/// <summary>
/// Evaluate the specified expression, for the given element and model.
/// </summary>
/// <param name="expression">The expression to evaluate.</param>
/// <param name="context">The rendering context for the expression being evaluated.</param>
/// <param name="model">The ZPT model, providing the context for evaluation.</param>
public override ExpressionResult Evaluate(Expression expression, IRenderingContext context, ITalesModel model)
{
object result;
try
{
result = _host.Evaluate(expression.Content, model.GetAllDefinitions());
}
catch(Exception ex)
{
string message = String.Format(Resources.ExceptionMessages.EvaluationFailureFormat, expression.Content);
throw new ModelEvaluationException(message, ex);
}
return new ExpressionResult(result);
}
/// <summary>
/// Evaluate the specified expression, for the given element and model.
/// </summary>
/// <param name="expression">The expression to evaluate.</param>
/// <param name="context">The rendering context for the expression being evaluated.</param>
/// <param name="model">The ZPT model, providing the context for evaluation.</param>
public override ExpressionResult Evaluate(Expression expression, IRenderingContext context, ITalesModel model)
{
if(expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
if(context == null)
{
throw new ArgumentNullException(nameof(context));
}
if(model == null)
{
throw new ArgumentNullException(nameof(model));
}
var trimmedContent = expression.Content.TrimStart();
var result = model.Evaluate(ExpressionCreator.Create(trimmedContent), context);
bool booleanResult = this.CoerceToBoolean(result);
return new ExpressionResult(!booleanResult);
}
/// <summary>
/// Evaluate the specified expression, for the given element and model.
/// </summary>
/// <param name="expression">The expression to evaluate.</param>
/// <param name="context">The rendering context for the expression being evaluated.</param>
/// <param name="model">The ZPT model, providing the context for evaluation.</param>
public override ExpressionResult Evaluate(Expression expression, IRenderingContext context, ITalesModel model)
{
if(expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
if(context == null)
{
throw new ArgumentNullException(nameof(context));
}
if(model == null)
{
throw new ArgumentNullException(nameof(model));
}
string source = expression.Content, output;
var escapeSequenceIndices = this.FindAndUnescapePlaceholders(source, out output);
output = this.ApplyPlaceholderReplacements(output, escapeSequenceIndices, context, model);
return new ExpressionResult(output);
}
/// <summary>
/// Evaluate the specified expression, for the given element and model.
/// </summary>
/// <param name="expression">The expression to evaluate.</param>
/// <param name="context">The rendering context for the expression being evaluated.</param>
/// <param name="model">The ZPT model, providing the context for evaluation.</param>
public override ExpressionResult Evaluate(Expression expression, IRenderingContext context, ITalesModel model)
{
if(expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
if(context == null)
{
throw new ArgumentNullException(nameof(context));
}
if(model == null)
{
throw new ArgumentNullException(nameof(model));
}
var expressionText = expression.Content;
var allDefinitions = model.GetAllDefinitions();
var csharpExpression = _expressionService.GetExpression(expressionText, allDefinitions.Keys);
return new ExpressionResult(csharpExpression.Evaluate(allDefinitions));
}
/// <summary>
/// Evaluate the specified expression, for the given element and model.
/// </summary>
/// <param name="expression">The expression to evaluate.</param>
/// <param name="context">The rendering context for the expression being evaluated.</param>
/// <param name="model">The ZPT model, providing the context for evaluation.</param>
public override ExpressionResult Evaluate(Expression expression, IRenderingContext context, ITalesModel model)
{
if(expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
if(context == null)
{
throw new ArgumentNullException(nameof(context));
}
if(model == null)
{
throw new ArgumentNullException(nameof(model));
}
var expressionText = expression.Content;
var path = Path.Create(expressionText);
var walker = new PathWalker(path);
object output;
try
{
output = this.WalkPath(walker, context, model);
}
catch(TraversalException ex)
{
string message = String.Format(Resources.ExceptionMessages.CouldNotWalkAnyPathsWithExpression,
expressionText,
context?.Element?.Name);
throw new ModelEvaluationException(message, ex) {
ExpressionText = expressionText,
ElementName = context?.Element?.Name
};
}
return new ExpressionResult(output);
}
/// <summary>
/// Walks and evaluates a TALES path.
