Refactor attachment loading to support incremental display once loaded

briar-android/src/androidTestOfficial/java/org/briarproject/briar/android/attachment/AttachmentRetrieverIntegrationTest.java

@@ -57,7 +57,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(smallKitten);
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(msgId, item.getMessageId());
 		assertEquals(160, item.getWidth());
 		assertEquals(240, item.getHeight());
@@ -73,7 +73,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(originalKitten);
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(msgId, item.getMessageId());
 		assertEquals(1728, item.getWidth());
 		assertEquals(2592, item.getHeight());
@@ -89,7 +89,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/png");
 		InputStream is = getUrlInputStream(pngKitten);
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(msgId, item.getMessageId());
 		assertEquals(737, item.getWidth());
 		assertEquals(510, item.getHeight());
@@ -105,7 +105,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(uberGif);
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(1, item.getWidth());
 		assertEquals(1, item.getHeight());
 		assertEquals(dimensions.minHeight, item.getThumbnailWidth());
@@ -120,7 +120,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(lottaPixel);
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(64250, item.getWidth());
 		assertEquals(64250, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
@@ -135,7 +135,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(imageIoCrash);
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(1184, item.getWidth());
 		assertEquals(448, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
@@ -150,7 +150,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(gimpCrash);
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(1, item.getWidth());
 		assertEquals(1, item.getHeight());
 		assertEquals(dimensions.minHeight, item.getThumbnailWidth());
@@ -165,7 +165,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(optiPngAfl);
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(32, item.getWidth());
 		assertEquals(32, item.getHeight());
 		assertEquals(dimensions.minHeight, item.getThumbnailWidth());
@@ -180,7 +180,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getUrlInputStream(librawError);
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertTrue(item.hasError());
 	}
 
@@ -189,7 +189,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("animated.gif");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(65535, item.getWidth());
 		assertEquals(65535, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
@@ -204,7 +204,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("animated2.gif");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(10000, item.getWidth());
 		assertEquals(10000, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
@@ -219,7 +219,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("error_large.gif");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(16384, item.getWidth());
 		assertEquals(16384, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
@@ -234,7 +234,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getAssetInputStream("error_high.jpg");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(1, item.getWidth());
 		assertEquals(10000, item.getHeight());
 		assertEquals(dimensions.minWidth, item.getThumbnailWidth());
@@ -249,7 +249,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getAssetInputStream("error_wide.jpg");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(1920, item.getWidth());
 		assertEquals(1, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentCreatorImpl.java

@@ -33,6 +33,7 @@ import javax.inject.Inject;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.ERROR;
 import static org.briarproject.briar.android.util.UiUtils.observeForeverOnce;
 import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_IMAGE_SIZE;
 
@@ -108,8 +109,8 @@ class AttachmentCreatorImpl implements AttachmentCreator {
 		// get and cache AttachmentItem for ImagePreview
 		try {
 			Attachment a = retriever.getMessageAttachment(h);
-			AttachmentItem item = retriever.getAttachmentItem(a, needsSize);
-			if (item.hasError()) throw new IOException();
+			AttachmentItem item = retriever.createAttachmentItem(a, needsSize);
+			if (item.getState() == ERROR) throw new IOException();
 			AttachmentItemResult itemResult =
 					new AttachmentItemResult(uri, item);
 			itemResults.add(itemResult);
@@ -166,13 +167,6 @@ class AttachmentCreatorImpl implements AttachmentCreator {
 	@Override
 	@UiThread
 	public void onAttachmentsSent(MessageId id) {
-		List<AttachmentItem> items = new ArrayList<>(itemResults.size());
-		for (AttachmentItemResult itemResult : itemResults) {
-			// check if we are trying to send attachment items with errors
-			if (itemResult.getItem() == null) throw new IllegalStateException();
-			items.add(itemResult.getItem());
-		}
-		retriever.cachePut(id, items);
 		resetState();
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentItem.java

@@ -8,22 +8,25 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 
-import java.util.concurrent.atomic.AtomicLong;
-
 import javax.annotation.concurrent.Immutable;
 
+import static java.lang.System.arraycopy;
 import static java.util.Objects.requireNonNull;
+import static org.briarproject.bramble.util.StringUtils.toHexString;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.LOADING;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.MISSING;
 
 @Immutable
 @NotNullByDefault
 public class AttachmentItem implements Parcelable {
 
