[android] OfflineManager#setResourceTransform to allow transforming URLs prior to internet requests

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/offline/OfflineManager.java

@@ -10,6 +10,7 @@ import android.support.annotation.NonNull;
 
 import com.mapbox.mapboxsdk.Mapbox;
 import com.mapbox.mapboxsdk.constants.MapboxConstants;
+import com.mapbox.mapboxsdk.storage.Resource;
 
 import java.io.File;
 
@@ -81,6 +82,22 @@ public class OfflineManager {
     void onError(String error);
   }
 
+  /**
+   * This callback allows implementors to transform URLs before they are requested
+   * from the internet. This can be used add or remove custom parameters, or reroute
+   * certain requests to other servers or endpoints.
+   */
+  public interface ResourceTransformCallback {
+    /**
+     * Called whenever a URL needs to be transformed.
+     *
+     * @param kind The kind of URL to be transformed.
+     * @param offlineRegions The original URL to be transformed.
+     * @return A URL that will now be downloaded.
+     */
+    String onURL(@Resource.Kind int kind, String url);
+  }
+
   /*
    * Constructors
    */
@@ -265,6 +282,18 @@ public class OfflineManager {
     });
   }
 
+  /**
+   * Sets a callback for transforming URLs requested from the internet
+   * <p>
+   * The callback will be executed on the main thread once for every requested URL.
+   * </p>
+   *
+   * @param callback the callback to be invoked
+   */
+  public void setResourceTransform(@NonNull final ResourceTransformCallback callback) {
+    setResourceTransform(mDefaultFileSourcePtr, callback);
+  }
+
   /*
   * Changing or bypassing this limit without permission from Mapbox is prohibited
   * by the Mapbox Terms of Service.
@@ -291,6 +320,9 @@ public class OfflineManager {
     long defaultFileSourcePtr, OfflineRegionDefinition definition,
     byte[] metadata, CreateOfflineRegionCallback callback);
 
+  private native void setResourceTransform(
+    long defaultFileSourcePtr, ResourceTransformCallback callback);
+
   private native void setOfflineMapboxTileCountLimit(
     long defaultFileSourcePtr, long limit);
 

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/storage/Resource.java

@@ -0,0 +1,54 @@
+package com.mapbox.mapboxsdk.storage;
+
+import android.support.annotation.IntDef;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+public final class Resource {
+  // Note: Keep this in sync with include/mbgl/storage/resource.hpp
+
+  @IntDef( {UNKNOWN, STYLE, SOURCE, TILE, GLYPHS, SPRITE_IMAGE, SPRITE_JSON})
+  @Retention(RetentionPolicy.SOURCE)
+  public @interface Kind {
+  }
+
+  /**
+   * Unknown type
+   */
+  public static final int UNKNOWN = 0;
+
+  /**
+   * Style sheet JSON file
+   */
+  public static final int STYLE = 1;
+
+  /**
+   * TileJSON file as specified in https://www.mapbox.com/mapbox-gl-js/style-spec/#root-sources
+   */
+  public static final int SOURCE = 2;
+
+  /**
+   * A vector or raster tile as described in the style sheet at
+   * https://www.mapbox.com/mapbox-gl-js/style-spec/#sources
+   */
+  public static final int TILE = 3;
+
+  /**
+   * Signed distance field glyphs for text rendering. These are the URLs specified in the style
+   * in https://www.mapbox.com/mapbox-gl-js/style-spec/#root-glyphs
+   */
+  public static final int GLYPHS = 4;
+
+  /**
+   * Image part of a sprite sheet. It is constructed of the prefix in
+   *  https://www.mapbox.com/mapbox-gl-js/style-spec/#root-sprite and a PNG file extension.
+   */
+  public static final int SPRITE_IMAGE = 5;
+
+  /**
+   * JSON part of a sprite sheet. It is constructed of the prefix in
+   * https://www.mapbox.com/mapbox-gl-js/style-spec/#root-sprite and a JSON file extension.
+   */
+  public static final int SPRITE_JSON = 6;
+}