[RN] Prefetch remote avatar images 2/2

react/features/mobile/image-cache/middleware.js

 
 import { APP_WILL_MOUNT } from '../../app';
 import { CONFERENCE_FAILED, CONFERENCE_LEFT } from '../../base/conference';
+import {
+    getAvatarURL,
+    getLocalParticipant,
+    getParticipantById,
+    PARTICIPANT_ID_CHANGED,
+    PARTICIPANT_JOINED,
+    PARTICIPANT_UPDATED
+} from '../../base/participants';
 import { MiddlewareRegistry } from '../../base/redux';
+import { prefetch } from '../../mobile/image-cache';
+
+/**
+ * The indicator which determines whether avatar URLs are to be prefetched in
+ * the middleware here. Unless/until the implementation starts observing the
+ * redux store instead of the respective redux actions, the value should very
+ * likely be <tt>false</tt> because the middleware here is pretty much the last
+ * to get a chance to figure out that an avatar URL may be used. Besides, it is
+ * somewhat uninformed to download just about anything that may eventually be
+ * used or not.
+ *
+ * @private
+ * @type {boolean}
+ */
+const _PREFETCH_AVATAR_URLS = false;
 
 /**
  * Middleware which captures app startup and conference actions in order to
  *
  * @returns {Function}
  */
-MiddlewareRegistry.register(() => next => action => {
+MiddlewareRegistry.register(({ getState }) => next => action => {
     switch (action.type) {
     case APP_WILL_MOUNT:
     case CONFERENCE_FAILED:
     case CONFERENCE_LEFT:
         ImageCache.get().clear();
         break;
+
+    case PARTICIPANT_ID_CHANGED:
+    case PARTICIPANT_JOINED:
+    case PARTICIPANT_UPDATED: {
+        if (!_PREFETCH_AVATAR_URLS) {
+            break;
+        }
+
+        const result = next(action);
+
+        // Initiate the downloads of participants' avatars as soon as possible.
+
+        // 1. Figure out the participant (instance).
+        let { participant } = action;
+
+        if (participant) {
+            if (participant.id) {
+                participant = getParticipantById(getState, participant.id);
+            } else if (participant.local) {
+                participant = getLocalParticipant(getState);
+            } else {
+                participant = undefined;
+            }
+        } else if (action.oldValue && action.newValue) {
+            participant = getParticipantById(getState, action.newValue);
+        }
+        if (participant) {
+            // 2. Get the participant's avatar URL.
+            const uri = getAvatarURL(participant);
+
+            if (uri) {
+                // 3. Initiate the download of the participant's avatar.
+                prefetch({ uri });
+            }
+        }
+
+        return result;
+    }
     }
 
     return next(action);