+	public enum State {LOADING, MISSING, AVAILABLE, ERROR}
+
 	private final AttachmentHeader header;
 	private final int width, height;
 	private final String extension;
 	private final int thumbnailWidth, thumbnailHeight;
-	private final boolean hasError;
-	private final long instanceId;
+	private final State state;
 
 	public static final Creator<AttachmentItem> CREATOR =
 			new Creator<AttachmentItem>() {
@@ -38,19 +41,33 @@ public class AttachmentItem implements Parcelable {
 				}
 			};
 
-	private static final AtomicLong NEXT_INSTANCE_ID = new AtomicLong(0);
-
 	AttachmentItem(AttachmentHeader header, int width, int height,
 			String extension, int thumbnailWidth, int thumbnailHeight,
-			boolean hasError) {
+			State state) {
 		this.header = header;
 		this.width = width;
 		this.height = height;
 		this.extension = extension;
 		this.thumbnailWidth = thumbnailWidth;
 		this.thumbnailHeight = thumbnailHeight;
-		this.hasError = hasError;
-		instanceId = NEXT_INSTANCE_ID.getAndIncrement();
+		this.state = state;
+	}
+
+	/**
+	 * Use only for {@link MISSING} or {@link LOADING} items.
+	 */
+	AttachmentItem(AttachmentHeader header, int width, int height,
+			State state) {
+		this(header, width, height, "", width, height, state);
+		if (state != MISSING && state != LOADING)
+			throw new IllegalArgumentException();
+	}
+
+	/**
+	 * Use when the item does not need a size.
+	 */
+	AttachmentItem(AttachmentHeader header, String extension, State state) {
+		this(header, 0, 0, extension, 0, 0, state);
 	}
 
 	protected AttachmentItem(Parcel in) {
@@ -63,8 +80,7 @@ public class AttachmentItem implements Parcelable {
 		extension = requireNonNull(in.readString());
 		thumbnailWidth = in.readInt();
 		thumbnailHeight = in.readInt();
-		hasError = in.readByte() != 0;
-		instanceId = in.readLong();
+		state = State.valueOf(requireNonNull(in.readString()));
 		header = new AttachmentHeader(messageId, mimeType);
 	}
 
@@ -100,12 +116,20 @@ public class AttachmentItem implements Parcelable {
 		return thumbnailHeight;
 	}
 
-	public boolean hasError() {
-		return hasError;
+	public State getState() {
+		return state;
+	}
+
+	public String getTransitionName(MessageId conversationItemId) {
+		int len = MessageId.LENGTH;
+		byte[] instanceId = new byte[len * 2];
+		arraycopy(header.getMessageId().getBytes(), 0, instanceId, 0, len);
+		arraycopy(conversationItemId.getBytes(), 0, instanceId, len, len);
+		return toHexString(instanceId);
 	}
 
-	public String getTransitionName() {
-		return String.valueOf(instanceId);
+	boolean hasSize() {
+		return width != 0 && height != 0;
 	}
 
 	@Override
@@ -122,14 +146,15 @@ public class AttachmentItem implements Parcelable {
 		dest.writeString(extension);
 		dest.writeInt(thumbnailWidth);
 		dest.writeInt(thumbnailHeight);
-		dest.writeByte((byte) (hasError ? 1 : 0));
-		dest.writeLong(instanceId);
+		dest.writeString(state.name());
 	}
 
 	@Override
 	public boolean equals(@Nullable Object o) {
 		return o instanceof AttachmentItem &&
-				instanceId == ((AttachmentItem) o).instanceId;
+				header.getMessageId().equals(
+						((AttachmentItem) o).header.getMessageId()
+				);
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentRetriever.java

 package org.briarproject.briar.android.attachment;
 
-import android.support.annotation.Nullable;
-
+import org.briarproject.bramble.api.Pair;
+import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
+import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 
 import java.io.InputStream;
 import java.util.List;
@@ -14,16 +15,26 @@ import java.util.List;
 @NotNullByDefault
 public interface AttachmentRetriever {
 
-	void cachePut(MessageId messageId, List<AttachmentItem> attachments);
+	@DatabaseExecutor
+	Attachment getMessageAttachment(AttachmentHeader h) throws DbException;
 
-	@Nullable
-	List<AttachmentItem> cacheGet(MessageId messageId);
+	List<AttachmentItem> getAttachmentItems(PrivateMessageHeader messageHeader);
 
