+        vec![
+            [1, 1, 1, 0, 0],
+            [1, 2, 0, 0, 0],
+            [2, 1, 0, 0, 0],
+            [3, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(
+        4,
+        4,
+        false,
+        vec![
+            [1, 1, 1, 1, 0],
+            [1, 1, 2, 0, 0],
+            [1, 2, 1, 0, 0],
+            [1, 3, 0, 0, 0],
+            [2, 1, 1, 0, 0],
+            [2, 2, 0, 0, 0],
+            [3, 1, 0, 0, 0],
+            [4, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(
+        5,
+        5,
+        false,
+        vec![
+            [1, 1, 1, 1, 1],
+            [1, 1, 1, 2, 0],
+            [1, 1, 2, 1, 0],
+            [1, 1, 3, 0, 0],
+            [1, 2, 1, 1, 0],
+            [1, 2, 2, 0, 0],
+            [1, 3, 1, 0, 0],
+            [1, 4, 0, 0, 0],
+            [2, 1, 1, 1, 0],
+            [2, 1, 2, 0, 0],
+            [2, 2, 1, 0, 0],
+            [2, 3, 0, 0, 0],
+            [3, 1, 1, 0, 0],
+            [3, 2, 0, 0, 0],
+            [4, 1, 0, 0, 0],
+            [5, 0, 0, 0, 0],
+        ],
+    );
+}
+
+#[test]
+fn test_truncated_drop_amounts() {
+    expect_get_drop_ammounts(
+        3,
+        2,
+        false,
+        vec![[1, 2, 0, 0, 0], [2, 1, 0, 0, 0], [3, 0, 0, 0, 0]],
+    );
+    expect_get_drop_ammounts(3, 1, false, vec![[3, 0, 0, 0, 0]]);
+    expect_get_drop_ammounts(
+        4,
+        3,
+        false,
+        vec![
+            [1, 1, 2, 0, 0],
+            [1, 2, 1, 0, 0],
+            [1, 3, 0, 0, 0],
+            [2, 1, 1, 0, 0],
+            [2, 2, 0, 0, 0],
+            [3, 1, 0, 0, 0],
+            [4, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(
+        4,
+        2,
+        false,
+        vec![
+            [1, 3, 0, 0, 0],
+            [2, 2, 0, 0, 0],
+            [3, 1, 0, 0, 0],
+            [4, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(
+        5,
+        4,
+        false,
+        vec![
+            [1, 1, 1, 2, 0],
+            [1, 1, 2, 1, 0],
+            [1, 1, 3, 0, 0],
+            [1, 2, 1, 1, 0],
+            [1, 2, 2, 0, 0],
+            [1, 3, 1, 0, 0],
+            [1, 4, 0, 0, 0],
+            [2, 1, 1, 1, 0],
+            [2, 1, 2, 0, 0],
+            [2, 2, 1, 0, 0],
+            [2, 3, 0, 0, 0],
+            [3, 1, 1, 0, 0],
+            [3, 2, 0, 0, 0],
+            [4, 1, 0, 0, 0],
+            [5, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(
+        5,
+        3,
+        false,
+        vec![
+            [1, 1, 3, 0, 0],
+            [1, 2, 2, 0, 0],
+            [1, 3, 1, 0, 0],
+            [1, 4, 0, 0, 0],
+            [2, 1, 2, 0, 0],
+            [2, 2, 1, 0, 0],
+            [2, 3, 0, 0, 0],
+            [3, 1, 1, 0, 0],
+            [3, 2, 0, 0, 0],
+            [4, 1, 0, 0, 0],
+            [5, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(
+        5,
+        2,
+        false,
+        vec![
+            [1, 4, 0, 0, 0],
+            [2, 3, 0, 0, 0],
+            [3, 2, 0, 0, 0],
+            [4, 1, 0, 0, 0],
+            [5, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(5, 1, false, vec![[5, 0, 0, 0, 0]]);
+}
+
+#[test]
+fn test_capstone_drops() {
+    expect_get_drop_ammounts(1, 1, true, vec![[1, 0]]);
+    expect_get_drop_ammounts(2, 2, true, vec![[1, 1, 0, 0, 0], [2, 0, 0, 0, 0]]);
+    expect_get_drop_ammounts::<5>(2, 1, true, vec![]);
+    expect_get_drop_ammounts(
+        3,
+        3,
+        true,
+        vec![
+            [1, 1, 1, 0, 0],
+            [1, 2, 0, 0, 0],
