Bugfix in the coalesce module

internal/coalesce/coalesce.go

@@ -29,16 +29,22 @@ func Apply(in model.MergedTranscript, gap float64) (model.MergedTranscript, Summ
 	current := newRun(in.Segments[0])
 	pendingSkipped := make([]model.Segment, 0)
 	for _, segment := range in.Segments[1:] {
-		if current.canMerge(segment, gap) {
-			current.add(segment)
-			continue
-		}
-		if segment.Speaker != current.speaker() && hasAnyCategory(segment, "backchannel", "filler") {
+		if segment.Speaker == current.speaker() {
+			if current.canMerge(segment, gap) {
+				current.add(segment)
+				continue
+			}
+		} else if isSkippableInterjection(segment) {
 			pendingSkipped = append(pendingSkipped, segment)
 			continue
 		}
 
 		coalescedID = appendRun(&out, current, coalescedID, &summary)
+		if seeded, remaining, ok := seedRunFromPending(pendingSkipped, segment, gap); ok {
+			pendingSkipped = remaining
+			current = seeded
+			continue
+		}
 		out.Segments = append(out.Segments, pendingSkipped...)
 		pendingSkipped = pendingSkipped[:0]
 		current = newRun(segment)
@@ -72,6 +78,37 @@ func (r *run) add(segment model.Segment) {
 	r.segments = append(r.segments, segment)
 }
 
+func seedRunFromPending(pending []model.Segment, segment model.Segment, gap float64) (run, []model.Segment, bool) {
+	for start := range pending {
+		if pending[start].Speaker != segment.Speaker {
+			continue
+		}
+
+		candidate := newRun(pending[start])
+		selected := map[int]struct{}{start: {}}
+		for index := start + 1; index < len(pending); index++ {
+			if pending[index].Speaker == segment.Speaker && candidate.canMerge(pending[index], gap) {
+				candidate.add(pending[index])
+				selected[index] = struct{}{}
+			}
+		}
+		if !candidate.canMerge(segment, gap) {
+			continue
+		}
+
+		candidate.add(segment)
+		remaining := make([]model.Segment, 0, len(pending)-len(selected))
+		for index, skipped := range pending {
+			if _, ok := selected[index]; ok {
+				continue
+			}
+			remaining = append(remaining, skipped)
+		}
+		return candidate, remaining, true
+	}
+	return run{}, pending, false
+}
+
 func appendRun(out *model.MergedTranscript, current run, coalescedID int, summary *Summary) int {
 	if len(current.segments) == 1 {
 		out.Segments = append(out.Segments, current.segments[0])
@@ -129,6 +166,10 @@ func segmentRef(segment model.Segment) string {
 	return segment.Source
 }
 
+func isSkippableInterjection(segment model.Segment) bool {
+	return hasAnyCategory(segment, "backchannel", "filler")
+}
+
 func hasAnyCategory(segment model.Segment, categories ...string) bool {
 	for _, existing := range segment.Categories {
 		for _, category := range categories {