-	Attachment getMessageAttachment(AttachmentHeader h) throws DbException;
+	/**
+	 * Retrieves item size and adds the item to the cache, if available.
+	 */
+	@DatabaseExecutor
+	void cacheAttachmentItem(MessageId conversationMessageId,
+			AttachmentHeader h) throws DbException;
 
 	/**
 	 * Creates an {@link AttachmentItem} from the {@link Attachment}'s
 	 * {@link InputStream} which will be closed when this method returns.
 	 */
-	AttachmentItem getAttachmentItem(Attachment a, boolean needsSize);
+	AttachmentItem createAttachmentItem(Attachment a, boolean needsSize);
+
+	@DatabaseExecutor
+	Pair<MessageId, AttachmentItem> loadAttachmentItem(MessageId attachmentId)
+			throws DbException;
+
 }

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentRetrieverImpl.java

 package org.briarproject.briar.android.attachment;
 
-import android.support.annotation.Nullable;
-
+import org.briarproject.bramble.api.Pair;
+import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.NoSuchMessageException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.briar.android.attachment.AttachmentItem.State;
 import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
+import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 
 import java.io.BufferedInputStream;
 import java.io.InputStream;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -20,6 +24,10 @@ import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.AVAILABLE;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.ERROR;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.LOADING;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.MISSING;
 
 @NotNullByDefault
 class AttachmentRetrieverImpl implements AttachmentRetriever {
@@ -34,7 +42,11 @@ class AttachmentRetrieverImpl implements AttachmentRetriever {
 	private final int minWidth, maxWidth;
 	private final int minHeight, maxHeight;
 
-	private final Map<MessageId, List<AttachmentItem>> attachmentCache =
+	// Info for AttachmentItems that are either still LOADING or MISSING
+	private final Map<MessageId, UnavailableItem> unavailableItems =
+			new ConcurrentHashMap<>();
+	// We cache only items in their final state: AVAILABLE or ERROR
+	private final Map<MessageId, AttachmentItem> itemCache =
 			new ConcurrentHashMap<>();
 
 	@Inject
@@ -52,40 +64,95 @@ class AttachmentRetrieverImpl implements AttachmentRetriever {
 	}
 
 	@Override
-	public void cachePut(MessageId messageId,
-			List<AttachmentItem> attachments) {
-		attachmentCache.put(messageId, attachments);
+	@DatabaseExecutor
+	public Attachment getMessageAttachment(AttachmentHeader h)
+			throws DbException {
+		return messagingManager.getAttachment(h);
 	}
 
 	@Override
-	@Nullable
-	public List<AttachmentItem> cacheGet(MessageId messageId) {
-		return attachmentCache.get(messageId);
+	public List<AttachmentItem> getAttachmentItems(
+			PrivateMessageHeader messageHeader) {
+		List<AttachmentHeader> headers = messageHeader.getAttachmentHeaders();
+		List<AttachmentItem> items = new ArrayList<>(headers.size());
+		boolean needsSize = headers.size() == 1;
+		for (AttachmentHeader h : headers) {
+			AttachmentItem item = itemCache.get(h.getMessageId());
+			if (item == null || (needsSize && !item.hasSize())) {
+				item = new AttachmentItem(h, defaultSize, defaultSize, LOADING);
+				UnavailableItem unavailableItem = new UnavailableItem(
+						messageHeader.getId(), h, needsSize);
+				unavailableItems.put(h.getMessageId(), unavailableItem);
+			}
+			items.add(item);
+		}
+		return items;
 	}
 
 	@Override
-	public Attachment getMessageAttachment(AttachmentHeader h)
-			throws DbException {
-		return messagingManager.getAttachment(h);
+	@DatabaseExecutor
+	public void cacheAttachmentItem(MessageId conversationMessageId,
+			AttachmentHeader h) throws DbException {
+		try {
+			Attachment a = messagingManager.getAttachment(h);
+			// this adds it to the cache automatically
+			createAttachmentItem(a, true);
+		} catch (NoSuchMessageException e) {
+			LOG.info("Attachment not received yet");
+		}
+	}
+
+	@Override
+	@DatabaseExecutor
+	public Pair<MessageId, AttachmentItem> loadAttachmentItem(
+			MessageId attachmentId) throws DbException {
+		UnavailableItem unavailableItem = unavailableItems.get(attachmentId);
+		if (unavailableItem == null) throw new AssertionError();
+
+		MessageId conversationMessageId =
+				unavailableItem.getConversationMessageId();
+		AttachmentHeader h = unavailableItem.getHeader();
+		boolean needsSize = unavailableItem.needsSize();
+
+		AttachmentItem item;
+		try {
+			Attachment a = messagingManager.getAttachment(h);
+			item = createAttachmentItem(a, needsSize);
+			unavailableItems.remove(attachmentId);
+		} catch (NoSuchMessageException e) {
+			LOG.info("Attachment not received yet");
+			// unavailable item is still tracked, no need to add it again
+			item = new AttachmentItem(h, defaultSize, defaultSize, MISSING);
+		}
+		return new Pair<>(conversationMessageId, item);
 	}
 