+            [2, 1, 0, 0, 0],
+            [3, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(3, 2, true, vec![[2, 1, 0, 0, 0], [3, 0, 0, 0, 0]]);
+    expect_get_drop_ammounts(
+        4,
+        4,
+        true,
+        vec![
+            [1, 1, 1, 1, 0],
+            [1, 1, 2, 0, 0],
+            [1, 2, 1, 0, 0],
+            [1, 3, 0, 0, 0],
+            [2, 1, 1, 0, 0],
+            [2, 2, 0, 0, 0],
+            [3, 1, 0, 0, 0],
+            [4, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(
+        4,
+        3,
+        true,
+        vec![
+            [1, 2, 1, 0, 0],
+            [1, 3, 0, 0, 0],
+            [2, 1, 1, 0, 0],
+            [2, 2, 0, 0, 0],
+            [3, 1, 0, 0, 0],
+            [4, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(4, 2, true, vec![[3, 1, 0, 0, 0], [4, 0, 0, 0, 0]]);
+    expect_get_drop_ammounts::<5>(4, 1, true, vec![]);
+    expect_get_drop_ammounts(
+        5,
+        5,
+        true,
+        vec![
+            [1, 1, 1, 1, 1],
+            [1, 1, 1, 2, 0],
+            [1, 1, 2, 1, 0],
+            [1, 1, 3, 0, 0],
+            [1, 2, 1, 1, 0],
+            [1, 2, 2, 0, 0],
+            [1, 3, 1, 0, 0],
+            [1, 4, 0, 0, 0],
+            [2, 1, 1, 1, 0],
+            [2, 1, 2, 0, 0],
+            [2, 2, 1, 0, 0],
+            [2, 3, 0, 0, 0],
+            [3, 1, 1, 0, 0],
+            [3, 2, 0, 0, 0],
+            [4, 1, 0, 0, 0],
+            [5, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(
+        5,
+        4,
+        true,
+        vec![
+            [1, 1, 2, 1, 0],
+            [1, 1, 3, 0, 0],
+            [1, 2, 1, 1, 0],
+            [1, 2, 2, 0, 0],
+            [1, 3, 1, 0, 0],
+            [1, 4, 0, 0, 0],
+            [2, 1, 1, 1, 0],
+            [2, 1, 2, 0, 0],
+            [2, 2, 1, 0, 0],
+            [2, 3, 0, 0, 0],
+            [3, 1, 1, 0, 0],
+            [3, 2, 0, 0, 0],
+            [4, 1, 0, 0, 0],
+            [5, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(
+        5,
+        3,
+        true,
+        vec![
+            [1, 3, 1, 0, 0],
+            [1, 4, 0, 0, 0],
+            [2, 2, 1, 0, 0],
+            [2, 3, 0, 0, 0],
+            [3, 1, 1, 0, 0],
+            [3, 2, 0, 0, 0],
+            [4, 1, 0, 0, 0],
+            [5, 0, 0, 0, 0],
+        ],
+    );
+    expect_get_drop_ammounts(5, 2, true, vec![[4, 1, 0, 0, 0], [5, 0, 0, 0, 0]]);
+    expect_get_drop_ammounts::<5>(5, 1, true, vec![]);
+}
+
+#[test]
+fn test_get_moves() {
+    use crate::{Board5x5, Color};
+
+    let from = (1, 2);
+    let mut tiles = Board5x5::new().tiles;
+    tiles[from.0 as usize][from.1 as usize] = Tile::new(
+        ColoredPiece::WhiteFlat,
+        &[Color::White, Color::Black, Color::White, Color::Black],
+    );
+    let mut actual = Vec::new();
+    get_movement_moves(from.0, from.1, &tiles, &mut actual);
+
+    const LEN1_DROPS: [(u8, [u8; 5]); 5] = [
+        (1, [1, 0, 0, 0, 0]),
+        (2, [2, 0, 0, 0, 0]),
+        (3, [3, 0, 0, 0, 0]),
+        (4, [4, 0, 0, 0, 0]),
+        (5, [5, 0, 0, 0, 0]),
+    ];
+    const LEN2_DROPS: [(u8, [u8; 5]); 15] = [
+        // 1
+        (1, [1, 0, 0, 0, 0]),
+        // 2
+        (2, [1, 1, 0, 0, 0]),
+        (2, [2, 0, 0, 0, 0]),
+        // 3
+        (3, [1, 2, 0, 0, 0]),
+        (3, [2, 1, 0, 0, 0]),
+        (3, [3, 0, 0, 0, 0]),
+        // 4
+        (4, [1, 3, 0, 0, 0]),
+        (4, [2, 2, 0, 0, 0]),
+        (4, [3, 1, 0, 0, 0]),
+        (4, [4, 0, 0, 0, 0]),
+        // 5
+        (5, [1, 4, 0, 0, 0]),
