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+/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
+
+#pragma once
+
+#include "antlr4-common.h"
+
+namespace antlr4 {
+namespace dfa {
+
+  /// <summary>
+  /// A DFA state represents a set of possible ATN configurations.
+  ///  As Aho, Sethi, Ullman p. 117 says "The DFA uses its state
+  ///  to keep track of all possible states the ATN can be in after
+  ///  reading each input symbol.  That is to say, after reading
+  ///  input a1a2..an, the DFA is in a state that represents the
+  ///  subset T of the states of the ATN that are reachable from the
+  ///  ATN's start state along some path labeled a1a2..an."
+  ///  In conventional NFA->DFA conversion, therefore, the subset T
+  ///  would be a bitset representing the set of states the
+  ///  ATN could be in.  We need to track the alt predicted by each
+  ///  state as well, however.  More importantly, we need to maintain
+  ///  a stack of states, tracking the closure operations as they
+  ///  jump from rule to rule, emulating rule invocations (method calls).
+  ///  I have to add a stack to simulate the proper lookahead sequences for
+  ///  the underlying LL grammar from which the ATN was derived.
+  /// <p/>
+  ///  I use a set of ATNConfig objects not simple states.  An ATNConfig
+  ///  is both a state (ala normal conversion) and a RuleContext describing
+  ///  the chain of rules (if any) followed to arrive at that state.
+  /// <p/>
+  ///  A DFA state may have multiple references to a particular state,
+  ///  but with different ATN contexts (with same or different alts)
+  ///  meaning that state was reached via a different set of rule invocations.
+  /// </summary>
+  class ANTLR4CPP_PUBLIC DFAState {
+  public:
+    class PredPrediction {
+    public:
+      Ref<atn::SemanticContext> pred; // never null; at least SemanticContext.NONE
+      int alt;
+
+      PredPrediction(const Ref<atn::SemanticContext> &pred, int alt);
+      virtual ~PredPrediction();
+
+      virtual std::string toString();
+
+    private:
+      void InitializeInstanceFields();
+    };
+
+    int stateNumber;
+
+    std::unique_ptr<atn::ATNConfigSet> configs;
+
+    /// {@code edges[symbol]} points to target of symbol. Shift up by 1 so (-1)
+    ///  <seealso cref="Token#EOF"/> maps to {@code edges[0]}.
+    // ml: this is a sparse list, so we use a map instead of a vector.
+    //     Watch out: we no longer have the -1 offset, as it isn't needed anymore.
+    std::unordered_map<size_t, DFAState *> edges;
+
+    bool isAcceptState;
+
+    /// if accept state, what ttype do we match or alt do we predict?
+    /// This is set to <seealso cref="ATN#INVALID_ALT_NUMBER"/> when <seealso cref="#predicates"/>{@code !=null} or
+    /// <seealso cref="#requiresFullContext"/>.
+    size_t prediction;
+
+    Ref<atn::LexerActionExecutor> lexerActionExecutor;
+
+    /// <summary>
+    /// Indicates that this state was created during SLL prediction that
+    /// discovered a conflict between the configurations in the state. Future
+    /// <seealso cref="ParserATNSimulator#execATN"/> invocations immediately jumped doing
+    /// full context prediction if this field is true.
+    /// </summary>
+    bool requiresFullContext;
+
+    /// <summary>
+    /// During SLL parsing, this is a list of predicates associated with the
+    ///  ATN configurations of the DFA state. When we have predicates,
+    ///  <seealso cref="#requiresFullContext"/> is {@code false} since full context prediction evaluates predicates
+    ///  on-the-fly. If this is not null, then <seealso cref="#prediction"/> is
+    ///  <seealso cref="ATN#INVALID_ALT_NUMBER"/>.
+    /// <p/>
+    ///  We only use these for non-<seealso cref="#requiresFullContext"/> but conflicting states. That
+    ///  means we know from the context (it's $ or we don't dip into outer
+    ///  context) that it's an ambiguity not a conflict.
+    /// <p/>
+    ///  This list is computed by <seealso cref="ParserATNSimulator#predicateDFAState"/>.
+    /// </summary>
+    std::vector<PredPrediction *> predicates;
+
+    /// Map a predicate to a predicted alternative.
+    DFAState();
+    DFAState(int state);
+    DFAState(std::unique_ptr<atn::ATNConfigSet> configs);
+    virtual ~DFAState();
+
+    /// <summary>
+    /// Get the set of all alts mentioned by all ATN configurations in this
+    ///  DFA state.
+    /// </summary>
+    virtual std::set<size_t> getAltSet();
+
+    virtual size_t hashCode() const;
+
+    /// Two DFAState instances are equal if their ATN configuration sets
+    /// are the same. This method is used to see if a state already exists.
+    ///
+    /// Because the number of alternatives and number of ATN configurations are
+    /// finite, there is a finite number of DFA states that can be processed.
+    /// This is necessary to show that the algorithm terminates.
+    ///
+    /// Cannot test the DFA state numbers here because in
+    /// ParserATNSimulator#addDFAState we need to know if any other state
+    /// exists that has this exact set of ATN configurations. The
+    /// stateNumber is irrelevant.
+    bool operator == (const DFAState &o) const;
+
+    virtual std::string toString();
+
+    struct Hasher
+    {
+      size_t operator()(DFAState *k) const {
+        return k->hashCode();
+      }
+    };
+
+    struct Comparer {
+      bool operator()(DFAState *lhs, DFAState *rhs) const
+      {
+        return *lhs == *rhs;
+      }
+    };
+
+  private:
+    void InitializeInstanceFields();
+  };
+
+} // namespace atn
+} // namespace antlr4