feat([2fd88f42]): implement zoom-adaptive color and legend scaling

heatmap-tool/frontend/src/components/MapDisplay.tsx

@@ -1,6 +1,6 @@
 // src/components/MapDisplay.tsx
-import React from 'react';
+import React, { useState, useEffect } from 'react';
-import { MapContainer, TileLayer, CircleMarker, Tooltip } from 'react-leaflet';
+import { MapContainer, TileLayer, CircleMarker, Tooltip, useMapEvents } from 'react-leaflet';
 import { HeatmapLayer } from 'react-leaflet-heatmap-layer-v3';
 import 'leaflet/dist/leaflet.css';
 import 'leaflet.heat';
@@ -17,20 +17,50 @@ interface MapDisplayProps {
 
 const MapDisplay: React.FC<MapDisplayProps> = ({ heatmapData, radiusMultiplier, viewMode }) => {
   const germanyCenter: [number, number] = [51.1657, 10.4515];
-  const maxCount = Math.max(...heatmapData.map(p => p.count), 1);
+  
+  // State for the data currently visible in the map viewport
+  const [visibleData, setVisibleData] = useState<HeatmapPoint[]>(heatmapData);
+  
+  // The dynamic max count based only on visible data
+  const dynamicMaxCount = Math.max(...visibleData.map(p => p.count), 1);
 
   const calculateRadius = (count: number) => {
     return 3 + Math.log(count + 1) * 5 * radiusMultiplier;
   };
   
+  // getColor now uses the dynamicMaxCount
   const getColor = (count: number) => {
-    const ratio = count / maxCount;
+    const ratio = count / dynamicMaxCount;
     if (ratio > 0.8) return '#d73027'; // Red
     if (ratio > 0.5) return '#fdae61'; // Orange
     if (ratio > 0.2) return '#fee08b'; // Yellow
     return '#66bd63'; // Green
   };
 
+  // This component listens to map events and updates the visible data
+  const DynamicLegendHandler = () => {
+    const map = useMapEvents({
+      zoomend: () => updateVisibleData(),
+      moveend: () => updateVisibleData(),
+    });
+
+    const updateVisibleData = () => {
+      const bounds = map.getBounds();
+      const visible = heatmapData.filter(p => 
+        bounds.contains([p.lat, p.lon])
+      );
+      setVisibleData(visible.length > 0 ? visible : heatmapData); // Fallback to all data if none are visible
+    };
+    
+    // Initial load
+    useEffect(() => {
+        updateVisibleData();
+    }, [heatmapData]);
+
+
+    return null;
+  };
+
   const renderPoints = () => (
     <MarkerClusterGroup>
       {heatmapData.map((point, idx) => (
@@ -66,7 +96,7 @@ const MapDisplay: React.FC<MapDisplayProps> = ({ heatmapData, radiusMultiplier,
         intensityExtractor={(p: HeatmapPoint) => p.count}
         radius={25}
         blur={20}
-        max={maxCount * 0.1} // Adjust max intensity for better visualization
+        max={dynamicMaxCount * 0.1}
     />
   );
 
@@ -74,7 +104,6 @@ const MapDisplay: React.FC<MapDisplayProps> = ({ heatmapData, radiusMultiplier,
     return (
       <div style={{ textAlign: 'center', paddingTop: '50px' }}>
         <p>No data to display on the map.</p>
-        <p>Upload a file and apply filters to see the heatmap.</p>
       </div>
     );
   }
@@ -86,8 +115,9 @@ const MapDisplay: React.FC<MapDisplayProps> = ({ heatmapData, radiusMultiplier,
         attribution='&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors'
       />
       <MapBoundsManager data={heatmapData} />
+      <DynamicLegendHandler />
       {viewMode === 'points' ? renderPoints() : renderHeatmap()}
-      {viewMode === 'points' && <Legend getColor={getColor} maxCount={maxCount} />}
+      {viewMode === 'points' && <Legend getColor={getColor} maxCount={dynamicMaxCount} />}
     </MapContainer>
   );
 };