breakpilot-lehrer/edu-search-service/internal/search/search_query.go

package search

// buildQuery constructs the OpenSearch query
func (s *Service) buildQuery(req *SearchRequest) map[string]interface{} {
	// Main query
	must := []map[string]interface{}{}
	filter := []map[string]interface{}{}

	// Text search
	if req.Query != "" {
		must = append(must, map[string]interface{}{
			"multi_match": map[string]interface{}{
				"query":  req.Query,
				"fields": []string{"title^3", "content_text"},
				"type":   "best_fields",
			},
		})
	}

	// Filters
	if len(req.Filters.Language) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"language": req.Filters.Language},
		})
	}

	if len(req.Filters.CountryHint) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"country_hint": req.Filters.CountryHint},
		})
	}

	if len(req.Filters.SourceCategory) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"source_category": req.Filters.SourceCategory},
		})
	}

	if len(req.Filters.DocType) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"doc_type": req.Filters.DocType},
		})
	}

	if len(req.Filters.SchoolLevel) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"school_level": req.Filters.SchoolLevel},
		})
	}

	if len(req.Filters.Subjects) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"subjects": req.Filters.Subjects},
		})
	}

	if len(req.Filters.State) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"state": req.Filters.State},
		})
	}

	if req.Filters.MinTrustScore > 0 {
		filter = append(filter, map[string]interface{}{
			"range": map[string]interface{}{
				"trust_score": map[string]interface{}{"gte": req.Filters.MinTrustScore},
			},
		})
	}

	if req.Filters.DateFrom != "" {
		filter = append(filter, map[string]interface{}{
			"range": map[string]interface{}{
				"fetch_time": map[string]interface{}{"gte": req.Filters.DateFrom},
			},
		})
	}

	// Build bool query
	boolQuery := map[string]interface{}{}
	if len(must) > 0 {
		boolQuery["must"] = must
	}
	if len(filter) > 0 {
		boolQuery["filter"] = filter
	}

	// Construct full query
	query := map[string]interface{}{
		"query": map[string]interface{}{
			"bool": boolQuery,
		},
		"from": req.Offset,
		"size": req.Limit,
		"_source": []string{
			"doc_id", "title", "url", "domain", "language",
			"doc_type", "school_level", "subjects",
			"trust_score", "quality_score", "snippet_text",
		},
	}

	// Add highlighting if requested
	if req.Include.Highlights {
		query["highlight"] = map[string]interface{}{
			"fields": map[string]interface{}{
				"title":        map[string]interface{}{},
				"content_text": map[string]interface{}{"fragment_size": 150, "number_of_fragments": 3},
			},
		}
	}

	// Add function score for trust/quality boosting
	query["query"] = map[string]interface{}{
		"function_score": map[string]interface{}{
			"query": query["query"],
			"functions": []map[string]interface{}{
				{
					"field_value_factor": map[string]interface{}{
						"field":    "trust_score",
						"factor":   1.5,
						"modifier": "sqrt",
						"missing":  0.5,
					},
				},
				{
					"field_value_factor": map[string]interface{}{
						"field":    "quality_score",
						"factor":   1.0,
						"modifier": "sqrt",
						"missing":  0.5,
					},
				},
			},
			"score_mode": "multiply",
			"boost_mode": "multiply",
		},
	}

	return query
}

// buildSemanticQuery constructs a pure vector search query using k-NN
func (s *Service) buildSemanticQuery(req *SearchRequest, embedding []float32) map[string]interface{} {
	filter := s.buildFilters(req)

	// k-NN query for semantic search
	knnQuery := map[string]interface{}{
		"content_embedding": map[string]interface{}{
			"vector": embedding,
			"k":      req.Limit + req.Offset, // Get enough results for pagination
		},
	}

	// Add filter if present
	if len(filter) > 0 {
		knnQuery["content_embedding"].(map[string]interface{})["filter"] = map[string]interface{}{
			"bool": map[string]interface{}{
				"filter": filter,
			},
		}
	}

	query := map[string]interface{}{
		"knn":   knnQuery,
		"from":  req.Offset,
		"size":  req.Limit,
		"_source": []string{
			"doc_id", "title", "url", "domain", "language",
			"doc_type", "school_level", "subjects",
			"trust_score", "quality_score", "snippet_text",
		},
	}

	// Add highlighting if requested
	if req.Include.Highlights {
		query["highlight"] = map[string]interface{}{
			"fields": map[string]interface{}{
				"title":        map[string]interface{}{},
				"content_text": map[string]interface{}{"fragment_size": 150, "number_of_fragments": 3},
			},
		}
	}

	return query
}

// buildHybridQuery constructs a combined BM25 + vector search query
func (s *Service) buildHybridQuery(req *SearchRequest, embedding []float32) map[string]interface{} {
	filter := s.buildFilters(req)

