return BufferHandles from the media repository

BufferHandles are platform specific handles to a buffer. On web,
they have a .blob and .url property.

src/domain/session/room/timeline/tiles/ImageTile.js

@@ -35,11 +35,12 @@ export class ImageTile extends MessageTile {
     }
 
     async _loadEncryptedFile(file) {
-        const buffer = await this._mediaRepository.downloadEncryptedFile(file);
+        const bufferHandle = await this._mediaRepository.downloadEncryptedFile(file);
         if (this.isDisposed) {
+            bufferHandle.dispose();
             return;
         }
-        return this.track(this.platform.createBufferURL(buffer, file.mimetype));
+        return this.track(bufferHandle);
     }
 
     async load() {

src/matrix/SessionContainer.js

@@ -167,8 +167,7 @@ export class SessionContainer {
         this._requestScheduler.start();
         const mediaRepository = new MediaRepository({
             homeServer: sessionInfo.homeServer,
-            crypto: this._platform.crypto,
-            request: this._platform.request,
+            platform: this._platform,
         });
         this._session = new Session({
             storage: this._storage,

src/matrix/net/MediaRepository.js

@@ -18,10 +18,9 @@ import {encodeQueryParams} from "./common.js";
 import {decryptAttachment} from "../e2ee/attachment.js";
 
 export class MediaRepository {
-    constructor({homeServer, crypto, request}) {
+    constructor({homeServer, platform}) {
         this._homeServer = homeServer;
-        this._crypto = crypto;
-        this._request = request;
+        this._platform = platform;
     }
 
     mxcUrlThumbnail(url, width, height, method) {
@@ -55,8 +54,8 @@ export class MediaRepository {
 
     async downloadEncryptedFile(fileEntry) {
         const url = this.mxcUrl(fileEntry.url);
-        const {body: encryptedBuffer} = await this._request(url, {method: "GET", format: "buffer", cache: true}).response();
-        const decryptedBuffer = await decryptAttachment(this._crypto, encryptedBuffer, fileEntry);
-        return decryptedBuffer;
+        const {body: encryptedBuffer} = await this._platform.request(url, {method: "GET", format: "buffer", cache: true}).response();
+        const decryptedBuffer = await decryptAttachment(this._platform.crypto, encryptedBuffer, fileEntry);
+        return this._platform.createBufferHandle(decryptedBuffer, fileEntry.mimetype);
     }
 }

src/platform/web/Platform.js

@@ -27,7 +27,7 @@ import {OnlineStatus} from "./dom/OnlineStatus.js";
 import {Crypto} from "./dom/Crypto.js";
 import {estimateStorageUsage} from "./dom/StorageEstimate.js";
 import {WorkerPool} from "./dom/WorkerPool.js";
-import {BufferURL} from "./dom/BufferURL.js";
+import {BufferHandle} from "./dom/BufferHandle.js";
 
 function addScript(src) {
     return new Promise(function (resolve, reject) {
@@ -129,7 +129,7 @@ export class Platform {
         this._serviceWorkerHandler?.setNavigation(navigation);
     }
 
-    createBufferURL(buffer, mimetype) {
-        return new BufferURL(buffer, mimetype);
+    createBufferHandle(buffer, mimetype) {
+        return new BufferHandle(buffer, mimetype);
     }
 }

src/platform/web/dom/BufferHandle.js

@@ -69,18 +69,27 @@ const ALLOWED_BLOB_MIMETYPES = {
     'audio/x-flac': true,
 };
 
-export class BufferURL {
+export class BufferHandle {
     constructor(buffer, mimetype) {
         mimetype = mimetype ? mimetype.split(";")[0].trim() : '';
         if (!ALLOWED_BLOB_MIMETYPES[mimetype]) {
             mimetype = 'application/octet-stream';
         }
-        const blob = new Blob([buffer], {type: mimetype});
-        this.url = URL.createObjectURL(blob);
+        this.blob = new Blob([buffer], {type: mimetype});
+        this._url = null;
+    }
+
+    get url() {
+        if (!this._url) {
+             this._url = URL.createObjectURL(this.blob);
+        }
+        return this._url;
     }
 
     dispose() {
-        URL.revokeObjectURL(this.url);
-        this.url = null;
+        if (this._url) {
+            URL.revokeObjectURL(this._url);
+            this._url = null;
+        }
     }
 }