Add redux actions/reducer for metrics

ui/src/reducers/metricsReducer.ts

@@ -0,0 +1,49 @@
+import {
+  GET_METRICS_BEGIN,
+  GET_METRICS_ERROR,
+  GET_METRICS_SUCCESS,
+  MetricsActionTypes,
+} from "../actions/metricsActions";
+import { MetricsResponse } from "../api";
+
+interface MetricsState {
+  loading: boolean;
+  error: string;
+  data: MetricsResponse | null;
+}
+
+const initialState: MetricsState = {
+  loading: false,
+  error: "",
+  data: null,
+};
+
+export default function metricsReducer(
+  state = initialState,
+  action: MetricsActionTypes
+): MetricsState {
+  switch (action.type) {
+    case GET_METRICS_BEGIN:
+      return {
+        ...state,
+        loading: true,
+      };
+
+    case GET_METRICS_ERROR:
+      return {
+        ...state,
+        loading: false,
+        error: action.error,
+      };
+
+    case GET_METRICS_SUCCESS:
+      return {
+        loading: false,
+        error: "",
+        data: action.payload,
+      };
+
+    default:
+      return state;
+  }
+}