+        (5, [2, 3, 0, 0, 0]),
+        (5, [3, 2, 0, 0, 0]),
+        (5, [4, 1, 0, 0, 0]),
+        (5, [5, 0, 0, 0, 0]),
+    ];
+    const LEN3_DROPS: [(u8, [u8; 5]); 25] = [
+        // 1
+        (1, [1, 0, 0, 0, 0]),
+        // 2
+        (2, [1, 1, 0, 0, 0]),
+        (2, [2, 0, 0, 0, 0]),
+        // 3
+        (3, [1, 1, 1, 0, 0]),
+        (3, [1, 2, 0, 0, 0]),
+        (3, [2, 1, 0, 0, 0]),
+        (3, [3, 0, 0, 0, 0]),
+        // 4
+        (4, [1, 1, 2, 0, 0]),
+        (4, [1, 2, 1, 0, 0]),
+        (4, [1, 3, 0, 0, 0]),
+        (4, [2, 1, 1, 0, 0]),
+        (4, [2, 2, 0, 0, 0]),
+        (4, [3, 1, 0, 0, 0]),
+        (4, [4, 0, 0, 0, 0]),
+        // 5
+        (5, [1, 1, 3, 0, 0]),
+        (5, [1, 2, 2, 0, 0]),
+        (5, [1, 3, 1, 0, 0]),
+        (5, [1, 4, 0, 0, 0]),
+        (5, [2, 1, 2, 0, 0]),
+        (5, [2, 2, 1, 0, 0]),
+        (5, [2, 3, 0, 0, 0]),
+        (5, [3, 1, 1, 0, 0]),
+        (5, [3, 2, 0, 0, 0]),
+        (5, [4, 1, 0, 0, 0]),
+        (5, [5, 0, 0, 0, 0]),
+    ];
+
+    let east_list: Vec<_> = LEN3_DROPS
+        .into_iter()
+        .map(|(count, drop)| Move::Move {
+            from,
+            count,
+            dir: Direction::East,
+            drop,
+        })
+        .collect();
+    let north_list: Vec<_> = LEN2_DROPS
+        .into_iter()
+        .map(|(count, drop)| Move::Move {
+            from,
+            count,
+            dir: Direction::North,
+            drop,
+        })
+        .collect();
+    let west_list: Vec<_> = LEN1_DROPS
+        .into_iter()
+        .map(|(count, drop)| Move::Move {
+            from,
+            count,
+            dir: Direction::West,
+            drop,
+        })
+        .collect();
+    let south_list: Vec<_> = LEN2_DROPS
+        .into_iter()
+        .map(|(count, drop)| Move::Move {
+            from,
+            count,
+            dir: Direction::South,
+            drop,
+        })
+        .collect();
+    let expected: Vec<_> = east_list
+        .into_iter()
+        .chain(north_list.into_iter())
+        .chain(west_list.into_iter())
+        .chain(south_list.into_iter())
+        .collect();
+
+    let result = assert_uo_list_eq(expected, actual);
+
+    if let Err(err) = result {
+        panic!("incorrect move list!\n{}", err);
+    }
+}
+
+#[test]
+fn test_get_caps_moves() {
+    use crate::{Board5x5, Color};
+
+    let from = (1, 2);
+    let mut tiles = Board5x5::new().tiles;
+    tiles[from.0 as usize][from.1 as usize] = Tile::new(
+        ColoredPiece::WhiteCaps,
+        &[Color::White, Color::Black, Color::White, Color::Black],
+    );
+    tiles[1][0] = Tile::new(ColoredPiece::WhiteWall, &[]);
+    tiles[1][3] = Tile::new(ColoredPiece::BlackWall, &[]);
+    tiles[4][2] = Tile::new(ColoredPiece::BlackWall, &[]);
+    let mut actual = Vec::new();
+    get_movement_moves(from.0, from.1, &tiles, &mut actual);
+
+    const LEN1_DROPS: [(u8, [u8; 5]); 5] = [
+        (1, [1, 0, 0, 0, 0]),
+        (2, [2, 0, 0, 0, 0]),
+        (3, [3, 0, 0, 0, 0]),
+        (4, [4, 0, 0, 0, 0]),
+        (5, [5, 0, 0, 0, 0]),
+    ];
+    const LEN1_CAPS_DROPS: [(u8, [u8; 5]); 1] = [(1, [1, 0, 0, 0, 0])];
+    const LEN2_CAPS_DROPS: [(u8, [u8; 5]); 9] = [
+        // 1
+        (1, [1, 0, 0, 0, 0]),
+        // 2
+        (2, [1, 1, 0, 0, 0]),
+        (2, [2, 0, 0, 0, 0]),
+        // 3
+        (3, [2, 1, 0, 0, 0]),
+        (3, [3, 0, 0, 0, 0]),
+        // 4
+        (4, [3, 1, 0, 0, 0]),
+        (4, [4, 0, 0, 0, 0]),
+        // 5
