[core] Stop download when tile limit is reached

The tile limit guard (when used) stops a download from continuing
when the tile limit is reached. This wraps the guard in a method
and employs it in both places currently necessary to ensure the
guard has a chance to function. Tests have been updated to
ensure the fix works for a less trivial tile limit scenario.

platform/default/mbgl/storage/offline_download.cpp

@@ -229,12 +229,8 @@ void OfflineDownload::ensureResource(const Resource& resource, std::function<voi
 
             return;
         }
-
-        if (resource.kind == Resource::Kind::Tile
-            && util::mapbox::isMapboxURL(resource.url)
-            && offlineDatabase.offlineMapboxTileCountLimitExceeded()) {
-            observer->mapboxTileCountLimitExceeded(offlineDatabase.getOfflineMapboxTileCountLimit());
-            setState(OfflineRegionDownloadState::Inactive);
+        
+        if (checkTileCountLimit(resource)) {
             return;
         }
 
@@ -256,6 +252,10 @@ void OfflineDownload::ensureResource(const Resource& resource, std::function<voi
 
             observer->statusChanged(status);
             
+            if (checkTileCountLimit(resource)) {
+                return;
+            }
+            
             if (status.complete()) {
                 setState(OfflineRegionDownloadState::Inactive);
             }
@@ -263,4 +263,16 @@ void OfflineDownload::ensureResource(const Resource& resource, std::function<voi
     });
 }
 
+bool OfflineDownload::checkTileCountLimit(const Resource& resource) {
+    if (resource.kind == Resource::Kind::Tile
+        && util::mapbox::isMapboxURL(resource.url)
+        && offlineDatabase.offlineMapboxTileCountLimitExceeded()) {
+        observer->mapboxTileCountLimitExceeded(offlineDatabase.getOfflineMapboxTileCountLimit());
+        setState(OfflineRegionDownloadState::Inactive);
+        return true;
+    }
+    
+    return false;
+}
+
 } // namespace mbgl

platform/default/mbgl/storage/offline_download.hpp

@@ -49,7 +49,8 @@ private:
      */
     void ensureResource(const Resource&, std::function<void (Response)> = {});
     void ensureTiles(SourceType, uint16_t, const SourceInfo&);
-
+    bool checkTileCountLimit(const Resource& resource);
+    
     int64_t id;
     OfflineRegionDefinition definition;
     OfflineDatabase& offlineDatabase;

test/storage/offline_download.cpp

@@ -364,7 +364,7 @@ TEST(OfflineDownload, RequestErrorsAreRetried) {
     test.loop.run();
 }
 
-TEST(OfflineDownload, TileCountLimitExceeded) {
+TEST(OfflineDownload, TileCountLimitExceededNoTileResponse) {
     OfflineTest test;
     OfflineRegion region = test.createRegion();
     OfflineDownload download(
@@ -372,7 +372,9 @@ TEST(OfflineDownload, TileCountLimitExceeded) {
         OfflineTilePyramidRegionDefinition("http://127.0.0.1:3000/offline/style.json", LatLngBounds::world(), 0.0, 0.0, 1.0),
         test.db, test.fileSource);
 
-    test.db.setOfflineMapboxTileCountLimit(0);
+    uint64_t tileLimit = 0;
+
+    test.db.setOfflineMapboxTileCountLimit(tileLimit);
 
     test.fileSource.styleResponse = [&] (const Resource& resource) {
         EXPECT_EQ("http://127.0.0.1:3000/offline/style.json", resource.url);
@@ -384,18 +386,72 @@ TEST(OfflineDownload, TileCountLimitExceeded) {
 
     observer->mapboxTileCountLimitExceededFn = [&] (uint64_t limit) {
         EXPECT_FALSE(mapboxTileCountLimitExceededCalled);
-        EXPECT_EQ(0, limit);
+        EXPECT_EQ(tileLimit, limit);
         mapboxTileCountLimitExceededCalled = true;
     };
 
     observer->statusChangedFn = [&] (OfflineRegionStatus status) {
-        EXPECT_FALSE(status.complete());
+        if (!mapboxTileCountLimitExceededCalled) {            
+            EXPECT_FALSE(status.complete());
+            EXPECT_EQ(OfflineRegionDownloadState::Active, status.downloadState);
+        } else {
+            EXPECT_EQ(OfflineRegionDownloadState::Inactive, status.downloadState);
+            test.loop.stop();
+        }
+    };
+
+    download.setObserver(std::move(observer));
+    download.setState(OfflineRegionDownloadState::Active);
+
+    test.loop.run();
+}
+
+TEST(OfflineDownload, TileCountLimitExceededWithTileResponse) {
+    OfflineTest test;
+    OfflineRegion region = test.createRegion();
+    OfflineDownload download(
+        region.getID(),
+        OfflineTilePyramidRegionDefinition("http://127.0.0.1:3000/offline/style.json", LatLngBounds::world(), 0.0, 0.0, 1.0),
+        test.db, test.fileSource);
+
+    uint64_t tileLimit = 1;
+
+    test.db.setOfflineMapboxTileCountLimit(tileLimit);
+
+    test.fileSource.styleResponse = [&] (const Resource& resource) {
+        EXPECT_EQ("http://127.0.0.1:3000/offline/style.json", resource.url);
+        return test.response("offline/mapbox_source.style.json");
+    };
+    
+    test.fileSource.tileResponse = [&] (const Resource& resource) {
+        const Resource::TileData& tile = *resource.tileData;
+        EXPECT_EQ("mapbox://{z}-{x}-{y}.vector.pbf", tile.urlTemplate);
+        EXPECT_EQ(1, tile.pixelRatio);
+        EXPECT_EQ(0, tile.x);
+        EXPECT_EQ(0, tile.y);
+        EXPECT_EQ(0, tile.z);
+        return test.response("offline/0-0-0.vector.pbf");
+    };
+
+    auto observer = std::make_unique<MockObserver>();
+    bool mapboxTileCountLimitExceededCalled = false;
+
+    observer->mapboxTileCountLimitExceededFn = [&] (uint64_t limit) {
+        EXPECT_FALSE(mapboxTileCountLimitExceededCalled);
+        EXPECT_EQ(tileLimit, limit);
+        mapboxTileCountLimitExceededCalled = true;
+    };
+
+    observer->statusChangedFn = [&] (OfflineRegionStatus status) {        
         if (!mapboxTileCountLimitExceededCalled) {
             EXPECT_EQ(OfflineRegionDownloadState::Active, status.downloadState);
         } else {
             EXPECT_EQ(OfflineRegionDownloadState::Inactive, status.downloadState);
             test.loop.stop();
         }
+        if (status.completedResourceCount > tileLimit) {
+            test.loop.stop();
+        }
     };
 
     download.setObserver(std::move(observer));