Checkmate detection

Author: Aversefun

README.md

@@ -1,15 +1,19 @@
 # X3139 Chess
 
 15 sliding puzzle, but chess! Inspired by [xkcd 3139](https://xkcd.com/3139). Currently supports most chess features, including:
+
 - Castling
 - En passant
 - Showing available moves
 - Requiring you to get out of check if you are in check
+- Checkmate detection (working on)
 
 Stuff that will be implemented Soon :tm::
-- Checkmate detection (working on)
+
+- nothing, make an issue if you have a suggestion
 
 Stuff that will probably never be implemented:
+
 - Pawn promotion - pawns are still useful after they reach the back rank because of the tiles, and because of the tiles it's easier to get them to the back rank
 
 If you like this, please star on github!

index.ts

@@ -376,24 +376,26 @@ function get_allowed_moves(piece: [Piece, Color], from: Square, ignore_check: bo
       allowed_movements.push([1, 0], [0, 1], [-1, 0], [0, -1]);
       allowed_movements.push([1, 1], [-1, -1], [1, -1], [-1, 1]);
 
-      switch (piece[1]) {
-        case Color.White:
-          if (!moved_pieces[7][7]) {
-            movement_dirs[MoveDirection.Right].push([2, 0]);
-          }
-          if (!moved_pieces[7][0]) {
-            movement_dirs[MoveDirection.Left].push([-2, 0]);
-          }
-          break;
+      if (!moved_pieces[from[1]][from[0]]) {
+        switch (piece[1]) {
+          case Color.White:
+            if (!moved_pieces[7][7]) {
+              movement_dirs[MoveDirection.Right].push([2, 0]);
+            }
+            if (!moved_pieces[7][0]) {
+              movement_dirs[MoveDirection.Left].push([-2, 0]);
+            }
+            break;
 
-        case Color.Black:
-          if (!moved_pieces[0][7]) {
-            movement_dirs[MoveDirection.Right].push([2, 0]);
-          }
-          if (!moved_pieces[0][0]) {
-            movement_dirs[MoveDirection.Left].push([-2, 0]);
-          }
-          break;
+          case Color.Black:
+            if (!moved_pieces[0][7]) {
+              movement_dirs[MoveDirection.Right].push([2, 0]);
+            }
+            if (!moved_pieces[0][0]) {
+              movement_dirs[MoveDirection.Left].push([-2, 0]);
+            }
+            break;
+        }
       }
       break;
   }
@@ -461,6 +463,15 @@ function in_check(color: Color, after_move: [Piece, Square, Square] | null = nul
   return moves.length > 0;
 }
 
+function in_checkmate(color: Color): boolean {
+  const moves = find_pieces((piece) => piece[0] !== null && piece[0][1] === color)
+    .map((v) => {
+      return get_allowed_moves(v![0], v![1], false, true);
+    });
+  return (in_check(color) && moves
+    .reduce<Square[]>((accumulator, value) => accumulator.concat(value), []).length == 0) || moves.length == 0;
+}
+
 function get_tile_squares(tile: Tile): FixedLengthArray<Square, 4> {
   const base: Square = [tile[0] * 2, tile[1] * 2];
   return [
@@ -483,6 +494,7 @@ function offset_to_square(pos: CanvasPosition): Tile {
 
 var squareToMove: Square | null = null;
 var active = false;
+var checkmate = false;
 var can_move_all = false;
 var move_piece_and_tile = false;
 
@@ -555,7 +567,9 @@ function draw_turn() {
   ctx.strokeRect(635, 275, 50, 50);
 
   ctx.fillStyle = ctx.strokeStyle;
-  if (!active) {
+  if (checkmate) {
+    ctx.fillText("Checkmate", 660, 350, 100);
+  } else if (!active) {
     ctx.fillText("Start", 660, 350, 100);
     ctx.fillText("the game", 660, 365, 100);
   } else if (turn === Color.Black) {
@@ -624,6 +638,11 @@ function switch_turn() {
   has_moved_tile = false;
   indicators = [];
   show_tile_indicator = false;
+
+  if (in_checkmate(turn)) {
+    checkmate = true;
+    turn = Color.opposite(turn);
+  }
 }
 
 tick(0);