private void advance() {
if (current == null) {
if (!subGraphIterator.hasNext()) return;
current = subGraphIterator.next();
pathsIterator = null;
}
if (pathsIterator == null) {
Set<FlowElement> sources = findSources(current, FlowElement.class);
Set<FlowElement> sinks = findSinks(current, FlowElement.class);
if (sources.size() > 1 || sinks.size() > 1)
throw new IllegalArgumentException("only supports single source and single sink graphs");
FlowElement source = getFirst(sources);
FlowElement sink = getFirst(sinks);
pairs.add(new Pair<>(source, sink));
List<GraphPath<FlowElement, Scope>> paths = getAllShortestPathsBetween(current, source, sink);
if (longestFirst) Collections.reverse(paths); // break off longest paths into own partitions
pathsIterator = paths.iterator();
}
}
