From 57b82de1e997f4c3de1bcacb5a8e3d442158234b Mon Sep 17 00:00:00 2001
From: Brandon Liu <bdon@bdon.org>
Date: Tue, 12 Sep 2023 17:19:33 +0800
Subject: [PATCH] mbtiles convert: default bounds to world if bounds metadata
 missing. [#60]

* error out if bounds is degenerate (zero or less area)
---
 pmtiles/convert.go      | 15 +++++++++++++++
 pmtiles/convert_test.go | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/pmtiles/convert.go b/pmtiles/convert.go
index 4abc492..7d076bb 100644
--- a/pmtiles/convert.go
+++ b/pmtiles/convert.go
@@ -578,6 +578,7 @@ func parse_center(center string) (int32, int32, uint8, error) {
 func mbtiles_to_header_json(mbtiles_metadata []string) (HeaderV3, map[string]interface{}, error) {
 	header := HeaderV3{}
 	json_result := make(map[string]interface{})
+	boundsSet := false
 	for i := 0; i < len(mbtiles_metadata); i += 2 {
 		value := mbtiles_metadata[i+1]
 		switch key := mbtiles_metadata[i]; key {
@@ -604,10 +605,15 @@ func mbtiles_to_header_json(mbtiles_metadata []string) (HeaderV3, map[string]int
 			if err != nil {
 				return header, json_result, err
 			}
+
+			if min_lon >= max_lon || min_lat >= max_lat {
+				return header, json_result, fmt.Errorf("Error: zero-area bounds in mbtiles metadata.")
+			}
 			header.MinLonE7 = min_lon
 			header.MinLatE7 = min_lat
 			header.MaxLonE7 = max_lon
 			header.MaxLatE7 = max_lat
+			boundsSet = true
 		case "center":
 			center_lon, center_lat, center_zoom, err := parse_center(value)
 			if err != nil {
@@ -637,5 +643,14 @@ func mbtiles_to_header_json(mbtiles_metadata []string) (HeaderV3, map[string]int
 			json_result[key] = value
 		}
 	}
+
+	E7 := 10000000.0
+	if !boundsSet {
+		header.MinLonE7 = int32(-180 * E7)
+		header.MinLatE7 = int32(-85 * E7)
+		header.MaxLonE7 = int32(180 * E7)
+		header.MaxLatE7 = int32(85 * E7)
+	}
+
 	return header, json_result, nil
 }
diff --git a/pmtiles/convert_test.go b/pmtiles/convert_test.go
index add93f8..0ce8464 100644
--- a/pmtiles/convert_test.go
+++ b/pmtiles/convert_test.go
@@ -175,3 +175,38 @@ func TestMbtiles(t *testing.T) {
 	_, ok = json_metadata["tilestats"]
 	assert.True(t, ok)
 }
+
+func TestMbtilesMissingBoundsCenter(t *testing.T) {
+	header, _, err := mbtiles_to_header_json([]string{
+		"name", "test_name",
+		"format", "pbf",
+		"attribution", "<div>abc</div>",
+		"description", "a description",
+		"type", "overlay",
+		"version", "1",
+		"json", "{\"vector_layers\":[{\"abc\":123}],\"tilestats\":{\"def\":456}}",
+		"compression", "gzip",
+	})
+	assert.Nil(t,err)
+	assert.Equal(t,int32(-180*10000000), header.MinLonE7)
+	assert.Equal(t,int32(-85*10000000), header.MinLatE7)
+	assert.Equal(t,int32(180*10000000), header.MaxLonE7)
+	assert.Equal(t,int32(85*10000000), header.MaxLatE7)
+	assert.Equal(t,int32(0), header.CenterLonE7)
+	assert.Equal(t,int32(0), header.CenterLatE7)
+}
+
+func TestMbtilesDegenerateBounds(t *testing.T) {
+	_, _, err := mbtiles_to_header_json([]string{
+		"name", "test_name",
+		"format", "pbf",
+		"bounds", "0,0,0,0",
+		"attribution", "<div>abc</div>",
+		"description", "a description",
+		"type", "overlay",
+		"version", "1",
+		"json", "{\"vector_layers\":[{\"abc\":123}],\"tilestats\":{\"def\":456}}",
+		"compression", "gzip",
+	})
+	assert.NotNil(t,err)
+}