Added basic rules

script.js

@@ -28,6 +28,7 @@ const COLOR_PIECE_WHITE = '#fff';
 const game = {
     state: '',
     stateData: {},
+    turn: 'black',
     pieces: [
         {position: 'A1', color: 'black', isKing: false},
         {position: 'A3', color: 'black', isKing: false},
@@ -88,6 +89,7 @@ function gameUpdate() {
 }
 
 function moveStart(position) {
+    if (!getPieceByPosition(position)) return;
     if (game.state == 'moving') return;
 
     game.state = 'moving';
@@ -105,7 +107,13 @@ function moveGoing(x, y) {
 function moveEnd(position) {
     if (game.state != 'moving') return;
 
+    if (move(game.stateData.piece, game.stateData.originalPosition, position)) {
         game.stateData.piece.position = position;
+        becomeKing(game.stateData.piece);
+        nextTurn();
+    } else {
+        game.stateData.piece.position = game.stateData.originalPosition;
+    }
     game.stateData = {};
     game.state = 'waiting';
     gameUpdate();
@@ -121,6 +129,46 @@ function getPieceIndexByPosition(position) {
     }).indexOf(position);
 }
 
+// Rules
+
+function move(piece, oldPosition, newPosition) {
+    if (piece.color != game.turn) return false;
+    if (getPieceByPosition(newPosition)) return false;
+
+    var ox = oldPosition.charCodeAt(0);
+    var oy = oldPosition.charCodeAt(1);
+    var nx = newPosition.charCodeAt(0);
+    var ny = newPosition.charCodeAt(1);
+
+    return piece.color == 'black' && (ny - oy) == 1 && Math.abs(nx - ox) == 1
+        || piece.color == 'black' && (ny - oy) == 2 && Math.abs(nx - ox) == 2 && beat(piece, fromCharCodes((ox+nx)/2, (oy+ny)/2))
+        || piece.color == 'white' && (oy - ny) == 1 && Math.abs(nx - ox) == 1
+        || piece.color == 'white' && (oy - ny) == 2 && Math.abs(nx - ox) == 2 && beat(piece, fromCharCodes((ox+nx)/2, (oy+ny)/2))
+        || piece.isKing && piece.color == 'black' && Math.abs(ny - oy) == 1 && Math.abs(nx - ox) == 1
+        || piece.isKing && piece.color == 'black' && Math.abs(ny - oy) == 2 && Math.abs(nx - ox) == 2 && beat(piece, fromCharCodes((ox+nx)/2, (oy+ny)/2))
+        || piece.isKing && piece.color == 'white' && Math.abs(oy - ny) == 1 && Math.abs(nx - ox) == 1
+        || piece.isKing && piece.color == 'white' && Math.abs(oy - ny) == 2 && Math.abs(nx - ox) == 2 && beat(piece, fromCharCodes((ox+nx)/2, (oy+ny)/2));
+}
+
+function beat(piece, position) {
+    var index = getPieceIndexByPosition(position);
+    if (!~index) return false;
+    if (piece.color == game.pieces[index].color) return false;
+    game.pieces.splice(index, 1);
+    return true;
+}
+
+function becomeKing(piece) {
+    piece.isKing = piece.isKing
+        || piece.color == 'black' && piece.position[1] == '8'
+        || piece.color == 'white' && piece.position[1] == '1';
+}
+
+function nextTurn() {
+    game.turn = game.turn == 'black' ? 'white' : 'black';
+    console.log(game.turn);
+}
+
 // Graphics
 
 function init() {
@@ -230,3 +278,13 @@ function getPositionByCoordinates(x, y) {
 
     return String.fromCharCode(col + 65) + String.fromCharCode((7-row) + 49);
 }
+
+// Utils
+
+function fromCharCodes() {
+    var s = '';
+    for (var i = 0; i < arguments.length; i++) {
+        s += String.fromCharCode(arguments[i]);
+    }
+    return s;
+}