/// <summary>Parses RDF in the form of N-Quads.</summary>
/// <remarks>Parses RDF in the form of N-Quads.</remarks>
/// <param name="input">the N-Quads input to parse.</param>
/// <returns>an RDF dataset.</returns>
/// <exception cref="JsonLD.Core.JsonLdError"></exception>
public static RDFDataset ParseNQuads(string input)
{
// build RDF dataset
RDFDataset dataset = new RDFDataset();
// split N-Quad input into lines
string[] lines = RDFDatasetUtils.Regex.Eoln.Split(input);
int lineNumber = 0;
foreach (string line in lines)
{
lineNumber++;
// skip empty lines
if (RDFDatasetUtils.Regex.EmptyOrComment.Matcher(line).Matches())
{
continue;
}
// parse quad
Matcher match = RDFDatasetUtils.Regex.Quad.Matcher(line);
if (!match.Matches())
{
throw new JsonLdError(JsonLdError.Error.SyntaxError, "Error while parsing N-Quads; invalid quad. line:"
+ lineNumber);
}
// get subject
RDFDataset.Node subject;
if (match.Group(1) != null)
{
var subjectIri = Unescape(match.Group(1));
AssertAbsoluteIri(subjectIri);
subject = new RDFDataset.IRI(subjectIri);
}
else
{
subject = new RDFDataset.BlankNode(Unescape(match.Group(2)));
}
// get predicate
var predicateIri = Unescape(match.Group(3));
AssertAbsoluteIri(predicateIri);
RDFDataset.Node predicate = new RDFDataset.IRI(predicateIri);
// get object
RDFDataset.Node @object;
if (match.Group(4) != null)
{
var objectIri = Unescape(match.Group(4));
AssertAbsoluteIri(objectIri);
@object = new RDFDataset.IRI(objectIri);
}
else
{
if (match.Group(5) != null)
{
@object = new RDFDataset.BlankNode(Unescape(match.Group(5)));
}
else
{
string language = Unescape(match.Group(8));
string datatype = match.Group(7) != null?Unescape(match.Group(7)) : match.Group
(8) != null ? JSONLDConsts.RdfLangstring : JSONLDConsts.XsdString;
AssertAbsoluteIri(datatype);
string unescaped = Unescape(match.Group(6));
@object = new RDFDataset.Literal(unescaped, datatype, language);
}
}
// get graph name ('@default' is used for the default graph)
string name = "@default";
if (match.Group(9) != null)
{
name = Unescape(match.Group(9));
AssertAbsoluteIri(name);
}
else
{
if (match.Group(10) != null)
{
name = Unescape(match.Group(10));
}
}
RDFDataset.Quad triple = new RDFDataset.Quad(subject, predicate, @object, name);
// initialise graph in dataset
if (!dataset.ContainsKey(name))
{
IList <RDFDataset.Quad> tmp = new List <RDFDataset.Quad>();
tmp.Add(triple);
dataset[name] = tmp;
}
else
{
// add triple if unique to its graph
IList <RDFDataset.Quad> triples = (IList <RDFDataset.Quad>)dataset[name];
if (!triples.Contains(triple))
{
triples.Add(triple);
}
}
}
return(dataset);
}