commit ce16748258b0efd87d2a58bfb552801c9ad1b835
Author: dece <shgck@pistache.land>
Date:   Sun May 31 02:41:02 2020 +0200

    init: board and basic move rules

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..53eaa21
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/target
+**/*.rs.bk
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..7a58565
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,6 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "vatu"
+version = "0.1.0"
+
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..c5100cb
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "vatu"
+version = "0.1.0"
+authors = ["dece <shgck@pistache.land>"]
+edition = "2018"
+
+[dependencies]
diff --git a/src/.rules.rs.swp b/src/.rules.rs.swp
new file mode 100644
index 0000000..72d6200
Binary files /dev/null and b/src/.rules.rs.swp differ
diff --git a/src/board.rs b/src/board.rs
new file mode 100644
index 0000000..6d06e48
--- /dev/null
+++ b/src/board.rs
@@ -0,0 +1,165 @@
+//! Basic type definitions and functions.
+
+// Piece type flags.
+pub const SQ_E: u8 = 0;
+pub const SQ_P: u8 = 0b00000001;
+pub const SQ_B: u8 = 0b00000010;
+pub const SQ_N: u8 = 0b00000100;
+pub const SQ_R: u8 = 0b00001000;
+pub const SQ_Q: u8 = 0b00010000;
+pub const SQ_K: u8 = 0b00100000;
+
+// Piece color flags.
+pub const SQ_WH: u8 = 0b01000000;
+pub const SQ_BL: u8 = 0b10000000;
+
+// Piece flags helpers.
+pub const SQ_WH_P: u8 = SQ_WH|SQ_P;
+pub const SQ_WH_B: u8 = SQ_WH|SQ_B;
+pub const SQ_WH_N: u8 = SQ_WH|SQ_N;
+pub const SQ_WH_R: u8 = SQ_WH|SQ_R;
+pub const SQ_WH_Q: u8 = SQ_WH|SQ_Q;
+pub const SQ_WH_K: u8 = SQ_WH|SQ_K;
+pub const SQ_BL_P: u8 = SQ_BL|SQ_P;
+pub const SQ_BL_B: u8 = SQ_BL|SQ_B;
+pub const SQ_BL_N: u8 = SQ_BL|SQ_N;
+pub const SQ_BL_R: u8 = SQ_BL|SQ_R;
+pub const SQ_BL_Q: u8 = SQ_BL|SQ_Q;
+pub const SQ_BL_K: u8 = SQ_BL|SQ_K;
+
+#[inline]
+pub fn has_flag(i: u8, flag: u8) -> bool { i & flag == flag }
+
+// Wrappers for clearer naming.
+#[inline]
+pub fn is_piece(square: u8, piece: u8) -> bool { has_flag(square, piece) }
+#[inline]
+pub fn is_color(square: u8, color: u8) -> bool { has_flag(square, color) }
+#[inline]
+pub fn is_white(square: u8) -> bool { is_color(square, SQ_WH) }
+#[inline]
+pub fn is_black(square: u8) -> bool { is_color(square, SQ_BL) }
+
+pub const POS_MIN: i8 = 0;
+pub const POS_MAX: i8 = 7;
+/// Coords (file, rank) of a square on a board, both components are in [0, 7].
+pub type Pos = (i8, i8);
+
+#[inline]
+pub fn is_valid_pos_c(component: i8) -> bool { component >= 0 && component <= 7 }
+
+#[inline]
+pub fn is_valid_pos(pos: Pos) -> bool { is_valid_pos_c(pos.0) && is_valid_pos_c(pos.1) }
+
+/// Convert string coordinates to Pos.
+///
+/// `s` has to be valid UTF8, or the very least ASCII because chars
+/// are interpreted as raw bytes.
+#[inline]
+pub fn pos(s: &str) -> Pos {
+    let chars = s.as_bytes();
+    ((chars[0] - 0x61) as i8, (chars[1] - 0x31) as i8)
+}
+
+/// Bitboard representation of a chess board.
+///
+/// 64 squares, from A1, A2 to H7, H8. A square is an u8, with bits
+/// defining the state of the square.
