/// <summary>
/// Main evaluation method which is divided in two phases: Argument processing and
/// Function evaluation.
/// </summary>
/// <param name="context">The evaluation context instance.</param>
/// <returns>The result of the evaluation in an EvaluationValue instance.</returns>
public virtual EvaluationValue Evaluate(EvaluationContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
// Validate the function exists
context.Trace("Calling function: {0}", _applyBase.FunctionId);
inf.IFunction function = EvaluationEngine.GetFunction(_applyBase.FunctionId);
if (function == null)
{
context.Trace("ERR: function not found {0}", _applyBase.FunctionId);
context.ProcessingError = true;
return(EvaluationValue.Indeterminate);
}
// Process the arguments.
IFunctionParameterCollection arguments = ProcessArguments(context, new pol.IExpressionCollection((pol.IExpressionReadWriteCollection)_applyBase.Arguments));
// Call the function with the arguments processed.
EvaluationValue returnValue = EvaluationEngine.EvaluateFunction(context, function, arguments.ToArray());
return(returnValue);
}
/// <summary>
/// THe argument processing method resolves all the attribute designators, attribute
/// selectors. If there is an internal Apply it will be evaulated within this method.
/// </summary>
/// <remarks>All the processed arguments are converted into an IFunctionParameter instance
/// because this is the only value that can be used to call a function.</remarks>
/// <param name="context">The evaluation context instance.</param>
/// <param name="arguments">The arguments to process.</param>
/// <returns>A list of arguments ready to be used by a function.</returns>
private IFunctionParameterCollection ProcessArguments( EvaluationContext context, pol.IExpressionCollection arguments )
{
context.Trace( "Processing arguments" );
context.AddIndent();
// Create a list to return the processed values.
IFunctionParameterCollection processedArguments = new IFunctionParameterCollection();
// Iterate through the arguments, the IExpressionType is a mark interface
foreach( inf.IExpression arg in arguments )
{
if( arg is pol.ApplyElement )
{
context.Trace( "Nested apply" );
// There is a nested apply un this policy a new Apply will be created and also
// evaluated. It's return value will be used as the processed argument.
Apply _childApply = new Apply( (pol.ApplyElement)arg );
// Evaluate the Apply
EvaluationValue retVal = _childApply.Evaluate( context );
context.TraceContextValues();
// If the results were Indeterminate the Indeterminate value will be placed in
// the processed arguments, later another method will validate the parameters
// and cancel the evaluation propperly.
if( !retVal.IsIndeterminate )
{
if( !context.IsMissingAttribute )
{
processedArguments.Add( retVal );
}
}
else
{
processedArguments.Add( retVal );
}
}
else if( arg is pol.FunctionElementReadWrite )
{
// Search for the function and place it in the processed arguments.
pol.FunctionElement functionId = new pol.FunctionElement( ((pol.FunctionElementReadWrite)arg).FunctionId, ((pol.FunctionElementReadWrite)arg).SchemaVersion );
context.Trace( "Function {0}", functionId.FunctionId );
inf.IFunction function = EvaluationEngine.GetFunction( functionId.FunctionId );
if( function == null )
{
context.Trace( "ERR: function not found {0}", _applyBase.FunctionId );
context.ProcessingError = true;
processedArguments.Add( EvaluationValue.Indeterminate );
}
else
{
processedArguments.Add( function );
}
}
else if( arg is pol.VariableReferenceElement )
{
pol.VariableReferenceElement variableRef = arg as pol.VariableReferenceElement;
VariableDefinition variableDef = context.CurrentPolicy.VariableDefinition[ variableRef.VariableId ] as VariableDefinition;
context.TraceContextValues();
if( !variableDef.IsEvaluated )
{
processedArguments.Add( variableDef.Evaluate( context ) );
}
else
{
processedArguments.Add( variableDef.Value );
}
}
else if( arg is pol.AttributeValueElementReadWrite )
{
// The AttributeValue does not need to be processed
context.Trace( "Attribute value {0}", arg.ToString() );
processedArguments.Add( new pol.AttributeValueElement( ((pol.AttributeValueElementReadWrite)arg).DataType, ((pol.AttributeValueElementReadWrite)arg).Contents, ((pol.AttributeValueElementReadWrite)arg).SchemaVersion ));
}
else if( arg is pol.AttributeDesignatorBase )
{
// Resolve the AttributeDesignator using the EvaluationEngine public methods.
