/* 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 "atn/DecisionEventInfo.h"
#include "support/BitSet.h"

namespace antlr4 {
namespace atn {

/// <summary>
/// This class represents profiling event information for an ambiguity.
/// Ambiguities are decisions where a particular input resulted in an SLL
/// conflict, followed by LL prediction also reaching a conflict state
/// (indicating a true ambiguity in the grammar).
///
/// <para>
/// This event may be reported during SLL prediction in cases where the
/// conflicting SLL configuration set provides sufficient information to
/// determine that the SLL conflict is truly an ambiguity. For example, if none
/// of the ATN configurations in the conflicting SLL configuration set have
/// traversed a global follow transition (i.e.
/// <seealso cref="ATNConfig#reachesIntoOuterContext"/> is 0 for all configurations), then
/// the result of SLL prediction for that input is known to be equivalent to the
/// result of LL prediction for that input.</para>
///
/// <para>
/// In some cases, the minimum represented alternative in the conflicting LL
/// configuration set is not equal to the minimum represented alternative in the
/// conflicting SLL configuration set. Grammars and inputs which result in this
/// scenario are unable to use <seealso cref="PredictionMode#SLL"/>, which in turn means
/// they cannot use the two-stage parsing strategy to improve parsing performance
/// for that input.</para>
/// </summary>
/// <seealso cref= ParserATNSimulator#reportAmbiguity </seealso>
/// <seealso cref= ANTLRErrorListener#reportAmbiguity
///
/// @since 4.3 </seealso>
class ANTLR4CPP_PUBLIC AmbiguityInfo : public DecisionEventInfo {
public:
    /// The set of alternative numbers for this decision event that lead to a valid parse.
    antlrcpp::BitSet ambigAlts;

    /// <summary>
    /// Constructs a new instance of the <seealso cref="AmbiguityInfo"/> class with the
    /// specified detailed ambiguity information.
    /// </summary>
    /// <param name="decision"> The decision number </param>
    /// <param name="configs"> The final configuration set identifying the ambiguous
    /// alternatives for the current input </param>
    /// <param name="ambigAlts"> The set of alternatives in the decision that lead to a valid parse.
    ///                  The predicted alt is the min(ambigAlts) </param>
    /// <param name="input"> The input token stream </param>
    /// <param name="startIndex"> The start index for the current prediction </param>
    /// <param name="stopIndex"> The index at which the ambiguity was identified during
    /// prediction </param>
    /// <param name="fullCtx"> {@code true} if the ambiguity was identified during LL
    /// prediction; otherwise, {@code false} if the ambiguity was identified
    /// during SLL prediction </param>
    AmbiguityInfo(size_t decision, ATNConfigSet* configs, const antlrcpp::BitSet& ambigAlts,
        TokenStream* input, size_t startIndex, size_t stopIndex, bool fullCtx);
};

} // namespace atn
} // namespace antlr4
