Steev_code/Svrnty.Sample/AI/LangfuseHttpClient.cs

using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace Svrnty.Sample.AI;

/// <summary>
/// Simple HTTP client for sending traces directly to Langfuse ingestion API
/// </summary>
public class LangfuseHttpClient
{
    private readonly HttpClient _httpClient;
    private readonly string _publicKey;
    private readonly string _secretKey;
    private readonly bool _enabled;

    public LangfuseHttpClient(HttpClient httpClient, IConfiguration configuration)
    {
        _httpClient = httpClient;
        _publicKey = configuration["Langfuse:PublicKey"] ?? "";
        _secretKey = configuration["Langfuse:SecretKey"] ?? "";
        _enabled = !string.IsNullOrEmpty(_publicKey) && !string.IsNullOrEmpty(_secretKey);

        _ = Console.Out.WriteLineAsync($"[Langfuse] Initialized: Enabled={_enabled}, PublicKey={(_publicKey.Length > 0 ? "present" : "missing")}, SecretKey={(_secretKey.Length > 0 ? "present" : "missing")}");
    }

    public bool IsEnabled => _enabled;

    public async Task<LangfuseTrace> CreateTraceAsync(string name, string userId = "system")
    {
        return new LangfuseTrace(this, name, userId);
    }

    internal async Task SendBatchAsync(List<LangfuseEvent> events)
    {
        // File-based debug logging
        try
        {
            await File.AppendAllTextAsync("/tmp/langfuse_debug.log",
                $"{DateTime.UtcNow:O} [SendBatchAsync] Called: Enabled={_enabled}, Events={events.Count}\n");
        }
        catch { }

        if (!_enabled || events.Count == 0) return;

        try
        {
            var batch = new { batch = events };
            var json = JsonSerializer.Serialize(batch, new JsonSerializerOptions
            {
                PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
                DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
            });

            _ = Console.Out.WriteLineAsync($"[Langfuse] Sending {events.Count} events to {_httpClient.BaseAddress}/api/public/ingestion");

            var request = new HttpRequestMessage(HttpMethod.Post, "/api/public/ingestion")
            {
                Content = new StringContent(json, Encoding.UTF8, "application/json")
            };

            // Basic Auth with public/secret keys
            var authBytes = Encoding.UTF8.GetBytes($"{_publicKey}:{_secretKey}");
            request.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue(
                "Basic", Convert.ToBase64String(authBytes));

            var response = await _httpClient.SendAsync(request);
            response.EnsureSuccessStatusCode();

            _ = Console.Out.WriteLineAsync($"[Langfuse] Successfully sent batch, status: {response.StatusCode}");
        }
        catch (Exception ex)
        {
            // Log but don't throw - tracing shouldn't break the application
            _ = Console.Out.WriteLineAsync($"[Langfuse] Failed to send trace: {ex.Message}");
            _ = Console.Out.WriteLineAsync($"[Langfuse] Stack trace: {ex.StackTrace}");
        }
    }
}

/// <summary>
/// Represents a Langfuse trace that can contain multiple observations
/// </summary>
public class LangfuseTrace
{
    private readonly LangfuseHttpClient _client;
    private readonly string _traceId;
    private readonly List<LangfuseEvent> _events = new();
    private string? _input;
    private string? _output;
    private Dictionary<string, object>? _metadata;

    internal LangfuseTrace(LangfuseHttpClient client, string name, string userId)
    {
        _client = client;
        _traceId = Guid.NewGuid().ToString();

        _events.Add(new LangfuseEvent
        {
            Id = _traceId,
            Type = "trace-create",
            Timestamp = DateTime.UtcNow,
            Body = new Dictionary<string, object>
            {
                ["id"] = _traceId,
                ["name"] = name,
                ["userId"] = userId,
                ["timestamp"] = DateTime.UtcNow
            }
        });
    }

    public string TraceId => _traceId;

    public void SetInput(object input)
    {
        _input = input is string s ? s : JsonSerializer.Serialize(input);
    }

    public void SetOutput(object output)
    {
        _output = output is string s ? s : JsonSerializer.Serialize(output);
    }

    public void SetMetadata(Dictionary<string, object> metadata)
    {
        _metadata = metadata;
    }

    public LangfuseSpan CreateSpan(string name)
    {
        return new LangfuseSpan(this, name);
    }

    public LangfuseGeneration CreateGeneration(string name, string model = "qwen2.5-coder:7b")
    {
        return new LangfuseGeneration(this, name, model);
    }

    internal void AddEvent(LangfuseEvent evt)
    {
        _events.Add(evt);
    }

    public async Task FlushAsync()
    {
        // File-based debug logging
        try
        {
            await File.AppendAllTextAsync("/tmp/langfuse_debug.log",
                $"{DateTime.UtcNow:O} [FlushAsync] Called: Events={_events.Count}, HasInput={_input != null}, HasOutput={_output != null}, Enabled={_client.IsEnabled}\n");
        }
        catch { }

