/// <summary>
/// Given a double bond edge traverse the neighbors of one of the endpoints
/// and accumulate any explicit replacements in the <paramref name="acc"/> accumulator.
/// </summary>
/// <param name="g">the chemical graph</param>
/// <param name="e">a edge in the graph ('double bond type')</param>
/// <param name="u">a endpoint of the edge <paramref name="e"/></param>
/// <param name="acc">accumulator for new edges</param>
/// <returns>does the edge <paramref name="e"/> need to be reconsidered later</returns>
/// <exception cref="InvalidSmilesException">thrown if the edge could not be converted</exception>
private bool ReplaceImplWithExpl(Graph g,
Edge e,
int u,
Dictionary <Edge, Edge> acc)
{
Edge implicit_ = null;
Edge explicit_ = null;
foreach (var f in g.GetEdges(u))
{
Edge f2 = acc.ContainsKey(f) ? acc[f] : f;
var aa = f2.GetBond(u);
if (aa == Bond.Single || aa == Bond.Implicit)
{
if (implicit_ != null)
{
return(true);
}
implicit_ = f;
}
else if (aa == Bond.Double)
{
if (!f.Equals(e))
{
return(false);
}
}
else if (aa == Bond.Up || aa == Bond.Down)
{
if (explicit_ != null)
{
if (acc.ContainsKey(explicit_))
{
explicit_ = acc[explicit_];
}
// original bonds are invalid
if ((f.Bond == Bond.Up || f.Bond == Bond.Down) &&
explicit_.GetBond(u).Inverse() != f.GetBond(u))
{
throw new InvalidSmilesException("invalid double bond configuration");
}
if (explicit_.GetBond(u).Inverse() != f2.GetBond(u))
{
acc[f] = f2.Inverse();
BitArray visited = new BitArray(g.Order);
visited.Set(u, true);
InvertExistingDirectionalLabels(g, visited, acc, f2
.Other(u));
}
return(false);
}
explicit_ = f;
}
}
// no implicit or explicit bond? don't do anything
if (implicit_ == null || explicit_ == null)
{
return(false);
}
if (acc.ContainsKey(explicit_))
{
explicit_ = acc[explicit_];
}
int v = implicit_.Other(u);
if (!acc.TryGetValue(implicit_, out Edge existing))
{
existing = null;
}
acc[implicit_] = new Edge(u,
v,
explicit_.GetBond(u)
.Inverse());
if (existing != null && existing.GetBond(u) != explicit_.GetBond(u).Inverse())
{
throw new InvalidSmilesException("unable to assign explicit type for " + implicit_);
}
return(false);
}