lossless-cut/src/Timeline.jsx

import React, { memo, useRef, useMemo, useCallback, useEffect, useState } from 'react';
import { motion, useMotionValue, useSpring } from 'framer-motion';
import debounce from 'lodash/debounce';
import { useTranslation } from 'react-i18next';
import { FaCaretDown, FaCaretUp } from 'react-icons/fa';

import TimelineSeg from './TimelineSeg';
import BetweenSegments from './BetweenSegments';
import useContextMenu from './hooks/useContextMenu';
import useUserSettings from './hooks/useUserSettings';


import { timelineBackground, darkModeTransition } from './colors';

const currentTimeWidth = 1;

const Waveform = memo(({ waveform, calculateTimelinePercent, durationSafe }) => {
  const [style, setStyle] = useState({ display: 'none' });

  const leftPos = calculateTimelinePercent(waveform.from);

  const toTruncated = Math.min(waveform.to, durationSafe);

  // Prevents flash
  function onLoad() {
    setStyle({
      position: 'absolute', height: '100%', left: leftPos, width: `${((toTruncated - waveform.from) / durationSafe) * 100}%`,
    });
  }
  return (
    <img src={waveform.url} draggable={false} style={style} alt="" onLoad={onLoad} />
  );
});

const Waveforms = memo(({ calculateTimelinePercent, durationSafe, waveforms, zoom, height }) => (
  <div style={{ height, width: `${zoom * 100}%`, position: 'relative' }}>
    {waveforms.map((waveform) => (
      <Waveform key={`${waveform.from}-${waveform.to}`} waveform={waveform} calculateTimelinePercent={calculateTimelinePercent} durationSafe={durationSafe} />
    ))}
  </div>
));

const CommandedTime = memo(({ commandedTimePercent }) => {
  const color = 'var(--gray12)';
  const commonStyle = { left: commandedTimePercent, position: 'absolute', zIndex: 4, pointerEvents: 'none' };
  return (
    <>
      <FaCaretDown style={{ ...commonStyle, top: 0, color, fontSize: 14, marginLeft: -7, marginTop: -6 }} />
      <div style={{ ...commonStyle, bottom: 0, top: 0, backgroundColor: color, width: currentTimeWidth }} />
      <FaCaretUp style={{ ...commonStyle, bottom: 0, color, fontSize: 14, marginLeft: -7, marginBottom: -5 }} />
    </>
  );
});

const Timeline = memo(({
  durationSafe, startTimeOffset, playerTime, commandedTime, relevantTime,
  zoom, neighbouringKeyFrames, seekAbs, apparentCutSegments,
  setCurrentSegIndex, currentSegIndexSafe, inverseCutSegments, formatTimecode, formatTimeAndFrames,
  waveforms, shouldShowWaveform, shouldShowKeyframes, thumbnails,
  onZoomWindowStartTimeChange, waveformEnabled, showThumbnails,
  playing, isFileOpened, onWheel, commandedTimeRef, goToTimecode, isSegmentSelected,
}) => {
  const { t } = useTranslation();

  const timelineHeight = 36;

  const { invertCutSegments } = useUserSettings();

  const timelineScrollerRef = useRef();
  const timelineScrollerSkipEventRef = useRef();
  const timelineScrollerSkipEventDebounce = useRef();
  const timelineWrapperRef = useRef();

  const [hoveringTime, setHoveringTime] = useState();

  const displayTime = (hoveringTime != null && isFileOpened && !playing ? hoveringTime : relevantTime) + startTimeOffset;
  const displayTimePercent = useMemo(() => `${Math.round((displayTime / durationSafe) * 100)}%`, [displayTime, durationSafe]);

  const isZoomed = zoom > 1;

