chart-app/src/main/java/com/example/widgets/WidgetRegistry.java

package com.example.widgets;

import com.example.components.ApexChart;
import com.example.components.AxisChart;
import com.example.components.BarChart;
import com.example.components.LineChart;
import com.example.components.PieChart;
import com.example.data.ChartDataService;
import com.example.data.ChartSeries;
import com.example.data.DashboardFilter;
import com.vaadin.flow.component.Component;
import com.vaadin.flow.component.notification.Notification;
import com.vaadin.flow.shared.Registration;
import org.springframework.stereotype.Service;

import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Consumer;

/**
 * The widget types a dashboard can show. Holding them here rather than inline in
 * the view is what lets the "add widget" picker offer real content and lets a
 * closed widget be brought back: the view only decides <em>where</em> a widget
 * sits, the registry decides what one <em>is</em>.
 * <p>
 * Numbers come from {@link ChartDataService}, queried with the filter the
 * widget's {@link DashboardContext} currently holds; the factories resolve the
 * data's translation keys against the bundle through the chart component
 * itself, so they follow the current UI locale without the registry being a
 * component. Every widget also subscribes to the context, so a filter change
 * re-feeds it — in place, through {@code updateData}, rather than by rebuilding
 * the chart.
 */
@Service
public class WidgetRegistry {

    public static final String REVENUE_TREND = "revenue-trend";
    public static final String REVENUE_MONTH = "revenue-month";
    public static final String REVENUE_REGION = "revenue-region";

    private final ChartDataService dataService;
    /** Insertion-ordered: the picker lists definitions in registration order. */
    private final Map<String, WidgetDefinition> definitions = new LinkedHashMap<>();

    public WidgetRegistry(ChartDataService dataService) {
        this.dataService = dataService;

        register(new WidgetDefinition(REVENUE_TREND, "card.revenueTrend", 6, 3,
                context -> axisChart(new LineChart(), context)));
        register(new WidgetDefinition(REVENUE_MONTH, "card.revenueByMonth", 6, 3,
                context -> axisChart(new BarChart(), context)));
        register(new WidgetDefinition(REVENUE_REGION, "card.revenueByRegion", 5, 3,
                this::pieChart));
    }

    /** Adds a definition, replacing any earlier one of the same type. */
    public final void register(WidgetDefinition definition) {
        definitions.put(definition.type(), definition);
    }

    public List<WidgetDefinition> definitions() {
        return List.copyOf(definitions.values());
    }

    /** The definition for the given type. Unknown types are a programming
     *  error, not user input — the picker only ever offers registered ones. */
    public WidgetDefinition require(String type) {
        WidgetDefinition definition = definitions.get(type);
        if (definition == null) {
            throw new IllegalArgumentException("unknown widget type: " + type);
        }
        return definition;
    }

    private Component axisChart(AxisChart chart, DashboardContext context) {
        chart.addPointClickListener(e -> Notification.show(chart.getTranslation(
                "chart.pointClick", e.getSeriesIndex(), e.getDataPointIndex())));
        return bind(chart, context, filter -> {
            ChartSeries series = dataService.revenueByMonth(filter);
            chart.updateData(chart.getTranslation(series.nameKey()), series.values(),
                    translate(chart, series.categoryKeys()));
        });
    }

    private Component pieChart(DashboardContext context) {
        PieChart chart = new PieChart();
        chart.addPointClickListener(e -> Notification.show(
                chart.getTranslation("chart.sliceClick", e.getDataPointIndex())));
        return bind(chart, context, filter -> {
            ChartSeries series = dataService.revenueByRegion(filter);
            // A pie has no series name — its categories are the slice labels.
            chart.updateData(series.values(), translate(chart, series.categoryKeys()));
        });
    }

    /**
     * Feeds the chart from the current filter and keeps it fed: the
     * subscription is dropped when the widget is detached (closed, or the
     * dashboard left), so a chart that is gone is not updated any more.
     * <p>
     * The first feed goes through the same {@code updateData} path as later
     * ones, which falls back to a full render while nothing has been drawn yet.
     */
    private Component bind(ApexChart chart, DashboardContext context,
                           Consumer<DashboardFilter> feed) {
        feed.accept(context.getFilter());
        Registration registration = context.addFilterChangeListener(feed);
        chart.addDetachListener(e -> registration.remove());
        return sizeFull(chart);
    }

    /** Charts fill their grid item instead of using a fixed pixel height, so
     *  resizing a widget resizes the chart (grid-stack.ts fires a window
     *  resize on resizestop, which ApexCharts reflows on). */
    private Component sizeFull(ApexChart chart) {
        chart.setWidthFull();
        chart.setHeight("100%");
        return chart;
    }

    /** Data sets carry translation keys, not display text — see
     *  {@link ChartSeries}. */
    private List<String> translate(Component component, List<String> keys) {
        return keys.stream().map(component::getTranslation).toList();
    }
}