From a504840bd53bae142af7641bb25959dd1d083e4d Mon Sep 17 00:00:00 2001
From: Eric Fischer <enf@pobox.com>
Date: Wed, 1 Jun 2016 16:55:52 -0700
Subject: [PATCH] Warn if the GeoJSON specifies a different projection

---
 geojson.cpp    | 21 ++++++++++++++++++++-
 main.cpp       | 18 +++++++++---------
 main.hpp       |  2 --
 projection.hpp |  8 ++++++++
 4 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/geojson.cpp b/geojson.cpp
index 7531296..c2ef911 100644
--- a/geojson.cpp
+++ b/geojson.cpp
@@ -90,7 +90,7 @@ long long parse_geometry(int t, json_object *j, long long *bbox, long long *fpos
 			long long x, y;
 			double lon = j->array[0]->number;
 			double lat = j->array[1]->number;
-			projection(lon, lat, 32, &x, &y);
+			projection->project(lon, lat, 32, &x, &y);
 
 			if (j->length > 2) {
 				static int warned = 0;
@@ -405,6 +405,21 @@ int serialize_geometry(json_object *geometry, json_object *properties, const cha
 	return 1;
 }
 
+void check_crs(json_object *j, const char *reading) {
+	json_object *crs = json_hash_get(j, "crs");
+	if (crs != NULL) {
+		json_object *properties = json_hash_get(crs, "properties");
+		if (properties != NULL) {
+			json_object *name = json_hash_get(properties, "name");
+			if (name->type == JSON_STRING) {
+				if (strcmp(name->string, projection->alias) != 0) {
+					fprintf(stderr, "%s: Warning: GeoJSON specified projection \"%s\", not \"%s\".\n", reading, name->string, projection->alias);
+				}
+			}
+		}
+	}
+}
+
 void parse_json(json_pull *jp, const char *reading, volatile long long *layer_seq, volatile long long *progress_seq, long long *metapos, long long *geompos, long long *indexpos, std::set<std::string> *exclude, std::set<std::string> *include, int exclude_all, FILE *metafile, FILE *geomfile, FILE *indexfile, struct memfile *poolfile, struct memfile *treefile, char *fname, int basezoom, int layer, double droprate, long long *file_bbox, int segment, int *initialized, unsigned *initial_x, unsigned *initial_y, struct reader *readers, std::set<type_and_string> *file_keys, int maxzoom) {
 	long long found_hashes = 0;
 	long long found_features = 0;
@@ -476,6 +491,10 @@ void parse_json(json_pull *jp, const char *reading, volatile long long *layer_se
 			}
 		}
 
+		if (strcmp(type->string, "FeatureCollection") == 0) {
+			check_crs(j, reading);
+		}
+
 		if (strcmp(type->string, "Feature") != 0) {
 			continue;
 		}
diff --git a/main.cpp b/main.cpp
index 770ef1d..db7b716 100644
--- a/main.cpp
+++ b/main.cpp
@@ -58,7 +58,6 @@ int geometry_scale = 0;
 
 int prevent[256];
 int additional[256];
-void (*projection)(double ix, double iy, int zoom, long long *ox, long long *oy) = lonlat2tile;
 
 struct source {
 	std::string layer;
@@ -1706,17 +1705,14 @@ static bool has_name(struct option *long_options, int *pl) {
 	return false;
 }
 
-struct projection {
-	const char *name;
-	void (*project)(double ix, double iy, int zoom, long long *ox, long long *oy);
-};
-
 struct projection projections[] = {
-	{"EPSG:4326", lonlat2tile},
-	{"EPSG:3857", epsg3857totile},
+	{"EPSG:4326", lonlat2tile, "urn:ogc:def:crs:OGC:1.3:CRS84"},
+	{"EPSG:3857", epsg3857totile, "urn:ogc:def:crs:EPSG::3857"},
 	{NULL, NULL},
 };
 
+struct projection *projection = &projections[0];
+
 int main(int argc, char **argv) {
 #ifdef MTRACE
 	mtrace();
@@ -1995,7 +1991,11 @@ int main(int argc, char **argv) {
 			struct projection *p;
 			for (p = projections; p->name != NULL; p++) {
 				if (strcmp(p->name, optarg) == 0) {
-					projection = p->project;
+					projection = p;
+					break;
+				}
+				if (strcmp(p->alias, optarg) == 0) {
+					projection = p;
 					break;
 				}
 			}
diff --git a/main.hpp b/main.hpp
index 9e4c4ed..e842511 100644
--- a/main.hpp
+++ b/main.hpp
@@ -13,5 +13,3 @@ extern int quiet;
 
 extern int CPUS;
 extern int TEMP_FILES;
-
-extern void (*projection)(double ix, double iy, int zoom, long long *ox, long long *oy);
diff --git a/projection.hpp b/projection.hpp
index 8d18b2e..8543aaf 100644
--- a/projection.hpp
+++ b/projection.hpp
@@ -3,3 +3,11 @@ void epsg3857totile(double ix, double iy, int zoom, long long *x, long long *y);
 void tile2lonlat(long long x, long long y, int zoom, double *lon, double *lat);
 unsigned long long encode(unsigned int wx, unsigned int wy);
 void decode(unsigned long long index, unsigned *wx, unsigned *wy);
+
+struct projection {
+	const char *name;
+	void (*project)(double ix, double iy, int zoom, long long *ox, long long *oy);
+	const char *alias;
+};
+
+extern struct projection *projection;