[FA-27] Need to test events but seems to mostly work

FictionArchive.Service.UserNovelDataService/Services/EventHandlers/ChapterCreatedEventHandler.cs

@@ -0,0 +1,53 @@
+using FictionArchive.Service.Shared.Services.EventBus;
+using FictionArchive.Service.UserNovelDataService.Models.Database;
+using FictionArchive.Service.UserNovelDataService.Models.IntegrationEvents;
+using Microsoft.EntityFrameworkCore;
+
+namespace FictionArchive.Service.UserNovelDataService.Services.EventHandlers;
+
+public class ChapterCreatedEventHandler : IIntegrationEventHandler<ChapterCreatedEvent>
+{
+    private readonly UserNovelDataServiceDbContext _dbContext;
+    private readonly ILogger<ChapterCreatedEventHandler> _logger;
+
+    public ChapterCreatedEventHandler(
+        UserNovelDataServiceDbContext dbContext,
+        ILogger<ChapterCreatedEventHandler> logger)
+    {
+        _dbContext = dbContext;
+        _logger = logger;
+    }
+
+    public async Task Handle(ChapterCreatedEvent @event)
+    {
+        // Ensure novel exists
+        var novelExists = await _dbContext.Novels.AnyAsync(n => n.Id == @event.NovelId);
+        if (!novelExists)
+        {
+            var novel = new Novel { Id = @event.NovelId };
+            _dbContext.Novels.Add(novel);
+        }
+
+        // Ensure volume exists
+        var volumeExists = await _dbContext.Volumes.AnyAsync(v => v.Id == @event.VolumeId);
+        if (!volumeExists)
+        {
+            var volume = new Volume { Id = @event.VolumeId };
+            _dbContext.Volumes.Add(volume);
+        }
+
+        // Create chapter if not exists
+        var chapterExists = await _dbContext.Chapters.AnyAsync(c => c.Id == @event.ChapterId);
+        if (chapterExists)
+        {
+            _logger.LogDebug("Chapter {ChapterId} already exists, skipping", @event.ChapterId);
+            return;
+        }
+
+        var chapter = new Chapter { Id = @event.ChapterId };
+        _dbContext.Chapters.Add(chapter);
+        await _dbContext.SaveChangesAsync();
+
+        _logger.LogInformation("Created chapter stub for {ChapterId} in novel {NovelId}", @event.ChapterId, @event.NovelId);
+    }
+}