feature/#147 - local look-up - first step towards autocomplete text f…

…ield

Implemented a look-up on the local database, and linked it to the text field.
For the moment, the matching products are only printed in the console.
The next step would be to display the results with an autocomplete text field.

Impacted files:
* `dao_product.dart`: new method `List<Product> getSuggestions(String)`
* `home_page.dart`: added an `onUpdate` method on the text field to print the products that match locally

packages/smooth_app/lib/database/dao_product.dart

@@ -77,6 +77,37 @@ class DaoProduct {
     return result;
   }
 
+  /// Returns the products that match a string
+  ///
+  /// The search is actually ugly, but it's a start.
+  // TODO(monsieurtanuki): check only the fields that are deemed relevant
+  // TODO(monsieurtanuki): consider space-separated fields as distinct keywords
+  Future<List<Product>> getSuggestions(
+      final String pattern, final int minLength) async {
+    final List<Product> result = <Product>[];
+    if (pattern == null || pattern.trim().length < minLength) {
+      return result;
+    }
+    final List<Map<String, dynamic>> queryResults =
+        await localDatabase.database.query(
+      TABLE_PRODUCT,
+      columns: <String>[
+        TABLE_PRODUCT_COLUMN_BARCODE,
+        _TABLE_PRODUCT_COLUMN_JSON,
+      ],
+      where: '$TABLE_PRODUCT_COLUMN_BARCODE like ?'
+          ' or $_TABLE_PRODUCT_COLUMN_JSON like ?',
+      whereArgs: <String>['%$pattern%', '%$pattern%'],
+    );
+    if (queryResults.isEmpty) {
+      return result;
+    }
+    for (final Map<String, dynamic> row in queryResults) {
+      result.add(_getProductFromQueryResult(row));
+    }
+    return result;
+  }
+
   Future<void> put(final Product product) async =>
       await _upsert(product, localDatabase.database);
 

packages/smooth_app/lib/pages/home_page.dart

@@ -20,6 +20,7 @@ import 'package:openfoodfacts/model/Attribute.dart';
 import 'package:smooth_app/data_models/user_preferences_model.dart';
 import 'package:smooth_app/themes/smooth_theme.dart';
 import 'package:smooth_app/cards/product_cards/product_list_preview.dart';
+import 'package:openfoodfacts/model/Product.dart';
 
 class HomePage extends StatefulWidget {
   @override
@@ -93,6 +94,16 @@ class _HomePageState extends State<HomePage> {
                   ),
                 ),
                 title: TextField(
+                  onChanged: (final String value) =>
+                      _daoProduct.getSuggestions(value, 3).then(
+                    (List<Product> list) {
+                      print(
+                          '${list.length} products locally found with $value:');
+                      for (final Product item in list) {
+                        print('${item.barcode}: ${item.productName}');
+                      }
+                    },
+                  ),
                   onSubmitted: (final String value) => ChoosePage.onSubmitted(
                     value,
                     context,