Extract ModalManagerState from ModalManager (#2162)

js/src/common/states/ModalManagerState.js

@@ -0,0 +1,56 @@
+import Modal from '../components/Modal';
+
+export default class ModalManagerState {
+  constructor() {
+    this.modal = null;
+  }
+
+  /**
+   * Show a modal dialog.
+   *
+   * @public
+   */
+  show(componentClass, attrs) {
+    // Breaking Change Compliance Warning, Remove in Beta 15.
+    if (!(componentClass.prototype instanceof Modal)) {
+      // This is duplicated so that if the error is caught, an error message still shows up in the debug console.
+      console.error('The ModalManager can only show Modals');
+      throw new Error('The ModalManager can only show Modals');
+    }
+    if (componentClass.init) {
+      // This is duplicated so that if the error is caught, an error message still shows up in the debug console.
+      console.error(
+        'The componentClass parameter must be a modal class, not a modal instance. Whichever extension triggered this modal should be updated to comply with beta 14.'
+      );
+      throw new Error(
+        'The componentClass parameter must be a modal class, not a modal instance. Whichever extension triggered this modal should be updated to comply with beta 14.'
+      );
+    }
+    // End Change Compliance Warning, Remove in Beta 15
+
+    clearTimeout(this.closeTimeout);
+
+    this.modal = { componentClass, attrs };
+
+    m.redraw(true);
+  }
+
+  /**
+   * Close the modal dialog.
+   *
+   * @public
+   */
+  close() {
+    if (!this.modal) return;
+
+    // Don't hide the modal immediately, because if the consumer happens to call
+    // the `show` method straight after to show another modal dialog, it will
+    // cause Bootstrap's modal JS to misbehave. Instead we will wait for a tiny
+    // bit to give the `show` method the opportunity to prevent this from going
+    // ahead.
+    this.closeTimeout = setTimeout(() => {
+      this.modal = null;
+      m.lazyRedraw();
+    });
+  }
+}