use PartDatabase to look up thumbnails async

// FREEBIE

Closes #2286

androidTest/java/org/thoughtcrime/securesms/database/PartDatabaseTest.java

@@ -0,0 +1,64 @@
+package org.thoughtcrime.securesms.database;
+
+import android.net.Uri;
+import android.test.InstrumentationTestCase;
+
+import org.thoughtcrime.securesms.crypto.MasterSecret;
+
+import java.io.FileNotFoundException;
+import java.io.InputStream;
+
+import ws.com.google.android.mms.pdu.PduPart;
+
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.anyFloat;
+import static org.mockito.Matchers.anyLong;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.doNothing;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+public class PartDatabaseTest extends InstrumentationTestCase {
+  private static final long PART_ID = 1L;
+
+  private PartDatabase database;
+
+  @Override
+  public void setUp() {
+    database = spy(DatabaseFactory.getPartDatabase(getInstrumentation().getTargetContext()));
+  }
+
+  public void testTaskNotRunWhenThumbnailExists() throws Exception {
+    when(database.getPart(eq(PART_ID))).thenReturn(getPduPartSkeleton("x/x"));
+    doReturn(mock(InputStream.class)).when(database).getDataStream(any(MasterSecret.class), anyLong(), eq("thumbnail"));
+
+    database.getThumbnailStream(null, PART_ID);
+
+    verify(database, never()).updatePartThumbnail(any(MasterSecret.class), anyLong(), any(PduPart.class), any(InputStream.class), anyFloat());
+  }
+
+  public void testTaskRunWhenThumbnailMissing() throws Exception {
+    when(database.getPart(eq(PART_ID))).thenReturn(getPduPartSkeleton("image/png"));
+    doReturn(null).when(database).getDataStream(any(MasterSecret.class), anyLong(), eq("thumbnail"));
+    doNothing().when(database).updatePartThumbnail(any(MasterSecret.class), anyLong(), any(PduPart.class), any(InputStream.class), anyFloat());
+
+    try {
+      database.new ThumbnailFetchCallable(mock(MasterSecret.class), PART_ID).call();
+      throw new AssertionError("didn't try to generate thumbnail");
+    } catch (FileNotFoundException fnfe) {
+      // success
+    }
+  }
+
+  private PduPart getPduPartSkeleton(String contentType) {
+    PduPart part = new PduPart();
+    part.setContentType(contentType.getBytes());
+    part.setDataUri(Uri.EMPTY);
+    return part;
+  }
+}