Remove dummy concept in favor of editor group and editors

app/assets/javascripts/ui_models/editor_group.ts

@@ -0,0 +1,69 @@
+import { removeFromArray } from 'snjs';
+import { Editor } from './editor';
+import { WebApplication } from './application';
+
+type EditorGroupChangeCallback = () => void
+
+export class EditorGroup {
+
+  public editors: Editor[] = []
+  private application: WebApplication
+  changeObservers: EditorGroupChangeCallback[] = []
+
+  constructor(application: WebApplication) {
+    this.application = application;
+  }
+
+  public deinit() {
+    (this.application as any) = undefined;
+    for (const editor of this.editors) {
+      this.deleteEditor(editor);
+    }
+  }
+
+  createEditor(noteUuid?: string, noteTitle?: string) {
+    const editor = new Editor(this.application, noteUuid, noteTitle);
+    this.editors.push(editor);
+    this.notifyObservers();
+  }
+
+  deleteEditor(editor: Editor) {
+    editor.deinit();
+    removeFromArray(this.editors, editor);
+  }
+
+  closeEditor(editor: Editor) {
+    this.deleteEditor(editor);
+    this.notifyObservers();
+  }
+
+  closeActiveEditor() {
+    this.deleteEditor(this.editors[0]);
+  }
+
+  closeAllEditors() {
+    for(const editor of this.editors) {
+      this.deleteEditor(editor);
+    }
+  }
+
+  get activeEditor() {
+    return this.editors[0];
+  }
+
+  /**
+   * Notifies observer when the active editor has changed.
+   */
+  public addChangeObserver(callback: EditorGroupChangeCallback) {
+    this.changeObservers.push(callback);
+    if (this.activeEditor) {
+      callback();
+    }
+  }
+
+  private notifyObservers() {
+    for (const observer of this.changeObservers) {
+      observer();
+    }
+  }
+}