2 files changed, 169 insertions, 1 deletions

diff --git a/src/core/parser/ParserState.cpp b/src/core/parser/ParserState.cpp
index b0b02d2..9d3aa7e 100644
--- a/src/core/parser/ParserState.cpp
+++ b/src/core/parser/ParserState.cpp
@@ -25,10 +25,12 @@ namespace ousia {
 ParserState::ParserState() : elementHandler(nullptr), childHandler(nullptr) {}
 
 ParserState::ParserState(ParserStateSet parents, Arguments arguments,
+                         RttiSet createdNodeTypes,
                          HandlerConstructor elementHandler,
                          HandlerConstructor childHandler)
     : parents(parents),
       arguments(arguments),
+      createdNodeTypes(createdNodeTypes),
       elementHandler(elementHandler),
       childHandler(childHandler)
 {
@@ -65,6 +67,18 @@ ParserStateBuilder &ParserStateBuilder::arguments(const Arguments &arguments)
 	return *this;
 }
 
+ParserStateBuilder &ParserStateBuilder::createdNodeType(const Rtti *type)
+{
+	state.createdNodeTypes = RttiSet{type};
+	return *this;
+}
+
+ParserStateBuilder &ParserStateBuilder::createdNodeTypes(const RttiSet &types)
+{
+	state.createdNodeTypes = types;
+	return *this;
+}
+
 ParserStateBuilder &ParserStateBuilder::elementHandler(
     HandlerConstructor elementHandler)
 {
@@ -81,6 +95,71 @@ ParserStateBuilder &ParserStateBuilder::childHandler(
 
 const ParserState &ParserStateBuilder::build() const { return state; }
 
+/* Class ParserStateDeductor */
+
+ParserStateDeductor::ParserStateDeductor(
+    std::vector<const Rtti *> signature,
+    std::vector<const ParserState *> states)
+    : tbl(signature.size()),
+      signature(std::move(signature)),
+      states(std::move(states))
+{
+}
+
+bool ParserStateDeductor::isActive(size_t d, const ParserState *s)
+{
+	// Lookup the "active" state of (d, s), if it was not already set
+	// (e.second is true) we'll have to calculate it
+	auto e = tbl[d].emplace(s, false);
+	bool &res = e.first->second;
+	if (!e.second) {
+		return res;
+	}
+
+	// Check whether this node is generative (may have produced the Node
+	// described by the current Signature element)
+	bool isGenerative = signature[d]->isOneOf(s->createdNodeTypes);
+
+	if (isGenerative && d == 0) {
+		// End of recursion -- the last signature element is reached and the
+		// node was generative
+		res = true;
+	} else {
+		// Try repetition of this node
+		if (isGenerative && isActive(d - 1, s)) {
+			res = true;
+		} else {
+			// Check whether any of the parent nodes were active -- either for
+			// the previous element (if this one is generative) or for the
+			// current element (assuming this node was not generative)
+			for (const ParserState *parent : s->parents) {
+				if ((isGenerative && isActive(d - 1, parent)) ||
+					isActive(d, parent)) {
+					res = true;
+					break;
+				}
+			}
+		}
+	}
+
+	return res;
+}
+
+std::vector<const ParserState *> ParserStateDeductor::deduce()
+{
+	std::vector<const ParserState *> res;
+	if (!signature.empty()) {
+		const size_t D = signature.size();
+		for (auto s : states) {
+			if (signature[D - 1]->isOneOf(s->createdNodeTypes) &&
+			    isActive(D - 1, s)) {
+				res.push_back(s);
+			}
+		}
+	}
+	return res;
+}
+
 /* Constant initializations */
 
 namespace ParserStates {
diff --git a/src/core/parser/ParserState.hpp b/src/core/parser/ParserState.hpp
index 81e118d..43b8035 100644
--- a/src/core/parser/ParserState.hpp
+++ b/src/core/parser/ParserState.hpp
@@ -65,6 +65,13 @@ struct ParserState {
 	Arguments arguments;
 
