Use JSON over strings as payload format

backend/src/Model/Base64Message.ts

@@ -0,0 +1,27 @@
+import { Base64 } from 'js-base64'
+
+export class Base64Message {
+  private base64Message: string
+  public length: number
+
+  private constructor(base64Str: string) {
+    this.base64Message = base64Str
+    this.length = base64Str.length
+  }
+
+  public static toUnicodeString(message: Base64Message) {
+    return Base64.decode(message.base64Message)
+  }
+
+  public static fromBuffer(buffer: Buffer) {
+    return new Base64Message(buffer.toString('base64'))
+  }
+
+  public static fromString(str: string) {
+    return new Base64Message(Base64.encode(str))
+  }
+
+  public static toDataUri(message: Base64Message, mimeType: string) {
+    return `data:${mimeType};base64,${message.base64Message}`
+  }
+}

backend/src/Model/Message.ts

@@ -1,5 +1,7 @@
+import { Base64Message } from './Base64Message'
+
 export interface Message {
-  value?: any | undefined
+  value?: Base64Message
   length: number
   received: Date
 }

backend/src/Model/Tree.ts

@@ -32,7 +32,7 @@ export class Tree<ViewModel> extends TreeNode<ViewModel> {
   public applyUnmergedChanges() {
     this.unmergedMessages.forEach((msg) => {
       const edges = msg.topic.split('/')
-      const node = TreeNodeFactory.fromEdgesAndValue<ViewModel, any>(edges, msg.payload)
+      const node = TreeNodeFactory.fromEdgesAndValue<ViewModel>(edges, msg.payload)
       node.mqttMessage = msg
 
       if (!this.nodeFilter || this.nodeFilter(node)) {

backend/src/Model/TreeNodeFactory.ts

@@ -1,3 +1,4 @@
+import { Base64Message } from './Base64Message'
 import { Edge, Tree, TreeNode } from './'
 
 interface HasLength {
@@ -18,10 +19,10 @@ export abstract class TreeNodeFactory {
     node.sourceEdge!.target = node
   }
 
-  public static fromEdgesAndValue<ViewModel, T extends HasLength>(edgeNames: string[], value?: T): TreeNode<ViewModel> {
+  public static fromEdgesAndValue<ViewModel>(edgeNames: string[], value?: Base64Message | null): TreeNode<ViewModel> {
     const node = new TreeNode<ViewModel>()
     node.setMessage({
-      value,
+      value: value || undefined,
       length: value ? value.length : 0,
       received: new Date(),
     })