managing-apps/src/Managing.Api/Controllers/LlmController.cs

using Managing.Application.Abstractions.Services;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;

namespace Managing.Api.Controllers;

/// <summary>
/// Controller for LLM (Large Language Model) operations with MCP tool calling support.
/// Provides endpoints for chat interactions with automatic provider selection and BYOK (Bring Your Own Key) support.
/// </summary>
[ApiController]
[Authorize]
[Route("[controller]")]
[Produces("application/json")]
public class LlmController : BaseController
{
    private readonly ILlmService _llmService;
    private readonly IMcpService _mcpService;
    private readonly ILogger<LlmController> _logger;

    public LlmController(
        ILlmService llmService,
        IMcpService mcpService,
        IUserService userService,
        ILogger<LlmController> logger) : base(userService)
    {
        _llmService = llmService;
        _mcpService = mcpService;
        _logger = logger;
    }

    /// <summary>
    /// Sends a chat message to an LLM with automatic provider selection and MCP tool calling support.
    /// Supports both auto mode (backend selects provider) and BYOK (user provides API key).
    /// </summary>
    /// <param name="request">The chat request with messages and optional provider/API key</param>
    /// <returns>The LLM response with tool calls if applicable</returns>
    [HttpPost]
    [Route("Chat")]
    public async Task<ActionResult<LlmChatResponse>> Chat([FromBody] LlmChatRequest request)
    {
        if (request == null)
        {
            return BadRequest("Chat request is required");
        }

        if (request.Messages == null || !request.Messages.Any())
        {
            return BadRequest("At least one message is required");
        }

        try
        {
            var user = await GetUser();

            // Get available MCP tools
            var availableTools = await _mcpService.GetAvailableToolsAsync();
            request.Tools = availableTools.ToList();

            // Add system message to clarify that tools are optional and the LLM can respond directly
            // Check if a system message already exists
            var hasSystemMessage = request.Messages.Any(m => m.Role == "system");
            if (!hasSystemMessage)
            {
                var systemMessage = new LlmMessage
                {
                    Role = "system",
                    Content = "You are a helpful AI assistant with expertise in quantitative finance, algorithmic trading, and financial mathematics. " +
                              "You can answer questions directly using your knowledge. " +
                              "Tools are available for specific operations (backtesting, agent management, market data retrieval, etc.) but are optional. " +
                              "Use tools only when they are needed for the specific task. " +
                              "For general questions, explanations, calculations, or discussions, respond directly without using tools."
                };
                request.Messages.Insert(0, systemMessage);
            }

            // Send chat request to LLM
            var response = await _llmService.ChatAsync(user, request);

            // If LLM wants to call tools, execute them and get final response
            if (response.RequiresToolExecution && response.ToolCalls?.Any() == true)
            {
                _logger.LogInformation("LLM requested {Count} tool calls for user {UserId}",
                    response.ToolCalls.Count, user.Id);

                // Execute all tool calls
                var toolResults = new List<LlmMessage>();
                foreach (var toolCall in response.ToolCalls)
                {
                    try
                    {
                        var toolResult = await _mcpService.ExecuteToolAsync(user, toolCall.Name, toolCall.Arguments);
                        toolResults.Add(new LlmMessage
                        {
                            Role = "tool",
                            Content = System.Text.Json.JsonSerializer.Serialize(toolResult),
                            ToolCallId = toolCall.Id
                        });
                        _logger.LogInformation("Successfully executed tool {ToolName} for user {UserId}",
                            toolCall.Name, user.Id);
                    }
                    catch (Exception ex)
                    {
                        _logger.LogError(ex, "Error executing tool {ToolName} for user {UserId}",
                            toolCall.Name, user.Id);
                        toolResults.Add(new LlmMessage
                        {
                            Role = "tool",
                            Content = $"Error executing tool: {ex.Message}",
                            ToolCallId = toolCall.Id
                        });
                    }
                }

                // Add assistant message with tool calls
                request.Messages.Add(new LlmMessage
                {
                    Role = "assistant",
                    Content = response.Content,
                    ToolCalls = response.ToolCalls
                });

                // Add tool results
                request.Messages.AddRange(toolResults);

                // Get final response from LLM
                var finalResponse = await _llmService.ChatAsync(user, request);
                return Ok(finalResponse);
            }

            return Ok(response);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error processing chat request for user");
            return StatusCode(500, $"Error processing chat request: {ex.Message}");
        }
    }

    /// <summary>
    /// Gets the list of available LLM providers configured on the backend.
    /// </summary>
    /// <returns>List of provider names</returns>
    [HttpGet]
    [Route("Providers")]
    public async Task<ActionResult<IEnumerable<string>>> GetProviders()
    {
        try
        {
            var providers = await _llmService.GetAvailableProvidersAsync();
            return Ok(providers);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error getting available providers");
            return StatusCode(500, $"Error getting available providers: {ex.Message}");
        }
    }

    /// <summary>
    /// Gets the list of available MCP tools that the LLM can call.
    /// </summary>
    /// <returns>List of MCP tools with their descriptions and parameters</returns>
    [HttpGet]
    [Route("Tools")]
    public async Task<ActionResult<IEnumerable<McpToolDefinition>>> GetTools()
    {
        try
        {
            var tools = await _mcpService.GetAvailableToolsAsync();
            return Ok(tools);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error getting available tools");
            return StatusCode(500, $"Error getting available tools: {ex.Message}");
        }
    }
}