/// </summary>
/// <returns>The evaluated value of the path.</returns>
/// <param name="walker">A TALES path walker, containing a path.</param>
/// <param name="context">The rendering context for the expression being evaluated.</param>
/// <param name="model">The ZPT model, providing the context for evaluation.</param>
private object WalkPath(PathWalker walker, IRenderingContext context, ITalesModel model)
{
object output = null;
bool success = false;
while(walker.NextComponent() && !success)
{
success = this.WalkComponent(walker, context, model, out output);
}
if(!success)
{
throw new TraversalException(Resources.ExceptionMessages.CouldNotWalkAnyPaths);
}
return output;
}
/// <summary>
/// Walks and evaluates a single TALES path component.
/// </summary>
/// <returns>
/// <c>true</c>, if the path component was successfully evaluated, <c>false</c> otherwise.
/// </returns>
/// <param name="walker">A TALES path walker, containing a path.</param>
/// <param name="context">The rendering context for the expression being evaluated.</param>
/// <param name="model">The ZPT model, providing the context for evaluation.</param>
/// <param name="result">Exposes the result of the evaluation.</param>
private bool WalkComponent(PathWalker walker, IRenderingContext context, ITalesModel model, out object result)
{
bool output;
if(this.TryGetTraversalRoot(walker, context, model, out result))
{
object traversalChild;
output = true;
while(walker.NextPart())
{
string partName;
if(this.TryGetPartName(walker.CurrentPart, context, model, out partName)
&& ObjectTraverser.Default.Traverse(result, partName, out traversalChild, context))
{
result = traversalChild;
}
else
{
output = false;
result = null;
break;
}
}
}
else
{
output = false;
result = null;
}
return output;
}
/// <summary>
/// Attempts to get a part-name for traversal, expanding interpolated part-names if appropriate.
/// </summary>
/// <returns><c>true</c>, if a part name was resolved, <c>false</c> otherwise.</returns>
/// <param name="part">A TALES path part.</param>
/// <param name="context">The rendering context.</param>
/// <param name="model">The TALES model.</param>
/// <param name="result">Exposes the result of this operation.</param>
private bool TryGetPartName(PathPart part, IRenderingContext context, ITalesModel model, out string result)
{
result = part.Value;
bool output = true;
if(part.IsInterpolated)
{
object interpolatedValue;
if(model.TryGetRootObject(result, context, out interpolatedValue)
&& interpolatedValue != null)
{
output = true;
result = interpolatedValue.ToString();
}
else
{
output = false;
result = null;
}
}
return output;
}
/// <summary>
/// Attempts to get a root object, from which to begin traversal of the path.
/// </summary>
/// <returns><c>true</c>, if the root object was retrieved, <c>false</c> otherwise.</returns>
/// <param name="walker">A TALES path walker.</param>
/// <param name="context">The rendering context.</param>
/// <param name="model">The TALES model.</param>
/// <param name="result">Exposes the result of this operation.</param>
protected virtual bool TryGetTraversalRoot(PathWalker walker,
IRenderingContext context,
ITalesModel model,
out object result)
{
bool output;
if(walker.NextPart()
&& model.TryGetRootObject(walker.CurrentPart.Value, context, out result))
{
output = true;
}
else
{
output = false;
result = null;
}
return output;
}
/// <summary>
/// Applies placeholder replacements to the input string.
/// </summary>
/// <returns>The result of the application of placeholders.</returns>
/// <param name="input">The input string.</param>
/// <param name="escapedPlaceholderIndices">A collection containing the indices of escaped placeholder sequences.</param>
/// <param name="context">The rendering context.</param>
/// <param name="model">The TALES model.</param>
private string ApplyPlaceholderReplacements(string input,
ISet<int> escapedPlaceholderIndices,
IRenderingContext context,
ITalesModel model)
{
var pathEvaluator = EvaluatorSelector.GetEvaluator<PathExpressionEvaluator>();
return ReplacementFinder.Replace(input, match => {
string output;
if(escapedPlaceholderIndices.Contains(match.Index))
{
output = match.Value;
}
else
{
string val = match.Groups[1].Success? match.Groups[1].Value : match.Groups[2].Value;
var pathResult = pathEvaluator.Evaluate(ExpressionCreator.Create(val),
context,
model);
if(pathResult.Value == null)
{
output = String.Empty;
}
else
{
output = pathResult.Value.ToString();
}
}
return output;
});
}
/// <summary> /// Evaluate the specified expression, for the given element and model. /// </summary> /// <param name="expression">The expression to evaluate.</param> /// <param name="context">The rendering context for the expression being evaluated.</param> /// <param name="model">The ZPT model, providing the context for evaluation.</param> public abstract ExpressionResult Evaluate(Expression expression, IRenderingContext context, ITalesModel model);
