public Combinator(MatchedVariables variables, IList <Predicate> predicates,
IList <Expression> expressions, HashSet <Fact> allFacts)
{
this.variables = variables;
this.expressions = expressions;
this.allFacts = allFacts;
this.currentIt = null;
this.pred = predicates.FirstOrDefault();
this.fit = allFacts.Where(fact => fact.MatchPredicate(this.pred)).GetEnumerator();
this.nextPredicates = predicates.Skip(1).ToList();
}
// do not produce new facts, only find one matching set of facts
public bool Test(HashSet <Fact> facts)
{
HashSet <ulong> variables_set = new HashSet <ulong>();
foreach (Predicate pred in this.Body)
{
variables_set.AddAll(pred.Ids.Where((id) => id is ID.Variable).Select(id => ((ID.Variable)id).Value));
}
MatchedVariables variables = new MatchedVariables(variables_set);
if (!this.Body.Any())
{
return(variables.CheckExpressions(this.Expressions).IsDefined);
}
Combinator c = new Combinator(variables, this.Body, this.Expressions, facts);
return(c.Next().IsDefined);
}
public Option <MatchedVariables> Next()
{
bool hasNext = true;
while (hasNext)
{
if (this.currentIt == null)
{
// we iterate over the facts that match the current predicate
if (this.fit.MoveNext())
{
Fact currentFact = this.fit.Current;
// create a new MatchedVariables in which we fix variables we could unify from our first predicate and the current fact
MatchedVariables vars = this.variables.Clone();
bool match_ids = true;
// we know the fact matches the predicate's format so they have the same number of terms
// fill the MatchedVariables before creating the next combinator
for (int i = 0; i < pred.Ids.Count && match_ids; ++i)
{
ID id = pred.Ids[i];
if (id is ID.Variable idVariable)
{
ulong key = idVariable.Value;
ID value = currentFact.Predicate.Ids[i];
if (!vars.Insert(key, value))
{
match_ids = false;
}
}
}
if (match_ids)
{
// there are no more predicates to check
if (!nextPredicates.Any())
{
Option <Dictionary <ulong, ID> > v_opt = vars.CheckExpressions(this.expressions);
if (v_opt.IsDefined)
{
return(Option <MatchedVariables> .Some(vars));
}
}
else
{
// we found a matching fact, we create a new combinator over the rest of the predicates
// no need to copy all of the expressions at all levels
this.currentIt = new Combinator(vars, nextPredicates, new List <Expression>(), this.allFacts);
}
}
}
else
{
hasNext = false;
}
}
else
{
Option <MatchedVariables> nextVarsOpt = this.currentIt.Next();
// the iterator is empty, try with the next fact
if (nextVarsOpt.IsDefined)
{
MatchedVariables nextVars = nextVarsOpt.Get();
Option <Dictionary <ulong, ID> > v_opt = nextVars.CheckExpressions(this.expressions);
if (v_opt.IsDefined)
{
return(Option <MatchedVariables> .Some(nextVars));
}
}
else
{
this.currentIt = null;
}
}
}
return(Option <MatchedVariables> .None());
}
public void Apply(HashSet <Fact> facts, HashSet <Fact> newFacts, HashSet <ulong> restrictedSymbols)
{
HashSet <ulong> variablesSet = new HashSet <ulong>();
foreach (Predicate pred in this.Body)
{
variablesSet.AddAll(pred.Ids.Where(id => id is ID.Variable).Select(id => ((ID.Variable)id).Value));
}
MatchedVariables variables = new MatchedVariables(variablesSet);
if (!this.Body.Any())
{
Option <Dictionary <ulong, ID> > h_opt = variables.CheckExpressions(this.Expressions);
if (h_opt.IsDefined)
{
Dictionary <ulong, ID> h = h_opt.Get();
Predicate predicate = this.Head.Clone();
for (int i = 0; i < predicate.Ids.Count; i++)
{
ID id = predicate.Ids[i];
if (id is ID.Variable)
{
ID value = h[((ID.Variable)id).Value];
predicate.Ids[i] = value;
}
}
newFacts.Add(new Fact(predicate));
}
}
var combined = new Combinator(variables, this.Body, this.Expressions, facts).Combine();
foreach (Dictionary <ulong, ID> h in combined)
{
Predicate predicate = this.Head.Clone();
bool unbound_variable = false;
for (int i = 0; i < predicate.Ids.Count; i++)
{
ID id = predicate.Ids[i];
if (id is ID.Variable)
{
bool isInDictionnary = h.TryGetValue(((ID.Variable)id).Value, out ID value);
predicate.Ids[i] = value;
// variables that appear in the head should appear in the body and constraints as well
if (value == null)
{
unbound_variable = true;
}
}
}
// if the generated fact has #authority or #ambient as first element and we're n ot in a privileged rule
// do not generate it
bool isRestrictedSymbol = false;
ID first = predicate.Ids.FirstOrDefault();
if (first != null && first is ID.Symbol)
{
if (restrictedSymbols.Contains(((ID.Symbol)first).Value))
{
isRestrictedSymbol = true;
}
}
if (!unbound_variable && !isRestrictedSymbol)
{
newFacts.Add(new Fact(predicate));
}
}
}