Converting xliff to resx/resw as a build task

ConvertXliffToResx.targets

 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">  
 
   <Target Name="UpdateRuntimeResources">
        <ItemGroup>
           <XLiffResources Include="$(MSBuildThisFileDirectory)\xliff_resources\**\*.xliff" />
        </ItemGroup>
       <ImportResourceFiles XliffFiles="@(XLiffResources)" OutputDirectory="$(MSBuildThisFileDirectory)\LocalizedStrings" IsUWP="False" />
   </Target>
   
    <UsingTask TaskName="ImportResourceFiles" TaskFactory="CodeTaskFactory" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll">
        <ParameterGroup>
          <XliffFiles ParameterType="Microsoft.Build.Framework.ITaskItem[]" Required="true" />
          <OutputDirectory ParameterType="System.String" Required="true" />
          <IsUWP ParameterType="System.Boolean" Required="true" />
        </ParameterGroup>
        <Task>
            <Reference Include="System.Core" />
            <Reference Include="System.Xml" />
            <Reference Include="WindowsBase" />
            <Using Namespace="System" />
            <Using Namespace="System.IO" />
            <Using Namespace="System.IO.Packaging" />
            <Using Namespace="System.Linq" />
            <Using Namespace="System.Net" />
            <Using Namespace="System.Xml" />
            <Using Namespace="Microsoft.Build.Framework" />
            <Using Namespace="Microsoft.Build.Utilities" />
            <Code Type="Fragment" Language="cs">
            <![CDATA[
                string zipTempPath = null;
                string outfileDir = OutputDirectory;
                Log.LogMessage("Output directory: " + OutputDirectory, MessageImportance.High);  
                try {
                    var inFiles = XliffFiles.Select(f => f.GetMetadata("FullPath"));
                    string outputFilename = "Resources";
                    
                    var files = new Dictionary<string, List<string>>();
                    foreach (var infile in inFiles)
                    {
                        var file = new System.IO.FileInfo(infile);
                        string languageId = file.Directory.Parent.Name;
                        if (!files.ContainsKey(languageId))
                            files[languageId] = new List<string>();
                        files[languageId].Add(infile);
                    }

                    foreach(var filelist in files)
                    {
                        string languageId = filelist.Key;
                        string outfile = outfileDir;

                        if (languageId == "en")
                            languageId = "en-US";
                        else if (languageId == "nb")
                            languageId = "nb-NO";

                        if (IsUWP)
                        {
                            outfile = System.IO.Path.Combine(outfile, languageId, outputFilename);
                        }
                        else
                        {
                            if (languageId == "en-US")
                                outfile = System.IO.Path.Combine(outfile, outputFilename);
                            else
                                outfile = System.IO.Path.Combine(outfile, outputFilename + "." + languageId);
                        }
                        outfile += IsUWP ? ".resw" : ".resx";
                        string message = "Generating resource for language '" + languageId + "'...";
                        Console.WriteLine(message);

                        var d = new FileInfo(outfile).Directory;
                        if (!d.Exists)
                            d.Create();
                        XmlWriterSettings settings = new XmlWriterSettings();
                        settings.Indent = true;
                        using (XmlWriter writer = XmlWriter.Create(outfile, settings))
                        {
                            Dictionary<string, object> idChecker = new Dictionary<string, object>();
                            writer.WriteStartDocument();
                            writer.WriteStartElement("root");

                            writer.WriteStartElement("resheader");
                            writer.WriteAttributeString("name", "resmimetype");
                            writer.WriteElementString("value", "text/microsoft-resx");
                            writer.WriteEndElement(); //resheader

                            writer.WriteStartElement("resheader");
                            writer.WriteAttributeString("name", "version");
                            writer.WriteElementString("value", "2.0");
                            writer.WriteEndElement(); //resheader

                            writer.WriteStartElement("resheader");
                            writer.WriteAttributeString("name", "reader");
                            writer.WriteElementString("value", "System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089");
                            writer.WriteEndElement(); //resheader

                            writer.WriteStartElement("resheader");
                            writer.WriteAttributeString("name", "writer");
                            writer.WriteElementString("value", "System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089");
                            writer.WriteEndElement(); //resheader

                            writer.WriteStartElement("data");
                            writer.WriteAttributeString("name", "Resources_Language");
                            writer.WriteAttributeString("xml", "space", "", "preserve");
                            writer.WriteElementString("value", languageId);
                            writer.WriteEndElement(); //data

                            foreach (var infile in filelist.Value)
                            {
                                var file = new System.IO.FileInfo(infile);
                                string filename = file.Name.Substring(0, file.Name.LastIndexOf('.'));
                                Console.WriteLine("\tProcessing ' " + infile + "'...");
                                var fileExt = file.Extension.ToLowerInvariant();

                                if (fileExt == ".xliff")
                                {
                                    using (XmlReader reader = XmlReader.Create(infile))
                                    {
                                        while (reader.ReadToFollowing("trans-unit"))
                                        {
                                            string id = reader.GetAttribute("id");
                                            if (idChecker.ContainsKey(id))
                                                throw new InvalidOperationException("Duplicate resource ids detected");
                                            idChecker[id] = null;
                                            string resourceString = null;
                                            while (reader.Read() && reader.Name != "trans-unit")
                                            {
                                                if (reader.Name == "target")
                                                {
                                                    resourceString = reader.ReadElementContentAsString();
                                                    break; //target takes precedence over source
                                                }
                                                if (reader.Name == "source")
                                                {
                                                    resourceString = reader.ReadElementContentAsString();
                                                }
                                            }
                                            if (resourceString != null)
                                            {
                                                writer.WriteStartElement("data");
                                                writer.WriteAttributeString("name", id);

                                                writer.WriteAttributeString("xml", "space", "", "preserve");
                                                int index = -1;
                                                for (int i = 1; i < 10; i++)
                                                {
                                                    while ((index = resourceString.IndexOf("%" + i.ToString() + "$s")) > -1)
                                                    {
                                                        resourceString = resourceString.Replace("%" + i.ToString() + "$s", "{" + (i-1).ToString() + "}");
                                                    }
                                                }
                                                if (resourceString.Contains("%"))
                                                {
                                                    throw new InvalidOperationException("String parameter placeholder not supported");
                                                }
                                                writer.WriteElementString("value", resourceString);
                                                writer.WriteEndElement(); //data
                                    
                                            }
                                        }
                                    }
                                }
                                else if (fileExt == ".json")
                                {
                                    // Example: "output\resources\navigation\abbreviations\<LANG>.json" becomes "abbreviations__json" key
                                    var id = file.Directory.Name + "_json";
                                    if (idChecker.ContainsKey(id))
                                        throw new InvalidOperationException("Duplicate resource ID detected: " + id);
                                    idChecker[id] = null;
                                    var jsonText = File.ReadAllText(infile);
                                    
                                    writer.WriteStartElement("data");
                                    writer.WriteAttributeString("name", id);
                                    writer.WriteElementString("value", jsonText);
                                    writer.WriteEndElement(); //data
                                }
                                else
                                {
                                    throw new ArgumentException("Found a resource file of unknown file: " + infile);
                                }
                            }
                            writer.WriteEndElement(); //root
                            writer.WriteEndDocument();
                            writer.Flush();
                            writer.Close();
                        }
                    }
                    return true;
                }
                catch (Exception ex)
                {
                    Log.LogErrorFromException(ex);
                    return false;
                }
            ]]>
            </Code>
        </Task>
  </UsingTask>

</Project>