  // Don't show keyframes if too packed together (at current zoom)
  // See https://github.com/mifi/lossless-cut/issues/259
  // todo
  // const areKeyframesTooClose = keyframes.length > zoom * 200;
  const areKeyframesTooClose = false;

  const calculateTimelinePos = useCallback((time) => (time !== undefined ? Math.min(time / durationSafe, 1) : undefined), [durationSafe]);
  const calculateTimelinePercent = useCallback((time) => {
    const pos = calculateTimelinePos(time);
    return pos !== undefined ? `${pos * 100}%` : undefined;
  }, [calculateTimelinePos]);

  const currentTimePercent = useMemo(() => calculateTimelinePercent(playerTime), [calculateTimelinePercent, playerTime]);
  const commandedTimePercent = useMemo(() => calculateTimelinePercent(commandedTime), [calculateTimelinePercent, commandedTime]);

  const timeOfInterestPosPixels = useMemo(() => {
    // https://github.com/mifi/lossless-cut/issues/676
    const pos = calculateTimelinePos(relevantTime);
    if (pos != null && timelineScrollerRef.current) return pos * zoom * timelineScrollerRef.current.offsetWidth;
    return undefined;
  }, [calculateTimelinePos, relevantTime, zoom]);

  const calcZoomWindowStartTime = useCallback(() => (timelineScrollerRef.current
    ? (timelineScrollerRef.current.scrollLeft / (timelineScrollerRef.current.offsetWidth * zoom)) * durationSafe
    : 0), [durationSafe, zoom]);

  // const zoomWindowStartTime = calcZoomWindowStartTime(duration, zoom);

  useEffect(() => {
    timelineScrollerSkipEventDebounce.current = debounce(() => {
      timelineScrollerSkipEventRef.current = false;
    }, 1000);
  }, []);

  function suppressScrollerEvents() {
    timelineScrollerSkipEventRef.current = true;
    timelineScrollerSkipEventDebounce.current();
  }

  const scrollLeftMotion = useMotionValue(0);

  const spring = useSpring(scrollLeftMotion, { damping: 100, stiffness: 1000 });

  useEffect(() => {
    spring.on('change', (value) => {
      if (timelineScrollerSkipEventRef.current) return; // Don't animate while zooming
      timelineScrollerRef.current.scrollLeft = value;
    });
  }, [spring]);

  // Pan timeline when cursor moves out of timeline window
  useEffect(() => {
    if (timeOfInterestPosPixels == null || timelineScrollerSkipEventRef.current) return;

    if (timeOfInterestPosPixels > timelineScrollerRef.current.scrollLeft + timelineScrollerRef.current.offsetWidth) {
      const timelineWidth = timelineWrapperRef.current.offsetWidth;
      const scrollLeft = timeOfInterestPosPixels - (timelineScrollerRef.current.offsetWidth * 0.1);
      scrollLeftMotion.set(Math.min(scrollLeft, timelineWidth - timelineScrollerRef.current.offsetWidth));
    } else if (timeOfInterestPosPixels < timelineScrollerRef.current.scrollLeft) {
      const scrollLeft = timeOfInterestPosPixels - (timelineScrollerRef.current.offsetWidth * 0.9);
      scrollLeftMotion.set(Math.max(scrollLeft, 0));
    }
  }, [timeOfInterestPosPixels, scrollLeftMotion]);

  // Keep cursor in middle while zooming
  useEffect(() => {
    suppressScrollerEvents();

    if (isZoomed) {
      const zoomedTargetWidth = timelineScrollerRef.current.offsetWidth * zoom;

      const scrollLeft = Math.max((commandedTimeRef.current / durationSafe) * zoomedTargetWidth - timelineScrollerRef.current.offsetWidth / 2, 0);
      scrollLeftMotion.set(scrollLeft);
      timelineScrollerRef.current.scrollLeft = scrollLeft;
    }
  }, [zoom, durationSafe, commandedTimeRef, scrollLeftMotion, isZoomed]);


  useEffect(() => {
    const cancelWheel = (event) => event.preventDefault();

    const scroller = timelineScrollerRef.current;
    scroller.addEventListener('wheel', cancelWheel, { passive: false });

    return () => {
      scroller.removeEventListener('wheel', cancelWheel);
    };
  }, []);

  const onTimelineScroll = useCallback(() => {
    onZoomWindowStartTimeChange(calcZoomWindowStartTime());
  }, [calcZoomWindowStartTime, onZoomWindowStartTimeChange]);

