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/config/config.ts

@@ -0,0 +1,121 @@
+/*---------------------------------------------------------------------------------------------
+ *  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 { Host } from '../kubectl/host';
+import { Shell, Platform } from '../utility/shell';
+
+const EXTENSION_CONFIG_KEY = "mssql-bdc";
+const KUBECONFIG_PATH_KEY = "mssql-bdc.kubeconfig";
+const KNOWN_KUBECONFIGS_KEY = "mssql-bdc.knownKubeconfigs";
+
+export async function addPathToConfig(configKey: string, value: string): Promise<void> {
+    await setConfigValue(configKey, value);
+}
+
+async function setConfigValue(configKey: string, value: any): Promise<void> {
+    await atAllConfigScopes(addValueToConfigAtScope, configKey, value);
+}
+
+async function addValueToConfigAtScope(configKey: string, value: any, scope: vscode.ConfigurationTarget, valueAtScope: any, createIfNotExist: boolean): Promise<void> {
+    if (!createIfNotExist) {
+        if (!valueAtScope || !(valueAtScope[configKey])) {
+            return;
+        }
+    }
+
+    let newValue: any = {};
+    if (valueAtScope) {
+        newValue = Object.assign({}, valueAtScope);
+    }
+    newValue[configKey] = value;
+    await vscode.workspace.getConfiguration().update(EXTENSION_CONFIG_KEY, newValue, scope);
+}
+
+async function addValueToConfigArray(configKey: string, value: string): Promise<void> {
+    await atAllConfigScopes(addValueToConfigArrayAtScope, configKey, value);
+}
+
+async function addValueToConfigArrayAtScope(configKey: string, value: string, scope: vscode.ConfigurationTarget, valueAtScope: any, createIfNotExist: boolean): Promise<void> {
+    if (!createIfNotExist) {
+        if (!valueAtScope || !(valueAtScope[configKey])) {
+            return;
+        }
+    }
+
+    let newValue: any = {};
+    if (valueAtScope) {
+        newValue = Object.assign({}, valueAtScope);
+    }
+    const arrayEntry: string[] = newValue[configKey] || [];
+    arrayEntry.push(value);
+    newValue[configKey] = arrayEntry;
+    await vscode.workspace.getConfiguration().update(EXTENSION_CONFIG_KEY, newValue, scope);
+}
+
+type ConfigUpdater<T> = (configKey: string, value: T, scope: vscode.ConfigurationTarget, valueAtScope: any, createIfNotExist: boolean) => Promise<void>;
+
+async function atAllConfigScopes<T>(fn: ConfigUpdater<T>, configKey: string, value: T): Promise<void> {
+    const config = vscode.workspace.getConfiguration().inspect(EXTENSION_CONFIG_KEY)!;
+    await fn(configKey, value, vscode.ConfigurationTarget.Global, config.globalValue, true);
+    await fn(configKey, value, vscode.ConfigurationTarget.Workspace, config.workspaceValue, false);
+    await fn(configKey, value, vscode.ConfigurationTarget.WorkspaceFolder, config.workspaceFolderValue, false);
+}
+
+// Functions for working with the list of known kubeconfigs
+
+export function getKnownKubeconfigs(): string[] {
+    const kkcConfig = vscode.workspace.getConfiguration(EXTENSION_CONFIG_KEY)[KNOWN_KUBECONFIGS_KEY];
+    if (!kkcConfig || !kkcConfig.length) {
+        return [];
+    }
+    return kkcConfig as string[];
+}
+
+export async function addKnownKubeconfig(kubeconfigPath: string) {
+    await addValueToConfigArray(KNOWN_KUBECONFIGS_KEY, kubeconfigPath);
+}
+
+// Functions for working with the active kubeconfig setting
+
+export async function setActiveKubeconfig(kubeconfig: string): Promise<void> {
+    await addPathToConfig(KUBECONFIG_PATH_KEY, kubeconfig);
+}
+
+export function getActiveKubeconfig(): string {
+    return vscode.workspace.getConfiguration(EXTENSION_CONFIG_KEY)[KUBECONFIG_PATH_KEY];
+}
+
+// Functions for working with tool paths
+
+export function getToolPath(host: Host, shell: Shell, tool: string): string | undefined {
+    const baseKey = toolPathBaseKey(tool);
+    return getPathSetting(host, shell, baseKey);
+}
+
+function getPathSetting(host: Host, shell: Shell, baseKey: string): string | undefined {
+    const os = shell.platform();
+    const osOverridePath = host.getConfiguration(EXTENSION_CONFIG_KEY)[osOverrideKey(os, baseKey)];
+    return osOverridePath || host.getConfiguration(EXTENSION_CONFIG_KEY)[baseKey];
+}
+
+export function toolPathBaseKey(tool: string): string {
+    return `mssql-bdc.${tool}-path`;
+}
+
+function osOverrideKey(os: Platform, baseKey: string): string {
+    const osKey = osKeyString(os);
+    return osKey ? `${baseKey}.${osKey}` : baseKey;  // The 'else' clause should never happen so don't worry that this would result in double-checking a missing base key
+}
+
+function osKeyString(os: Platform): string | null {
+    switch (os) {
+        case Platform.Windows: return 'windows';
+        case Platform.MacOS: return 'mac';
+        case Platform.Linux: return 'linux';
+        default: return null;
+    }
+}
+