lossless-cut/src/segments.js

import { v4 as uuidv4 } from 'uuid';
import sortBy from 'lodash/sortBy';

export const createSegment = ({ start, end, name, tags, segColorIndex } = {}) => ({
  start,
  end,
  name: name || '',
  segId: uuidv4(),
  segColorIndex,

  // `tags` is an optional object (key-value). Values must always be string
  // See https://github.com/mifi/lossless-cut/issues/879
  tags: tags != null && typeof tags === 'object'
    ? Object.fromEntries(Object.entries(tags).map(([key, value]) => [key, String(value)]))
    : undefined,
});

// Because segments could have undefined start / end
// (meaning extend to start of timeline or end duration)
export function getSegApparentStart(seg) {
  const time = seg.start;
  return time !== undefined ? time : 0;
}

export const getCleanCutSegments = (cs) => cs.map((seg) => ({
  start: seg.start,
  end: seg.end,
  name: seg.name,
  tags: seg.tags,
}));

export function findSegmentsAtCursor(apparentSegments, currentTime) {
  const indexes = [];
  apparentSegments.forEach((segment, index) => {
    if (segment.start < currentTime && segment.end > currentTime) indexes.push(index);
  });
  return indexes;
}

export const getSegmentTags = (segment) => (segment.tags || {});

export const sortSegments = (segments) => sortBy(segments, 'start');

export function hasAnySegmentOverlap(sortedSegments) {
  if (sortedSegments.length < 1) return false;

  return sortedSegments.some((cutSegment, i) => {
    if (i === 0) return false;
    const previousSeg = sortedSegments[i - 1];
    return previousSeg.end > cutSegment.start;
  });
}

export function invertSegments(sortedCutSegments, includeFirstSegment, includeLastSegment, duration) {
  if (sortedCutSegments.length < 1) return undefined;

  if (hasAnySegmentOverlap(sortedCutSegments)) return undefined;

  const ret = [];

  if (includeFirstSegment) {
    if (sortedCutSegments[0].start > 0) {
      ret.push({
        start: 0,
        end: sortedCutSegments[0].start,
      });
    }
  }

  sortedCutSegments.forEach((cutSegment, i) => {
    if (i === 0) return;
    ret.push({
      start: sortedCutSegments[i - 1].end,
      end: cutSegment.start,
    });
  });

  if (includeLastSegment) {
    const last = sortedCutSegments[sortedCutSegments.length - 1];
    if (last.end < duration || duration == null) {
      ret.push({
        start: last.end,
        end: duration,
      });
    }
  }

  // Filter out zero length resulting segments
  // https://github.com/mifi/lossless-cut/issues/909
  return ret.filter(({ start, end }) => end == null || start == null || end > start);
}

// because chapters need to be contiguous, we need to insert gaps in-between
export function convertSegmentsToChapters(sortedSegments) {
  if (sortedSegments.length < 1) return [];
  if (hasAnySegmentOverlap(sortedSegments)) throw new Error('Segments cannot overlap');

  sortedSegments.map((segment) => ({ start: segment.start, end: segment.end, name: segment.name }));
  const invertedSegments = invertSegments(sortedSegments, true, false);

  // inverted segments will be "gap" segments. Merge together with normal segments
  return sortSegments([...sortedSegments, ...invertedSegments]);
}