fix: migrate to IDbContextFactory and remove direct AppDbContext from DI (#11)

Reviewed-on: #11
Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Co-committed-by: Marek Jasiński <jasins.marek@gmail.com>

src/NexusReader.Application/Queries/Library/SearchLibrarySemanticallyQuery.cs

@@ -4,7 +4,8 @@ using MediatR;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.AI;
 using NexusReader.Application.DTOs.AI;
-using NexusReader.Application.Abstractions.Persistence;
+
+using NexusReader.Data.Persistence;
 using Pgvector;
 using Pgvector.EntityFrameworkCore;
 using System.Text.Json;
@@ -16,14 +17,14 @@ public record SearchLibrarySemanticallyQuery(string QueryText, string TenantId,
 
 public class SearchLibrarySemanticallyQueryHandler : IRequestHandler<SearchLibrarySemanticallyQuery, Result<List<SemanticSearchResultDto>>>
 {
-    private readonly IApplicationDbContext _dbContext;
+    private readonly IDbContextFactory<AppDbContext> _dbContextFactory;
     private readonly IEmbeddingGenerator<string, Embedding<float>> _embeddingGenerator;
-
+    
     public SearchLibrarySemanticallyQueryHandler(
-        IApplicationDbContext dbContext,
+        IDbContextFactory<AppDbContext> dbContextFactory,
         IEmbeddingGenerator<string, Embedding<float>> embeddingGenerator)
     {
-        _dbContext = dbContext;
+        _dbContextFactory = dbContextFactory;
         _embeddingGenerator = embeddingGenerator;
     }
 
@@ -34,6 +35,7 @@ public class SearchLibrarySemanticallyQueryHandler : IRequestHandler<SearchLibra
             return Result.Fail("Query text cannot be empty.");
         }
 
+        using var dbContext = _dbContextFactory.CreateDbContext();
         try
         {
             // 1. Generate embedding for user query
@@ -41,7 +43,7 @@ public class SearchLibrarySemanticallyQueryHandler : IRequestHandler<SearchLibra
             var queryVector = new Vector(embeddingResponse.First().Vector.ToArray());
 
             // 2. Perform Cosine Similarity Search on Knowledge Units
-            var candidates = await _dbContext.KnowledgeUnits
+            var candidates = await dbContext.KnowledgeUnits
                 .AsNoTracking()
                 .Where(x => (x.TenantId == request.TenantId || x.TenantId == "global") && x.Vector != null)
                 .OrderBy(x => x.Vector!.CosineDistance(queryVector))
@@ -51,7 +53,7 @@ public class SearchLibrarySemanticallyQueryHandler : IRequestHandler<SearchLibra
             if (!candidates.Any())
             {
                 // Fallback to legacy cache if no granular units found
-                var legacyResults = await _dbContext.SemanticKnowledgeCache
+                var legacyResults = await dbContext.SemanticKnowledgeCache
                     .AsNoTracking()
                     .Where(x => x.TenantId == request.TenantId && x.Vector != null)
                     .OrderBy(x => x.Vector!.CosineDistance(queryVector))
@@ -68,13 +70,13 @@ public class SearchLibrarySemanticallyQueryHandler : IRequestHandler<SearchLibra
 
             // 3. Graph Expansion: Pull related units (e.g. Definitions, Next steps)
             var candidateIds = candidates.Select(c => c.Id).ToList();
-            var links = await _dbContext.KnowledgeUnitLinks
+            var links = await dbContext.KnowledgeUnitLinks
                 .AsNoTracking()
                 .Where(l => candidateIds.Contains(l.SourceUnitId) && (l.RelationType == "Defines" || l.RelationType == "Next"))
                 .ToListAsync(cancellationToken);
 
             var relatedIds = links.Select(l => l.TargetUnitId).Distinct().ToList();
-            var relatedUnits = await _dbContext.KnowledgeUnits
+            var relatedUnits = await dbContext.KnowledgeUnits
                 .AsNoTracking()
                 .Where(u => relatedIds.Contains(u.Id))
                 .ToDictionaryAsync(u => u.Id, cancellationToken);