New "feast" game mode (alpha)

feast.go

@@ -0,0 +1,41 @@
+package rules
+
+import ()
+
+type FeastRuleset struct {
+	StandardRuleset
+}
+
+func (r *FeastRuleset) CreateInitialBoardState(width int32, height int32, snakeIDs []string) (*BoardState, error) {
+	initialBoardState, err := r.StandardRuleset.CreateInitialBoardState(width, height, snakeIDs)
+	if err != nil {
+		return nil, err
+	}
+
+	err = r.fillBoardWithFood(initialBoardState)
+	if err != nil {
+		return nil, err
+	}
+
+	return initialBoardState, nil
+}
+
+func (r *FeastRuleset) CreateNextBoardState(prevState *BoardState, moves []SnakeMove) (*BoardState, error) {
+	nextState, err := r.StandardRuleset.CreateNextBoardState(prevState, moves)
+	if err != nil {
+		return nil, err
+	}
+
+	err = r.fillBoardWithFood(nextState)
+	if err != nil {
+		return nil, err
+	}
+
+	return nextState, nil
+}
+
+func (r *FeastRuleset) fillBoardWithFood(b *BoardState) error {
+	unoccupiedPoints := r.getUnoccupiedPoints(b, true)
+	b.Food = append(b.Food, unoccupiedPoints...)
+	return nil
+}