From b81e3c8b21ba1e40895938a833b74670ab57bd1b Mon Sep 17 00:00:00 2001
From: NatureFreshMilk <naturefreshmilk@github.com>
Date: Thu, 17 Jan 2019 15:37:33 +0100
Subject: [PATCH] speed improvement

---
 db/sqlite.go             | 32 ++++++++++++++++----------------
 tilerenderer/renderer.go | 27 +++++++++++++++++++++++++--
 2 files changed, 41 insertions(+), 18 deletions(-)

diff --git a/db/sqlite.go b/db/sqlite.go
index dfb554f..cdac3d9 100644
--- a/db/sqlite.go
+++ b/db/sqlite.go
@@ -104,28 +104,28 @@ func (db *Sqlite3Accessor) GetBlock(pos coords.MapBlockCoords) (*Block, error) {
 	return nil, nil
 }
 
+func sortAsc(a, b int) (int, int){
+	if a > b {
+		return b, a
+	} else {
+		return a, b
+	}
+}
 
 func (db *Sqlite3Accessor) CountBlocks(pos1 coords.MapBlockCoords, pos2 coords.MapBlockCoords) (int, error){
 
 	poslist := make([]interface{}, 0)
 
-	if pos1.X != pos2.X {
-		return 0, errors.New("x does not line up")
-	}
+	minX, maxX := sortAsc(pos1.X, pos2.X)
+	minY, maxY := sortAsc(pos1.Y, pos2.Y)
+	minZ, maxZ := sortAsc(pos1.Z, pos2.Z)
 
-	if pos1.Z != pos2.Z {
-		return 0, errors.New("z does not line up")
-	}
-
-	minY := pos1.Y
-	maxY := pos2.Y
-
-	if minY > maxY {
-		minY, maxY = maxY, minY
-	}
-
-	for y := minY; y <= maxY; y++ {
-		poslist = append(poslist, coords.CoordToPlain(coords.NewMapBlockCoords(pos1.X, y, pos1.Z)))
+	for x := minX; x <= maxX; x++ {
+		for y := minY; y <= maxY; y++ {
+			for z := minZ; z <= maxZ; z++ {
+				poslist = append(poslist, coords.CoordToPlain(coords.NewMapBlockCoords(x,y,z)))
+			}
+		}
 	}
 
 	getBlocksQuery := "select count(*) from blocks b where b.pos in (?" + strings.Repeat(",?", len(poslist)-1) + ")"
diff --git a/tilerenderer/renderer.go b/tilerenderer/renderer.go
index 14f1660..d01623d 100644
--- a/tilerenderer/renderer.go
+++ b/tilerenderer/renderer.go
@@ -55,6 +55,11 @@ func (tr *TileRenderer) Render(tc coords.TileCoords) ([]byte, error) {
 			return nil, err
 		}
 
+		if img == nil {
+			//empty tile
+			return nil, nil
+		}
+
 		buf := new(bytes.Buffer)
 		png.Encode(buf, img)
 
@@ -95,12 +100,17 @@ func (tr *TileRenderer) RenderImage(tc coords.TileCoords) (*image.NRGBA, error)
 		return nil, errors.New("No layer found")
 	}
 
+	if tc.Zoom > 13 || tc.Zoom < 1 {
+		return nil, errors.New("Invalid zoom")
+	}
+
 	if tc.Zoom == 13 {
 		//max zoomed in on mapblock level
 		mbr := coords.GetMapBlockRangeFromTile(tc, 0)
 		mbr.Pos1.Y = layer.From
 		mbr.Pos2.Y = layer.To
 
+		//count blocks
 		count, err := tr.dba.CountBlocks(mbr.Pos1, mbr.Pos2)
 
 		if err != nil {
@@ -114,8 +124,21 @@ func (tr *TileRenderer) RenderImage(tc coords.TileCoords) (*image.NRGBA, error)
 		return tr.mapblockrenderer.Render(mbr.Pos1, mbr.Pos2)
 	}
 
-	if tc.Zoom > 13 || tc.Zoom < 1 {
-		return nil, errors.New("Invalid zoom")
+	if tc.Zoom == 12 {
+		//count blocks and ignore empty tiles
+		mbr := coords.GetMapBlockRangeFromTile(tc, 0)
+		mbr.Pos1.Y = layer.From
+		mbr.Pos2.Y = layer.To
+
+		count, err := tr.dba.CountBlocks(mbr.Pos1, mbr.Pos2)
+
+		if err != nil {
+			return nil, err
+		}
+
+		if count == 0 {
+			return nil, nil
+		}
 	}
 
 	//zoom 1-12