+pub type Board = [u8; 64];
+
+pub fn new() -> Board {
+    [
+        /*            1        2     3     4     5     6        7        8 */
+        /* A */ SQ_WH_R, SQ_WH_P, SQ_E, SQ_E, SQ_E, SQ_E, SQ_BL_P, SQ_BL_R,
+        /* B */ SQ_WH_N, SQ_WH_P, SQ_E, SQ_E, SQ_E, SQ_E, SQ_BL_P, SQ_BL_N,
+        /* C */ SQ_WH_B, SQ_WH_P, SQ_E, SQ_E, SQ_E, SQ_E, SQ_BL_P, SQ_BL_B,
+        /* D */ SQ_WH_Q, SQ_WH_P, SQ_E, SQ_E, SQ_E, SQ_E, SQ_BL_P, SQ_BL_Q,
+        /* E */ SQ_WH_K, SQ_WH_P, SQ_E, SQ_E, SQ_E, SQ_E, SQ_BL_P, SQ_BL_K,
+        /* F */ SQ_WH_B, SQ_WH_P, SQ_E, SQ_E, SQ_E, SQ_E, SQ_BL_P, SQ_BL_B,
+        /* G */ SQ_WH_N, SQ_WH_P, SQ_E, SQ_E, SQ_E, SQ_E, SQ_BL_P, SQ_BL_N,
+        /* H */ SQ_WH_R, SQ_WH_P, SQ_E, SQ_E, SQ_E, SQ_E, SQ_BL_P, SQ_BL_R,
+    ]
+}
+
+pub fn new_empty() -> Board {
+    [SQ_E; 64]
+}
+
+#[inline]
+pub fn get_square(board: &Board, coords: Pos) -> u8 {
+    board[(coords.0 * 8 + coords.1) as usize]
+}
+
+#[inline]
+pub fn set_square(board: &mut Board, coords: Pos, piece: u8) {
+    board[(coords.0 * 8 + coords.1) as usize] = piece;
+}
+
+#[inline]
+pub fn clear_square(board: &mut Board, coords: Pos) {
+    set_square(board, coords, SQ_E);
+}
+
+#[inline]
+pub fn is_empty(board: &Board, coords: Pos) -> bool { get_square(board, coords) == SQ_E }
+
+/// A movement, with before/after positions.
+pub type Move = (Pos, Pos);
+
+pub fn draw(board: &Board) {
+    for r in (0..8).rev() {
+        let mut rank = String::with_capacity(8);
+        for f in 0..8 {
+            let s = get_square(board, (f, r));
+            let piece =
+                if is_piece(s, SQ_P) { 'p' }
+                else if is_piece(s, SQ_B) { 'b' }
+                else if is_piece(s, SQ_N) { 'n' }
+                else if is_piece(s, SQ_R) { 'r' }
+                else if is_piece(s, SQ_Q) { 'q' }
+                else if is_piece(s, SQ_K) { 'k' }
+                else { '.' };
+            let piece = if is_color(s, SQ_WH) { piece.to_ascii_uppercase() } else { piece };
+            rank.push(piece);
+        }
+        println!("{}", rank);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_pos() {
+        assert_eq!(pos("a1"), (0, 0));
+        assert_eq!(pos("a2"), (0, 1));
+        assert_eq!(pos("a8"), (0, 7));
+        assert_eq!(pos("b1"), (1, 0));
+        assert_eq!(pos("h8"), (7, 7));
+    }
+
+    #[test]
+    fn test_get_square() {
+        let b = new();
+        assert_eq!(get_square(&b, pos("a1")), SQ_WH_R);
+        assert_eq!(get_square(&b, pos("a2")), SQ_WH_P);
+        assert_eq!(get_square(&b, pos("a3")), SQ_E);
+
+        assert_eq!(get_square(&b, pos("a7")), SQ_BL_P);
+        assert_eq!(get_square(&b, pos("a8")), SQ_BL_R);
+
+        assert_eq!(get_square(&b, pos("d1")), SQ_WH_Q);
+        assert_eq!(get_square(&b, pos("d8")), SQ_BL_Q);
+        assert_eq!(get_square(&b, pos("e1")), SQ_WH_K);
+        assert_eq!(get_square(&b, pos("e8")), SQ_BL_K);
+    }
+
+    #[test]
+    fn test_is_empty() {
+        let b = new();
+        assert_eq!(is_empty(&b, pos("a1")), false);
+        assert_eq!(is_empty(&b, pos("a2")), false);
+        assert_eq!(is_empty(&b, pos("a3")), true);
+    }
+}
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..5245eac
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,7 @@
+pub mod board;
+pub mod rules;
+
+fn main() {
+    let b = board::new();
+    board::draw(&b);
+}
diff --git a/src/rules.rs b/src/rules.rs
new file mode 100644
index 0000000..8aff838
--- /dev/null
+++ b/src/rules.rs
@@ -0,0 +1,311 @@
+//! Functions to determine legal moves.
