generic way to support scriptable operations (#438)

* implemented a generic way to support scriptable operations

src/Microsoft.SqlTools.ServiceLayer/TaskServices/SmoScriptableTaskOperation.cs

@@ -0,0 +1,146 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Text;
+using Microsoft.SqlServer.Management.Common;
+using Microsoft.SqlServer.Management.Smo;
+
+namespace Microsoft.SqlTools.ServiceLayer.TaskServices
+{
+    /// <summary>
+    /// Any SMO operation that supports scripting should implement this class. 
+    /// It provides all of the configuration needed to choose between scripting or execution mode, 
+    /// hook into the Task manager framework, and send success / completion notifications to the caller.
+    /// </summary>
+    public abstract class SmoScriptableTaskOperation : IScriptableTaskOperation
+    {
+        /// <summary>
+        /// Script content
+        /// </summary>
+        public string ScriptContent
+        {
+            get; set;
+        }
+
+        /// <summary>
+        /// If an error occurred during task execution, this field contains the error message text
+        /// </summary>
+        public abstract string ErrorMessage { get; }
+
+        /// <summary>
+        /// SMO Server instance used for the operation
+        /// </summary>
+        public abstract Server Server { get; }
+
+        /// <summary>
+        /// Cancels the operation
+        /// </summary>
+        public abstract void Cancel();
+
+        /// <summary>
+        /// Updates messages in sql task given new progress message
+        /// </summary>
+        /// <param name="message"></param>
+        public void OnMessageAdded(TaskMessage message)
+        {
+            if (this.SqlTask != null)
+            {
+                this.SqlTask.AddMessage(message.Description, message.Status);
+            }
+        }
+
+        /// <summary>
+        /// Updates scripts in sql task given new script
+        /// </summary>
+        /// <param name="script"></param>
+        public void OnScriptAdded(TaskScript script)
+        {
+            this.SqlTask.AddScript(script.Status, script.Script, script.ErrorMessage);
+        }
+
+        /// <summary>
+        /// Executes the operations
+        /// </summary>
+        public abstract void Execute();
+
+
+        /// <summary>
+        /// Execute the operation for given execution mode
+        /// </summary>
+        /// <param name="mode"></param>
+        public virtual void Execute(TaskExecutionMode mode)
+        {
+            var currentExecutionMode = Server.ConnectionContext.SqlExecutionModes;
+            try
+            {
+                
+                if (Server != null)
+                {
+                    Server.ConnectionContext.CapturedSql.Clear();
+                    switch (mode)
+                    {
+                        case TaskExecutionMode.Execute:
+                            {
+                                Server.ConnectionContext.SqlExecutionModes = SqlExecutionModes.ExecuteSql;
+                                break;
+                            }
+                        case TaskExecutionMode.ExecuteAndScript:
+                            {
+                                Server.ConnectionContext.SqlExecutionModes = SqlExecutionModes.ExecuteAndCaptureSql;
+                                break;
+                            }
+                        case TaskExecutionMode.Script:
+                            {
+                                Server.ConnectionContext.SqlExecutionModes = SqlExecutionModes.CaptureSql;
+                                break;
+                            }
+                    }
+                }
+
+                Execute();
+                if (mode == TaskExecutionMode.Script || mode == TaskExecutionMode.ExecuteAndScript)
+                {
+                    this.ScriptContent = GetScriptContent();
+                    if (SqlTask != null)
+                    {
+                        OnScriptAdded(new TaskScript
+                        {
+                            Status = SqlTaskStatus.Succeeded,
+                            Script = this.ScriptContent
+                        });
+                    }
+                }
+            }
+            catch
+            {
+                throw;
+            }
+            finally
+            {
+                Server.ConnectionContext.CapturedSql.Clear();
+                Server.ConnectionContext.SqlExecutionModes = currentExecutionMode;
+            }
+
+        }
+
+        private string GetScriptContent()
+        {
+            StringBuilder sb = new StringBuilder();
+            foreach (String s in this.Server.ConnectionContext.CapturedSql.Text)
+            {
+                sb.Append(s);
+                sb.Append(Environment.NewLine);
+            }
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// The sql task to run the operations
+        /// </summary>
+        public SqlTask SqlTask { get; set; }
+
+    }
+}