DeutschLernen/GermanApp/Presentation/Controllers/MistralController.cs

using GermanApp.Domain.Interfaces;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;

namespace GermanApp.Presentation.Controllers;

/// <summary>
/// API controller for Mistral AI text generation.
/// This is part of the Presentation layer.
/// </summary>
[ApiController]
[Route("api/[controller]")]
[Authorize]
public class MistralController : ControllerBase
{
    private readonly IMistralService _mistralService;

    public MistralController(IMistralService mistralService)
    {
        _mistralService = mistralService;
    }

    /// <summary>
    /// Generates text from a prompt.
    /// </summary>
    /// <param name="request">Text generation request</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>Generated text</returns>
    [HttpPost("generate")]
    public async Task<IActionResult> GenerateText(
        [FromBody] TextGenerationRequest request,
        CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(request.Prompt))
            return BadRequest("Prompt is required");

        try
        {
            var result = await _mistralService.GenerateTextAsync(
                request.Prompt,
                request.Model,
                request.Temperature,
                request.MaxTokens,
                cancellationToken);

            return Ok(new TextGenerationResponse(result));
        }
        catch (Exception ex)
        {
            return StatusCode(500, new { Error = ex.Message });
        }
    }

    /// <summary>
    /// Generates text from chat messages.
    /// </summary>
    /// <param name="request">Chat generation request</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>Generated text</returns>
    [HttpPost("chat")]
    public async Task<IActionResult> GenerateChat(
        [FromBody] ChatGenerationRequest request,
        CancellationToken cancellationToken = default)
    {
        if (request.Messages == null || request.Messages.Count == 0)
            return BadRequest("Messages are required");

        try
        {
            var result = await _mistralService.GenerateChatAsync(
                request.Messages,
                request.Model,
                request.Temperature,
                request.MaxTokens,
                cancellationToken);

            return Ok(new TextGenerationResponse(result));
        }
        catch (Exception ex)
        {
            return StatusCode(500, new { Error = ex.Message });
        }
    }

    /// <summary>
    /// Generates a story based on lesson context.
    /// </summary>
    /// <param name="request">Story generation request</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>Generated story</returns>
    [HttpPost("story")]
    public async Task<IActionResult> GenerateStory(
        [FromBody] StoryGenerationRequest request,
        CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(request.Level))
            return BadRequest("Level is required");

        try
        {
            var result = await _mistralService.GenerateStoryAsync(
                request.Level,
                request.Topic ?? string.Empty,
                request.VocabularyWords ?? new List<string>(),
                request.Length,
                cancellationToken);

            return Ok(new StoryGenerationResponse(result));
        }
        catch (Exception ex)
        {
            return StatusCode(500, new { Error = ex.Message });
        }
    }

    /// <summary>
    /// Provides feedback on user writing.
    /// </summary>
    /// <param name="request">Writing feedback request</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>Generated feedback</returns>
    [HttpPost("writing-feedback")]
    public async Task<IActionResult> GenerateWritingFeedback(
        [FromBody] WritingFeedbackRequest request,
        CancellationToken cancellationToken = default)
    {
        if (string.IsNullOrWhiteSpace(request.UserText))
            return BadRequest("User text is required");
        if (string.IsNullOrWhiteSpace(request.Level))
            return BadRequest("Level is required");

        try
        {
            var result = await _mistralService.GenerateWritingFeedbackAsync(
                request.UserText,
                request.Level,
                request.Prompt,
                cancellationToken);

            return Ok(new WritingFeedbackResponse(result));
        }
        catch (Exception ex)
        {
            return StatusCode(500, new { Error = ex.Message });
        }
    }

    /// <summary>
    /// Tests the Mistral API connection.
    /// </summary>
    /// <returns>Health check result</returns>
    [HttpGet("health")]
    [AllowAnonymous]
    public async Task<IActionResult> HealthCheck(CancellationToken cancellationToken = default)
    {
        try
        {
            var isHealthy = await _mistralService.TestConnectionAsync(cancellationToken);
            return Ok(new { Healthy = isHealthy });
        }
        catch (Exception ex)
        {
            return StatusCode(500, new { Error = ex.Message });
        }
    }
}

/// <summary>
/// Request DTO for text generation.
/// </summary>
public record TextGenerationRequest(
    string Prompt,
    string? Model = null,
    float Temperature = 0.7f,
    int? MaxTokens = null);

/// <summary>
/// Request DTO for chat generation.
/// </summary>
public record ChatGenerationRequest(
    IReadOnlyList<(string Role, string Content)> Messages,
    string? Model = null,
    float Temperature = 0.7f,
    int? MaxTokens = null);

/// <summary>
/// Request DTO for story generation.
/// </summary>
public record StoryGenerationRequest(
    string Level,
    string? Topic = null,
    IReadOnlyList<string>? VocabularyWords = null,
    int Length = 200);

/// <summary>
/// Request DTO for writing feedback.
/// </summary>
public record WritingFeedbackRequest(
    string UserText,
    string Level,
    string? Prompt = null);

/// <summary>
/// Response DTO for text generation.
/// </summary>
public record TextGenerationResponse(string Text);

/// <summary>
/// Response DTO for story generation.
/// </summary>
public record StoryGenerationResponse(string Story);

/// <summary>
/// Response DTO for writing feedback.
/// </summary>
public record WritingFeedbackResponse(string Feedback);