prevent labels from overlapping

pdb-plotting/src/main/java/org/lucares/pdb/plot/api/BarChartAggregatorForIntervals.java

@@ -8,6 +8,7 @@ import java.util.UUID;
 import java.util.concurrent.atomic.AtomicLong;
 
 import org.lucares.recommind.logs.GnuplotAxis;
+import org.lucares.recommind.logs.GnuplotSettings;
 
 public class BarChartAggregatorForIntervals implements CustomAggregator, IndexedAggregator, BarChart {
 
@@ -24,8 +25,11 @@ public class BarChartAggregatorForIntervals implements CustomAggregator, Indexed
 
     private int count;
 
-    public BarChartAggregatorForIntervals(final Interval interval) {
+    private final PlotSettings settings;
-        this.interval = interval;
+
+    public BarChartAggregatorForIntervals(final PlotSettings settings) {
+        this.settings = settings;
+        this.interval = settings.getInterval().get();
         buckets = interval.getBuckets();
     }
 
@@ -72,20 +76,35 @@ public class BarChartAggregatorForIntervals implements CustomAggregator, Indexed
         final StringBuilder csv = new StringBuilder();
         final boolean isMiddleSeries = getIndex() == numberOfDataSeries / 2;
 
+        int i = 0;
         int offset = 0;
         for (final String bucketId : bucketIds()) {
             final long count = buckets.get(bucketId).get();
             csv.append(String.format(Locale.US, "%f", offset + getIndex() * SPACE_BETWEEN_BARS + 0.5));
             csv.append(",");
-            csv.append(renderLabels && isMiddleSeries ? bucketId : "");
+            csv.append(renderLabels && isMiddleSeries && showLabel(i, buckets.size()) ? bucketId : "");
             csv.append(",");
             csv.append(count);
             csv.append("\n");
             offset += numberOfDataSeries;
+            i++;
         }
         return csv.toString();
     }
 
+    private boolean showLabel(final int index, final int numberOfBuckets) {
+        final int width = settings.getWidth();
+        final int widthInPx = width - GnuplotSettings.GNUPLOT_LEFT_RIGHT_MARGIN;
+
+        final long maxLabels = Math.max(1, widthInPx / (GnuplotSettings.TICKS_FONT_SIZE * 8));
+
+        if (maxLabels >= numberOfBuckets) {
+            return true;
+        } else {
+            return index % (int) Math.ceil(numberOfBuckets / maxLabels) == 0;
+        }
+    }
+
     private SortedSet<String> bucketIds() {
 
         return new TreeSet<>(buckets.keySet());

pdb-plotting/src/main/java/org/lucares/pdb/plot/api/BarChartHandler.java

@@ -82,7 +82,7 @@ public class BarChartHandler extends AggregateHandler {
     CustomAggregator createCustomAggregator(final Path tmpDir, final PlotSettings plotSettings,
             final long fromEpochMilli, final long toEpochMilli) {
         if (plotSettings.getInterval().isPresent()) {
-            return new BarChartAggregatorForIntervals(plotSettings.getInterval().get());
+            return new BarChartAggregatorForIntervals(plotSettings);
         } else {
             return new BarChartAggregator();
         }