Fix compare chart date alignment

components/charts/utils/chart-data-transformers.ts

@@ -1,6 +1,15 @@
 import { subWeeks, subMonths, subYears } from 'date-fns';
 import type { TimeRange, ChartDataPoint } from '@/lib/types';
 
+function toTradingDayKey(value: string): string {
+  const parsed = Date.parse(value);
+  if (!Number.isFinite(parsed)) {
+    return value;
+  }
+
+  return new Date(parsed).toISOString().slice(0, 10);
+}
+
 /**
  * Filter chart data by time range
  */
@@ -128,30 +137,55 @@ export function calculateVolumeMax<T extends ChartDataPoint>(data: T[]): number
  */
 export function mergeDataSeries<T extends ChartDataPoint>(
   seriesArray: Array<{ id: string; data: T[] }>
-): Array<T & Record<string, number>> {
+): Array<{ date: string } & Record<string, string | number>> {
   if (!seriesArray || seriesArray.length === 0) return [];
 
-  // Create map indexed by date
-  const dateMap = new Map<string, T & Record<string, number>>();
+  // Create map indexed by normalized trading day.
+  const dateMap = new Map<string, { date: string } & Record<string, string | number>>();
+  const seriesPointMaps = seriesArray.map((series) => {
+    const pointMap = new Map<string, number>();
 
-  seriesArray.forEach(series => {
     series.data.forEach(point => {
-      const date = point.date;
-      const existing = dateMap.get(date) || { date } as T & Record<string, number>;
+      const date = toTradingDayKey(point.date);
 
-      // Add value for this series
       if (isOHLCVData(point)) {
-        existing[series.id] = point.close;
+        pointMap.set(date, point.close);
       } else if (isPriceData(point)) {
-        existing[series.id] = point.price;
+        pointMap.set(date, point.price);
+      }
+    });
+
+    pointMap.forEach((_value, date) => {
+      const existing = dateMap.get(date) || { date } as { date: string } & Record<string, string | number>;
+      dateMap.set(date, existing);
+    });
+
+    return {
+      id: series.id,
+      pointMap
+    };
+  });
+
+  const mergedDates = Array.from(dateMap.keys()).sort((a, b) =>
+    new Date(a).getTime() - new Date(b).getTime()
+  );
+
+  // Fill forward each series to keep benchmark/comparison lines aligned on trading days.
+  seriesPointMaps.forEach(({ id, pointMap }) => {
+    let lastKnownValue: number | null = null;
+
+    mergedDates.forEach((date) => {
+      const currentValue = pointMap.get(date);
+      if (typeof currentValue === 'number') {
+        lastKnownValue = currentValue;
       }
 
-      dateMap.set(date, existing);
+      const existing = dateMap.get(date);
+      if (existing && lastKnownValue !== null) {
+        existing[id] = lastKnownValue;
+      }
     });
   });
 
-  // Convert to array and sort by date
-  return Array.from(dateMap.values()).sort((a, b) =>
-    new Date(a.date).getTime() - new Date(b.date).getTime()
-  );
+  return mergedDates.map((date) => dateMap.get(date)!);
 }