Implementing a generic "ordering" option configuration for paginated list widget

lib/widget/bom_list.dart

@@ -1,8 +1,9 @@
 
-
 import "package:flutter/material.dart";
+import "package:font_awesome_flutter/font_awesome_flutter.dart";
 
 import "package:inventree/api.dart";
+import "package:inventree/api_form.dart";
 import "package:inventree/helpers.dart";
 import "package:inventree/inventree/bom.dart";
 import "package:inventree/l10.dart";
@@ -15,6 +16,7 @@ import "package:inventree/widget/part_detail.dart";
 import "package:inventree/widget/refreshable_state.dart";
 
 
+
 /*
  * Widget for displaying a list of BomItems for the specified 'parent' Part instance
  */
@@ -30,7 +32,7 @@ class BomList extends StatefulWidget {
 }
 
 
-class _BomListState extends RefreshableState<BomList> {
+class _BomListState extends PaginatedState<BomList> {
 
   _BomListState(this.parent);
 
@@ -39,6 +41,15 @@ class _BomListState extends RefreshableState<BomList> {
   @override
   String getAppBarTitle(BuildContext context) => L10().billOfMaterials;
 
+  @override
+  String get prefix => "bom_";
+
+  @override
+  Map<String, String> get orderingOptions => {
+    "quantity": L10().quantity,
+    "part": L10().part,
+  };
+
   @override
   Widget getBody(BuildContext context) {
     return PaginatedBomList({

lib/widget/paginator.dart

@@ -3,9 +3,129 @@ import "package:flutter/material.dart";
 import "package:font_awesome_flutter/font_awesome_flutter.dart";
 import "package:infinite_scroll_pagination/infinite_scroll_pagination.dart";
 
+import "package:inventree/api_form.dart";
+import "package:inventree/l10.dart";
+
 import "package:inventree/inventree/model.dart";
 import "package:inventree/inventree/sentry.dart";
-import "package:inventree/l10.dart";
+import "package:inventree/preferences.dart";
+
+import "package:inventree/widget/refreshable_state.dart";
+
+
+/*
+ * Generic widget class for displaying a "paginated list".
+ * Provides some basic functionality for adjusting ordering and filtering options
+ */
+abstract class PaginatedState<T extends StatefulWidget> extends RefreshableState<T> {
+
+  // Prefix for storing and loading pagination options
+  String get prefix => "prefix_";
+
+  // Ordering options for this paginated state (override in implementing class)
+  Map<String, String> get orderingOptions => {};
+
+  @override
+  List<Widget> getAppBarActions(BuildContext context) {
+    List<Widget> actions = [];
+
+    // If ordering options have been provided
+    if (orderingOptions.isNotEmpty) {
+      actions.add(IconButton(
+        icon: FaIcon(FontAwesomeIcons.sort),
+        onPressed: () => _updateFilters(context),
+      ));
+    }
+
+    return actions;
+  }
+
+  // Return the selected ordering "field" for this list widget
+  Future<String> orderingField() async {
+    dynamic field = await InvenTreeSettingsManager().getValue("${prefix}ordering_field", null);
+
+    if (field != null) {
+      return field.toString();
+    } else if (orderingOptions.isNotEmpty) {
+      // By default, return the first specified key
+      return orderingOptions.keys.first;
+    } else {
+      return "";
+    }
+  }
+
+  // Return the selected ordering "order" ("+" or "-") for this list widget
+  Future<String> orderingOrder() async {
+    dynamic order = await InvenTreeSettingsManager().getValue("${prefix}ordering_order", "+");
+
+    return order == "+" ? "+" : "-";
+  }
+
+  // Update the (configurable) filters for this paginated list
+  Future<void> _updateFilters(BuildContext context) async {
+
+    // Retrieve stored setting
+    dynamic _field = await orderingField();
+    dynamic _order = await orderingOrder();
+
+    // Construct the 'ordering' options
+    List<Map<String, dynamic>> _opts = [];
+
+    orderingOptions.forEach((k, v) => _opts.add({
+      "value": k.toString(),
+      "display_name": v.toString()
+    }));
+
+    if (_field == null && _opts.isNotEmpty) {
+      _field = _opts.first["value"];
+    }
+
+    Map<String, dynamic> fields = {
+      "ordering_field": {
+        "type": "choice",
+        "label": "Ordering Field",
+        "required": true,
+        "choices": _opts,
+        "value": _field,
+      },
+      "ordering_order": {
+        "type": "choice",
+        "label": "Ordering Direction",
+        "required": true,
+        "value": _order,
+        "choices": [
+          {
+            "value": "+",
+            "display_name": "Ascending",
+          },
+          {
+            "value": "-",
+            "display_name": "Descending",
+          }
+        ]
+      }
+    };
+
+    launchApiForm(
+      context,
+      "...filtering...",
+      "",
+      fields,
+      icon: FontAwesomeIcons.checkCircle,
+      onSuccess: (Map<String, dynamic> data) async {
+
+        // Extract data from the processed form
+        String f = (data["ordering_field"] ?? _field) as String;
+        String o = (data["ordering_order"] ?? _order) as String;
+
+        // Save values to settings
+        await InvenTreeSettingsManager().setValue("${prefix}ordering_field", f);
+        await InvenTreeSettingsManager().setValue("${prefix}ordering_order", o);
+      }
+    );
+  }
+
+}
 
 
 class PaginatedSearchState<T extends StatefulWidget> extends State<T> {
@@ -21,6 +141,10 @@ class PaginatedSearchState<T extends StatefulWidget> extends State<T> {
 
   int resultCount = 0;
 
+  // List of variables by which the list can be "ordered".
+  // Override in any implementing sub-class
+  List<String> orderingFilters = [];
+
   // Text controller
   final TextEditingController searchController = TextEditingController();