refactor: new timeline component

- Create new timeline component (extracted from asset-gird) without removing old code
- Add timeline/, timeline/actions/, timeline/base-components/, and timeline/internal-components/ directories
- Copy needed components (delete-asset-dialog, scrubber, skeleton) to new locations
- Add new timeline components (base-timeline, base-timeline-viewer, timeline-month, etc.)
- Update timeline-util.ts with new functions (findMonthAtScrollPosition, formatGroupTitleFull)
- Add asset-viewer-actions and asset-viewer-and-actions components

This allows the timeline to exist alongside the current AssetGrid component.

web/src/lib/utils/timeline-util.ts

@@ -23,11 +23,12 @@ export type TimelineDateTime = TimelineDate & {
   millisecond: number;
 };
 
-export type ScrubberListener = (
-  scrubberMonth: { year: number; month: number },
-  overallScrollPercent: number,
-  scrubberMonthScrollPercent: number,
-) => void | Promise<void>;
+export type ScrubberListener = (scrubberData: {
+  scrubberMonth: { year: number; month: number };
+  overallScrollPercent: number;
+  scrubberMonthScrollPercent: number;
+  scrollToFunction?: (top: number) => void;
+}) => void | Promise<void>;
 
 // used for AssetResponseDto.dateTimeOriginal, amongst others
 export const fromISODateTime = (isoDateTime: string, timeZone: string): DateTime<true> =>
@@ -151,6 +152,14 @@ export function formatGroupTitle(_date: DateTime): string {
   return getDateLocaleString(date, { locale: get(locale) });
 }
 
+export const formatGroupTitleFull = (_date: DateTime): string => {
+  if (!_date.isValid) {
+    return _date.toString();
+  }
+  const date = _date as DateTime<true>;
+  return getDateLocaleString(date);
+};
+
 export const getDateLocaleString = (date: DateTime, opts?: LocaleOptions): string =>
   date.toLocaleString(DateTime.DATE_MED_WITH_WEEKDAY, opts);
 
@@ -234,3 +243,79 @@ export function setDifference<T>(setA: Set<T>, setB: Set<T>): SvelteSet<T> {
   }
   return result;
 }
+
+export interface MonthGroupForSearch {
+  yearMonth: TimelineYearMonth;
+  top: number;
+  height: number;
+}
+
+export interface BinarySearchResult {
+  month: TimelineYearMonth;
+  monthScrollPercent: number;
+}
+
+export function findMonthAtScrollPosition(
+  months: MonthGroupForSearch[],
+  scrollPosition: number,
+  maxScrollPercent: number,
+): BinarySearchResult | null {
+  const SUBPIXEL_TOLERANCE = -1; // Tolerance for scroll position checks
+  const NEAR_END_THRESHOLD = 0.9999; // Threshold for detecting near-end of month
+
+  if (months.length === 0) {
+    return null;
+  }
+
+  // Check if we're before the first month
+  const firstMonthTop = months[0].top * maxScrollPercent;
+  if (scrollPosition < firstMonthTop - SUBPIXEL_TOLERANCE) {
+    return null;
+  }
+
+  // Check if we're after the last month
+  const lastMonth = months.at(-1)!;
+  const lastMonthBottom = (lastMonth.top + lastMonth.height) * maxScrollPercent;
+  if (scrollPosition >= lastMonthBottom - SUBPIXEL_TOLERANCE) {
+    return null;
+  }
+
+  // Binary search to find the month containing the scroll position
+  let left = 0;
+  let right = months.length - 1;
+
+  while (left <= right) {
+    const mid = Math.floor((left + right) / 2);
+    const month = months[mid];
+    const monthTop = month.top * maxScrollPercent;
+    const monthBottom = monthTop + month.height * maxScrollPercent;
+
+    if (scrollPosition >= monthTop - SUBPIXEL_TOLERANCE && scrollPosition < monthBottom - SUBPIXEL_TOLERANCE) {
+      // Found the month containing the scroll position
+      const distanceIntoMonth = scrollPosition - monthTop;
+      const monthScrollPercent = Math.max(0, distanceIntoMonth / (month.height * maxScrollPercent));
+
+      // Handle month boundary edge case
+      if (monthScrollPercent > NEAR_END_THRESHOLD && mid < months.length - 1) {
+        return {
+          month: months[mid + 1].yearMonth,
+          monthScrollPercent: 0,
+        };
+      }
+
+      return {
+        month: month.yearMonth,
+        monthScrollPercent,
+      };
+    }
+
+    if (scrollPosition < monthTop) {
+      right = mid - 1;
+    } else {
+      left = mid + 1;
+    }
+  }
+
+  // Shouldn't reach here, but return null if we do
+  return null;
+}