	// Build the bool query for BM25
	must := []map[string]interface{}{}
	if req.Query != "" {
		must = append(must, map[string]interface{}{
			"multi_match": map[string]interface{}{
				"query":  req.Query,
				"fields": []string{"title^3", "content_text"},
				"type":   "best_fields",
			},
		})
	}

	boolQuery := map[string]interface{}{}
	if len(must) > 0 {
		boolQuery["must"] = must
	}
	if len(filter) > 0 {
		boolQuery["filter"] = filter
	}

	// Convert embedding to []interface{} for JSON
	embeddingInterface := make([]interface{}, len(embedding))
	for i, v := range embedding {
		embeddingInterface[i] = v
	}

	// Hybrid query using script_score to combine BM25 and cosine similarity
	// This is a simpler approach than OpenSearch's neural search plugin
	query := map[string]interface{}{
		"query": map[string]interface{}{
			"script_score": map[string]interface{}{
				"query": map[string]interface{}{
					"bool": boolQuery,
				},
				"script": map[string]interface{}{
					"source": "cosineSimilarity(params.query_vector, 'content_embedding') + 1.0 + _score * 0.5",
					"params": map[string]interface{}{
						"query_vector": embeddingInterface,
					},
				},
			},
		},
		"from": req.Offset,
		"size": req.Limit,
		"_source": []string{
			"doc_id", "title", "url", "domain", "language",
			"doc_type", "school_level", "subjects",
			"trust_score", "quality_score", "snippet_text",
		},
	}

	// Add highlighting if requested
	if req.Include.Highlights {
		query["highlight"] = map[string]interface{}{
			"fields": map[string]interface{}{
				"title":        map[string]interface{}{},
				"content_text": map[string]interface{}{"fragment_size": 150, "number_of_fragments": 3},
			},
		}
	}

	return query
}

// buildFilters constructs the filter array for queries
func (s *Service) buildFilters(req *SearchRequest) []map[string]interface{} {
	filter := []map[string]interface{}{}

	if len(req.Filters.Language) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"language": req.Filters.Language},
		})
	}

	if len(req.Filters.CountryHint) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"country_hint": req.Filters.CountryHint},
		})
	}

	if len(req.Filters.SourceCategory) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"source_category": req.Filters.SourceCategory},
		})
	}

	if len(req.Filters.DocType) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"doc_type": req.Filters.DocType},
		})
	}

	if len(req.Filters.SchoolLevel) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"school_level": req.Filters.SchoolLevel},
		})
	}

	if len(req.Filters.Subjects) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"subjects": req.Filters.Subjects},
		})
	}

	if len(req.Filters.State) > 0 {
		filter = append(filter, map[string]interface{}{
			"terms": map[string]interface{}{"state": req.Filters.State},
		})
	}

	if req.Filters.MinTrustScore > 0 {
		filter = append(filter, map[string]interface{}{
			"range": map[string]interface{}{
				"trust_score": map[string]interface{}{"gte": req.Filters.MinTrustScore},
			},
		})
	}

	if req.Filters.DateFrom != "" {
		filter = append(filter, map[string]interface{}{
			"range": map[string]interface{}{
				"fetch_time": map[string]interface{}{"gte": req.Filters.DateFrom},
			},
		})
	}

	return filter
}

// hitToResult converts an OpenSearch hit to SearchResult
func (s *Service) hitToResult(source map[string]interface{}, score float64, highlight map[string][]string, include SearchInclude) SearchResult {
	result := SearchResult{
		DocID:       getString(source, "doc_id"),
		Title:       getString(source, "title"),
		URL:         getString(source, "url"),
		Domain:      getString(source, "domain"),
		Language:    getString(source, "language"),
		DocType:     getString(source, "doc_type"),
		SchoolLevel: getString(source, "school_level"),
		Subjects:    getStringArray(source, "subjects"),
		Scores: Scores{
			BM25:    score,
			Trust:   getFloat(source, "trust_score"),
			Quality: getFloat(source, "quality_score"),
			Final:   score, // MVP: final = BM25 * trust * quality (via function_score)
		},
	}

	if include.Snippets {
		result.Snippet = getString(source, "snippet_text")
	}

	if include.Highlights && highlight != nil {
		if h, ok := highlight["content_text"]; ok {
			result.Highlights = h
		}
	}

	return result
}