stackdriver: return values for services and metric types

public/app/plugins/datasource/stackdriver/StackdriverMetricFindQuery.ts

@@ -0,0 +1,36 @@
+import { extractServicesFromMetricDescriptors, getMetricTypesByService } from './functions';
+
+export default class StackdriverMetricFindQuery {
+  constructor(private datasource) {}
+
+  async query(query: any) {
+    switch (query.type) {
+      case 'services':
+        return this.handleServiceQueryType();
+      case 'metricTypes':
+        return this.handleMetricTypesQueryType(query);
+      default:
+        return [];
+    }
+  }
+
+  async handleServiceQueryType() {
+    const metricDescriptors = await this.datasource.getMetricTypes(this.datasource.projectName);
+    const services = extractServicesFromMetricDescriptors(metricDescriptors);
+    return services.map(s => ({
+      text: s.name,
+      expandable: true,
+    }));
+  }
+
+  async handleMetricTypesQueryType({ service }) {
+    if (!service) {
+      return [];
+    }
+    const metricDescriptors = await this.datasource.getMetricTypes(this.datasource.projectName);
+    return getMetricTypesByService(metricDescriptors, service).map(s => ({
+      text: s.name,
+      expandable: true,
+    }));
+  }
+}