 	/**
+	 * Set containing the types of the nodes that may be created in this
+	 * ParserState. This information is needed for Parsers to reconstruct the
+	 * current ParserState from a given ParserScope when a file is included.
+	 */
+	RttiSet createdNodeTypes;
+
+	/**
 	 * Pointer at a function which creates a new concrete Handler instance for
 	 * the elements described by this state. May be nullptr in which case no
 	 * handler instance is created.
@@ -90,6 +97,10 @@ struct ParserState {
 	 * @param parents is a vector containing all possible parent states.
 	 * @param arguments is a descriptor of arguments that should be passed to
 	 * the handler.
+	 * @param createdNodeTypes is a set containing the types of the nodes tha
+	 * may be created in this ParserState. This information is needed for
+	 * Parsers to reconstruct the current ParserState from a given ParserScope
+	 * when a file is included.
 	 * @param elementHandler is a pointer at a function which creates a new
 	 * concrete Handler instance for the elements described by this state. May
 	 * be nullptr in which case no handler instance is created.
@@ -99,6 +110,7 @@ struct ParserState {
 	 * allowed.
 	 */
 	ParserState(ParserStateSet parents, Arguments arguments = Arguments{},
+	            RttiSet createdNodeTypes = RttiSet{},
 	            HandlerConstructor elementHandler = nullptr,
 	            HandlerConstructor childHandler = nullptr);
 
@@ -164,6 +176,26 @@ public:
 	ParserStateBuilder &arguments(const Arguments &arguments);
 
 	/**
+	 * Sets the Node types this state may produce to the given Rtti descriptor.
+	 *
+	 * @param type is the Rtti descriptor of the Type that may be produced by
+	 * this state.
+	 * @return a reference at this ParserStateBuilder instance for method
+	 * chaining.
+	 */
+	ParserStateBuilder &createdNodeType(const Rtti *type);
+
+	/**
+	 * Sets the Node types this state may produce to the given Rtti descriptors.
+	 *
+	 * @param types is a set of Rtti descriptors of the Types that may be
+	 * produced by this state.
+	 * @return a reference at this ParserStateBuilder instance for method
+	 * chaining.
+	 */
+	ParserStateBuilder &createdNodeTypes(const RttiSet &types);
+
+	/**
 	 * Sets the constructor for the element handler. The constructor creates a
 	 * new concrete Handler instance for the elements described by this state.
 	 * May be nullptr in which case no handler instance is created (this is
@@ -199,6 +231,64 @@ public:
 };
 
 /**
+ * Class used to deduce the ParserState a Parser is currently in based on the
+ * types of the Nodes that currently are on the ParserStack. Uses dynamic
+ * programming in order to solve this problem.
+ */
+class ParserStateDeductor {
+public:
+	/**
+	 * Type containing the dynamic programming table.
+	 */
+	using Table = std::vector<std::unordered_map<const ParserState *, bool>>;
+
+private:
+	/**
+	 * Dynamic programming table.
+	 */
+	Table tbl;
+
+	/**
+	 * Signature given in the constructor.
+	 */
+	const std::vector<const Rtti *> signature;
+
+	/**
+	 * List of states that should be checked for being active.
+	 */
+	const std::vector<const ParserState *> states;
+
+	/**
+	 * Used internally to check whether the given parser stack s may have been
+	 * active for signature element d.
+	 *
+	 * @param d is the signature element.
+	 * @param s is the parser state.
+	 * @return true if the the given ParserState may have been active.
+	 */
+	bool isActive(size_t d, const ParserState *s);
+
+public:
+	/**
+	 * Constructor of the ParserStateDeductor class.
+	 *
+	 * @param signature a Node type signature describing the types of the nodes
+	 * which currently reside on e.g. the ParserScope stack.
+	 * @param states is a list of states that should be checked.
+	 */
+	ParserStateDeductor(std::vector<const Rtti *> signature,
+	                    std::vector<const ParserState *> states);
+
+	/**
+	 * Selects all active states from the given states. Only considers those
+	 * states that may have produced the last signature element.
+	 *
+	 * @return a list of states that may actually have been active.
+	 */
+	std::vector<const ParserState *> deduce();
+};
+
+/**
  * The ParserStates namespace contains all the global state constants used
  * in the ParserStack class.
  */
@@ -213,7 +303,6 @@ extern const ParserState All;
  */
 extern const ParserState None;
 }
-
 }
 
 #endif /* _OUSIA_PARSER_STATE_HPP_ */