From edfe44c1e39bd43d2d6912427292654f11424205 Mon Sep 17 00:00:00 2001
From: Josh Hawkins <32435876+hawkeye217@users.noreply.github.com>
Date: Fri, 29 Nov 2024 20:16:47 -0600
Subject: [PATCH] virtualize event segments

---
 web/src/components/timeline/EventSegment.tsx  |  54 +----
 .../timeline/VirtualizedEventSegments.tsx     | 205 ++++++++++++++++++
 2 files changed, 213 insertions(+), 46 deletions(-)
 create mode 100644 web/src/components/timeline/VirtualizedEventSegments.tsx

diff --git a/web/src/components/timeline/EventSegment.tsx b/web/src/components/timeline/EventSegment.tsx
index 242ca3248..b6bd9d137 100644
--- a/web/src/components/timeline/EventSegment.tsx
+++ b/web/src/components/timeline/EventSegment.tsx
@@ -8,7 +8,6 @@ import React, {
   useEffect,
   useMemo,
   useRef,
-  useState,
 } from "react";
 import {
   HoverCard,
@@ -31,6 +30,7 @@ type EventSegmentProps = {
   severityType: ReviewSeverity;
   contentRef: RefObject<HTMLDivElement>;
   setHandlebarTime?: React.Dispatch<React.SetStateAction<number>>;
+  scrollToSegment: (segmentTime: number, ifNeeded?: boolean) => void;
   dense: boolean;
 };
 
@@ -45,6 +45,7 @@ export function EventSegment({
   severityType,
   contentRef,
   setHandlebarTime,
+  scrollToSegment,
   dense,
 }: EventSegmentProps) {
   const {
@@ -95,7 +96,10 @@ export function EventSegment({
   }, [getEventThumbnail, segmentTime]);
 
   const timestamp = useMemo(() => new Date(segmentTime * 1000), [segmentTime]);
-  const segmentKey = useMemo(() => segmentTime, [segmentTime]);
+  const segmentKey = useMemo(
+    () => `${segmentTime}_${segmentDuration}`,
+    [segmentTime, segmentDuration],
+  );
 
   const alignedMinimapStartTime = useMemo(
     () => alignStartDateToTimeline(minimapStartTime ?? 0),
@@ -133,10 +137,7 @@ export function EventSegment({
     // Check if the first segment is out of view
     const firstSegment = firstMinimapSegmentRef.current;
     if (firstSegment && showMinimap && isFirstSegmentInMinimap) {
-      scrollIntoView(firstSegment, {
-        scrollMode: "if-needed",
-        behavior: "smooth",
-      });
+      scrollToSegment(alignedMinimapStartTime);
     }
     // we know that these deps are correct
     // eslint-disable-next-line react-hooks/exhaustive-deps
@@ -196,49 +197,10 @@ export function EventSegment({
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [startTimestamp]);
 
