/// <summary>
/// Decide the bond to use for a ring bond. The bond symbol can be present on
/// either or both bonded atoms. This method takes those bonds, chooses the
/// correct one or reports an error if there is a conflict.
/// </summary>
/// <remarks>
/// Equivalent SMILES:
/// <list type="bullet">
/// <item>C=1CCCCC=1</item>
/// <item>C=1CCCCC1 (preferred)</item>
/// <item>C1CCCCC=1</item>
/// </list>
/// </remarks>
/// <param name="a">a bond</param>
/// <param name="b">other bond</param>
/// <param name="pos">the position in the string of bond <paramref name="a"/></param>
/// <param name="buffer"></param>
/// <returns>the bond to use for this edge</returns>
/// <exception cref="InvalidSmilesException">ring bonds did not match</exception>
public Bond DecideBond(Bond a, Bond b, int pos, CharBuffer buffer)
{
if (a == b)
{
return(a);
}
else if (a == Bond.Implicit)
{
return(b);
}
else if (b == Bond.Implicit)
{
return(a);
}
if (strict || a.Inverse() != b)
{
throw new InvalidSmilesException($"Ring closure bonds did not match, '{a}'!='{b}':" +
InvalidSmilesException.Display(buffer,
pos - buffer.Position,
lastBondPos - buffer.Position));
}
warnings.Add("Ignored invalid Cis/Trans on ring closure, should flip:" +
InvalidSmilesException.Display(buffer,
pos - buffer.Position,
lastBondPos - buffer.Position));
return(Bond.Implicit);
}
/// <summary>
/// Read a bracket atom from the buffer. A bracket atom optionally defines
/// isotope, chirality, hydrogen count, formal charge and the atom class.
/// <para>
/// bracket_atom ::= '[' isotope? symbol chiral? hcount? charge? class? ']'
/// </para>
/// </summary>
/// <param name="buffer">a character buffer</param>
/// <returns>a bracket atom</returns>
/// <exception cref="InvalidSmilesException">if the bracket atom did not match the grammar, invalid symbol, missing closing bracket or invalid chiral specification.</exception>
public IAtom ReadBracketAtom(CharBuffer buffer)
{
int start = buffer.Position;
bool arbitraryLabel = false;
if (!buffer.HasRemaining())
{
throw new InvalidSmilesException("Unclosed bracket atom, SMILES may be truncated", buffer);
}
var isotope = buffer.GetNumber();
var aromatic = buffer.NextChar >= 'a' && buffer.NextChar <= 'z';
var element = Element.Read(buffer);
if (element == Element.Unknown)
{
hasAstrix = true;
}
if (strict && element == null)
{
throw new InvalidSmilesException("unrecognised element symbol, SMILES may be truncated: ", buffer);
}
if (element != null && aromatic)
{
g.AddFlags(Graph.HAS_AROM);
}
// element isn't aromatic as per the OpenSMILES specification
if (strict && aromatic && !element.IsAromatic(Element.AromaticSpecification.OpenSmiles))
{
throw new InvalidSmilesException("abnormal aromatic element", buffer);
}
if (element == null)
{
arbitraryLabel = true;
}
configuration = Configuration.Read(buffer);
var hCount = ReadHydrogens(buffer);
var charge = ReadCharge(buffer);
var atomClass = ReadClass(buffer);
if (!arbitraryLabel && !buffer.GetIf(']'))
{
if (strict)
{
throw InvalidSmilesException.InvalidBracketAtom(buffer);
}
else
{
arbitraryLabel = true;
}
}
if (arbitraryLabel)
{
var end = buffer.Position;
int depth = 1;
while (buffer.HasRemaining())
{
char c = buffer.Get();
if (c == '[')
{
depth++;
}
else if (c == ']')
{
depth--;
if (depth == 0)
{
break;
}
}
end++;
}
if (depth != 0)
{
throw new InvalidSmilesException("unparsable label in bracket atom",
buffer,
buffer.Position - 1);
}
var label = buffer.Substr(start, end);
hasAstrix = true;
return(new AtomImpl.BracketAtom(label));
}
return(new AtomImpl.BracketAtom(isotope,
element,
hCount,
charge,
atomClass,
aromatic));
}
/// <summary>
/// Create the topologies (stereo configurations) for the chemical graph. The
/// topologies define spacial arrangement around atoms.
/// </summary>
private void CreateTopologies(CharBuffer buffer)
{
// create topologies (stereo configurations)
foreach (var e in configurations)
{
AddTopology(e.Key,
Topology.ToExplicit(g, e.Key, e.Value));
}
for (int v = BitArrays.NextSetBit(checkDirectionalBonds, 0); v >= 0; v = BitArrays.NextSetBit(checkDirectionalBonds, v + 1))
{
int nUpV = 0;
int nDownV = 0;
int nUpW = 0;
int nDownW = 0;
int w = -1;
{
int d = g.Degree(v);
for (int j = 0; j < d; ++j)
{
Edge e = g.EdgeAt(v, j);
Bond bond = e.GetBond(v);
if (bond == Bond.Up)
{
nUpV++;
}
else if (bond == Bond.Down)
{
nDownV++;
}
else if (bond == Bond.Double)
{
w = e.Other(v);
}
}
}
if (w < 0)
{
continue;
}
BitArrays.EnsureCapacity(checkDirectionalBonds, w + 1);
checkDirectionalBonds.Set(w, false);
{
int d = g.Degree(w);
for (int j = 0; j < d; ++j)
{
Edge e = g.EdgeAt(w, j);
Bond bond = e.GetBond(w);
if (bond == Bond.Up)
{
nUpW++;
}
else if (bond == Bond.Down)
{
nDownW++;
}
}
}
if (nUpV + nDownV == 0 || nUpW + nDownW == 0)
{
continue;
}
if (nUpV > 1 || nDownV > 1)
{
int offset1 = -1, offset2 = -1;
foreach (var e in g.GetEdges(v))
{
if (e.Bond.IsDirectional)
{
if (offset1 < 0)
{
offset1 = bondStrPos[e];
}
else
{
offset2 = bondStrPos[e];
}
}
}
var errorPos = InvalidSmilesException.Display(buffer,
offset1 - buffer.Length,
offset2 - buffer.Length);
if (strict)
{
throw new InvalidSmilesException($"Ignored invalid Cis/Trans specification: {errorPos}");
}
else
{
warnings.Add($"Ignored invalid Cis/Trans specification: {errorPos}");
}
}
if (nUpW > 1 || nDownW > 1)
{
int offset1 = -1;
int offset2 = -1;
foreach (var e in g.GetEdges(w))
{
if (e.Bond.IsDirectional)
{
if (offset1 < 0)
{
offset1 = bondStrPos[e];
}
else
{
offset2 = bondStrPos[e];
}
}
}
var errorPos = InvalidSmilesException.Display(buffer,
offset1 - buffer.Length,
offset2 - buffer.Length);
if (strict)
{
throw new InvalidSmilesException($"Ignored invalid Cis/Trans specification: {errorPos}");
}
else
{
warnings.Add($"Ignored invalid Cis/Trans specification: {errorPos}");
}
}
}
}