 	@Override
-	public AttachmentItem getAttachmentItem(Attachment a, boolean needsSize) {
+	public AttachmentItem createAttachmentItem(Attachment a,
+			boolean needsSize) {
 		AttachmentHeader h = a.getHeader();
-		if (!needsSize) {
+		AttachmentItem item = itemCache.get(h.getMessageId());
+		if (item != null && (needsSize && item.hasSize())) return item;
+
+		if (needsSize) {
+			InputStream is = new BufferedInputStream(a.getStream());
+			Size size = imageSizeCalculator.getSize(is, h.getContentType());
+			item = createAttachmentItem(h, size);
+		} else {
 			String extension =
 					imageHelper.getExtensionFromMimeType(h.getContentType());
-			boolean hasError = false;
+			State state = AVAILABLE;
 			if (extension == null) {
 				extension = "";
-				hasError = true;
+				state = ERROR;
 			}
-			return new AttachmentItem(h, 0, 0, extension, 0, 0, hasError);
+			item = new AttachmentItem(h, extension, state);
 		}
+		itemCache.put(h.getMessageId(), item);
+		return item;
+	}
 
-		InputStream is = new BufferedInputStream(a.getStream());
-		Size size = imageSizeCalculator.getSize(is, h.getContentType());
-
+	private AttachmentItem createAttachmentItem(AttachmentHeader h, Size size) {
 		// calculate thumbnail size
 		Size thumbnailSize = new Size(defaultSize, defaultSize, size.mimeType);
 		if (!size.error) {
@@ -104,8 +171,9 @@ class AttachmentRetrieverImpl implements AttachmentRetriever {
 			hasError = true;
 		}
 		if (extension == null) extension = "";
-		return new AttachmentItem(h, size.width, size.height, extension,
-				thumbnailSize.width, thumbnailSize.height, hasError);
+		State state = hasError ? ERROR : AVAILABLE;
+		return new AttachmentItem(h, size.width, size.height,
+				extension, thumbnailSize.width, thumbnailSize.height, state);
 	}
 
 	private Size getThumbnailSize(int width, int height, String mimeType) {

briar-android/src/main/java/org/briarproject/briar/android/attachment/UnavailableItem.java

+package org.briarproject.briar.android.attachment;
+
+import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+class UnavailableItem {
+
+	private final MessageId conversationMessageId;
+	private final AttachmentHeader header;
+	private final boolean needsSize;
+
+	UnavailableItem(MessageId conversationMessageId,
+			AttachmentHeader header, boolean needsSize) {
+		this.conversationMessageId = conversationMessageId;
+		this.header = header;
+		this.needsSize = needsSize;
+	}
+
+	MessageId getConversationMessageId() {
+		return conversationMessageId;
+	}
+
+	AttachmentHeader getHeader() {
+		return header;
+	}
+
+	boolean needsSize() {
+		return needsSize;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -37,7 +37,6 @@ import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.NoSuchContactException;
-import org.briarproject.bramble.api.db.NoSuchMessageException;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
@@ -73,12 +72,12 @@ import org.briarproject.briar.api.client.ProtocolStateException;
 import org.briarproject.briar.api.client.SessionId;
 import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.conversation.ConversationMessageHeader;
+import org.briarproject.briar.api.conversation.ConversationMessageVisitor;
 import org.briarproject.briar.api.conversation.ConversationRequest;
 import org.briarproject.briar.api.conversation.ConversationResponse;
 import org.briarproject.briar.api.conversation.event.ConversationMessageReceivedEvent;
 import org.briarproject.briar.api.forum.ForumSharingManager;
 import org.briarproject.briar.api.introduction.IntroductionManager;
-import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
@@ -108,8 +107,6 @@ import static android.support.v4.view.ViewCompat.setTransitionName;
 import static android.support.v7.util.SortedList.INVALID_POSITION;
 import static android.view.Gravity.RIGHT;
 import static android.widget.Toast.LENGTH_SHORT;
-import static java.util.Collections.emptyList;
-import static java.util.Collections.singletonList;
 import static java.util.Collections.sort;
 import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.INFO;
@@ -121,9 +118,11 @@ import static org.briarproject.bramble.util.LogUtils.now;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_ATTACH_IMAGE;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_INTRODUCTION;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.LOADING;
 import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHMENTS;
 import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHMENT_POSITION;
 import static org.briarproject.briar.android.conversation.ImageActivity.DATE;
+import static org.briarproject.briar.android.conversation.ImageActivity.ITEM_ID;
 import static org.briarproject.briar.android.conversation.ImageActivity.NAME;
 import static org.briarproject.briar.android.util.UiUtils.getAvatarTransitionName;
 import static org.briarproject.briar.android.util.UiUtils.getBulbTransitionName;
@@ -175,8 +174,6 @@ public class ConversationActivity extends BriarActivity
 	volatile GroupInvitationManager groupInvitationManager;
 
