public async Task <bool> SatisfiesPredicate(object entity, ScriptPredicate predicate)
{
Check.NotNull(entity, nameof(entity));
Check.NotNull(predicate, nameof(predicate));
var attributedEntity = entity as IAttributedEntity;
if (attributedEntity == null)
{
throw new InvalidOperationException(
$"The entity being evaluated must implement: {typeof(IAttributedEntity)}");
}
await ExecuteAsync(entity, predicate.ScriptName);
if (!attributedEntity.Attributes.Contains(predicate.AttributeName))
{
throw new InvalidOperationException(
$"After the predicate script named: {predicate.ScriptName} was executed, " +
$"the expected predicate attribute named: {predicate.AttributeName} was not" +
$"calculated.");
}
object value = attributedEntity.Attributes.GetValue(predicate.AttributeName);
if (value.GetType() != typeof(bool))
{
throw new InvalidOperationException(
$"After the predicate script named: {predicate.ScriptName} was executed, " +
$"the expected predicate attribute named: {predicate.AttributeName} was not" +
$"a Boolean value type. The type of the value was: {value.GetType()}.");
}
return((bool)value);
}
// Determines if the message should be delivered to the queue. If the exchange is marked
// with a predicate attribute, the corresponding externally named script is executed to
// determine if the message has passing criteria. If no external script is specified,
// the exchange's Satisfies method is called.
private async Task <bool> SatisfiesExchangeCriteria(MessageExchangeDefinition exchangeDef, IMessage message)
{
ScriptPredicate predicate = exchangeDef.Exchange.Settings.Predicate;
if (predicate != null)
{
return(await _scriptingSrv.SatisfiesPredicate(message, predicate));
}
return(exchangeDef.Exchange.Satisfies(message));
}
private async Task <bool> PassesDispatchCriteria(MessageDispatchInfo dispatchInfo, IMessage message)
{
ScriptPredicate predicate = dispatchInfo.Predicate;
if (predicate != null)
{
return(await _scriptingSrv.SatisfiesPredicate(message, predicate));
}
return(dispatchInfo.IsMatch(message));
}
// Determines message dispatchers that apply to the message being published. This is optional and
// specified by decorating the message handler method with attributes.
private async Task <bool> PassesDispatchCriteria(MessageDispatchInfo dispatchInfo, IMessage message)
{
ScriptPredicate predicate = dispatchInfo.Predicate;
// Run a dynamic script against the message and check the result of the specified predicate property.
// This allow storing rule predicates external from the code.
if (predicate != null)
{
return(await _scriptingSrv.SatisfiesPredicateAsync(message, predicate));
}
// Check static rules to determine if message meets criteria.
return(dispatchInfo.IsMatch(message));
}
/// <summary>
/// Specifies a named script that should be evaluated for the message to determine if
/// it applies to the exchange and should be published.
/// </summary>
/// <param name="scriptName">The name of the script to execute against the message.</param>
/// <param name="attributeName">The script predicate attribute to check value of after
/// the script's expression has been evaluated.</param>
public void SetPredicate(string scriptName, string attributeName)
{
if (string.IsNullOrWhiteSpace(scriptName))
{
throw new ArgumentException("Script name not specified.", nameof(scriptName));
}
if (string.IsNullOrWhiteSpace(attributeName))
{
throw new ArgumentException("Attribute name not specified.", nameof(attributeName));
}
ScriptPredicate = new ScriptPredicate
{
ScriptName = scriptName,
AttributeName = attributeName
};
}
