﻿/* 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 "Token.h"
#include "support/BitSet.h"
#include "atn/PredictionContext.h"
#include "atn/ATNConfig.h"

namespace antlr4 {
namespace atn {

  class ANTLR4CPP_PUBLIC LL1Analyzer {
  public:
    /// Special value added to the lookahead sets to indicate that we hit
    ///  a predicate during analysis if {@code seeThruPreds==false}.
#if __cplusplus >= 201703L
    static constexpr size_t HIT_PRED = Token::INVALID_TYPE;
#else
    enum : size_t {
      HIT_PRED = Token::INVALID_TYPE,
    };
#endif

    const atn::ATN &_atn;

    LL1Analyzer(const atn::ATN &atn);
    virtual ~LL1Analyzer();

    /// <summary>
    /// Calculates the SLL(1) expected lookahead set for each outgoing transition
    /// of an <seealso cref="ATNState"/>. The returned array has one element for each
    /// outgoing transition in {@code s}. If the closure from transition
    /// <em>i</em> leads to a semantic predicate before matching a symbol, the
    /// element at index <em>i</em> of the result will be {@code null}.
    /// </summary>
    /// <param name="s"> the ATN state </param>
    /// <returns> the expected symbols for each outgoing transition of {@code s}. </returns>
    virtual std::vector<misc::IntervalSet> getDecisionLookahead(ATNState *s) const;

    /// <summary>
    /// Compute set of tokens that can follow {@code s} in the ATN in the
    /// specified {@code ctx}.
    /// <p/>
    /// If {@code ctx} is {@code null} and the end of the rule containing
    /// {@code s} is reached, <seealso cref="Token#EPSILON"/> is added to the result set.
    /// If {@code ctx} is not {@code null} and the end of the outermost rule is
    /// reached, <seealso cref="Token#EOF"/> is added to the result set.
    /// </summary>
    /// <param name="s"> the ATN state </param>
    /// <param name="ctx"> the complete parser context, or {@code null} if the context
    /// should be ignored
    /// </param>
    /// <returns> The set of tokens that can follow {@code s} in the ATN in the
    /// specified {@code ctx}. </returns>
    virtual misc::IntervalSet LOOK(ATNState *s, RuleContext *ctx) const;

    /// <summary>
    /// Compute set of tokens that can follow {@code s} in the ATN in the
    /// specified {@code ctx}.
    /// <p/>
    /// If {@code ctx} is {@code null} and the end of the rule containing
    /// {@code s} is reached, <seealso cref="Token#EPSILON"/> is added to the result set.
    /// If {@code ctx} is not {@code null} and the end of the outermost rule is
    /// reached, <seealso cref="Token#EOF"/> is added to the result set.
    /// </summary>
    /// <param name="s"> the ATN state </param>
    /// <param name="stopState"> the ATN state to stop at. This can be a
    /// <seealso cref="BlockEndState"/> to detect epsilon paths through a closure. </param>
    /// <param name="ctx"> the complete parser context, or {@code null} if the context
    /// should be ignored
    /// </param>
    /// <returns> The set of tokens that can follow {@code s} in the ATN in the
    /// specified {@code ctx}. </returns>
    virtual misc::IntervalSet LOOK(ATNState *s, ATNState *stopState, RuleContext *ctx) const;

    /// <summary>
    /// Compute set of tokens that can follow {@code s} in the ATN in the
    /// specified {@code ctx}.
    /// <p/>
    /// If {@code ctx} is {@code null} and {@code stopState} or the end of the
    /// rule containing {@code s} is reached, <seealso cref="Token#EPSILON"/> is added to
    /// the result set. If {@code ctx} is not {@code null} and {@code addEOF} is
    /// {@code true} and {@code stopState} or the end of the outermost rule is
    /// reached, <seealso cref="Token#EOF"/> is added to the result set.
    /// </summary>
    /// <param name="s"> the ATN state. </param>
    /// <param name="stopState"> the ATN state to stop at. This can be a
    /// <seealso cref="BlockEndState"/> to detect epsilon paths through a closure. </param>
    /// <param name="ctx"> The outer context, or {@code null} if the outer context should
    /// not be used. </param>
    /// <param name="look"> The result lookahead set. </param>
    /// <param name="lookBusy"> A set used for preventing epsilon closures in the ATN
    /// from causing a stack overflow. Outside code should pass
    /// {@code new HashSet<ATNConfig>} for this argument. </param>
    /// <param name="calledRuleStack"> A set used for preventing left recursion in the
    /// ATN from causing a stack overflow. Outside code should pass
    /// {@code new BitSet()} for this argument. </param>
    /// <param name="seeThruPreds"> {@code true} to true semantic predicates as
    /// implicitly {@code true} and "see through them", otherwise {@code false}
    /// to treat semantic predicates as opaque and add <seealso cref="#HIT_PRED"/> to the
    /// result if one is encountered. </param>
    /// <param name="addEOF"> Add <seealso cref="Token#EOF"/> to the result if the end of the
    /// outermost context is reached. This parameter has no effect if {@code ctx}
    /// is {@code null}. </param>
  protected:
    virtual void _LOOK(ATNState *s, ATNState *stopState, Ref<PredictionContext> const& ctx, misc::IntervalSet &look,
      ATNConfig::Set &lookBusy, antlrcpp::BitSet &calledRuleStack, bool seeThruPreds, bool addEOF) const;
  };

} // namespace atn
} // namespace antlr4