Add the ability to reply

src/domain/session/room/RoomViewModel.js

@@ -155,7 +155,7 @@ export class RoomViewModel extends ViewModel {
         this._room.join();
     }
     
-    async _sendMessage(message) {
+    async _sendMessage(message, replyTo) {
         if (!this._room.isArchived && message) {
             try {
                 let msgtype = "m.text";
@@ -163,7 +163,11 @@ export class RoomViewModel extends ViewModel {
                     message = message.substr(4).trim();
                     msgtype = "m.emote";
                 }
-                await this._room.sendEvent("m.room.message", {msgtype, body: message});
+                const content = {msgtype, body: message};
+                if (replyTo) {
+                    content["m.relates_to"] = replyTo.reply();
+                }
+                await this._room.sendEvent("m.room.message", content);
             } catch (err) {
                 console.error(`room.sendMessage(): ${err.message}:\n${err.stack}`);
                 this._sendError = err;
@@ -327,7 +331,7 @@ class ComposerViewModel extends ViewModel {
     }
 
     sendMessage(message) {
-        const success = this._roomVM._sendMessage(message);
+        const success = this._roomVM._sendMessage(message, this._replyTo);
         if (success) {
             this._isEmpty = true;
             this.emitChange("canSend");

src/matrix/room/timeline/entries/BaseEventEntry.js

@@ -16,7 +16,7 @@ limitations under the License.
 
 import {BaseEntry} from "./BaseEntry.js";
 import {REDACTION_TYPE} from "../../common.js";
-import {createAnnotation, ANNOTATION_RELATION_TYPE, getRelationFromContent} from "../relations.js";
+import {createAnnotation, createReply, ANNOTATION_RELATION_TYPE, getRelationFromContent} from "../relations.js";
 import {PendingAnnotation} from "../PendingAnnotation.js";
 
 /** Deals mainly with local echo for relations and redactions,
@@ -151,6 +151,10 @@ export class BaseEventEntry extends BaseEntry {
         return createAnnotation(this.id, key);
     }
 
+    reply() {
+        return createReply(this.id);
+    }
+
     /** takes both remote event id and local txn id into account, see overriding in PendingEventEntry */
     isRelatedToId(id) {
         return id && this.relatedEventId === id;

src/matrix/room/timeline/relations.js

@@ -29,6 +29,14 @@ export function createAnnotation(targetId, key) {
     };
 }
 
+export function createReply(targetId) {
+    return {
+        "m.in_reply_to": {
+            "event_id": targetId
+        }
+    };
+}
+
 export function getRelationTarget(relation) {
     return relation.event_id || relation["m.in_reply_to"]?.event_id
 }