+
+use crate::board::*;
+
+/// Get a list of legal moves for all pieces of either white or black.
+pub fn get_legal_player_moves(board: &Board, color: u8) -> Vec<Move> {
+    let mut moves = vec!();
+    for r in 0..8 {
+        for f in 0..8 {
+            if is_color(get_square(board, (f, r)), color) {
+                moves.append(&mut get_legal_piece_moves(board, (f, r)));
+            }
+        }
+    }
+    moves
+}
+
+/// Get a list of legal moves for the piece at position `at`.
+pub fn get_legal_piece_moves(board: &Board, at: Pos) -> Vec<Move> {
+    match get_square(board, at) {
+        p if is_piece(p, SQ_P) => get_legal_pawn_moves(board, at, p),
+        p if is_piece(p, SQ_B) => get_legal_bishop_moves(board, at, p),
+        p if is_piece(p, SQ_N) => get_legal_knight_moves(board, at, p),
+        p if is_piece(p, SQ_R) => get_legal_rook_moves(board, at, p),
+        p if is_piece(p, SQ_Q) => get_legal_queen_moves(board, at, p),
+        p if is_piece(p, SQ_K) => get_legal_king_moves(board, at, p),
+        _ => vec!(),
+    }
+}
+
+fn get_legal_pawn_moves(board: &Board, at: Pos, piece: u8) -> Vec<Move> {
+    let (f, r) = at;
+    let mut moves = vec!();
+    let movement: i8 = if is_white(piece) { 1 } else { -1 };
+    // Check 1 or 2 square forward.
+    let move_len = if (is_white(piece) && r == 1) || (is_black(piece) && r == 6) { 2 } else { 1 };
+    for i in 1..=move_len {
+        let forward_r = r + movement * i;
+        if movement > 0 && forward_r > POS_MAX {
+            return moves
+        }
+        if movement < 0 && forward_r < POS_MIN {
+            return moves
+        }
+        let forward: Pos = (f, forward_r);
+        if is_empty(board, forward) {
+            moves.push((at, forward))
+        }
+        // Check diagonals for pieces to attack.
+        if i == 1 {
+            let df = f - 1;
+            if df >= POS_MIN {
+                let diag: Pos = (df, forward_r);
+                if let Some(m) = move_on_enemy(piece, at, get_square(board, diag), diag) {
+                    moves.push(m);
+                }
+            }
+            let df = f + 1;
+            if df <= POS_MAX {
+                let diag: Pos = (df, forward_r);
+                if let Some(m) = move_on_enemy(piece, at, get_square(board, diag), diag) {
+                    moves.push(m);
+                }
+            }
+        }
+        // TODO en passant
+    }
+    moves
+}
+
+fn get_legal_bishop_moves(board: &Board, at: Pos, piece: u8) -> Vec<Move> {
+    let (f, r) = at;
+    let mut sight = [true; 4];  // Store diagonals where a piece blocks sight.
+    let mut moves = vec!();
+    for dist in 1..=7 {
+        for (dir, offset) in [(1, -1), (1, 1), (-1, 1), (-1, -1)].iter().enumerate() {
+            if !sight[dir] {
+                continue
+            }
+            let p = (f + offset.0 * dist, r + offset.1 * dist);
+            if !is_valid_pos(p) {
+                continue
+            }
+            if is_empty(board, p) {
+                moves.push((at, p));
+            } else {
+                if let Some(m) = move_on_enemy(piece, at, get_square(board, p), p) {
+                    moves.push(m);
+                }
+                sight[dir] = false;  // Stop looking in that direction.
+            }
+        }
+    }
+    moves
+}
+
+fn get_legal_knight_moves(board: &Board, at: Pos, piece: u8) -> Vec<Move> {
+    let (f, r) = at;
+    let mut moves = vec!();
+    for offset in [(1, 2), (2, 1), (2, -1), (1, -2), (-1, -2), (-2, -1), (-2, 1), (-1, 2)].iter() {
+        let p = (f + offset.0, r + offset.1);
+        if !is_valid_pos(p) {
+            continue
+        }
+        if is_empty(board, p) {
+            moves.push((at, p));
+        } else if let Some(m) = move_on_enemy(piece, at, get_square(board, p), p) {
+            moves.push(m);
+        }
+    }
+    moves
+}
+
+fn get_legal_rook_moves(board: &Board, at: Pos, piece: u8) -> Vec<Move> {
+    let (f, r) = at;
+    let mut moves = vec!();
+    let mut sight = [true; 4];  // Store lines where a piece blocks sight.
