// Answer returns the filtered trace by performing a depth-first traversal on
// the graph. The traversal goes from source to sink, where a sink is one of the
// exits events of the top-level query.
func (t *truth) Answer() (result []*topdown.Event) {
byQuery := t.byQuery[t.source.event.QueryID]
var sink *node
for _, node := range byQuery {
if node.event.Op == topdown.ExitOp {
sink = node
break
}
}
if sink == nil {
return nil
}
traversal := newTruthTraversal(t)
nodes := util.DFS(traversal, t.source, sink)
for _, n := range nodes {
node := n.(*node)
result = append(result, node.event)
}
return result
}
// checkRecursion ensures that there are no recursive rule definitions, i.e., there are
// no cycles in the RuleGraph.
func (c *Compiler) checkRecursion() {
for r := range c.RuleGraph {
t := &ruleGraphTraveral{
graph: c.RuleGraph,
visited: map[*Rule]struct{}{},
}
if p := util.DFS(t, r, r); len(p) > 0 {
n := []string{}
for _, x := range p {
n = append(n, string(x.(*Rule).Name))
}
c.err(NewError(RecursionErr, r.Location, "%v: recursive reference: %v (recursion is not allowed)", r.Name, strings.Join(n, " -> ")))
}
}
}
