dramaling-vocab-learning/backend/DramaLing.Api/Services/AI/Generation/ImageGenerationWorkflow.cs

using DramaLing.Api.Data;
using DramaLing.Api.Models.DTOs;
using DramaLing.Api.Models.Entities;
using DramaLing.Api.Services.Storage;
using Microsoft.EntityFrameworkCore;
using System.Text.Json;

namespace DramaLing.Api.Services.AI.Generation;

public class ImageGenerationWorkflow : IImageGenerationWorkflow
{
    private readonly IServiceProvider _serviceProvider;
    private readonly IGenerationPipelineService _pipelineService;
    private readonly ILogger<ImageGenerationWorkflow> _logger;

    public ImageGenerationWorkflow(
        IServiceProvider serviceProvider,
        IGenerationPipelineService pipelineService,
        ILogger<ImageGenerationWorkflow> logger)
    {
        _serviceProvider = serviceProvider ?? throw new ArgumentNullException(nameof(serviceProvider));
        _pipelineService = pipelineService ?? throw new ArgumentNullException(nameof(pipelineService));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    public async Task<GenerationRequestResult> StartGenerationAsync(Guid flashcardId, GenerationRequest request)
    {
        using var scope = _serviceProvider.CreateScope();
        var dbContext = scope.ServiceProvider.GetRequiredService<DramaLingDbContext>();

        try
        {
            // 檢查詞卡是否存在
            var flashcard = await dbContext.Flashcards.FindAsync(flashcardId);
            if (flashcard == null)
            {
                throw new ArgumentException($"Flashcard {flashcardId} not found");
            }

            // 建立生成請求記錄
            var generationRequest = new ImageGenerationRequest
            {
                Id = Guid.NewGuid(),
                UserId = request.UserId,
                FlashcardId = flashcardId,
                OverallStatus = "pending",
                GeminiStatus = "pending",
                ReplicateStatus = "pending",
                OriginalRequest = JsonSerializer.Serialize(request),
                CreatedAt = DateTime.UtcNow
            };

            dbContext.ImageGenerationRequests.Add(generationRequest);
            await dbContext.SaveChangesAsync();

            _logger.LogInformation("Created generation request {RequestId} for flashcard {FlashcardId}",
                generationRequest.Id, flashcardId);

            // 後台執行生成流程 - 使用獨立的 Scope 避免 ObjectDisposedException
            _ = Task.Run(async () =>
            {
                using var backgroundScope = _serviceProvider.CreateScope();
                var backgroundPipelineService = backgroundScope.ServiceProvider.GetRequiredService<IGenerationPipelineService>();

                try
                {
                    await backgroundPipelineService.ExecuteGenerationPipelineAsync(generationRequest.Id);
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex, "Background generation pipeline failed for request {RequestId}", generationRequest.Id);
                }
            });

            return new GenerationRequestResult
            {
                RequestId = generationRequest.Id,
                OverallStatus = "pending",
                CurrentStage = "description_generation",
                EstimatedTimeMinutes = new EstimatedTimeDto
                {
                    Gemini = 0.5,
                    Replicate = 2.0,
                    Total = 2.5
                },
                CostEstimate = new CostEstimateDto
                {
                    Gemini = 0.002m,
                    Replicate = 0.025m,
                    Total = 0.027m
                }
            };
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to start generation for flashcard {FlashcardId}", flashcardId);
            throw;
        }
    }

    public async Task<GenerationStatusResponse> GetGenerationStatusAsync(Guid requestId)
    {
        using var scope = _serviceProvider.CreateScope();
        var dbContext = scope.ServiceProvider.GetRequiredService<DramaLingDbContext>();
        var storageService = scope.ServiceProvider.GetRequiredService<IImageStorageService>();

        var request = await dbContext.ImageGenerationRequests
            .Include(r => r.GeneratedImage)
            .FirstOrDefaultAsync(r => r.Id == requestId);

        if (request == null)
        {
            throw new ArgumentException($"Generation request {requestId} not found");
        }

        return new GenerationStatusResponse
        {
            RequestId = request.Id,
            OverallStatus = request.OverallStatus,
            Stages = new StageStatusDto
            {
                Gemini = new GeminiStageDto
                {
                    Status = request.GeminiStatus,
                    StartedAt = request.GeminiStartedAt,
                    CompletedAt = request.GeminiCompletedAt,
                    ProcessingTimeMs = request.GeminiProcessingTimeMs,
                    Cost = request.GeminiCost,
                    GeneratedDescription = request.GeneratedDescription
                },
                Replicate = new ReplicateStageDto
                {
                    Status = request.ReplicateStatus,
                    StartedAt = request.ReplicateStartedAt,
                    CompletedAt = request.ReplicateCompletedAt,
                    ProcessingTimeMs = request.ReplicateProcessingTimeMs,
                    Cost = request.ReplicateCost
                }
            },
            TotalCost = request.TotalCost,
            CompletedAt = request.CompletedAt,
            Result = request.GeneratedImage != null ? new GenerationResultDto
            {
                ImageUrl = await storageService.GetImageUrlAsync(request.GeneratedImage.RelativePath),
                ImageId = request.GeneratedImage.Id.ToString(),
                QualityScore = request.GeneratedImage.QualityScore,
                Dimensions = new DimensionsDto
                {
                    Width = request.GeneratedImage.ImageWidth ?? 512,
                    Height = request.GeneratedImage.ImageHeight ?? 512
                },
                FileSize = request.GeneratedImage.FileSize
            } : null
        };
    }

    public async Task<bool> CancelGenerationAsync(Guid requestId)
    {
        using var scope = _serviceProvider.CreateScope();
        var dbContext = scope.ServiceProvider.GetRequiredService<DramaLingDbContext>();

        try
        {
            var request = await dbContext.ImageGenerationRequests.FindAsync(requestId);
            if (request == null || request.OverallStatus == "completed")
            {
                return false;
            }

            request.OverallStatus = "cancelled";
            await dbContext.SaveChangesAsync();

            _logger.LogInformation("Generation request {RequestId} cancelled", requestId);
            return true;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to cancel generation request {RequestId}", requestId);
            return false;
        }
    }
}