implementation of config framework

src/Accounts/Authentication/Authentication.csproj

@@ -30,4 +30,8 @@
     </EmbeddedResource>
   </ItemGroup>
 
+  <ItemGroup>
+    <Folder Include="Config\Definitions\" />
+  </ItemGroup>
+
 </Project>

src/Accounts/Authentication/AzureSessionInitializer.cs

@@ -24,10 +24,11 @@
 using Microsoft.Azure.Commands.Common.Authentication.Authentication.TokenCache;
 using Microsoft.Azure.Commands.Common.Authentication.Factories;
 using Microsoft.Azure.Commands.Common.Authentication.Properties;
-
+using Microsoft.Azure.Commands.Common.Authentication.Config;
 using Newtonsoft.Json;
 
 using TraceLevel = System.Diagnostics.TraceLevel;
+using System.Collections.Generic;
 
 namespace Microsoft.Azure.Commands.Common.Authentication
 {
@@ -244,12 +245,23 @@ static IAzureSession CreateInstance(IDataStore dataStore = null)
             session.TokenCacheDirectory = autoSave.CacheDirectory;
             session.TokenCacheFile = autoSave.CacheFile;
 
+            InitializeConfigs(session);
             InitializeDataCollection(session);
             session.RegisterComponent(HttpClientOperationsFactory.Name, () => HttpClientOperationsFactory.Create());
             session.TokenCache = session.TokenCache ?? new AzureTokenCache();
             return session;
         }
 
+        private static void InitializeConfigs(AzureSession session)
+        {
+            var fallbackList = new List<string>()
+            {
+                Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".Azure", "PSConfig.json"),
+                Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), ".Azure", "PSConfig.json")
+            };
+            new ConfigInitializer(fallbackList).InitializeForAzureSession(session);
+        }
+
         public class AdalSession : AzureSession
         {
 #if !NETSTANDARD

src/Accounts/Authentication/Config/ConfigInitializer.cs

@@ -0,0 +1,156 @@
+// ----------------------------------------------------------------------------------
+//
+// Copyright Microsoft Corporation
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// ----------------------------------------------------------------------------------
+
+using Microsoft.Azure.Commands.Common.Authentication.Abstractions;
+using Microsoft.Azure.Commands.Common.Authentication.Config.Internal.Interfaces;
+using Microsoft.Azure.PowerShell.Common.Config;
+using Newtonsoft.Json.Linq;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+
+namespace Microsoft.Azure.Commands.Common.Authentication.Config
+{
+    /// <summary>
+    /// Initializes the config file and config manager.
+    /// </summary>
+    internal class ConfigInitializer
+    {
+        internal IDataStore DataStore { get; set; } = new DiskDataStore();
+        private static readonly object _fsLock = new object();
+
+        internal IEnvironmentVariableProvider EnvironmentVariableProvider { get; set; } = new DefaultEnvironmentVariableProvider();
+
+        private readonly string _pathToConfigFile;
+
+        public ConfigInitializer(IEnumerable<string> paths)
+        {
+            _ = paths ?? throw new ArgumentNullException(nameof(paths));
+            _pathToConfigFile = GetPathToConfigFile(paths);
+        }
+
+        /// <summary>
+        /// Loop through the fallback list of paths of the config file. Returns the first usable one.
+        /// </summary>
+        /// <param name="paths">A list of paths to the config file. When one is not usable, it will fallback to the next.</param>
+        /// <returns></returns>
+        /// <exception cref="ApplicationException">When no one in the list is usable.</exception>
+        private string GetPathToConfigFile(IEnumerable<string> paths)
+        {
+            // find first exist path and use it
+            foreach (string path in paths)
+            {
+                if (DataStore.FileExists(path))
+                {
+                    return path;
+                }
+            }
+            // if not found, use the first writable path
+            foreach (string path in paths)
+            {
+                try
+                {
+                    DirectoryInfo dir = new FileInfo(path).Directory;
+                    DataStore.CreateDirectory(dir.FullName); // create directory if not exists
+                    using (var _ = DataStore.OpenForExclusiveWrite(path)) { }
+                    return path;
+                }
+                catch (Exception)
+                {
+                    continue;
+                }
+            }
+            throw new ApplicationException($"Failed to store the config file. Please make sure any one of the following paths is accessible: {string.Join(", ", paths)}");
+        }
+
+        internal IConfigManager GetConfigManager()
+        {
+            lock (_fsLock)
+            {
+                ValidateConfigFile();
+            }
+            return new ConfigManager(_pathToConfigFile, DataStore, EnvironmentVariableProvider);
+        }
+
+        private void ValidateConfigFileContent()
+        {
+            string json = DataStore.ReadFileAsText(_pathToConfigFile);
+
+            bool isValidJson = true;
+            try
+            {
+                JObject.Parse(json);
+            }
+            catch (Exception)
+            {
+                isValidJson = false;
+            }
+
+            if (string.IsNullOrEmpty(json) || !isValidJson)
+            {
+                Debug.Write($"[ConfigInitializer] Failed to parse the config file at {_pathToConfigFile}. Clearing the file.");
+                ResetConfigFileToDefault();
+            }
+        }
+
+        private void ValidateConfigFile()
+        {
+            if (!DataStore.FileExists(_pathToConfigFile))
+            {
+                ResetConfigFileToDefault();
+            }
+            else
+            {
+                ValidateConfigFileContent();
+            }
+        }
+
+        private void ResetConfigFileToDefault()
+        {
+            try
+            {
+                DataStore.WriteFile(_pathToConfigFile, @"{}");
+            }
+            catch (Exception ex)
+            {
+                // do not halt for IO exception
+                Debug.WriteLine(ex.Message);
+            }
+        }
+
+        // todo: tests initializes configs in a different way. Maybe there should be an abstraction IConfigInitializer and two concrete classes ConfigInitializer + TestConfigInitializer
+        internal void InitializeForAzureSession(AzureSession session)
+        {
+            IConfigManager configManager = GetConfigManager();
+            session.RegisterComponent(nameof(IConfigManager), () => configManager);
+            RegisterConfigs(configManager);
+            configManager.BuildConfig();
+        }
+
+        private void RegisterConfigs(IConfigManager configManager)
+        {
+            // simple configs
+            // todo: review the help messages
+            //configManager.RegisterConfig(new SimpleTypedConfig<bool>(ConfigKeys.SuppressWarningMessage, "Controls if the warning messages of upcoming breaking changes are enabled or suppressed. The messages are typically displayed when a cmdlet that will have breaking change in the future is executed.", false, BreakingChangeAttributeHelper.SUPPRESS_ERROR_OR_WARNING_MESSAGE_ENV_VARIABLE_NAME));
+            //configManager.RegisterConfig(new SimpleTypedConfig<bool>(ConfigKeys.EnableInterceptSurvey, "When enabled, a message of taking part in the survey about the user experience of Azure PowerShell will prompt at low frequency.", true, "Azure_PS_Intercept_Survey"));
+            // todo: when the input is not a valid subscription name or id. Connect-AzAccount will throw an error. Is it right?
+            //configManager.RegisterConfig(new SimpleTypedConfig<string>(ConfigKeys.DefaultSubscriptionForLogin, "Subscription name or GUID. If defined, when logging in Azure PowerShell without specifying the subscription, this one will be used to select the default context.", string.Empty));
+            // todo: add later
+            //configManager.RegisterConfig(new RetryConfig());
+            // todo: how to migrate old config
+        //configManager.RegisterConfig(new EnableDataCollectionConfig());
+        }
+    }
+}