Allow blog posts to be loaded within one transaction

briar-api/src/main/java/org/briarproject/briar/api/blog/BlogManager.java

@@ -10,6 +10,7 @@ import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 
 import java.util.Collection;
+import java.util.List;
 
 import javax.annotation.Nullable;
 
@@ -98,6 +99,11 @@ public interface BlogManager {
 	 */
 	Collection<Blog> getBlogs() throws DbException;
 
+	/**
+	 * Returns the group IDs of all blogs to which the user subscribes.
+	 */
+	Collection<GroupId> getBlogIds(Transaction txn) throws DbException;
+
 	/**
 	 * Returns the header of the blog post with the given ID.
 	 */
@@ -108,11 +114,22 @@ public interface BlogManager {
 	 */
 	String getPostText(MessageId m) throws DbException;
 
+	/**
+	 * Returns the text of the blog post with the given ID.
+	 */
+	String getPostText(Transaction txn, MessageId m) throws DbException;
+
 	/**
 	 * Returns the headers of all posts in the given blog.
 	 */
 	Collection<BlogPostHeader> getPostHeaders(GroupId g) throws DbException;
 
+	/**
+	 * Returns the headers of all posts in the given blog.
+	 */
+	List<BlogPostHeader> getPostHeaders(Transaction txn, GroupId g)
+			throws DbException;
+
 	/**
 	 * Marks a blog post as read or unread.
 	 */

briar-core/src/main/java/org/briarproject/briar/blog/BlogManagerImpl.java

@@ -445,6 +445,14 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 		}
 	}
 
+	@Override
+	public Collection<GroupId> getBlogIds(Transaction txn) throws DbException {
+		List<GroupId> groupIds = new ArrayList<>();
+		Collection<Group> groups = db.getGroups(txn, CLIENT_ID, MAJOR_VERSION);
+		for (Group g : groups) groupIds.add(g.getId());
+		return groupIds;
+	}
+
 	@Override
 	public BlogPostHeader getPostHeader(GroupId g, MessageId m)
 			throws DbException {
@@ -471,6 +479,15 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 		}
 	}
 
+	@Override
+	public String getPostText(Transaction txn, MessageId m) throws DbException {
+		try {
+			return getPostText(clientHelper.getMessageAsList(txn, m));
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
 	private String getPostText(BdfList message) throws FormatException {
 		MessageType type = MessageType.valueOf(message.getLong(0).intValue());
 		if (type == POST) {
@@ -488,7 +505,12 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 	@Override
 	public Collection<BlogPostHeader> getPostHeaders(GroupId g)
 			throws DbException {
+		return db.transactionWithResult(true, txn -> getPostHeaders(txn, g));
+	}
 
+	@Override
+	public List<BlogPostHeader> getPostHeaders(Transaction txn, GroupId g)
+			throws DbException {
 		// Query for posts and comments only
 		BdfDictionary query1 = BdfDictionary.of(
 				new BdfEntry(KEY_TYPE, POST.getInt())
@@ -497,8 +519,7 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 				new BdfEntry(KEY_TYPE, COMMENT.getInt())
 		);
 
-		Collection<BlogPostHeader> headers = new ArrayList<>();
+		List<BlogPostHeader> headers = new ArrayList<>();
-		Transaction txn = db.startTransaction(true);
 		try {
 			Map<MessageId, BdfDictionary> metadata1 =
 					clientHelper.getMessageMetadataAsDictionary(txn, g, query1);
@@ -528,13 +549,10 @@ class BlogManagerImpl extends BdfIncomingMessageHook implements BlogManager,
 						entry.getKey(), meta, authorInfos);
 				headers.add(h);
 			}
-			db.commitTransaction(txn);
-			return headers;
 		} catch (FormatException e) {
 			throw new DbException(e);
-		} finally {
-			db.endTransaction(txn);
 		}
+		return headers;
 	}
 
 	@Override