Enhance tender recommendation service with caching and parallel processing

- Introduced a caching mechanism for translation responses in the tender recommendation service, improving efficiency by reducing redundant translation requests.
- Refactored the `enrichWithTranslation` method to support an optional translation cache, allowing for faster retrieval of stored translations.
- Implemented parallel processing for building recommended tender responses, utilizing goroutines to enhance performance and responsiveness.
- Added unit tests to validate the new caching behavior and ensure the correct application of translations in various scenarios.

This update significantly improves the performance and responsiveness of the tender recommendation service by integrating caching and parallel processing, enhancing the overall user experience.

internal/tender/service.go

@@ -176,7 +176,7 @@ func (s *tenderService) GetByIDs(ctx context.Context, ids []string) (map[string]
 // buildDetailResponse maps a tender to API form and enriches translation (MinIO) and summary.
 func (s *tenderService) buildDetailResponse(ctx context.Context, tender *Tender, language string) *TenderResponse {
 	resp := tender.ToResponseWithLanguage("")
-	s.enrichWithTranslation(ctx, tender, resp, language)
+	s.enrichWithTranslation(ctx, tender, resp, language, nil)
 	s.enrichWithAISummary(ctx, tender, resp)
 	return resp
 }
@@ -206,7 +206,7 @@ func (s *tenderService) enrichWithAISummary(ctx context.Context, t *Tender, resp
 
 // enrichWithTranslation overlays title/description from MinIO when the pipeline has finished
 // for the requested language. Does not call the AI translate API on GET.
-func (s *tenderService) enrichWithTranslation(ctx context.Context, t *Tender, resp *TenderResponse, language string) {
+func (s *tenderService) enrichWithTranslation(ctx context.Context, t *Tender, resp *TenderResponse, language string, cache *recommendationTranslationCache) {
 	if t == nil || resp == nil {
 		return
 	}
@@ -215,6 +215,17 @@ func (s *tenderService) enrichWithTranslation(ctx context.Context, t *Tender, re
 	}
 
 	targetLanguage := s.resolveDetailLanguage(language)
+	if cache != nil {
+		if stored, ok := cache.get(t.GetID(), targetLanguage); ok {
+			if strings.TrimSpace(stored.Title) != "" {
+				resp.Title = stored.Title
+				resp.Description = stored.Description
+				resp.Language = targetLanguage
+			}
+			return
+		}
+	}
+
 	enrichCtx, cancel := context.WithTimeout(ctx, aiTranslationEnrichmentTimeout)
 	defer cancel()
 
@@ -233,6 +244,10 @@ func (s *tenderService) enrichWithTranslation(ctx context.Context, t *Tender, re
 		return
 	}
 
+	if cache != nil {
+		cache.set(t.GetID(), targetLanguage, stored)
+	}
+
 	resp.Title = stored.Title
 	resp.Description = stored.Description
 	resp.Language = targetLanguage
@@ -947,7 +962,7 @@ func (s *tenderService) Recommend(ctx context.Context, form *SearchForm, paginat
 		return nil, fmt.Errorf("%w: cursor pagination is not supported for recommendations", response.ErrInvalidPagination)
 	}
 
-	s.logger.Info("Recommend tenders via AI service", map[string]interface{}{
+	s.logger.Debug("Recommend tenders request", map[string]interface{}{
 		"company_id":  companyID,
 		"company_ids": companyIDs,
 	})
@@ -968,39 +983,35 @@ func (s *tenderService) Recommend(ctx context.Context, form *SearchForm, paginat
 		return s.emptySearchResponse(pagination), nil
 	}
 
-	tenderByRef, err := s.resolveRecommendedTenders(ctx, recommendations)
-	if err != nil {
-		return nil, err
-	}
-
 	var (
+		tenderByRef       map[string]Tender
 		excluded          map[string]struct{}
 		excludedByCompany map[string]map[string]struct{}
 	)
-	if form.ExcludeRejectedTenders {
-		if len(companyIDs) > 0 {
-			excludedByCompany, err = s.buildRejectedTenderIDSetsForCompanies(ctx, companyIDs)
-		} else {
-			excluded, err = s.buildRejectedTenderIDSet(ctx, companyID)
-		}
-		if err != nil {
+	loadGroup, loadCtx := errgroup.WithContext(ctx)
+	loadGroup.Go(func() error {
+		var resolveErr error
+		tenderByRef, resolveErr = s.resolveRecommendedTenders(loadCtx, recommendations)
+		return resolveErr
+	})
+	loadGroup.Go(func() error {
+		var exclusionErr error
+		excluded, excludedByCompany, exclusionErr = s.loadRecommendationExclusions(loadCtx, form, companyID, companyIDs)
+		return exclusionErr
+	})
+	if err := loadGroup.Wait(); err != nil {
+		if form.ExcludeRejectedTenders {
 			s.logger.Error("Failed to build recommendation exclusions", map[string]interface{}{
 				"company_id":  companyID,
 				"company_ids": companyIDs,
 				"error":       err.Error(),
 			})
-			return nil, fmt.Errorf("failed to build recommendation exclusions: %w", err)
 		}
+		return nil, err
 	}
 
 	lang := s.pickResponseLanguage(form.Language)
 	now := time.Now().Unix()
-	type rankedRecommendedTender struct {
-		tender    Tender
-		rank      int
-		analysis  string
-		tenderRef string
-	}
 	ordered := make([]rankedRecommendedTender, 0, len(recommendations))
 	seenTenderIDs := make(map[string]struct{}, len(recommendations))
 	for _, rec := range recommendations {
@@ -1044,10 +1055,7 @@ func (s *tenderService) Recommend(ctx context.Context, form *SearchForm, paginat
 		end = len(ordered)
 	}
 
-	paged := make([]TenderResponse, 0, end-start)
-	for _, item := range ordered[start:end] {
-		paged = append(paged, s.buildRecommendedTenderResponse(ctx, item.tender, item.rank, item.analysis, item.tenderRef, lang))
-	}
+	paged := s.buildRecommendedTenderResponsesParallel(ctx, ordered[start:end], lang)
 
 	return &SearchResponse{
 		Tenders:  paged,
@@ -1055,9 +1063,9 @@ func (s *tenderService) Recommend(ctx context.Context, form *SearchForm, paginat
 	}, nil
 }
 
-func (s *tenderService) buildRecommendedTenderResponse(ctx context.Context, tender Tender, rank int, analysis, tenderRef, language string) TenderResponse {
+func (s *tenderService) buildRecommendedTenderResponse(ctx context.Context, tender Tender, rank int, analysis, tenderRef, language string, cache *recommendationTranslationCache) TenderResponse {
 	resp := tender.ToResponseWithLanguage(language)
-	s.enrichWithTranslation(ctx, &tender, resp, language)
+	s.enrichWithTranslation(ctx, &tender, resp, language, cache)
 	resp.Rank = rank
 	resp.Analysis = analysis
 	resp.ProcedureRef = tenderRef