fix: add a global dashboard filter bar (#24)

The reporting period was baked into the data service, so nothing could
change what the dashboard shows without editing code.

- DashboardFilter (period + optional region) parameterises every
  ChartDataService query; the no-arg overloads are the default filter.
- DashboardContext is the bus between the new DashboardFilterBar and the
  widgets: charts subscribe in WidgetRegistry, KPI tiles in DashboardView.
- Updates go through updateData, so widgets patch in place instead of
  being rebuilt; SparklineChart gained the same path.
- KpiData carries the number, the bundle the unit and number pattern, so
  a KPI value can follow the filter and stay locale-formatted.
- Filter state is deliberately not persisted, unlike the grid layout.

Closes #24

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0124BiJikbhbiEsNfJxdWM69

src/main/java/com/example/views/DashboardView.java

@@ -6,7 +6,9 @@ import com.example.components.GridStackItem;
 import com.example.components.GridStackLayout;
 import com.example.components.KpiTile;
 import com.example.data.ChartDataService;
+import com.example.data.DashboardFilter;
 import com.example.data.KpiData;
+import com.example.widgets.DashboardContext;
 import com.example.widgets.WidgetDefinition;
 import com.example.widgets.WidgetRegistry;
 import com.vaadin.flow.component.button.Button;
@@ -19,7 +21,9 @@ import com.vaadin.flow.component.orderedlayout.VerticalLayout;
 import com.vaadin.flow.router.HasDynamicTitle;
 import com.vaadin.flow.router.Route;
 
+import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
 
 /**
  * The dashboard: a {@link GridStackLayout} of draggable/resizable cards whose
@@ -31,6 +35,11 @@ import java.util.List;
  * All widget numbers come from {@link ChartDataService} and every chart widget
  * is built by the registry; this view only decides where a widget sits and
  * resolves the translation keys it is handed against the bundle.
+ * <p>
+ * A {@link DashboardFilterBar} above the grid drives every widget through one
+ * {@link DashboardContext}: the charts subscribe to it themselves (in the
+ * registry), the KPI tiles are re-fed here, since this view is what built them.
+ * The filter is view state and is not persisted — see {@link DashboardContext}.
  */
 @Route("")
 public class DashboardView extends VerticalLayout implements HasDynamicTitle {
@@ -40,12 +49,18 @@ public class DashboardView extends VerticalLayout implements HasDynamicTitle {
     /** A KPI tile is a quarter row wide, so the n-th one starts at 3n. */
     private static final int KPI_WIDTH = 3;
 
+    private final ChartDataService dataService;
     private final WidgetRegistry widgets;
+    private final DashboardContext context = new DashboardContext();
     private final GridStackLayout grid = new GridStackLayout();
     private final Span status = new Span();
+    /** The KPI tiles by KPI id, so a filter change re-feeds each tile with the
+     *  data of the same KPI rather than by position. */
+    private final Map<String, KpiTile> kpiTiles = new LinkedHashMap<>();
     private int extraWidgetCount;
 
     public DashboardView(ChartDataService dataService, WidgetRegistry widgets) {
+        this.dataService = dataService;
         this.widgets = widgets;
         addClassName("dialect-content");
 
@@ -58,12 +73,14 @@ public class DashboardView extends VerticalLayout implements HasDynamicTitle {
         // that explain them. They are 3x1 — a quarter row each, one cell high,
         // laid out left to right in the order the service returns them. The
         // grid id is the KPI's own id, so it survives reordering.
-        List<KpiData> kpis = dataService.kpis();
+        List<KpiData> kpis = dataService.kpis(context.getFilter());
         for (int i = 0; i < kpis.size(); i++) {
             KpiData kpi = kpis.get(i);
-            grid.add(new GridStackItem(kpi.id(), i * KPI_WIDTH, 0, KPI_WIDTH, 1,
-                    kpiTile(kpi)));
+            KpiTile tile = feed(new KpiTile(getTranslation(kpi.labelKey()), ""), kpi);
+            kpiTiles.put(kpi.id(), tile);
+            grid.add(new GridStackItem(kpi.id(), i * KPI_WIDTH, 0, KPI_WIDTH, 1, tile));
         }
+        context.addFilterChangeListener(this::updateKpiTiles);
 
         grid.add(
                 defaultWidget(WidgetRegistry.REVENUE_TREND, 0, 1, 6, 3),
@@ -76,7 +93,7 @@ public class DashboardView extends VerticalLayout implements HasDynamicTitle {
         status.setText(getTranslation("gridstack.statusInitial"));
         status.addClassName("dialect-muted");
 
-        add(toolbar(), grid);
+        add(toolbar(), new DashboardFilterBar(context), grid);
     }
 
     private HorizontalLayout toolbar() {
@@ -138,18 +155,29 @@ public class DashboardView extends VerticalLayout implements HasDynamicTitle {
 
     private GridStackItem widget(String id, WidgetDefinition definition,
                                  int x, int y, int w, int h) {
-        return new GridStackItem(id, x, y, w, h,
-                new Card(getTranslation(definition.titleKey()), definition.factory().get()));
+        return new GridStackItem(id, x, y, w, h, new Card(getTranslation(definition.titleKey()),
+                definition.factory().apply(context)));
     }
 
-    /** The displayed value comes from the bundle alongside the label, since it
-     *  carries locale-specific formatting (decimal separator, currency, "Mio.");
-     *  the service supplies the key, not the formatted text. */
-    private KpiTile kpiTile(KpiData kpi) {
-        String label = getTranslation(kpi.labelKey());
-        return new KpiTile(label, getTranslation(kpi.valueKey()))
+    /** Re-feeds the tiles still on the dashboard. A closed tile keeps its entry
+     *  in the map — the same KPI can be added back — but is detached, so
+     *  feeding it would queue a client call for a chart that is not there. */
+    private void updateKpiTiles(DashboardFilter filter) {
+        for (KpiData kpi : dataService.kpis(filter)) {
+            KpiTile tile = kpiTiles.get(kpi.id());
+            if (tile != null && tile.isAttached()) {
+                feed(tile, kpi);
+            }
+        }
+    }
+
+    /** The value's unit and number pattern come from the bundle, since they are
+     *  locale-specific (decimal separator, currency, "Mio."); the service
+     *  supplies only the number, which depends on the filter. */
+    private KpiTile feed(KpiTile tile, KpiData kpi) {
+        return tile.setValue(getTranslation(kpi.valueKey(), kpi.value()))
                 .setDelta(kpi.deltaPercent())
-                .setSparkline(label, kpi.trend());
+                .setSparkline(tile.getLabel(), kpi.trend());
     }
 
     @Override