refactor: update interface contract and applies some fixes

internal/repository/contact_repository.go

@@ -2,6 +2,7 @@ package repository
 
 import (
 	"database/sql"
+	"fmt"
 
 	"gitea.gabilandia.com/gabdlr/agenda-web-go/internal/models"
 )
@@ -10,7 +11,7 @@ type ContactRepository struct {
 	baseRepository[models.Contact]
 }
 
-func NewContactRepository(db *sql.DB) *ContactRepository {
+func NewContactRepository(db *sql.DB) Repository[models.Contact] {
 	return &ContactRepository{
 		baseRepository[models.Contact]{
 			db:        db,
@@ -38,20 +39,45 @@ func (r *ContactRepository) Create(contact *models.Contact) (int64, error) {
 	return id, nil
 }
 
-func (r *ContactRepository) Update(contact *models.Contact) (int64, error) {
-	query := r.BuildQuery("UPDATE %s SET name = ?, company = ?, phone = ? WHERE id = ?")
-	result, err := r.db.Exec(query,
-		contact.Name, contact.Company, contact.Phone, contact.ID,
+func (r *ContactRepository) Update(contact *models.Contact) error {
+	query := r.BuildQuery("UPDATE %s SET")
+	fieldsToUpdate := make([]string, 0, 4)
+	fields := make([]any, 0)
+
+	if contact.Name != "" {
+		fieldsToUpdate = append(fieldsToUpdate, "name")
+		fields = append(fields, &contact.Name)
+	}
+
+	if contact.Company != "" {
+		fieldsToUpdate = append(fieldsToUpdate, "company")
+		fields = append(fields, &contact.Company)
+	}
+
+	if contact.Phone != "" {
+		fieldsToUpdate = append(fieldsToUpdate, "phone")
+		fields = append(fields, &contact.Phone)
+	}
+
+	fields = append(fields, &contact.ID)
+
+	fieldsToUpdatelen := len(fieldsToUpdate)
+	for i, field := range fieldsToUpdate {
+		query += fmt.Sprintf(" %s = ?", field)
+		if i != fieldsToUpdatelen-1 {
+			query += ","
+		}
+	}
+
+	query += " WHERE id = ?"
+
+	_, err := r.db.Exec(query,
+		fields...,
 	)
 
 	if err != nil {
-		return 0, err
+		return err
 	}
 
-	rowsAffected, err := result.RowsAffected()
-	if err != nil {
-		return 0, err
-	}
-
-	return rowsAffected, nil
+	return nil
 }