BaseCodeGenerator.cs

//-----------------------------------------------------------------------
// <copyright company="CoApp Project">
//     Copyright (c) 2011 Garrett Serack. All rights reserved.
// </copyright>
//-----------------------------------------------------------------------

namespace CoApp.AnyGen {
    using System;
    using System.Diagnostics;
    using System.Runtime.InteropServices;
    using Microsoft.VisualStudio;
    using Microsoft.VisualStudio.Shell.Interop;

    /// <summary>
    ///   A managed wrapper for VS's concept of an IVsSingleFileGenerator which is
    ///   a custom tool invoked at design time which can take any file as an input
    ///   and provide any file as output.
    /// </summary>
    public abstract class BaseCodeGenerator : IVsSingleFileGenerator {
        public BaseCodeGenerator() {
            InputFilePath = String.Empty;
            FileNameSpace = String.Empty;
        }

        /// <summary>
        ///   Namespace for the file
        /// </summary>
        protected string FileNameSpace { get; set; }

        /// <summary>
        ///   File-path for the input file
        /// </summary>
        protected string InputFilePath { get; set; }

        /// <summary>
        ///   Interface to the VS shell object we use to tell our progress while we are generating
        /// </summary>
        internal IVsGeneratorProgress CodeGeneratorProgress { get; private set; }

        /// <summary>
        ///   Implements the IVsSingleFileGenerator.DefaultExtension method. 
        ///   Returns the extension of the generated file
        /// </summary>
        /// <param name = "defaultExtension">Out parameter, will hold the extension that is to be given to the output file name. The returned extension must include a leading period</param>
        /// <returns>S_OK if successful, E_FAIL if not</returns>
        public int DefaultExtension(out string defaultExtension) {
            try {
                defaultExtension = GetDefaultExtension();
                return VSConstants.S_OK;
            }
            catch (Exception e) {
                Trace.WriteLine("GetDefaultExtensionFailed");
                Trace.WriteLine(e.ToString());
                defaultExtension = string.Empty;
                return VSConstants.E_FAIL;
            }
        }

        /// <summary>
        ///   Implements the IVsSingleFileGenerator.Generate method.
        ///   Executes the transformation and returns the newly generated output file, whenever a custom tool is loaded, or the input file is saved
        /// </summary>
        /// <param name = "inputFilePath">The full path of the input file. May be a null reference (Nothing in Visual Basic) in future releases of Visual Studio, so generators should not rely on this value</param>
        /// <param name = "inputFileContents">The contents of the input file. This is either a UNICODE BSTR (if the input file is text) or a binary BSTR (if the input file is binary). If the input file is a text file, the project system automatically converts the BSTR to UNICODE</param>
        /// <param name = "defaultNamespace">This parameter is meaningful only for custom tools that generate code. It represents the namespace into which the generated code will be placed. If the parameter is not a null reference (Nothing in Visual Basic) and not empty, the custom tool can use the following syntax to enclose the generated code</param>
        /// <param name = "outputFileContents">[out] Returns an array of bytes to be written to the generated file. You must include UNICODE or UTF-8 signature bytes in the returned byte array, as this is a raw stream. The memory for outputFileContents must be allocated using the .NET Framework call, System.Runtime.InteropServices.AllocCoTaskMem, or the equivalent Win32 system call, CoTaskMemAlloc. The project system is responsible for freeing this memory</param>
        /// <param name = "pcbOutput">[out] Returns the count of bytes in the rgbOutputFileContent array</param>
        /// <param name = "pGenerateProgress">A reference to the IVsGeneratorProgress interface through which the generator can report its progress to the project system</param>
        /// <returns>If the method succeeds, it returns S_OK. If it fails, it returns E_FAIL</returns>
        public int Generate(string inputFilePath, string inputFileContents, string defaultNamespace, IntPtr[] outputFileContents, out uint pcbOutput, IVsGeneratorProgress pGenerateProgress) {
            if (inputFileContents == null) {
                throw new ArgumentNullException(inputFileContents);
            }

            InputFilePath = inputFilePath;
            FileNameSpace = defaultNamespace;
            CodeGeneratorProgress = pGenerateProgress;

            var bytes = GenerateCode(inputFileContents);

            if (bytes == null) {
                // This signals that GenerateCode() has failed. Tasklist items have been put up in GenerateCode()
                outputFileContents = null;
                pcbOutput = 0;

                // Return E_FAIL to inform Visual Studio that the generator has failed (so that no file gets generated)
                return VSConstants.E_FAIL;
            }
            else {
                // The contract between IVsSingleFileGenerator implementors and consumers is that 
                // any output returned from IVsSingleFileGenerator.Generate() is returned through  
                // memory allocated via CoTaskMemAlloc(). Therefore, we have to convert the 
                // byte[] array returned from GenerateCode() into an unmanaged blob.  

                var outputLength = bytes.Length;
                outputFileContents[0] = Marshal.AllocCoTaskMem(outputLength);
                Marshal.Copy(bytes, 0, outputFileContents[0], outputLength);
                pcbOutput = (uint) outputLength;
                return VSConstants.S_OK;
            }
        }

        /// <summary>
        ///   Gets the default extension for this generator
        /// </summary>
        /// <returns>String with the default extension for this generator</returns>
        protected abstract string GetDefaultExtension();

        /// <summary>
        ///   The method that does the actual work of generating code given the input file
        /// </summary>
        /// <param name = "inputFileContent">File contents as a string</param>
        /// <returns>The generated code file as a byte-array</returns>
        protected abstract byte[] GenerateCode(string inputFileContent);

        /// <summary>
        ///   Method that will communicate an error via the shell callback mechanism
        /// </summary>
        /// <param name = "level">Level or severity</param>
        /// <param name = "message">Text displayed to the user</param>
        /// <param name = "line">Line number of error</param>
        /// <param name = "column">Column number of error</param>
        protected virtual void GeneratorError(uint level, string message, uint line, uint column) {
            var progress = CodeGeneratorProgress;
            if (progress != null) {
                progress.GeneratorError(0, level, message, line, column);
            }
        }

        /// <summary>
        ///   Method that will communicate a warning via the shell callback mechanism
        /// </summary>
        /// <param name = "level">Level or severity</param>
        /// <param name = "message">Text displayed to the user</param>
        /// <param name = "line">Line number of warning</param>
        /// <param name = "column">Column number of warning</param>
        protected virtual void GeneratorWarning(uint level, string message, uint line, uint column) {
            var progress = CodeGeneratorProgress;
            if (progress != null) {
                progress.GeneratorError(1, level, message, line, column);
            }
        }
    }
}