-  const [segmentRendered, setSegmentRendered] = useState(false);
-  const segmentObserverRef = useRef<IntersectionObserver | null>(null);
-  const segmentRef = useRef(null);
-
-  useEffect(() => {
-    const segmentObserver = new IntersectionObserver(
-      ([entry]) => {
-        if (entry.isIntersecting && !segmentRendered) {
-          setSegmentRendered(true);
-        }
-      },
-      { threshold: 0 },
-    );
-
-    if (segmentRef.current) {
-      segmentObserver.observe(segmentRef.current);
-    }
-
-    segmentObserverRef.current = segmentObserver;
-
-    return () => {
-      if (segmentObserverRef.current) {
-        segmentObserverRef.current.disconnect();
-      }
-    };
-  }, [segmentRendered]);
-
-  if (!segmentRendered) {
-    return (
-      <div
-        key={segmentKey}
-        ref={segmentRef}
-        data-segment-id={segmentKey}
-        className={`segment ${segmentClasses}`}
-      />
-    );
-  }
-
   return (
     <div
       key={segmentKey}
-      ref={segmentRef}
-      data-segment-id={segmentKey}
+      data-segment-id={segmentTime}
       className={`segment ${segmentClasses}`}
       onClick={segmentClick}
       onTouchEnd={(event) => handleTouchStart(event, segmentClick)}
diff --git a/web/src/components/timeline/VirtualizedEventSegments.tsx b/web/src/components/timeline/VirtualizedEventSegments.tsx
new file mode 100644
index 000000000..cb9a97f56
--- /dev/null
+++ b/web/src/components/timeline/VirtualizedEventSegments.tsx
@@ -0,0 +1,205 @@
+import React, {
+  useCallback,
+  useEffect,
+  useRef,
+  useState,
+  forwardRef,
+  useImperativeHandle,
+} from "react";
+import { EventSegment } from "./EventSegment";
+import { ReviewSegment, ReviewSeverity } from "@/types/review";
+
+interface VirtualizedEventSegmentsProps {
+  timelineRef: React.RefObject<HTMLDivElement>;
+  segments: number[];
+  events: ReviewSegment[];
+  segmentDuration: number;
+  timestampSpread: number;
+  showMinimap: boolean;
+  minimapStartTime?: number;
+  minimapEndTime?: number;
+  severityType: ReviewSeverity;
+  contentRef: React.RefObject<HTMLDivElement>;
+  setHandlebarTime?: React.Dispatch<React.SetStateAction<number>>;
+  dense: boolean;
+  alignStartDateToTimeline: (timestamp: number) => number;
+}
+
+export interface VirtualizedEventSegmentsRef {
+  scrollToSegment: (segmentTime: number, ifNeeded?: boolean) => void;
+}
+
+const SEGMENT_HEIGHT = 8;
+const OVERSCAN_COUNT = 20;
+
+export const VirtualizedEventSegments = forwardRef<
+  VirtualizedEventSegmentsRef,
+  VirtualizedEventSegmentsProps
+>(
+  (
+    {
+      timelineRef,
+      segments,
+      events,
+      segmentDuration,
+      timestampSpread,
+      showMinimap,
+      minimapStartTime,
+      minimapEndTime,
+      severityType,
+      contentRef,
+      setHandlebarTime,
+      dense,
+      alignStartDateToTimeline,
+    },
+    ref,
+  ) => {
+    const [visibleRange, setVisibleRange] = useState({ start: 0, end: 0 });
+    const containerRef = useRef<HTMLDivElement>(null);
+
+    const updateVisibleRange = useCallback(() => {
+      if (timelineRef.current) {
+        const { scrollTop, clientHeight } = timelineRef.current;
+        const start = Math.max(
+          0,
+          Math.floor(scrollTop / SEGMENT_HEIGHT) - OVERSCAN_COUNT,
+        );
+        const end = Math.min(
+          segments.length,
+          Math.ceil((scrollTop + clientHeight) / SEGMENT_HEIGHT) +
+            OVERSCAN_COUNT,
+        );
+        setVisibleRange({ start, end });
+      }
+    }, [segments.length, timelineRef]);
+
+    useEffect(() => {
+      const container = timelineRef.current;
+      if (container) {
+        const handleScroll = () => {
+          window.requestAnimationFrame(updateVisibleRange);
+        };
+
+        container.addEventListener("scroll", handleScroll, { passive: true });
+        window.addEventListener("resize", updateVisibleRange);
+
+        updateVisibleRange();
+
+        return () => {
+          container.removeEventListener("scroll", handleScroll);
+          window.removeEventListener("resize", updateVisibleRange);
+        };
+      }
+    }, [updateVisibleRange, timelineRef]);
+
+    const scrollToSegment = useCallback(
+      (segmentTime: number, ifNeeded: boolean = true) => {
+        const alignedSegmentTime = alignStartDateToTimeline(segmentTime);
+        const segmentIndex = segments.findIndex(
+          (time) => time === alignedSegmentTime,
+        );
+        if (
+          segmentIndex !== -1 &&
+          containerRef.current &&
+          timelineRef.current
+        ) {
+          const timelineHeight = timelineRef.current.clientHeight;
+          const targetScrollTop = segmentIndex * SEGMENT_HEIGHT;
+          const centeredScrollTop =
+            targetScrollTop - timelineHeight / 2 + SEGMENT_HEIGHT / 2;
+
+          const isVisible =
+            segmentIndex > visibleRange.start + OVERSCAN_COUNT &&
+            segmentIndex < visibleRange.end - OVERSCAN_COUNT;
+
+          if (!ifNeeded || !isVisible) {
+            timelineRef.current.scrollTo({
+              top: Math.max(0, centeredScrollTop),
+              behavior: "smooth",
+            });
+          }
+          updateVisibleRange();
+        }
+      },
+      [
+        segments,
+        alignStartDateToTimeline,
+        updateVisibleRange,
+        timelineRef,
+        visibleRange,
+      ],
+    );
+
+    useImperativeHandle(ref, () => ({
+      scrollToSegment,
+    }));
+
+    const totalHeight = segments.length * SEGMENT_HEIGHT;
+    const visibleSegments = segments.slice(
+      visibleRange.start,
+      visibleRange.end,
+    );
+
+    return (
+      <div
+        ref={containerRef}
+        className="h-full w-full"
+        style={{ position: "relative", willChange: "transform" }}
+      >
+        <div style={{ height: `${totalHeight}px`, position: "relative" }}>
+          {visibleRange.start > 0 && (
+            <div
+              style={{
+                position: "absolute",
+                top: 0,
+                height: `${visibleRange.start * SEGMENT_HEIGHT}px`,
+                width: "100%",
+              }}
+              aria-hidden="true"
+            />
+          )}
+          {visibleSegments.map((segmentTime, index) => {
+            const segmentId = `${segmentTime}_${segmentDuration}`;
+            return (
+              <div
+                key={segmentId}
+                style={{
+                  position: "absolute",
+                  top: `${(visibleRange.start + index) * SEGMENT_HEIGHT}px`,
+                  height: `${SEGMENT_HEIGHT}px`,
+                  width: "100%",
+                }}
+              >
+                <EventSegment
+                  events={events}
+                  segmentTime={segmentTime}
+                  segmentDuration={segmentDuration}
+                  timestampSpread={timestampSpread}
+                  showMinimap={showMinimap}
+                  minimapStartTime={minimapStartTime}
+                  minimapEndTime={minimapEndTime}
+                  severityType={severityType}
+                  contentRef={contentRef}
+                  setHandlebarTime={setHandlebarTime}
+                  scrollToSegment={scrollToSegment}
+                  dense={dense}
+                />
+              </div>
+            );
+          })}
+          {visibleRange.end < segments.length && (
+            <div
+              style={{
+                position: "absolute",
+                top: `${visibleRange.end * SEGMENT_HEIGHT}px`,
+                height: `${(segments.length - visibleRange.end) * SEGMENT_HEIGHT}px`,
+                width: "100%",
+              }}
+              aria-hidden="true"
+            />
+          )}
+        </div>
+      </div>
+    );
+  },
+);