 	private final Map<MessageId, String> textCache = new ConcurrentHashMap<>();
-	private final Map<MessageId, PrivateMessageHeader> missingAttachments =
-			new ConcurrentHashMap<>();
 	private final Observer<String> contactNameObserver = name -> {
 		requireNonNull(name);
 		loadMessages();
@@ -251,6 +248,7 @@ public class ConversationActivity extends BriarActivity
 		adapter = new ConversationAdapter(this, this);
 		list = findViewById(R.id.conversationView);
 		layoutManager = new LinearLayoutManager(this);
+		layoutManager.setStackFromEnd(true);
 		list.setLayoutManager(layoutManager);
 		list.setAdapter(adapter);
 		list.setEmptyText(getString(R.string.no_private_messages));
@@ -440,6 +438,7 @@ public class ConversationActivity extends BriarActivity
 		});
 	}
 
+	@DatabaseExecutor
 	private void eagerlyLoadMessageSize(PrivateMessageHeader h) {
 		try {
 			MessageId id = h.getId();
@@ -456,21 +455,10 @@ public class ConversationActivity extends BriarActivity
 			// images we use a grid so the size is fixed
 			List<AttachmentHeader> headers = h.getAttachmentHeaders();
 			if (headers.size() == 1) {
-				List<AttachmentItem> items = attachmentRetriever.cacheGet(id);
-				if (items == null) {
-					LOG.info("Eagerly loading image size for latest message");
-					AttachmentHeader header = headers.get(0);
-					try {
-						Attachment a = attachmentRetriever
-								.getMessageAttachment(header);
-						AttachmentItem item =
-								attachmentRetriever.getAttachmentItem(a, true);
-						attachmentRetriever.cachePut(id, singletonList(item));
-					} catch (NoSuchMessageException e) {
-						LOG.info("Attachment not received yet");
-						missingAttachments.put(header.getMessageId(), h);
-					}
-				}
+				LOG.info("Eagerly loading image size for latest message");
+				AttachmentHeader header = headers.get(0);
+				// get the item to retrieve its size
+				attachmentRetriever.cacheAttachmentItem(h.getId(), header);
 			}
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
@@ -551,44 +539,34 @@ public class ConversationActivity extends BriarActivity
 				&& adapter.isScrolledToBottom(layoutManager);
 	}
 
-	private void loadMessageAttachments(PrivateMessageHeader h) {
-		// TODO: Use placeholders for missing/invalid attachments
+	private void loadMessageAttachments(List<AttachmentItem> items) {
 		runOnDbThread(() -> {
-			try {
-				// TODO move getting the items off to IoExecutor, if size == 1
-				List<AttachmentHeader> headers = h.getAttachmentHeaders();
-				boolean needsSize = headers.size() == 1;
-				List<AttachmentItem> items = new ArrayList<>(headers.size());
-				for (AttachmentHeader header : headers) {
-					try {
-						Attachment a = attachmentRetriever
-								.getMessageAttachment(header);
-						AttachmentItem item = attachmentRetriever
-								.getAttachmentItem(a, needsSize);
-						items.add(item);
-					} catch (NoSuchMessageException e) {
-						LOG.info("Attachment not received yet");
-						missingAttachments.put(header.getMessageId(), h);
-						return;
-					}
-				}
-				// Don't cache items unless all are present and valid
-				attachmentRetriever.cachePut(h.getId(), items);