+    for dist in 1..=7 {
+        for (dir, offset) in [(0, 1), (1, 0), (0, -1), (-1, 0)].iter().enumerate() {
+            if !sight[dir] {
+                continue
+            }
+            let p = (f + offset.0 * dist, r + offset.1 * dist);
+            if !is_valid_pos(p) {
+                continue
+            }
+            if is_empty(board, p) {
+                moves.push((at, p));
+            } else {
+                if let Some(m) = move_on_enemy(piece, at, get_square(board, p), p) {
+                    moves.push(m);
+                }
+                sight[dir] = false;  // Stop looking in that direction.
+            }
+        }
+    }
+    moves
+}
+
+fn get_legal_queen_moves(board: &Board, at: Pos, piece: u8) -> Vec<Move> {
+    let mut moves = vec!();
+    // Easy way to get queen moves, but may be a bit quicker if everything was rewritten here.
+    moves.append(&mut get_legal_bishop_moves(board, at, piece));
+    moves.append(&mut get_legal_rook_moves(board, at, piece));
+    moves
+}
+
+fn get_legal_king_moves(board: &Board, at: Pos, piece: u8) -> Vec<Move> {
+    let (f, r) = at;
+    let mut moves = vec!();
+    for offset in [(-1, 1), (0, 1), (1, 1), (-1, 0), (1, 0), (-1, -1), (0, -1), (1, -1)].iter() {
+        let p = (f + offset.0, r + offset.1);
+        if !is_valid_pos(p) {
+            continue
+        }
+        if is_empty(board, p) {
+            moves.push((at, p));
+        } else if let Some(m) = move_on_enemy(piece, at, get_square(board, p), p) {
+            moves.push(m);
+        }
+    }
+    // TODO castling
+    moves
+}
+
+/// Return a move from pos1 to pos2 if piece1 & piece2 are enemies.
+fn move_on_enemy(piece1: u8, pos1: Pos, piece2: u8, pos2: Pos) -> Option<Move> {
+    if (is_white(piece1) && is_black(piece2)) || (is_black(piece1) && is_white(piece2)) {
+        Some((pos1, pos2))
+    } else {
+        None
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_get_legal_player_moves() {
+        let b = new();
+        // At first move, white has 16 pawn moves and 4 knight moves.
+        let moves = get_legal_player_moves(&b, SQ_WH);
+        assert_eq!(moves.len(), 20);
+    }
+
+    #[test]
+    fn test_get_legal_pawn_moves() {
+        let mut b = new_empty();
+
+        // Check that a pawn (here white queen's pawn) can move forward if the road is free.
+        set_square(&mut b, pos("d3"), SQ_WH_P);
+        let moves = get_legal_piece_moves(&b, pos("d3"));
+        assert!(moves.len() == 1 && moves.contains( &(pos("d3"), pos("d4")) ));
+
+        // Check that a pawn (here white king's pawn) can move 2 square forward on first move.
+        set_square(&mut b, pos("e2"), SQ_WH_P);
+        let moves = get_legal_piece_moves(&b, pos("e2"));
+        assert_eq!(moves.len(), 2);
+        assert!(moves.contains( &(pos("e2"), pos("e3")) ));
+        assert!(moves.contains( &(pos("e2"), pos("e4")) ));
+
+        // Check that a pawn cannot move forward if a piece is blocking its path.
+        // 1. black pawn 2 square forward:
+        set_square(&mut b, pos("e4"), SQ_BL_P);
+        let moves = get_legal_piece_moves(&b, pos("e2"));
+        assert!(moves.len() == 1 && moves.contains( &(pos("e2"), pos("e3")) ));
+        // 2. black pawn 1 square forward:
+        set_square(&mut b, pos("e3"), SQ_BL_P);
+        let moves = get_legal_piece_moves(&b, pos("e2"));
+        assert_eq!(moves.len(), 0);
+
+        // Check that a pawn can take a piece diagonally.
+        set_square(&mut b, pos("f3"), SQ_BL_P);
+        let moves = get_legal_piece_moves(&b, pos("e2"));
+        assert!(moves.len() == 1 && moves.contains( &(pos("e2"), pos("f3")) ));
+        set_square(&mut b, pos("d3"), SQ_BL_P);
+        let moves = get_legal_piece_moves(&b, pos("e2"));
+        assert_eq!(moves.len(), 2);
+        assert!(moves.contains( &(pos("e2"), pos("f3")) ));
+        assert!(moves.contains( &(pos("e2"), pos("d3")) ));
+    }
+
+    #[test]
+    fn test_get_legal_bishop_moves() {
+        let mut b = new_empty();
+
+        // A bishop has maximum range when it's in a center square.
