Extract the render ready status into an extra redux state

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

src/redux/renderer-status/reducers.ts

@@ -0,0 +1,34 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { RendererStatus, RendererStatusActions, RendererStatusActionType } from './types'
+import { Reducer } from 'redux'
+
+const initialState: RendererStatus = {
+  rendererReady: false
+}
+
+/**
+ * Applies {@link RendererStatusActions renderer status actions} to the global application state.
+ *
+ * @param state the current state
+ * @param action the action that should get applied
+ * @return The new changed state
+ */
+export const RendererStatusReducer: Reducer<RendererStatus, RendererStatusActions> = (
+  state: RendererStatus = initialState,
+  action: RendererStatusActions
+) => {
+  switch (action.type) {
+    case RendererStatusActionType.SET_RENDERER_STATUS:
+      return {
+        ...state,
+        rendererReady: action.rendererReady
+      }
+    default:
+      return state
+  }
+}