Wire up helpers for checking if a user can invite to a room and getting its join rule

Author: t3chguy

src/models/room-state.js

@@ -23,6 +23,7 @@ import {EventEmitter} from "events";
 import {RoomMember} from "./room-member";
 import {logger} from '../logger';
 import * as utils from "../utils";
+import {EventType} from "../@types/event";
 
 // possible statuses for out-of-band member loading
 const OOB_STATUS_NOTSTARTED = 1;
@@ -718,6 +719,16 @@ RoomState.prototype.mayTriggerNotifOfType = function(notifLevelKey, userId) {
     return member.powerLevel >= notifLevel;
 };
 
+/**
+ * Returns the join rule based on the m.room.join_rule state event, defaulting to `invite`.
+ * @returns {string} the join_rule applied to this room
+ */
+RoomState.prototype.getJoinRule = function() {
+    const joinRuleEvent = this.getStateEvents(EventType.RoomJoinRules, "");
+    const joinRuleContent = joinRuleEvent ? joinRuleEvent.getContent() : {};
+    return joinRuleContent["join_rule"] || "invite";
+};
+
 
 function _updateThirdPartyTokenCache(roomState, memberEvent) {
     if (!memberEvent.getContent().third_party_invite) {

src/models/room.js

@@ -30,6 +30,7 @@ import {RoomMember} from "./room-member";
 import {RoomSummary} from "./room-summary";
 import {logger} from '../logger';
 import {ReEmitter} from '../ReEmitter';
+import {EventType} from "../@types/event";
 
 // These constants are used as sane defaults when the homeserver doesn't support
 // the m.room_versions capability. In practice, KNOWN_SAFE_ROOM_VERSION should be
@@ -1831,6 +1832,30 @@ Room.prototype.maySendMessage = function() {
         this.currentState.maySendEvent('m.room.message', this.myUserId);
 };
 
+/**
+ * Returns whether the given user has permissions to issue an invite for this room.
+ * @param {string} userId the ID of the Matrix user to check permissions for
+ * @returns {boolean} true if the user should be permitted to issue invites for this room.
+ */
+Room.prototype.canInvite = function(userId) {
+    let canInvite = this.getMyMembership() === "join";
+    const powerLevelsEvent = this.currentState.getStateEvents(EventType.RoomPowerLevels, "");
+    const powerLevels = powerLevelsEvent && powerLevelsEvent.getContent();
+    const me = this.getMember(userId);
+    if (powerLevels && me && powerLevels.invite > me.powerLevel) {
+        canInvite = false;
+    }
+    return canInvite;
+};
+
+/**
+ * Returns the join rule based on the m.room.join_rule state event, defaulting to `invite`.
+ * @returns {string} the join_rule applied to this room
+ */
+Room.prototype.getJoinRule = function() {
+    return this.currentState.getJoinRule();
+};
+
 /**
  * This is an internal method. Calculates the name of the room from the current
  * room state.