  // Keep cursor in middle while scrolling
  /* const onTimelineScroll = useCallback((e) => {
    onZoomWindowStartTimeChange(zoomWindowStartTime);

    if (!zoomed || timelineScrollerSkipEventRef.current) return;

    seekAbs((((e.target.scrollLeft + (timelineScrollerRef.current.offsetWidth * 0.5))
      / (timelineScrollerRef.current.offsetWidth * zoom)) * duration));
  }, [duration, seekAbs, zoomed, zoom, zoomWindowStartTime, onZoomWindowStartTimeChange]); */

  const getMouseTimelinePos = useCallback((e) => {
    const target = timelineWrapperRef.current;
    const rect = target.getBoundingClientRect();
    const relX = e.pageX - (rect.left + document.body.scrollLeft);
    return (relX / target.offsetWidth) * durationSafe;
  }, [durationSafe]);

  const mouseDownRef = useRef();

  const handleScrub = useCallback((e) => seekAbs((getMouseTimelinePos(e))), [seekAbs, getMouseTimelinePos]);

  useEffect(() => {
    setHoveringTime();
  }, [relevantTime]);

  const onMouseDown = useCallback((e) => {
    if (e.nativeEvent.buttons !== 1) return; // not primary button

    handleScrub(e.nativeEvent);

    mouseDownRef.current = e.target;

    function onMouseMove(e2) {
      if (mouseDownRef.current == null) return;
      seekAbs(getMouseTimelinePos(e2));
    }

    function onMouseUp() {
      mouseDownRef.current = undefined;
      window.removeEventListener('mouseup', onMouseUp);
      window.removeEventListener('mousemove', onMouseMove);
    }

    // https://github.com/mifi/lossless-cut/issues/1432
    // https://stackoverflow.com/questions/11533098/how-to-catch-mouse-up-event-outside-of-element
    // https://stackoverflow.com/questions/6073505/what-is-the-difference-between-screenx-y-clientx-y-and-pagex-y
    window.addEventListener('mouseup', onMouseUp, { once: true });
    window.addEventListener('mousemove', onMouseMove);
  }, [getMouseTimelinePos, handleScrub, seekAbs]);

  const onMouseMove = useCallback((e) => {
    if (!mouseDownRef.current) { // no button pressed
      setHoveringTime(getMouseTimelinePos(e.nativeEvent));
    }
    e.preventDefault();
  }, [getMouseTimelinePos]);

  const onMouseOut = useCallback(() => setHoveringTime(), []);

  const contextMenuTemplate = useMemo(() => [
    { label: t('Seek to timecode'), click: goToTimecode },
  ], [goToTimecode, t]);

  useContextMenu(timelineScrollerRef, contextMenuTemplate);

  return (
    // eslint-disable-next-line jsx-a11y/no-static-element-interactions,jsx-a11y/mouse-events-have-key-events
    <div
      style={{ position: 'relative', borderTop: '1px solid var(--gray7)', borderBottom: '1px solid var(--gray7)' }}
      onMouseDown={onMouseDown}
      onMouseMove={onMouseMove}
      onMouseOut={onMouseOut}
    >
      {(waveformEnabled && !shouldShowWaveform) && (
        <div style={{ pointerEvents: 'none', display: 'flex', alignItems: 'center', justifyContent: 'center', height: timelineHeight, bottom: timelineHeight, left: 0, right: 0, color: 'var(--gray11)' }}>
          {t('Zoom in more to view waveform')}
        </div>
      )}

