Introduce Visible Networks Tracker.

chrome/android/java/src/org/chromium/chrome/browser/omnibox/geo/VisibleNetworksTracker.java

+// Copyright 2017 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.omnibox.geo;
+
+import android.content.Context;
+import android.os.AsyncTask;
+import android.os.SystemClock;
+
+import org.chromium.base.Log;
+import org.chromium.base.ThreadUtils;
+import org.chromium.base.VisibleForTesting;
+import org.chromium.base.annotations.SuppressFBWarnings;
+
+import javax.annotation.Nullable;
+
+/**
+ * VisibleNetworksTracker keeps track of the visible networks.
+ */
+public class VisibleNetworksTracker {
+    private static final String TAG = "VNTracker";
+
+    @VisibleForTesting
+    static final int AGE_THRESHOLD = 5 * 60 * 1000; // 5 min
+
+    @Nullable
+    private static VisibleNetworks sVisibleNetworks;
+    private static long sVisibleNetworksTime = Long.MAX_VALUE;
+
+    @Nullable
+    private static AsyncTask<Void, Void, VisibleNetworks> sOngoingRefresh;
+
+    private static VisibleNetworks sVisibleNetworksForTesting;
+    private static boolean sUseVisibleNetworksForTesting;
+
+    /**
+     * Returns last known visible networks. It returns the cached value if the cache is valid or it
+     * computes the simplest possible visibleNetworks fast, and triggers a background asynchronous
+     * refresh. Might return null if visible networks cannot be computed.
+     */
+    @Nullable
+    public static VisibleNetworks getLastKnownVisibleNetworks(final Context context) {
+        if (sUseVisibleNetworksForTesting) return sVisibleNetworksForTesting;
+
+        if (isValidCachedVisibleNetworks()) return getCachedVisibleNetworks();
+
+        VisibleNetworks visibleNetworks = null;
+        try {
+            // Include only the connected cell/wifi to minimize latency and compute the simplest
+            // visible networks possible.
+            visibleNetworks = PlatformNetworksManager.computeVisibleNetworks(
+                    context, false /* includeAllVisibleNotConnectedNetworks */);
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to get the visible networks. Error: ", e.toString());
+        }
+        // Update cache asynchronously.
+        refreshVisibleNetworks(context);
+
+        return visibleNetworks;
+    }
+
+    /**
+     * Determines if the visible networks need to be refreshed and asynchronously updates them if
+     * needed.
+     */
+    @SuppressFBWarnings("LI_LAZY_INIT_UPDATE_STATIC")
+    public static void refreshVisibleNetworks(final Context context) {
+        ThreadUtils.assertOnUiThread();
+        if (isValidCachedVisibleNetworks() || sOngoingRefresh != null) {
+            return;
+        }
+        sOngoingRefresh = new AsyncTask<Void, Void, VisibleNetworks>() {
+            @Override
+            protected VisibleNetworks doInBackground(Void... params) {
+                VisibleNetworks visibleNetworks = null;
+                try {
+                    // Include all visible wifis and cells.
+                    visibleNetworks = PlatformNetworksManager.computeVisibleNetworks(
+                            context, true /* includeAllVisibleNotConnectedNetworks */);
+                } catch (Exception e) {
+                    Log.e(TAG, "Failed to get the visible networks. Error: ", e.toString());
+                }
+                return visibleNetworks;
+            }
+
+            @Override
+            protected void onPostExecute(VisibleNetworks visibleNetworks) {
+                sOngoingRefresh = null;
+                setCachedVisibleNetworks(visibleNetworks);
+            }
+        };
+        sOngoingRefresh.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+    }
+
+    @Nullable
+    @VisibleForTesting
+    static VisibleNetworks getCachedVisibleNetworks() {
+        return sVisibleNetworks;
+    }
+
+    @VisibleForTesting
+    static long getCachedVisibleNetworksTime() {
+        return sVisibleNetworksTime;
+    }
+
+    @VisibleForTesting
+    static void clearCache() {
+        setCachedVisibleNetworks(null);
+        sVisibleNetworksTime = Long.MAX_VALUE;
+    }
+
+    @VisibleForTesting
+    static void setVisibleNetworksForTesting(VisibleNetworks visibleNetworksForTesting) {
+        sVisibleNetworksForTesting = visibleNetworksForTesting;
+        sUseVisibleNetworksForTesting = true;
+    }
+
+    private static void setCachedVisibleNetworks(VisibleNetworks visibleNetworks) {
+        ThreadUtils.assertOnUiThread();
+        sVisibleNetworks = visibleNetworks;
+        sVisibleNetworksTime = SystemClock.elapsedRealtime();
+    }
+
+    private static boolean isValidCachedVisibleNetworks() {
+        return sVisibleNetworks != null && sVisibleNetworksTime != Long.MAX_VALUE
+                && !sVisibleNetworks.isEmpty()
+                && SystemClock.elapsedRealtime() - sVisibleNetworksTime < AGE_THRESHOLD;
+    }
+}