/// <summary>
/// Substitutes a primary expression which is a Node term for a virtual Node term
/// </summary>
/// <param name="expr">Expression</param>
/// <returns></returns>
protected ISparqlExpression SubstitutePrimaryExpression(ISparqlExpression expr)
{
if (expr.GetType().Equals(this._exprType))
{
NodeExpressionTerm term = (NodeExpressionTerm)expr;
INode curr = term.Value(null, 0);
TNodeID id = this._provider.GetID(curr);
if (id == null || id.Equals(this._provider.NullID))
{
throw new RdfQueryException("Cannot transform the Expression to use Virtual Nodes");
}
INode virt = this.CreateVirtualNode(id, curr);
return(new NodeExpressionTerm(virt));
}
else
{
return(expr);
}
}
/// <summary>
/// Creates a new Same Term Filter
/// </summary>
/// <param name="pattern">Algebra the Filter applies over</param>
/// <param name="var">Variable to restrict on</param>
/// <param name="term">Expression Term</param>
public SameTermFilter(ISparqlAlgebra pattern, String var, NodeExpressionTerm term)
: base(pattern, var, term, new UnaryExpressionFilter(new SameTermFunction(new VariableExpressionTerm(var), term)))
{
}
/// <summary>
/// Creates a new Single Value Restriction Filter
/// </summary>
/// <param name="pattern">Algebra the filter applies over</param>
/// <param name="var">Variable to restrict on</param>
/// <param name="term">Value to restrict to</param>
/// <param name="filter">Filter to use</param>
public SingleValueRestrictionFilter(ISparqlAlgebra pattern, String var, NodeExpressionTerm term, ISparqlFilter filter)
: base(pattern, var, filter)
{
this._term = term;
}
/// <summary>
/// Creates a new Identity Filter
/// </summary>
/// <param name="pattern">Algebra the Filter applies over</param>
/// <param name="var">Variable to restrict on</param>
/// <param name="term">Expression Term</param>
public IdentityFilter(ISparqlAlgebra pattern, String var, NodeExpressionTerm term)
: base(pattern, var, term, new UnaryExpressionFilter(new EqualsExpression(new VariableExpressionTerm(var), term)))
{
}
/// <summary>
/// Formats a SPARQL Expression
/// </summary>
/// <param name="expr">SPARQL Expression</param>
/// <returns></returns>
protected virtual String FormatExpression(ISparqlExpression expr)
{
StringBuilder output = new StringBuilder();
try
{
switch (expr.Type)
{
case SparqlExpressionType.Aggregate:
if (expr is AggregateExpressionTerm)
{
AggregateExpressionTerm agg = (AggregateExpressionTerm)expr;
output.Append(this.FormatAggregate(agg.Aggregate));
}
else if (expr is NonNumericAggregateExpressionTerm)
{
NonNumericAggregateExpressionTerm nonNumAgg = (NonNumericAggregateExpressionTerm)expr;
output.Append(this.FormatAggregate(nonNumAgg.Aggregate));
}
else
{
output.Append(expr.ToString());
}
break;
case SparqlExpressionType.BinaryOperator:
ISparqlExpression lhs = expr.Arguments.First();
ISparqlExpression rhs = expr.Arguments.Skip(1).First();
//Format the Expression wrapping the LHS and/or RHS in brackets if required
//to ensure that ordering of operators is preserved
if (lhs.Type == SparqlExpressionType.BinaryOperator)
{
output.Append('(');
output.Append(this.FormatExpression(lhs));
output.Append(')');
}
else
{
output.Append(this.FormatExpression(lhs));
}
output.Append(' ');
output.Append(expr.Functor);
output.Append(' ');
if (rhs.Type == SparqlExpressionType.BinaryOperator)
{
output.Append('(');
output.Append(this.FormatExpression(rhs));
output.Append(')');
}
else
{
output.Append(this.FormatExpression(rhs));
}
break;
case SparqlExpressionType.Function:
//Show either a Keyword/URI/QName as appropriate
if (SparqlSpecsHelper.IsFunctionKeyword(expr.Functor))
{
output.Append(expr.Functor);
}
else
{
String funcQname;
if (this._qnameMapper.ReduceToQName(expr.Functor, out funcQname))
{
output.Append(funcQname);
}
else
{
output.Append('<');
output.Append(this.FormatUri(expr.Functor));
output.Append('>');
}
}
//Add Arguments list
output.Append('(');
List <ISparqlExpression> args = expr.Arguments.ToList();
for (int i = 0; i < args.Count; i++)
{
output.Append(this.FormatExpression(args[i]));
if (i < args.Count - 1)
{
output.Append(", ");
}
}
output.Append(')');
break;
case SparqlExpressionType.GraphOperator:
output.Append(expr.Functor);
output.Append(' ');
List <ISparqlExpression> gArgs = expr.Arguments.ToList();
if (gArgs.Count > 1)
{
throw new RdfOutputException("Error Formatting SPARQL Expression - Expressions of type GraphOperator are only allowed a single argument");
}
for (int i = 0; i < gArgs.Count; i++)
{
output.Append(this.FormatExpression(gArgs[i]));
if (i < gArgs.Count - 1)
{
output.Append(", ");
}
}
break;
case SparqlExpressionType.Primary:
//If Node/Numeric Term then use Node Formatting otherwise use ToString() on the expression
if (expr is NodeExpressionTerm)
{
NodeExpressionTerm nodeTerm = (NodeExpressionTerm)expr;
output.Append(this.Format(nodeTerm.Value(null, 0)));
}
else if (expr is NumericExpressionTerm)
{
NumericExpressionTerm numTerm = (NumericExpressionTerm)expr;
output.Append(this.Format(numTerm.Value(null, 0)));
}
else if (expr is GraphPatternExpressionTerm)
{
GraphPatternExpressionTerm gp = (GraphPatternExpressionTerm)expr;
output.Append(this.Format(gp.Pattern));
}
else
{
output.Append(expr.ToString());
}
break;
case SparqlExpressionType.SetOperator:
//Add First Argument and Set Operator
output.Append(this.FormatExpression(expr.Arguments.First()));
output.Append(' ');
output.Append(expr.Functor);
//Add Set
output.Append(" (");
List <ISparqlExpression> set = expr.Arguments.Skip(1).ToList();
for (int i = 0; i < set.Count; i++)
{
output.Append(this.FormatExpression(set[i]));
if (i < set.Count - 1)
{
output.Append(", ");
}
}
output.Append(')');
break;
case SparqlExpressionType.UnaryOperator:
//Just Functor then Expression
output.Append(expr.Functor);
output.Append(this.FormatExpression(expr.Arguments.First()));
break;
}
}
catch (RdfOutputException)
{
throw;
}
catch (Exception ex)
{
throw new RdfOutputException("Error formatting a SPARQL Expression - the Expression may have the wrong number of arguments for the reported expression type", ex);
}
return(output.ToString());
}