context.Trace( "Processing attribute designator: {0}", arg.ToString() );
pol.AttributeDesignatorBase attrDes = (pol.AttributeDesignatorBase)arg;
BagValue bag = EvaluationEngine.Resolve( context, attrDes );
// If the attribute was not resolved by the EvaluationEngine search the
// attribute in the context document, also using the EvaluationEngine public
// methods.
if( bag.BagSize == 0 )
{
if( arg is pol.SubjectAttributeDesignatorElement )
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute( context, attrDes );
if( attrib != null )
{
context.Trace( "Adding subject attribute designator: {0}", attrib.ToString() );
bag.Add( attrib );
break;
}
}
else if( arg is pol.ResourceAttributeDesignatorElement )
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute( context, attrDes );
if( attrib != null )
{
context.Trace( "Adding resource attribute designator {0}", attrib.ToString() );
bag.Add( attrib );
}
}
else if( arg is pol.ActionAttributeDesignatorElement )
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute( context, attrDes );
if( attrib != null )
{
context.Trace( "Adding action attribute designator {0}", attrib.ToString() );
bag.Add( attrib );
}
}
else if( arg is pol.EnvironmentAttributeDesignatorElement )
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute( context, attrDes );
if( attrib != null )
{
context.Trace( "Adding environment attribute designator {0}", attrib.ToString() );
bag.Add( attrib );
}
}
}
// If the argument was not found and the attribute must be present this is
// a MissingAttribute situation so set the flag. Otherwise add the attribute
// to the processed arguments.
if( bag.BagSize == 0 && attrDes.MustBePresent )
{
context.Trace( "Attribute is missing" );
context.IsMissingAttribute = true;
context.AddMissingAttribute( attrDes );
}
else
{
processedArguments.Add( bag );
}
}
else if( arg is pol.AttributeSelectorElement )
{
// Resolve the XPath query using the EvaluationEngine public methods.
context.Trace( "Attribute selector" );
try
{
BagValue bag = EvaluationEngine.Resolve( context, (pol.AttributeSelectorElement)arg );
if( bag.Elements.Count == 0 && ((pol.AttributeSelectorElement)arg).MustBePresent )
{
context.Trace( "Attribute is missing" );
context.IsMissingAttribute = true;
context.AddMissingAttribute( (pol.AttributeReferenceBase)arg );
}
else
{
processedArguments.Add( bag );
}
}
catch( EvaluationException e )
{
context.Trace( Resource.TRACE_ERROR, e.Message );
processedArguments.Add( EvaluationValue.Indeterminate );
context.ProcessingError = true;
}
}
}
context.RemoveIndent();
return processedArguments;
}
/// <summary>
/// THe argument processing method resolves all the attribute designators, attribute
/// selectors. If there is an internal Apply it will be evaulated within this method.
/// </summary>
/// <remarks>All the processed arguments are converted into an IFunctionParameter instance
/// because this is the only value that can be used to call a function.</remarks>
/// <param name="context">The evaluation context instance.</param>
/// <param name="arguments">The arguments to process.</param>
/// <returns>A list of arguments ready to be used by a function.</returns>
private IFunctionParameterCollection ProcessArguments(EvaluationContext context, pol.IExpressionCollection arguments)
{
context.Trace("Processing arguments");
context.AddIndent();
// Create a list to return the processed values.
IFunctionParameterCollection processedArguments = new IFunctionParameterCollection();
// Iterate through the arguments, the IExpressionType is a mark interface
foreach (inf.IExpression arg in arguments)
{
if (arg is pol.ApplyElement)
{
context.Trace("Nested apply");
// There is a nested apply un this policy a new Apply will be created and also
// evaluated. It's return value will be used as the processed argument.
