public static StateTransitionGraph Build(Grammar.Grammar grammar)
{
var root = StateTransitionGraphBuilder.BuildGraph(grammar);
return(new StateTransitionGraph(root));
}
public static RootNode BuildGraph(Grammar.Grammar grammar)
{
{
var nonTerminalHeads = ProcessNonTerminalsHeads();
ProcessRemainingNonTerminalsItems(nonTerminalHeads);
var rootHead = nonTerminalHeads[grammar.Root.NonTerminalUsage.Impl];
return(new RootNode().WithChild(rootHead));
}
IReadOnlyDictionary <GrammarNonTerminal, Node> ProcessNonTerminalsHeads()
{
var nonTerminalHeads = new Dictionary <GrammarNonTerminal, Node>();
foreach (var nonTerminal in grammar.NonTerminals)
{
ProcessSingle(nonTerminal);
}
return(nonTerminalHeads);
Node ProcessSingle(GrammarNonTerminal nonTerminal)
{
if (nonTerminalHeads.TryGetValue(nonTerminal, out var aleadyProcessed))
{
if (aleadyProcessed == null)
{
var msg = $"Recursive non-terminal {nonTerminal.Name} usage cannot be placed " +
"on the very start of non-terminal body. It would cause " +
"infinite recursion.";
throw new StateTransitionException(msg,
StateTransitionException.Id.InfiniteRecursion);
}
return(aleadyProcessed);
}
// marks that processing of `nonTerminal` started
nonTerminalHeads.Add(nonTerminal, null);
var heads = new NodesCollection();
foreach (var orConditionOperand in nonTerminal.Body.OrConditionOperands)
{
var bodyItem = orConditionOperand[0];
switch (bodyItem)
{
case GrammarTerminalUsage terminalUsage:
var terminalNode = new TerminalNode(terminalUsage);
heads.Add(terminalNode);
break;
case GrammarNonTerminalUsage nonTerminalUsage:
var newNonTerminalHead = ProcessSingle(nonTerminalUsage.Impl);
var nonTerminalUsageNode =
new NonTerminalUsageNode(nonTerminalUsage.Name, newNonTerminalHead);
heads.Add(nonTerminalUsageNode);
break;
default:
throw new StateTransitionException(
$"Unknown non-terminal body item type: {bodyItem.Type}",
StateTransitionException.Id.UnknownNonTerminalBodyItemType);
}
}
var head = heads.Count > 1 ? new BranchNode(heads) : heads[0];
if (nonTerminalHeads[nonTerminal] != null)
{
throw new StateTransitionException("Unexpected error.",
StateTransitionException.Id.UnexpectedError);
}
nonTerminalHeads[nonTerminal] = head;
return(head);
}
}
void ProcessRemainingNonTerminalsItems(IReadOnlyDictionary <GrammarNonTerminal, Node> nonTerminalHeads)
{
foreach (var nonTerminal in grammar.NonTerminals)
{
ProcessSingle(nonTerminal);
}
void ProcessSingle(GrammarNonTerminal nonTerminal)
{
var head = nonTerminalHeads[nonTerminal];
for (var operandIndex = 0;
operandIndex < nonTerminal.Body.OrConditionOperands.Count;
operandIndex++)
{
var currentTail = head is BranchNode node
? node.Heads.ToList()[operandIndex]
: head;
foreach (var bodyItem in nonTerminal.Body.OrConditionOperands[operandIndex].Skip(1))
{
switch (bodyItem)
{
case GrammarTerminalUsage terminalUsage:
var terminalNode = new TerminalNode(terminalUsage);
currentTail.AddChild(terminalNode);
currentTail = terminalNode;
break;
case GrammarNonTerminalUsage nonTerminalUsage:
var newNonTerminalHead = nonTerminalHeads[nonTerminalUsage.Impl];
var nonTerminalUsageNode =
new NonTerminalUsageNode(nonTerminalUsage.Name, newNonTerminalHead);
currentTail.AddChild(nonTerminalUsageNode);
currentTail = nonTerminalUsageNode;
break;
default:
throw new StateTransitionException(
$"Unknown non-terminal body item type: {bodyItem.Type}",
StateTransitionException.Id.UnknownNonTerminalBodyItemType);
}
}
}
}
}
}
/// <summary>
/// Crea la colección canónica a partir de la gramática suministrada
/// </summary>
public CanonicalCollection(Grammar.Grammar grammar)
{
this.States = new List <State>();
this.grammar = grammar;
getCanonicalCollection();
}
