/// <summary>
/// Applies backwards the relevant operator effects and operator preconditions to the given target conditions.
/// </summary>
/// <param name="conditions">Target conditions to be modified.</param>
/// <param name="operatorSubstitution">Variables substitution.</param>
/// <returns>Preceding conditions.</returns>
public IConditions ApplyBackwards(IConditions conditions, ISubstitution operatorSubstitution)
{
ConditionsCNF expression = (ConditionsCNF)conditions?.GetCNF();
if (expression == null)
{
return(null);
}
OperatorSubstitution = operatorSubstitution;
Effects.GroundEffectsByCurrentOperatorSubstitution(GroundingManager, operatorSubstitution);
if (expression.Parameters != null)
{
EffectsRelevanceConditionsEvaluator evaluator = new EffectsRelevanceConditionsEvaluator(Effects, GroundingManager);
List <ConditionsCNF> subResults = new List <ConditionsCNF>();
IEnumerable <ISubstitution> expressionSubstitutions = GroundingManager.GenerateAllLocalSubstitutions(expression.Parameters);
expression.Parameters = null;
foreach (var expressionSubstitution in expressionSubstitutions)
{
// do backward apply only when the effects are relevant to the current grounding of the expression
if (evaluator.Evaluate(expression, operatorSubstitution, expressionSubstitution))
{
subResults.Add(ApplyBackwardsImpl(expression, expressionSubstitution));
}
}
return(ConstructCNFFromDisjunction(subResults));
}
return(ApplyBackwardsImpl(expression, new Substitution()));
}
/// <summary>
/// Collects relevant when effects for the specified conditions.
/// </summary>
/// <param name="expression">Conditions in CNF.</param>
/// <returns>List of relevant when effects.</returns>
private List <WhenEffect> GetRelevantWhenEffectsForConditions(ConditionsCNF expression)
{
List <int> relevantWhenEffectsIndices = new List <int>();
EffectsRelevanceConditionsEvaluator relevanceEvaluator = new EffectsRelevanceConditionsEvaluator(Effects, GroundingManager);
relevanceEvaluator.Evaluate(expression, new Substitution(), ExpressionSubstitution, relevantWhenEffectsIndices); // empty substitution here because effects already grounded
List <WhenEffect> relevantWhenEffects = new List <WhenEffect>();
relevantWhenEffectsIndices.ForEach(index => relevantWhenEffects.Add(Effects.WhenEffects[index]));
return(relevantWhenEffects);
}
