Use Nearby to background scan for URLs

chrome/android/java/src/org/chromium/chrome/browser/physicalweb/NearbyBackgroundSubscription.java

Index: chrome/android/java/src/org/chromium/chrome/browser/physicalweb/NearbyBackgroundSubscription.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/NearbyBackgroundSubscription.java b/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/NearbyBackgroundSubscription.java
new file mode 100644
index 0000000000000000000000000000000000000000..be5d80e3bd1df6a57d4a6547db2c9661fca62bf2
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/physicalweb/NearbyBackgroundSubscription.java
@@ -0,0 +1,86 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.physicalweb;
+
+import android.app.PendingIntent;
+import android.content.Intent;
+
+import com.google.android.gms.common.api.PendingResult;
+import com.google.android.gms.common.api.Status;
+import com.google.android.gms.nearby.Nearby;
+
+import org.chromium.base.ContextUtils;
+
+
+/**
+ * This class represents a connection to Google Play Services that does foreground
+ * subscription/unsubscription to Nearby Eddystone-URLs.
+ */
+class NearbyBackgroundSubscription extends NearbySubscription {
+    private static final String TAG = "PhysicalWeb";
+    private static final int UNSUBSCRIBING = 0;
+    private static final int SUBSCRIBING = 1;
+    private int mMode;
+    private Runnable mCallback;
+
+    NearbyBackgroundSubscription() {
+        super(ContextUtils.getApplicationContext());
+        mMode = SUBSCRIBING;
+        mCallback = null;
+    }
+
+    private PendingIntent createNearbySubscribeIntent() {
+        Intent intent =
+                new Intent(ContextUtils.getApplicationContext(), NearbyMessageIntentService.class);
+        PendingIntent pendingIntent = PendingIntent.getService(
+                ContextUtils.getApplicationContext(), 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
+        return pendingIntent;
+    }
+
+    @Override
+    protected void onConnected() {
+        PendingResult<Status> pendingResult = null;
+        String action = null;
+        if (mMode == SUBSCRIBING) {
+            pendingResult = Nearby.Messages.unsubscribe(
+                    getGoogleApiClient(), createNearbySubscribeIntent());
+            action = "background subscribe";
+        } else {
+            pendingResult = Nearby.Messages.subscribe(
+                getGoogleApiClient(), createNearbySubscribeIntent(), createSubscribeOptions());

[gone, 2016/07/27 17:38:47]

indentation is off.  Also I'm guessing it's intentional that the SUBSCRIBING
mode unsubscribes and vice versa?  Not familiar with the API but it looks weird.

[cco3, 2016/07/27 18:54:59]

No, good catch!  I think I know why my testing didn't pick up on this.

+            action = "background unsubscribe";
+        }
+        pendingResult.setResultCallback(new SimpleResultCallback(action) {
+            @Override
+            public void onResult(final Status status) {
+                super.onResult(status);
+                disconnect();
+                if (mCallback != null) {
+                    mCallback.run();
+                }
+            }
+        });
+    }
+
+    void subscribe(Runnable callback) {

[gone, 2016/07/27 17:38:47]

This isn't something you need a queue for, is it?  If an unsubscribe() comes
immediately after a subscribe(), it'll wipe out the mode and run the wrong
callback.

[cco3, 2016/07/27 18:54:59]

I think it's OK (see reason below if you are curious), but I'm going to change
this to make it more clear, since we only use the object once before discarding
it anyway.

If an unsubscribe comes immediately after a subscribe, it will unsubscribe on
connection and the second callback will be run.  I'm not sure we would want to
run the callback sent with subscribe in that case since we would never have
subscribed.

+        mMode = SUBSCRIBING;
+        mCallback = callback;
+        connect();
+    }
+
+    void subscribe() {
+        subscribe(null);
+    }
+
+    void unsubscribe(Runnable callback) {
+        mMode = UNSUBSCRIBING;
+        mCallback = callback;
+        connect();
+    }
+
+    void unsubscribe() {
+        unsubscribe(null);
+    }
+}