      <div
        style={{ overflowX: 'scroll' }}
        className="hide-scrollbar"
        onWheel={onWheel}
        onScroll={onTimelineScroll}
        ref={timelineScrollerRef}
      >
        {waveformEnabled && shouldShowWaveform && waveforms.length > 0 && (
          <Waveforms
            calculateTimelinePercent={calculateTimelinePercent}
            durationSafe={durationSafe}
            waveforms={waveforms}
            zoom={zoom}
            height={40}
          />
        )}

        {showThumbnails && (
          <div style={{ height: 60, width: `${zoom * 100}%`, position: 'relative', marginBottom: 3 }}>
            {thumbnails.map((thumbnail, i) => {
              const leftPercent = (thumbnail.time / durationSafe) * 100;
              const nextThumbnail = thumbnails[i + 1];
              const nextThumbTime = nextThumbnail ? nextThumbnail.time : durationSafe;
              const maxWidthPercent = ((nextThumbTime - thumbnail.time) / durationSafe) * 100 * 0.9;
              return (
                <img key={thumbnail.url} src={thumbnail.url} alt="" style={{ position: 'absolute', left: `${leftPercent}%`, height: '100%', boxSizing: 'border-box', zIndex: 1, maxWidth: `${maxWidthPercent}%`, objectFit: 'cover', border: '1px solid rgba(255, 255, 255, 0.5)', borderBottomRightRadius: 15, borderTopLeftRadius: 15, borderTopRightRadius: 15, pointerEvents: 'none' }} />
              );
            })}
          </div>
        )}

        <div
          style={{ height: timelineHeight, width: `${zoom * 100}%`, position: 'relative', backgroundColor: timelineBackground, transition: darkModeTransition }}
          ref={timelineWrapperRef}
        >
          {currentTimePercent !== undefined && (
            <motion.div transition={{ type: 'spring', damping: 70, stiffness: 800 }} animate={{ left: currentTimePercent }} style={{ position: 'absolute', bottom: 0, top: 0, zIndex: 3, backgroundColor: 'var(--gray12)', width: currentTimeWidth, pointerEvents: 'none' }} />
          )}
          {commandedTimePercent !== undefined && (
            <CommandedTime commandedTimePercent={commandedTimePercent} />
          )}

          {apparentCutSegments.map((seg, i) => {
            if (seg.start === 0 && seg.end === 0) return null; // No video loaded

            const selected = invertCutSegments || isSegmentSelected({ segId: seg.segId });

            return (
              <TimelineSeg
                key={seg.segId}
                seg={seg}
                segNum={i}
                onSegClick={setCurrentSegIndex}
                isActive={i === currentSegIndexSafe}
                duration={durationSafe}
                invertCutSegments={invertCutSegments}
                formatTimecode={formatTimecode}
                selected={selected}
              />
            );
          })}

          {inverseCutSegments.map((seg) => (
            <BetweenSegments
              key={seg.segId}
              start={seg.start}
              end={seg.end}
              duration={durationSafe}
              invertCutSegments={invertCutSegments}
            />
          ))}

          {shouldShowKeyframes && !areKeyframesTooClose && neighbouringKeyFrames.map((f) => (
            <div key={f.time} style={{ position: 'absolute', top: 0, bottom: 0, left: `${(f.time / durationSafe) * 100}%`, marginLeft: -1, width: 1, background: 'var(--gray11)', pointerEvents: 'none' }} />
          ))}
        </div>
      </div>

      <div style={{ position: 'absolute', height: timelineHeight, left: 0, right: 0, bottom: 0, display: 'flex', alignItems: 'center', justifyContent: 'center', pointerEvents: 'none', zIndex: 2 }}>
        <div style={{ background: 'rgba(0,0,0,0.4)', borderRadius: 3, padding: '2px 4px', color: 'rgba(255, 255, 255, 0.8)' }}>
          {formatTimeAndFrames(displayTime)}{isZoomed ? ` ${displayTimePercent}` : ''}
        </div>
      </div>
    </div>
  );
});

export default Timeline;