From ef61e7a56876a06d8542721881dbcc88a86e85c3 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Fri, 29 Jul 2016 03:41:55 +0900
Subject: [PATCH] examples/2048: Bug fix: Should not add a new tile when no
 tiles are moved

---
 examples/2048/2048/board.go      | 13 ++++++++++---
 examples/2048/2048/board_test.go |  3 ++-
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/examples/2048/2048/board.go b/examples/2048/2048/board.go
index 1207f4669..fe0032656 100644
--- a/examples/2048/2048/board.go
+++ b/examples/2048/2048/board.go
@@ -81,7 +81,7 @@ func (b *Board) tileAt(x, y int) *Tile {
 	return tileAt(b.tiles, x, y)
 }
 
-func MoveTiles(tiles map[*Tile]struct{}, size int, dir Dir) map[*Tile]struct{} {
+func MoveTiles(tiles map[*Tile]struct{}, size int, dir Dir) (map[*Tile]struct{}, bool) {
 	vx, vy := dir.Vector()
 	tx := []int{}
 	ty := []int{}
@@ -98,6 +98,7 @@ func MoveTiles(tiles map[*Tile]struct{}, size int, dir Dir) map[*Tile]struct{} {
 
 	nextTiles := map[*Tile]struct{}{}
 	merged := map[*Tile]bool{}
+	moved := false
 	for _, j := range ty {
 		for _, i := range tx {
 			t := tileAt(tiles, i, j)
@@ -116,6 +117,7 @@ func MoveTiles(tiles map[*Tile]struct{}, size int, dir Dir) map[*Tile]struct{} {
 				if tt == nil {
 					ii = ni
 					jj = nj
+					moved = true
 					continue
 				}
 				if t.value != tt.value {
@@ -124,6 +126,7 @@ func MoveTiles(tiles map[*Tile]struct{}, size int, dir Dir) map[*Tile]struct{} {
 				if !merged[tt] {
 					ii = ni
 					jj = nj
+					moved = true
 				}
 				break
 			}
@@ -137,11 +140,15 @@ func MoveTiles(tiles map[*Tile]struct{}, size int, dir Dir) map[*Tile]struct{} {
 			nextTiles[t] = struct{}{}
 		}
 	}
-	return nextTiles
+	return nextTiles, moved
 }
 
 func (b *Board) Move(dir Dir) {
-	b.tiles = MoveTiles(b.tiles, b.size, dir)
+	moved := false
+	b.tiles, moved = MoveTiles(b.tiles, b.size, dir)
+	if !moved {
+		return
+	}
 	b.addRandomTile()
 }
 
diff --git a/examples/2048/2048/board_test.go b/examples/2048/2048/board_test.go
index 07f93f446..5a3c1c3c0 100644
--- a/examples/2048/2048/board_test.go
+++ b/examples/2048/2048/board_test.go
@@ -191,7 +191,8 @@ func TestMoveTiles(t *testing.T) {
 	for _, test := range testCases {
 		tiles := cellsToTiles(test.Input, size)
 		want := tilesToCells(cellsToTiles(test.Want, size), size)
-		got := tilesToCells(MoveTiles(tiles, size, test.Dir), size)
+		gotTiles, _ := MoveTiles(tiles, size, test.Dir)
+		got := tilesToCells(gotTiles, size)
 		if fmt.Sprint(got) != fmt.Sprint(want) {
 			t.Errorf("dir: %s, input: %v, got %v; want %v", test.Dir.String(), test.Input, got, want)
 		}