From 0b4747177794d494ae9f2169afeec8293c3db59f Mon Sep 17 00:00:00 2001
From: Eric Fischer <enf@pobox.com>
Date: Fri, 9 Oct 2015 12:41:28 -0700
Subject: [PATCH] Most of the way to making decode output GeoJSON

---
 decode.cc | 143 +++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 137 insertions(+), 6 deletions(-)

diff --git a/decode.cc b/decode.cc
index 8cc9769..f082f57 100644
--- a/decode.cc
+++ b/decode.cc
@@ -6,6 +6,7 @@
 #include <zlib.h>
 #include <math.h>
 #include "vector_tile.pb.h"
+#include "tile.h"
 
 extern "C" {
 #include "projection.h"
@@ -51,8 +52,35 @@ int dezig(unsigned n) {
 	return (n >> 1) ^ (-(n & 1));
 }
 
+void printq(const char *s) {
+	putchar('"');
+	for (; *s; s++) {
+		if (*s == '\\' || *s == '"') {
+			printf("\\%c", *s);
+		} else if (*s >= 0 && *s < ' ') {
+			printf("\\u%04x", *s);
+		} else {
+			putchar(*s);
+		}
+	}
+	putchar('"');
+}
+
+struct draw {
+	int op;
+	double lon;
+	double lat;
+
+	draw(int op, double lon, double lat) {
+		this->op = op;
+		this->lon = lon;
+		this->lat = lat;
+	}
+};
+
 void handle(std::string message, int z, unsigned x, unsigned y) {
 	GOOGLE_PROTOBUF_VERIFY_VERSION;
+	int within = 0;
 
 	// https://github.com/mapbox/mapnik-vector-tile/blob/master/examples/c%2B%2B/tileinfo.cpp
 	mapnik::vector::tile tile;
@@ -69,6 +97,8 @@ void handle(std::string message, int z, unsigned x, unsigned y) {
 		exit(EXIT_FAILURE);
 	}
 
+	printf("{ \"type\": \"FeatureCollection\", \"features\": [\n");
+
 	for (int l = 0; l < tile.layers_size(); l++) {
 		mapnik::vector::tile_layer layer = tile.layers(l);
 		int extent = layer.extent();
@@ -77,16 +107,57 @@ void handle(std::string message, int z, unsigned x, unsigned y) {
 			mapnik::vector::tile_feature feat = layer.features(f);
 			int px = 0, py = 0;
 
+			if (within) {
+				printf(",\n");
+			}
+			within = 1;
+
+			printf("{ \"type\": \"Feature\"");
+			printf(", \"properties\": { ");
+
+			for (unsigned t = 0; t + 1 < feat.tags_size(); t += 2) {
+				if (t != 0) {
+					printf(", ");
+				}
+
+				const char *key = layer.keys(feat.tags(t)).c_str();
+				mapnik::vector::tile_value const &val = layer.values(feat.tags(t + 1));
+
+				if (val.has_string_value()) {
+					printq(key);
+					printf(": ");
+					printq(val.string_value().c_str());
+				} else if (val.has_int_value()) {
+					printq(key);
+					printf(": %lld", (long long) val.int_value());
+				} else if (val.has_double_value()) {
+					printq(key);
+					printf(": %g", val.double_value());
+				} else if (val.has_float_value()) {
+					printq(key);
+					printf(": %g", val.float_value());
+				} else if (val.has_sint_value()) {
+					printq(key);
+					printf(": %lld", (long long) val.sint_value());
+				} else if (val.has_uint_value()) {
+					printq(key);
+					printf(": %lld", (long long) val.uint_value());
+				} else if (val.has_bool_value()) {
+					printq(key);
+					printf(": %s", val.bool_value() ? "true" : "false");
+				}
+			}
+
+			printf(" }, \"geometry\": { ");
+
+			std::vector<draw> ops;
+
 			for (int g = 0; g < feat.geometry_size(); g++) {
 				uint32_t geom = feat.geometry(g);
 				uint32_t op = geom & 7;
 				uint32_t count = geom >> 3;
 
-				if (op == 1 || op == 2) {
-					if (op == 1) {
-						printf("\n");
-					}
-
+				if (op == VT_MOVETO || op == VT_LINETO) {
 					for (unsigned k = 0; k < count; k++) {
 						px += dezig(feat.geometry(g + 1));
 						py += dezig(feat.geometry(g + 2));
@@ -98,12 +169,72 @@ void handle(std::string message, int z, unsigned x, unsigned y) {
 
 						double lat, lon;
 						tile2latlon(wx, wy, 32, &lat, &lon);
-						printf("%f,%f ", lat, lon);
+
+						ops.push_back(draw(op, lon, lat));
 					}
+				} else {
+					ops.push_back(draw(op, 0, 27));
 				}
 			}
+
+			if (feat.type() == VT_POINT) {
+				if (ops.size() == 1) {
+					printf("\"type\": \"Point\", \"coordinates\": [ %f, %f ]", ops[0].lon, ops[0].lat);
+				} else {
+					printf("\"type\": \"MultiPoint\", \"coordinates\": [ ");
+					for (unsigned i = 0; i < ops.size(); i++) {
+						if (i != 0) {
+							printf(", ");
+						}
+						printf("[ %f, %f ]", ops[i].lon, ops[i].lat);
+					}
+					printf(" ]");
+				}
+			} else if (feat.type() == VT_LINE) {
+				int movetos = 0;
+				for (unsigned i = 0; i < ops.size(); i++) {
+					if (ops[i].op == VT_MOVETO) {
+						movetos++;
+					}
+				}
+
+				if (movetos < 2) {
+					printf("\"type\": \"LineString\", \"coordinates\": [ ");
+					for (unsigned i = 0; i < ops.size(); i++) {
+						if (i != 0) {
+							printf(", ");
+						}
+						printf("[ %f, %f ]", ops[i].lon, ops[i].lat);
+					}
+					printf(" ]");
+				} else {
+					printf("\"type\": \"MultiLineString\", \"coordinates\": [ [ ");
+					int state = 0;
+					for (unsigned i = 0; i < ops.size(); i++) {
+						if (ops[i].op == VT_MOVETO) {
+							if (state == 0) {
+								printf("[ %f, %f ]", ops[i].lon, ops[i].lat);
+								state = 1;
+							} else {
+								printf(" ], [ ");
+								printf("[ %f, %f ]", ops[i].lon, ops[i].lat);
+								state = 1;
+							}
+						} else {
+							printf(", [ %f, %f ]", ops[i].lon, ops[i].lat);
+						}
+					}
+					printf(" ] ]");
+				}
+			} else if (feat.type() == VT_POLYGON) {
+
+			}
+
+			printf(" } }\n");
 		}
 	}
+
+	printf("] }\n");
 }
 
 void decode(char *fname, int z, unsigned x, unsigned y) {