+        set_square(&mut b, pos("d4"), SQ_WH_B);
+        let moves = get_legal_piece_moves(&b, pos("d4"));
+        assert_eq!(moves.len(), 13);
+        // Going top-right.
+        assert!(moves.contains( &(pos("d4"), pos("e5")) ));
+        assert!(moves.contains( &(pos("d4"), pos("f6")) ));
+        assert!(moves.contains( &(pos("d4"), pos("g7")) ));
+        assert!(moves.contains( &(pos("d4"), pos("h8")) ));
+        // Going bottom-right.
+        assert!(moves.contains( &(pos("d4"), pos("e3")) ));
+        assert!(moves.contains( &(pos("d4"), pos("f2")) ));
+        assert!(moves.contains( &(pos("d4"), pos("g1")) ));
+        // Going bottom-left.
+        assert!(moves.contains( &(pos("d4"), pos("c3")) ));
+        assert!(moves.contains( &(pos("d4"), pos("b2")) ));
+        assert!(moves.contains( &(pos("d4"), pos("a1")) ));
+        // Going top-left.
+        assert!(moves.contains( &(pos("d4"), pos("c5")) ));
+        assert!(moves.contains( &(pos("d4"), pos("b6")) ));
+        assert!(moves.contains( &(pos("d4"), pos("a7")) ));
+
+        // When blocking sight to one square with friendly piece, lose 2 moves.
+        set_square(&mut b, pos("b2"), SQ_WH_P);
+        assert_eq!(get_legal_piece_moves(&b, pos("d4")).len(), 11);
+
+        // When blocking sight to one square with enemy piece, lose only 1 move.
+        set_square(&mut b, pos("b2"), SQ_BL_P);
+        assert_eq!(get_legal_piece_moves(&b, pos("d4")).len(), 12);
+    }
+
+    #[test]
+    fn test_get_legal_knight_moves() {
+        let mut b = new_empty();
+
+        // A knight never has blocked sight; if it's in the center of the board, it can have up to
+        // 8 moves.
+        set_square(&mut b, pos("d4"), SQ_WH_N);
+        assert_eq!(get_legal_piece_moves(&b, pos("d4")).len(), 8);
+
+        // If on a side if has only 4 moves.
+        set_square(&mut b, pos("a4"), SQ_WH_N);
+        assert_eq!(get_legal_piece_moves(&b, pos("a4")).len(), 4);
+
+        // And in a corner, only 2 moves.
+        set_square(&mut b, pos("a1"), SQ_WH_N);
+        assert_eq!(get_legal_piece_moves(&b, pos("a1")).len(), 2);
+
+        // Add 2 friendly pieces and it is totally blocked.
+        set_square(&mut b, pos("b3"), SQ_WH_P);
+        set_square(&mut b, pos("c2"), SQ_WH_P);
+        assert_eq!(get_legal_piece_moves(&b, pos("a1")).len(), 0);
+    }
+
+    #[test]
+    fn test_get_legal_rook_moves() {
+        let mut b = new_empty();
+
+        set_square(&mut b, pos("d4"), SQ_WH_R);
+        assert_eq!(get_legal_piece_moves(&b, pos("d4")).len(), 14);
+        set_square(&mut b, pos("d6"), SQ_BL_P);
+        assert_eq!(get_legal_piece_moves(&b, pos("d4")).len(), 12);
+        set_square(&mut b, pos("d6"), SQ_WH_P);
+        assert_eq!(get_legal_piece_moves(&b, pos("d4")).len(), 11);
+    }
+
+    #[test]
+    fn test_get_legal_queen_moves() {
+        let mut b = new_empty();
+
+        set_square(&mut b, pos("d4"), SQ_WH_Q);
+        assert_eq!(get_legal_piece_moves(&b, pos("d4")).len(), 14 + 13);  // Bishop + rook moves.
+    }
+
+    #[test]
+    fn test_get_legal_king_moves() {
+        let mut b = new_empty();
+
+        set_square(&mut b, pos("d4"), SQ_WH_K);
+        assert_eq!(get_legal_piece_moves(&b, pos("d4")).len(), 8);
+        set_square(&mut b, pos("e5"), SQ_WH_P);
+        assert_eq!(get_legal_piece_moves(&b, pos("d4")).len(), 7);
+    }
+}