+        (5, [4, 1, 0, 0, 0]),
+        (5, [5, 0, 0, 0, 0]),
+    ];
+    const LEN3_CAPS_DROPS: [(u8, [u8; 5]); 21] = [
+        // 1
+        (1, [1, 0, 0, 0, 0]),
+        // 2
+        (2, [1, 1, 0, 0, 0]),
+        (2, [2, 0, 0, 0, 0]),
+        // 3
+        (3, [1, 1, 1, 0, 0]),
+        (3, [1, 2, 0, 0, 0]),
+        (3, [2, 1, 0, 0, 0]),
+        (3, [3, 0, 0, 0, 0]),
+        // 4
+        (4, [1, 2, 1, 0, 0]),
+        (4, [1, 3, 0, 0, 0]),
+        (4, [2, 1, 1, 0, 0]),
+        (4, [2, 2, 0, 0, 0]),
+        (4, [3, 1, 0, 0, 0]),
+        (4, [4, 0, 0, 0, 0]),
+        // 5
+        (5, [1, 3, 1, 0, 0]),
+        (5, [1, 4, 0, 0, 0]),
+        (5, [2, 2, 1, 0, 0]),
+        (5, [2, 3, 0, 0, 0]),
+        (5, [3, 1, 1, 0, 0]),
+        (5, [3, 2, 0, 0, 0]),
+        (5, [4, 1, 0, 0, 0]),
+        (5, [5, 0, 0, 0, 0]),
+    ];
+
+    let east_list: Vec<_> = LEN3_CAPS_DROPS
+        .into_iter()
+        .map(|(count, drop)| Move::Move {
+            from,
+            count,
+            dir: Direction::East,
+            drop,
+        })
+        .collect();
+    let north_list: Vec<_> = LEN1_CAPS_DROPS
+        .into_iter()
+        .map(|(count, drop)| Move::Move {
+            from,
+            count,
+            dir: Direction::North,
+            drop,
+        })
+        .collect();
+    let west_list: Vec<_> = LEN1_DROPS
+        .into_iter()
+        .map(|(count, drop)| Move::Move {
+            from,
+            count,
+            dir: Direction::West,
+            drop,
+        })
+        .collect();
+    let south_list: Vec<_> = LEN2_CAPS_DROPS
+        .into_iter()
+        .map(|(count, drop)| Move::Move {
+            from,
+            count,
+            dir: Direction::South,
+            drop,
+        })
+        .collect();
+    let expected: Vec<_> = east_list
+        .into_iter()
+        .chain(north_list.into_iter())
+        .chain(west_list.into_iter())
+        .chain(south_list.into_iter())
+        .collect();
+
+    let result = assert_uo_list_eq(expected, actual);
+
+    if let Err(err) = result {
+        panic!("incorrect move list!\n{}", err);
+    }
+}
+
+fn assert_uo_list_eq<T: Clone + Eq + std::hash::Hash + std::fmt::Debug>(
+    expected: Vec<T>,
+    actual: Vec<T>,
+) -> Result<(), String> {
+    use std::collections::HashSet;
+
+    let actual_set: HashSet<T> = actual.iter().cloned().collect();
+    let expected_set: HashSet<T> = expected.iter().cloned().collect();
+
+    if actual_set != expected_set {
+        Err(list_diff(expected, actual, expected_set, actual_set))
+    } else {
+        Ok(())
+    }
+}
+
+fn list_diff<T: Clone + Eq + std::hash::Hash + std::fmt::Debug>(
+    expected: Vec<T>,
+    actual: Vec<T>,
+    expected_set: std::collections::HashSet<T>,
+    actual_set: std::collections::HashSet<T>,
+) -> String {
+    let mut diff = String::new();
+    for entry in expected {
+        if actual_set.contains(&entry) {
+            diff += &format!("\t{:?}\t{:?}\n", entry, entry);
+        } else {
+            diff += &format!("\t{:?}\n", entry);
+        }
+    }
+    for entry in actual {
+        if expected_set.contains(&entry) {
+            continue;
+        }
+        let blank = format!("{:?}", entry)
+            .chars()
+            .map(|_| ' ')
+            .collect::<String>();
+        diff += &format!("\t{}\t{:?}\n", blank, entry);
+    }
+    diff
+}

tak_lib/src/tile.rs

@@ -0,0 +1,96 @@
+use std::fmt::Debug;
+
+use crate::piece::{Color, ColoredPiece};
+
+/// A tile on the board.