        // Update trace with final input/output
        if (_input != null || _output != null || _metadata != null)
        {
            var updateBody = new Dictionary<string, object> { ["id"] = _traceId };
            if (_input != null) updateBody["input"] = _input;
            if (_output != null) updateBody["output"] = _output;
            if (_metadata != null) updateBody["metadata"] = _metadata;

            _events.Add(new LangfuseEvent
            {
                Id = Guid.NewGuid().ToString(),
                Type = "trace-create", // Langfuse uses same type for updates
                Timestamp = DateTime.UtcNow,
                Body = updateBody
            });
        }

        await _client.SendBatchAsync(_events);
    }
}

/// <summary>
/// Represents a span (operation) within a trace
/// </summary>
public class LangfuseSpan : IDisposable
{
    private readonly LangfuseTrace _trace;
    private readonly string _spanId;
    private readonly DateTime _startTime;
    private object? _output;
    private Dictionary<string, object>? _metadata;

    internal LangfuseSpan(LangfuseTrace trace, string name)
    {
        _trace = trace;
        _spanId = Guid.NewGuid().ToString();
        _startTime = DateTime.UtcNow;

        _trace.AddEvent(new LangfuseEvent
        {
            Id = _spanId,
            Type = "span-create",
            Timestamp = _startTime,
            Body = new Dictionary<string, object>
            {
                ["id"] = _spanId,
                ["traceId"] = trace.TraceId,
                ["name"] = name,
                ["startTime"] = _startTime
            }
        });
    }

    public void SetOutput(object output)
    {
        _output = output;
    }

    public void SetMetadata(Dictionary<string, object> metadata)
    {
        _metadata = metadata;
    }

    public void Dispose()
    {
        var updateBody = new Dictionary<string, object>
        {
            ["id"] = _spanId,
            ["endTime"] = DateTime.UtcNow
        };

        if (_output != null)
            updateBody["output"] = _output is string s ? s : JsonSerializer.Serialize(_output);

        if (_metadata != null)
            updateBody["metadata"] = _metadata;

        _trace.AddEvent(new LangfuseEvent
        {
            Id = Guid.NewGuid().ToString(),
            Type = "span-update",
            Timestamp = DateTime.UtcNow,
            Body = updateBody
        });
    }
}

/// <summary>
/// Represents an LLM generation within a trace
/// </summary>
public class LangfuseGeneration : IDisposable
{
    private readonly LangfuseTrace _trace;
    private readonly string _generationId;
    private readonly DateTime _startTime;
    private readonly string _model;
    private object? _input;
    private object? _output;
    private Dictionary<string, object>? _metadata;

    internal LangfuseGeneration(LangfuseTrace trace, string name, string model)
    {
        _trace = trace;
        _generationId = Guid.NewGuid().ToString();
        _startTime = DateTime.UtcNow;
        _model = model;

        _trace.AddEvent(new LangfuseEvent
        {
            Id = _generationId,
            Type = "generation-create",
            Timestamp = _startTime,
            Body = new Dictionary<string, object>
            {
                ["id"] = _generationId,
                ["traceId"] = trace.TraceId,
                ["name"] = name,
                ["model"] = model,
                ["startTime"] = _startTime
            }
        });
    }

    public void SetInput(object input)
    {
        _input = input;
    }

    public void SetOutput(object output)
    {
        _output = output;
    }

    public void SetMetadata(Dictionary<string, object> metadata)
    {
        _metadata = metadata;
    }

    public void Dispose()
    {
        var updateBody = new Dictionary<string, object>
        {
            ["id"] = _generationId,
            ["endTime"] = DateTime.UtcNow
        };

        if (_input != null)
            updateBody["input"] = _input is string s ? s : JsonSerializer.Serialize(_input);

        if (_output != null)
            updateBody["output"] = _output is string o ? o : JsonSerializer.Serialize(_output);

        if (_metadata != null)
            updateBody["metadata"] = _metadata;

        _trace.AddEvent(new LangfuseEvent
        {
            Id = Guid.NewGuid().ToString(),
            Type = "generation-update",
            Timestamp = DateTime.UtcNow,
            Body = updateBody
        });
    }
}

/// <summary>
/// Internal event format for Langfuse ingestion API
/// </summary>
internal class LangfuseEvent
{
    [JsonPropertyName("id")]
    public string Id { get; set; } = "";

    [JsonPropertyName("type")]
    public string Type { get; set; } = "";

    [JsonPropertyName("timestamp")]
    public DateTime Timestamp { get; set; }

    [JsonPropertyName("body")]
    public Dictionary<string, object> Body { get; set; } = new();
}