add helper method to count reactions

src/androidTest/java/im/conversations/android/xmpp/TransformationTest.java

@@ -80,6 +80,48 @@ public class TransformationTest {
         Assert.assertEquals(REMOTE, onlyReaction.reactionBy);
     }
 
+    @Test
+    public void multipleReactions() {
+        final var group = Jid.ofEscaped("a@group.example.com");
+        final var message = new Message(Message.Type.GROUPCHAT);
+        message.addExtension(new Body("Please give me a thumbs up"));
+        message.setFrom(group.withResource("user-a"));
+        this.transformer.transform(
+                Transformation.of(message, Instant.now(), REMOTE, "stanza-a", "id-user-a"));
+
+        final var reactionA = new Message(Message.Type.GROUPCHAT);
+        reactionA.setFrom(group.withResource("user-b"));
+        reactionA.addExtension(Reactions.to("stanza-a")).addExtension(new Reaction("Y"));
+        this.transformer.transform(
+                Transformation.of(reactionA, Instant.now(), REMOTE, "stanza-b", "id-user-b"));
+
+        final var reactionB = new Message(Message.Type.GROUPCHAT);
+        reactionB.setFrom(group.withResource("user-c"));
+        reactionB.addExtension(Reactions.to("stanza-a")).addExtension(new Reaction("Y"));
+        this.transformer.transform(
+                Transformation.of(reactionB, Instant.now(), REMOTE, "stanza-c", "id-user-c"));
+
+        final var reactionC = new Message(Message.Type.GROUPCHAT);
+        reactionC.setFrom(group.withResource("user-d"));
+        final var reactions = reactionC.addExtension(Reactions.to("stanza-a"));
+        reactions.addExtension(new Reaction("Y"));
+        reactions.addExtension(new Reaction("Z"));
+        this.transformer.transform(
+                Transformation.of(reactionC, Instant.now(), REMOTE, "stanza-d", "id-user-d"));
+
+        final var messages = database.messageDao().getMessages(1L);
+        Assert.assertEquals(1, messages.size());
+        final var dbMessage = Iterables.getOnlyElement(messages);
+        Assert.assertEquals(4, dbMessage.reactions.size());
+        final var aggregated = dbMessage.getAggregatedReactions();
+        final var mostFrequentReaction = Iterables.get(aggregated, 0);
+        Assert.assertEquals("Y", mostFrequentReaction.getKey());
+        Assert.assertEquals(3L, (long) mostFrequentReaction.getValue());
+        final var secondReaction = Iterables.get(aggregated, 1);
+        Assert.assertEquals("Z", secondReaction.getKey());
+        Assert.assertEquals(1L, (long) secondReaction.getValue());
+    }
+
     @Test
     public void correctionBeforeOriginal() {
 

src/main/java/eu/siacs/conversations/xml/Element.java

@@ -1,6 +1,7 @@
 package eu.siacs.conversations.xml;
 
 import com.google.common.base.Optional;
+import com.google.common.base.Preconditions;
 import com.google.common.base.Strings;
 import com.google.common.collect.Collections2;
 import com.google.common.collect.Iterables;
@@ -159,18 +160,18 @@ public class Element {
         return content;
     }
 
-    public Element setAttribute(String name, String value) {
-        if (name != null && value != null) {
+    public Element setAttribute(final String name, final String value) {
+        Preconditions.checkArgument(name != null, "The attribute must have a name");
+        if (value == null) {
+            this.attributes.remove(name);
+        } else {
             this.attributes.put(name, value);
         }
         return this;
     }
 
-    public Element setAttribute(String name, Jid value) {
-        if (name != null && value != null) {
-            this.attributes.put(name, value.toEscapedString());
-        }
-        return this;
+    public Element setAttribute(final String name, final Jid value) {
+        return this.setAttribute(name, value == null ? null : value.toEscapedString());
     }
 
     public void removeAttribute(final String name) {

src/main/java/im/conversations/android/database/model/MessageWithContentReactions.java

@@ -1,11 +1,17 @@
 package im.conversations.android.database.model;
 
 import androidx.room.Relation;
+import com.google.common.collect.ImmutableSortedSet;
+import com.google.common.collect.Maps;
+import com.google.common.collect.Multimaps;
 import eu.siacs.conversations.xmpp.Jid;
 import im.conversations.android.database.entity.MessageContentEntity;
 import im.conversations.android.database.entity.MessageReactionEntity;
 import java.time.Instant;
+import java.util.Collection;
 import java.util.List;
+import java.util.Map;
+import java.util.Set;
 
 public class MessageWithContentReactions {
 
@@ -34,4 +40,13 @@ public class MessageWithContentReactions {
             parentColumn = "id",
             entityColumn = "messageEntityId")
     public List<MessageReaction> reactions;
+
+    public Set<Map.Entry<String, Integer>> getAggregatedReactions() {
+        final Map<String, Integer> aggregatedReactions =
+                Maps.transformValues(
+                        Multimaps.index(reactions, r -> r.reaction).asMap(), Collection::size);
+        return ImmutableSortedSet.copyOf(
+                (a, b) -> Integer.compare(b.getValue(), a.getValue()),
+                aggregatedReactions.entrySet());
+    }
 }

src/main/java/im/conversations/android/xmpp/model/jabber/Body.java

@@ -10,6 +10,11 @@ public class Body extends Extension {
         super(Body.class);
     }
 
+    public Body(final String content) {
+        this();
+        setContent(content);
+    }
+
     public String getLang() {
         return this.getAttribute("xml:lang");
     }

src/main/java/im/conversations/android/xmpp/model/reactions/Reaction.java

@@ -9,4 +9,9 @@ public class Reaction extends Extension {
     public Reaction() {
         super(Reaction.class);
     }
+
+    public Reaction(final String reaction) {
+        this();
+        setContent(reaction);
+    }
 }

src/main/java/im/conversations/android/xmpp/model/reactions/Reactions.java

@@ -27,4 +27,10 @@ public class Reactions extends Extension {
     public void setId(String id) {
         this.setAttribute("id", id);
     }
+
+    public static Reactions to(final String id) {
+        final var reactions = new Reactions();
+        reactions.setId(id);
+        return reactions;
+    }
 }

src/main/java/im/conversations/android/xmpp/model/stanza/Message.java

@@ -10,6 +10,11 @@ public class Message extends Stanza {
         super(Message.class);
     }
 
+    public Message(Type type) {
+        this();
+        this.setType(type);
+    }
+
     public String getBody() {
         return this.findChildContent("body");
     }
@@ -27,6 +32,14 @@ public class Message extends Stanza {
         }
     }
 
+    public void setType(final Type type) {
+        if (type == null || type == Type.NORMAL) {
+            this.removeAttribute("type");
+        } else {
+            this.setAttribute("type", type.toString().toLowerCase(Locale.ROOT));
+        }
+    }
+
     public enum Type {
         ERROR,
         NORMAL,