dotnet-cqrs/Svrnty.CQRS.Grpc.Generators/WriteProtoFileTask.cs

#pragma warning disable RS1035 // Do not use APIs banned for analyzers - This is an MSBuild task, not an analyzer

using System;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;

namespace Svrnty.CQRS.Grpc.Generators;

/// <summary>
/// MSBuild task that extracts the auto-generated proto file content from the source generator
/// output and writes it to disk so Grpc.Tools can process it
/// </summary>
public class WriteProtoFileTask : Task
{
    /// <summary>
    /// The project directory where we should look for generated files
    /// </summary>
    [Required]
    public string ProjectDirectory { get; set; } = string.Empty;

    /// <summary>
    /// The intermediate output path (typically obj/Debug/net10.0)
    /// </summary>
    [Required]
    public string IntermediateOutputPath { get; set; } = string.Empty;

    /// <summary>
    /// The output directory where the proto file should be written (typically Protos/)
    /// </summary>
    [Required]
    public string OutputDirectory { get; set; } = string.Empty;

    /// <summary>
    /// The name of the proto file to generate (typically cqrs_services.proto)
    /// </summary>
    [Required]
    public string ProtoFileName { get; set; } = string.Empty;

    public override bool Execute()
    {
        try
        {
            Log.LogMessage(MessageImportance.High,
                "Svrnty.CQRS.Grpc: Extracting auto-generated proto file...");

            // Look for the generated C# file containing the proto content
            // Source generators output to obj/Generated, not IntermediateOutputPath/Generated
            var generatedFilePath = Path.Combine(
                ProjectDirectory,
                "obj",
                "Generated",
                "Svrnty.CQRS.Grpc.Generators",
                "Svrnty.CQRS.Grpc.Generators.ProtoFileSourceGenerator",
                "GeneratedProtoFile.g.cs"
            );

            if (!File.Exists(generatedFilePath))
            {
                Log.LogWarning(
                    $"Generated proto file not found at {generatedFilePath}. " +
                    "The proto file may not have been generated yet. This is normal on first build.");
                return true; // Don't fail the build, just skip
            }

            // Read the generated C# file
            var csContent = File.ReadAllText(generatedFilePath);

            // Extract the proto content using a more robust approach
            // Looking for: public const string Content = @"...";
            var startMarker = "public const string Content = @\"";
            var startIndex = csContent.IndexOf(startMarker);

            if (startIndex < 0)
            {
                Log.LogError($"Could not find Content property in {generatedFilePath}");
                return false;
            }

            startIndex += startMarker.Length;

            // Find the closing "; - We need the LAST occurrence because the content contains escaped quotes
            // The pattern is: Content = @"...content...";
            // where content has "" for literal quotes
            var endMarker = "\";";

            // Find where the next field starts or class ends to limit our search
            var nextFieldOrEnd = csContent.IndexOf("\n    }", startIndex); // End of class
            if (nextFieldOrEnd < 0)
            {
                nextFieldOrEnd = csContent.Length;
            }

            var endIndex = csContent.LastIndexOf(endMarker, nextFieldOrEnd, nextFieldOrEnd - startIndex);

            if (endIndex < 0 || endIndex < startIndex)
            {
                Log.LogError($"Could not find end of Content property in {generatedFilePath}");
                return false;
            }

            // Extract and unescape doubled quotes
            var protoContent = csContent.Substring(startIndex, endIndex - startIndex);
            protoContent = protoContent.Replace("\"\"", "\"");

            Log.LogMessage(MessageImportance.High,
                $"Extracted proto content length: {protoContent.Length} characters");

            // Ensure output directory exists
            var fullOutputPath = Path.Combine(ProjectDirectory, OutputDirectory);
            Directory.CreateDirectory(fullOutputPath);

            // Write the proto file
            var protoFilePath = Path.Combine(fullOutputPath, ProtoFileName);
            File.WriteAllText(protoFilePath, protoContent);

            Log.LogMessage(MessageImportance.High,
                $"Svrnty.CQRS.Grpc: Successfully generated proto file at {protoFilePath}");

            return true;
        }
        catch (Exception ex)
        {
            Log.LogErrorFromException(ex, true);
            return false;
        }
    }
}