+///
+/// bits [2:0] represent the top piece (if any).
+/// - bit [2] being the color.
+/// - bits [1:0] being the piece type (if any).
+/// bits [15:8] represent the number of pieces underneath the top piece.
+/// bits [127:16] are the colors of the stacked pieces.
+/// - bit [16] is the top-most piece, and bit [127] is the bottom-most piece.
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Tile(u128);
+
+impl Debug for Tile {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        if self.stack_len() == 0 {
+            self.top_piece().fmt(f)
+        } else {
+            let stack = self.stack();
+            let stack: String = (0..self.stack_len())
+                .rev()
+                .map(|i| if (stack >> i) == 1 { 'b' } else { 'w' })
+                .collect();
+            write!(f, "{}:{:?}", stack, self.top_piece())
+        }
+    }
+}
+
+impl Tile {
+    /// An empty tile.
+    pub const EMPTY: Tile = Tile(0);
+
+    const PIECE_OFFSET: u8 = 0;
+    const PIECE_MASK: u128 = 0b111u128;
+
+    const LEN_OFFSET: u8 = 8;
+    const LEN_MASK: u128 = 0xFF00u128;
+
+    const STACK_OFFSET: u8 = 16;
+    const STACK_MASK: u128 = !0xFFFFu128;
+
+    pub fn new(top_piece: ColoredPiece, stack: &[Color]) -> Self {
+        let mut tile = Tile::EMPTY;
+        tile.set_top_piece(top_piece);
+        tile.set_stack_len(stack.len() as u8);
+        let mut stack_bits = 0u128;
+        for c in stack.iter().rev() {
+            stack_bits = (stack_bits << 1) | (*c) as u128
+        }
+        tile.set_stack(stack_bits);
+        tile
+    }
+
+    /// Gets the top piece.
+    pub fn top_piece(&self) -> ColoredPiece {
+        ColoredPiece::from_u8((self.0 & 0b111) as u8)
+    }
+
+    /// Sets the top piece.
+    pub fn set_top_piece(&mut self, piece: ColoredPiece) {
+        // clear top_piece
+        self.0 &= !Self::PIECE_MASK;
+        // set top_piece
+        self.0 |= (piece as u128) << Self::PIECE_OFFSET;
+    }
+
+    /// Gets the length of the stack.
+    pub fn stack_len(&self) -> u8 {
+        (self.0 >> 8) as u8
+    }
+
+    /// Sets the stack length.
+    pub fn set_stack_len(&mut self, len: u8) {
+        // clear stack_len
+        self.0 &= !Self::LEN_MASK;
+        // set stack_len
+        self.0 |= (len as u128) << Self::LEN_OFFSET;
+    }
+
+    /// Gets the stacked pieces as a bit array.
+    ///
+    /// The LSB is the top-most piece, whereas the MSB is the bottom-most piece.
+    pub fn stack(&self) -> u128 {
+        self.0 >> Self::STACK_OFFSET
+    }
+
+    /// Sets the stacked pieces.
+    pub fn set_stack(&mut self, stack: u128) {
+        // clear stack
+        self.0 &= !Self::STACK_MASK;
+        // set stack
+        self.0 |= (stack as u128) << Self::STACK_OFFSET;
+    }
+}