Add Uri for Message queries that include a LIMIT

* Use a query parameter (e.g. ?limit=2); LIMIT works with any
  query

Change-Id: Idd106ab4b61aec237ac9676a201e797c4f65f15b

src/com/android/email/provider/EmailContent.java

@@ -64,6 +64,8 @@ import java.util.UUID;
 public abstract class EmailContent {
     public static final String AUTHORITY = EmailProvider.EMAIL_AUTHORITY;
     public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY);
+    public static final String LIMIT_PARAMETER = "limit";
+
     // All classes share this
     public static final String RECORD_ID = "_id";
 
@@ -171,6 +173,11 @@ public abstract class EmailContent {
         return count(context, uri, null, null);
     }
 
+    static public Uri uriWithLimit(Uri uri, int limit) {
+        return uri.buildUpon().appendQueryParameter(EmailContent.LIMIT_PARAMETER,
+                Integer.toString(limit)).build();
+    }
+
     /**
      * no public constructor since this is a utility class
      */

src/com/android/email/provider/EmailProvider.java

@@ -1143,6 +1143,7 @@ public class EmailProvider extends ContentProvider {
         // See the comment at delete(), above
         SQLiteDatabase db = getDatabase(context);
         int table = match >> BASE_SHIFT;
+        String limit = uri.getQueryParameter(EmailContent.LIMIT_PARAMETER);
         String id;
 
         if (Email.LOGD) {
@@ -1160,7 +1161,7 @@ public class EmailProvider extends ContentProvider {
                 case ACCOUNT:
                 case HOSTAUTH:
                     c = db.query(TABLE_NAMES[table], projection,
-                            selection, selectionArgs, null, null, sortOrder);
+                            selection, selectionArgs, null, null, sortOrder, limit);
                     break;
                 case BODY_ID:
                 case MESSAGE_ID:
@@ -1172,14 +1173,15 @@ public class EmailProvider extends ContentProvider {
                 case HOSTAUTH_ID:
                     id = uri.getPathSegments().get(1);
                     c = db.query(TABLE_NAMES[table], projection,
-                            whereWithId(id, selection), selectionArgs, null, null, sortOrder);
+                            whereWithId(id, selection), selectionArgs, null, null, sortOrder,
+                            limit);
                     break;
                 case ATTACHMENTS_MESSAGE_ID:
                     // All attachments for the given message
                     id = uri.getPathSegments().get(2);
                     c = db.query(Attachment.TABLE_NAME, projection,
                             whereWith(Attachment.MESSAGE_KEY + "=" + id, selection),
-                            selectionArgs, null, null, sortOrder);
+                            selectionArgs, null, null, sortOrder, limit);
                     break;
                 default:
                     throw new IllegalArgumentException("Unknown URI " + uri);

tests/src/com/android/email/provider/ProviderTests.java

@@ -796,6 +796,59 @@ public class ProviderTests extends ProviderTestCase2<EmailProvider> {
         assertNotNull(loadBodyForMessageId(message2Id));
     }
 
+    /**
+     * Note that we can't use EmailContent.count() here because it uses a projection including
+     * count(*), and count(*) is incompatible with a LIMIT (i.e. the limit would be applied to the
+     * single column returned with count(*), rather than to the query itself)
+     */
+    private int count(Context context, Uri uri, String selection, String[] selectionArgs) {
+        Cursor c = context.getContentResolver().query(uri, EmailContent.ID_PROJECTION, selection,
+                selectionArgs, null);
+        try {
+            return c.getCount();
+        } finally {
+            c.close();
+        }
+    }
+
+    public void testMessageQueryWithLimit() {
+        final Context context = mMockContext;
+
+        // Create account and two mailboxes
+        Account acct = ProviderTestUtils.setupAccount("orphaned body", true, context);
+        Mailbox box1 = ProviderTestUtils.setupMailbox("box1", acct.mId, true, context);
+        Mailbox box2 = ProviderTestUtils.setupMailbox("box2", acct.mId, true, context);
+
+        // Create 4 messages in box1
+        ProviderTestUtils.setupMessage("message1", acct.mId, box1.mId, false, true, context);
+        ProviderTestUtils.setupMessage("message2", acct.mId, box1.mId, false, true, context);
+        ProviderTestUtils.setupMessage("message3", acct.mId, box1.mId, false, true, context);
+        ProviderTestUtils.setupMessage("message4", acct.mId, box1.mId, false, true, context);
+
+        // Create 4 messages in box2
+        ProviderTestUtils.setupMessage("message1", acct.mId, box2.mId, false, true, context);
+        ProviderTestUtils.setupMessage("message2", acct.mId, box2.mId, false, true, context);
+        ProviderTestUtils.setupMessage("message3", acct.mId, box2.mId, false, true, context);
+        ProviderTestUtils.setupMessage("message4", acct.mId, box2.mId, false, true, context);
+
+        // Check normal case, special case (limit 1), and arbitrary limits
+        assertEquals(8, count(mMockContext, Message.CONTENT_URI, null, null));
+        assertEquals(1, count(mMockContext, EmailContent.uriWithLimit(Message.CONTENT_URI, 1),
+                null, null));
+        assertEquals(3, count(mMockContext, EmailContent.uriWithLimit(Message.CONTENT_URI, 3),
+                null, null));
+        assertEquals(8, count(mMockContext, EmailContent.uriWithLimit(Message.CONTENT_URI, 100),
+                null, null));
+
+        // Check that it works with selection/selection args
+        String[] args = new String[] {Long.toString(box1.mId)};
+        assertEquals(4, count(mMockContext, Message.CONTENT_URI,
+                MessageColumns.MAILBOX_KEY + "=?", args));
+        assertEquals(1, count(mMockContext,
+                EmailContent.uriWithLimit(Message.CONTENT_URI, 1),
+                MessageColumns.MAILBOX_KEY + "=?", args));
+    }
+
     /**
      * Test delete orphan messages
      * 1. create message without body (message id 1)