Switch to use download GUID to indentify download items

chrome/android/java/src/org/chromium/chrome/browser/download/DownloadSharedPreferenceEntry.java

Index: chrome/android/java/src/org/chromium/chrome/browser/download/DownloadSharedPreferenceEntry.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadSharedPreferenceEntry.java b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadSharedPreferenceEntry.java
new file mode 100644
index 0000000000000000000000000000000000000000..a23149629849b266aa46ce6264ed6691caf2ac8e
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadSharedPreferenceEntry.java
@@ -0,0 +1,96 @@
+// 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.download;
+
+import org.chromium.base.Log;
+import org.chromium.base.VisibleForTesting;
+
+import java.util.UUID;
+
+/**
+ * Class representing the download information stored in SharedPreferences to construct a
+ * download notification.
+ */
+public class DownloadSharedPreferenceEntry {
+    private static final String TAG = "DownloadEntry";
+    // Current version of the DownloadSharedPreferenceEntry. When changing the SharedPreference,
+    // we need to change the version number too.
+    @VisibleForTesting static final int VERSION = 1;
+    public final int notificationId;
+    public final boolean isResumable;
+    // This field is not yet used, but will soon be used. We add it here to avoid changing the
+    // format of the SharedPreference string again.
+    public final boolean isStartedOnMeteredNetwork;
+    public final String fileName;
+    public final String downloadGuid;
+
+    DownloadSharedPreferenceEntry(int notificationId, boolean isResumable,
+            boolean isStartedOnMeteredNetwork, String guid, String fileName) {
+        this.notificationId = notificationId;
+        this.isResumable = isResumable;
+        this.isStartedOnMeteredNetwork = isStartedOnMeteredNetwork;
+        this.downloadGuid = guid;
+        this.fileName = fileName;
+    }
+
+    /**
+     * Parse the pending notification from a String object in SharedPrefs.
+     *
+     * @param sharedPrefString String from SharedPreference, containing the notification ID, GUID,
+     *        file name, whether it is resumable and whether download started on a metered network.
+     * @return a DownloadSharedPreferenceEntry object.
+     */
+    static DownloadSharedPreferenceEntry parseFromString(String sharedPrefString) {
+        String[] values = sharedPrefString.split(",", 6);
+        if (values.length == 6) {
+            try {
+                int version = Integer.parseInt(values[0]);
+                // Ignore all SharedPreference entries that has an invalid version for now.
+                if (version != VERSION) {
+                    return new DownloadSharedPreferenceEntry(-1, false, false, null, "");
+                }
+                int id = Integer.parseInt(values[1]);
+                boolean isResumable = "1".equals(values[2]);
+                boolean isStartedOnMeteredNetwork = "1".equals(values[3]);
+                if (!isValidGUID(values[4])) {
+                    return new DownloadSharedPreferenceEntry(-1, false, false, null, "");
+                }
+                return new DownloadSharedPreferenceEntry(
+                        id, isResumable, isStartedOnMeteredNetwork, values[4], values[5]);
+            } catch (NumberFormatException nfe) {
+                Log.w(TAG, "Exception while parsing pending download:" + sharedPrefString);
+            }
+        }
+        return new DownloadSharedPreferenceEntry(-1, false, false, null, "");
+    }
+
+    /**
+     * @return a string for the DownloadSharedPreferenceEntry instance to be inserted into
+     *         SharedPrefs.
+     */
+    String getSharedPreferenceString() {
+        return VERSION + "," + notificationId + "," + (isResumable ? "1" : "0") + ","
+                + (isStartedOnMeteredNetwork ? "1" : "0") + "," + downloadGuid + "," + fileName;
+    }
+
+    /**
+     * Check if a string is a valid GUID. GUID is RFC 4122 compliant, it should have format
+     * xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
+     * TODO(qinmin): move this to base/.
+     * @return true if the string is a valid GUID, or false otherwise.
+     */
+    static boolean isValidGUID(String guid) {
+        if (guid == null) return false;
+        try {
+            // Java UUID class doesn't check the length of the string. Need to convert it back to
+            // string so that we can validate the length of the original string.
+            UUID uuid = UUID.fromString(guid);
+            String uuidString = uuid.toString();
+            return guid.equalsIgnoreCase(uuidString);
+        } catch (IllegalArgumentException e) {
+            return false;
+        }
+    }
+}