+ const color = this.turn;
+ let moves = this.getAllValidMoves();
+ for (let move of moves) {
+ move.eval = 0; //a priori...
+
+ // Can I take something ? If yes, do it with some probability
+ if (move.vanish.length == 2 && move.vanish[1].c != color) {
+ // OK this isn't a castling move
+ const myPieceVal = V.VALUES[move.appear[0].p];
+ const hisPieceVal =
+ Object.keys(V.HIDDEN_DECODE).includes(move.vanish[1].p)
+ ? undefined
+ : V.VALUES[move.vanish[1].p];
+ if (!hisPieceVal) {
+ // Opponent's piece is unknown: do not take too much risk
+ move.eval = -myPieceVal + 1.5; //so that pawns always take
+ }
+ // Favor captures
+ else if (myPieceVal <= hisPieceVal)
+ move.eval = hisPieceVal - myPieceVal + 1;
+ else {
+ // Taking a pawn with minor piece,
+ // or minor piece or pawn with a rook,
+ // or anything but a queen with a queen,
+ // or anything with a king.
+ move.eval = hisPieceVal - myPieceVal;
+ }
+ } else {
+ // If no capture, favor small step moves,
+ // but sometimes move the knight anyway
+ const penalty = V.Decode(move.vanish[0].p) != V.KNIGHT
+ ? Math.abs(move.end.x - move.start.x) +
+ Math.abs(move.end.y - move.start.y)
+ : (Math.random() < 0.5 ? 3 : 1);
+ move.eval -= penalty / (V.size.x + V.size.y - 1);
+ }
+
+ // TODO: also favor movements toward the center?
+ }
+
+ moves.sort((a, b) => b.eval - a.eval);
+ let candidates = [0];
+ for (let j = 1; j < moves.length && moves[j].eval == moves[0].eval; j++)
+ candidates.push(j);
+ return moves[candidates[randInt(candidates.length)]];