Apply _childApply = new Apply((pol.ApplyElement)arg);
// Evaluate the Apply
EvaluationValue retVal = _childApply.Evaluate(context);
context.TraceContextValues();
// If the results were Indeterminate the Indeterminate value will be placed in
// the processed arguments, later another method will validate the parameters
// and cancel the evaluation propperly.
if (!retVal.IsIndeterminate)
{
if (!context.IsMissingAttribute)
{
processedArguments.Add(retVal);
}
}
else
{
processedArguments.Add(retVal);
}
}
else if (arg is pol.FunctionElementReadWrite)
{
// Search for the function and place it in the processed arguments.
pol.FunctionElement functionId = new pol.FunctionElement(((pol.FunctionElementReadWrite)arg).FunctionId, ((pol.FunctionElementReadWrite)arg).SchemaVersion);
context.Trace("Function {0}", functionId.FunctionId);
inf.IFunction function = EvaluationEngine.GetFunction(functionId.FunctionId);
if (function == null)
{
context.Trace("ERR: function not found {0}", _applyBase.FunctionId);
context.ProcessingError = true;
processedArguments.Add(EvaluationValue.Indeterminate);
}
else
{
processedArguments.Add(function);
}
}
else if (arg is pol.VariableReferenceElement)
{
pol.VariableReferenceElement variableRef = arg as pol.VariableReferenceElement;
VariableDefinition variableDef = context.CurrentPolicy.VariableDefinition[variableRef.VariableId] as VariableDefinition;
context.TraceContextValues();
if (!variableDef.IsEvaluated)
{
processedArguments.Add(variableDef.Evaluate(context));
}
else
{
processedArguments.Add(variableDef.Value);
}
}
else if (arg is pol.AttributeValueElementReadWrite)
{
// The AttributeValue does not need to be processed
context.Trace("Attribute value {0}", arg.ToString());
processedArguments.Add(new pol.AttributeValueElement(((pol.AttributeValueElementReadWrite)arg).DataType, ((pol.AttributeValueElementReadWrite)arg).Contents, ((pol.AttributeValueElementReadWrite)arg).SchemaVersion));
}
else if (arg is pol.AttributeDesignatorBase)
{
// Resolve the AttributeDesignator using the EvaluationEngine public methods.
context.Trace("Processing attribute designator: {0}", arg.ToString());
pol.AttributeDesignatorBase attrDes = (pol.AttributeDesignatorBase)arg;
BagValue bag = EvaluationEngine.Resolve(context, attrDes);
// If the attribute was not resolved by the EvaluationEngine search the
// attribute in the context document, also using the EvaluationEngine public
// methods.
if (bag.BagSize == 0)
{
if (arg is pol.SubjectAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding subject attribute designator: {0}", attrib.ToString());
bag.Add(attrib);
break;
}
}
else if (arg is pol.ResourceAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding resource attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
else if (arg is pol.ActionAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding action attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
else if (arg is pol.EnvironmentAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding environment attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
}
// If the argument was not found and the attribute must be present this is
// a MissingAttribute situation so set the flag. Otherwise add the attribute
// to the processed arguments.
if (bag.BagSize == 0 && attrDes.MustBePresent)
{
context.Trace("Attribute is missing");
context.IsMissingAttribute = true;
context.AddMissingAttribute(attrDes);
}
else
{
processedArguments.Add(bag);
}
}
else if (arg is pol.AttributeSelectorElement)
{
// Resolve the XPath query using the EvaluationEngine public methods.
context.Trace("Attribute selector");
try
{
BagValue bag = EvaluationEngine.Resolve(context, (pol.AttributeSelectorElement)arg);
if (bag.Elements.Count == 0 && ((pol.AttributeSelectorElement)arg).MustBePresent)
{
context.Trace("Attribute is missing");
context.IsMissingAttribute = true;
context.AddMissingAttribute((pol.AttributeReferenceBase)arg);
}
else
{
processedArguments.Add(bag);
}
}
catch (EvaluationException e)
{
context.Trace(Resource.TRACE_ERROR, e.Message);
processedArguments.Add(EvaluationValue.Indeterminate);
context.ProcessingError = true;
}
}
}
context.RemoveIndent();
return(processedArguments);
}
