Feature/mssql-big-data-cluster (#4107)

* Adding kubernetes installer.

* Adding variety of kubectl support and integrating into the kubeconfig target cluster page.

* Addressing PR comments, refactored utility file locations and added missing license headers.

extensions/big-data-cluster/src/kubectl/kubectlUtils.ts

@@ -0,0 +1,86 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from "vscode";
+import { Kubectl } from "./kubectl";
+import { failed } from "../interfaces";
+
+export interface KubectlContext {
+    readonly clusterName: string;
+    readonly contextName: string;
+    readonly userName: string;
+    readonly active: boolean;
+}
+
+interface Kubeconfig {
+    readonly apiVersion: string;
+    readonly 'current-context': string;
+    readonly clusters: {
+        readonly name: string;
+        readonly cluster: {
+            readonly server: string;
+            readonly 'certificate-authority'?: string;
+            readonly 'certificate-authority-data'?: string;
+        };
+    }[] | undefined;
+    readonly contexts: {
+        readonly name: string;
+        readonly context: {
+            readonly cluster: string;
+            readonly user: string;
+            readonly namespace?: string;
+        };
+    }[] | undefined;
+    readonly users: {
+        readonly name: string;
+        readonly user: {};
+    }[] | undefined;
+}
+
+export interface ClusterConfig {
+    readonly server: string;
+    readonly certificateAuthority: string | undefined;
+}
+
+
+
+async function getKubeconfig(kubectl: Kubectl): Promise<Kubeconfig | null> {
+    const shellResult = await kubectl.asJson<any>("config view -o json");
+    if (failed(shellResult)) {
+        vscode.window.showErrorMessage(shellResult.error[0]);
+        return null;
+    }
+    return shellResult.result;
+}
+
+export async function getCurrentClusterConfig(kubectl: Kubectl): Promise<ClusterConfig | undefined> {
+    const kubeConfig = await getKubeconfig(kubectl);
+    if (!kubeConfig || !kubeConfig.clusters || !kubeConfig.contexts) {
+        return undefined;
+    }
+    const contextConfig = kubeConfig.contexts.find((context) => context.name === kubeConfig["current-context"])!;
+    const clusterConfig = kubeConfig.clusters.find((cluster) => cluster.name === contextConfig.context.cluster)!;
+    return {
+        server: clusterConfig.cluster.server,
+        certificateAuthority: clusterConfig.cluster["certificate-authority"]
+    };
+}
+
+export async function getContexts(kubectl: Kubectl): Promise<KubectlContext[]> {
+    const kubectlConfig = await getKubeconfig(kubectl);
+    if (!kubectlConfig) {
+        return [];
+    }
+    const currentContext = kubectlConfig["current-context"];
+    const contexts = kubectlConfig.contexts || [];
+    return contexts.map((c) => {
+        return {
+            clusterName: c.context.cluster,
+            contextName: c.name,
+            userName: c.context.user,
+            active: c.name === currentContext
+        };
+    });
+}