/* 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.
 */

#include "atn/LL1Analyzer.h"

#include "atn/ATNConfig.h"
#include "atn/AbstractPredicateTransition.h"
#include "atn/EmptyPredictionContext.h"
#include "atn/NotSetTransition.h"
#include "atn/RuleStopState.h"
#include "atn/RuleTransition.h"
#include "atn/SingletonPredictionContext.h"
#include "atn/Transition.h"
#include "atn/WildcardTransition.h"
#include "misc/IntervalSet.h"
#include "support/CPPUtils.h"

using namespace antlr4;
using namespace antlr4::atn;
using namespace antlrcpp;

LL1Analyzer::LL1Analyzer(const ATN& atn) : _atn(atn) {}

LL1Analyzer::~LL1Analyzer() {}

std::vector<misc::IntervalSet> LL1Analyzer::getDecisionLookahead(ATNState* s) const {
    std::vector<misc::IntervalSet> look;

    if (s == nullptr) {
        return look;
    }

    look.resize(s->transitions.size()); // Fills all interval sets with defaults.
    for (size_t alt = 0; alt < s->transitions.size(); alt++) {
        bool seeThruPreds = false; // fail to get lookahead upon pred

        ATNConfig::Set lookBusy;
        antlrcpp::BitSet callRuleStack;
        _LOOK(s->transitions[alt]->target, nullptr, PredictionContext::EMPTY, look[alt], lookBusy,
            callRuleStack, seeThruPreds, false);

        // Wipe out lookahead for this alternative if we found nothing
        // or we had a predicate when we !seeThruPreds
        if (look[alt].size() == 0 || look[alt].contains(HIT_PRED)) {
            look[alt].clear();
        }
    }
    return look;
}

misc::IntervalSet LL1Analyzer::LOOK(ATNState* s, RuleContext* ctx) const {
    return LOOK(s, nullptr, ctx);
}

misc::IntervalSet LL1Analyzer::LOOK(ATNState* s, ATNState* stopState, RuleContext* ctx) const {
    misc::IntervalSet r;
    bool seeThruPreds = true; // ignore preds; get all lookahead
    Ref<PredictionContext> lookContext =
        ctx != nullptr ? PredictionContext::fromRuleContext(_atn, ctx) : nullptr;

    ATNConfig::Set lookBusy;
    antlrcpp::BitSet callRuleStack;
    _LOOK(s, stopState, lookContext, r, lookBusy, callRuleStack, seeThruPreds, true);

    return r;
}

void LL1Analyzer::_LOOK(ATNState* s, ATNState* stopState, Ref<PredictionContext> const& ctx,
    misc::IntervalSet& look, ATNConfig::Set& lookBusy, antlrcpp::BitSet& calledRuleStack,
    bool seeThruPreds, bool addEOF) const {

    Ref<ATNConfig> c = std::make_shared<ATNConfig>(s, 0, ctx);

    if (lookBusy.count(c) >
        0) // Keep in mind comparison is based on members of the class, not the actual instance.
        return;

    lookBusy.insert(c);

    // ml: s can never be null, hence no need to check if stopState is != null.
    if (s == stopState) {
        if (ctx == nullptr) {
            look.add(Token::EPSILON);
            return;
        } else if (ctx->isEmpty() && addEOF) {
            look.add(Token::EOF);
            return;
        }
    }

    if (s->getStateType() == ATNState::RULE_STOP) {
        if (ctx == nullptr) {
            look.add(Token::EPSILON);
            return;
        } else if (ctx->isEmpty() && addEOF) {
            look.add(Token::EOF);
            return;
        }

        if (ctx != PredictionContext::EMPTY) {
            // run thru all possible stack tops in ctx
            for (size_t i = 0; i < ctx->size(); i++) {
                ATNState* returnState = _atn.states[ctx->getReturnState(i)];

                bool removed = calledRuleStack.test(returnState->ruleIndex);
                auto onExit = finally([removed, &calledRuleStack, returnState] {
                    if (removed) {
                        calledRuleStack.set(returnState->ruleIndex);
                    }
                });

                calledRuleStack[returnState->ruleIndex] = false;
                _LOOK(returnState, stopState, ctx->getParent(i), look, lookBusy, calledRuleStack,
                    seeThruPreds, addEOF);
            }
            return;
        }
    }

    size_t n = s->transitions.size();
    for (size_t i = 0; i < n; i++) {
        Transition* t = s->transitions[i];

        if (t->getSerializationType() == Transition::RULE) {
            if (calledRuleStack[(static_cast<RuleTransition*>(t))->target->ruleIndex]) {
                continue;
            }

            Ref<PredictionContext> newContext = SingletonPredictionContext::create(
                ctx, (static_cast<RuleTransition*>(t))->followState->stateNumber);
            auto onExit = finally([t, &calledRuleStack] {
                calledRuleStack[(static_cast<RuleTransition*>(t))->target->ruleIndex] = false;
            });

            calledRuleStack.set((static_cast<RuleTransition*>(t))->target->ruleIndex);
            _LOOK(t->target, stopState, newContext, look, lookBusy, calledRuleStack, seeThruPreds,
                addEOF);

        } else if (is<AbstractPredicateTransition*>(t)) {
            if (seeThruPreds) {
                _LOOK(t->target, stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds,
                    addEOF);
            } else {
                look.add(HIT_PRED);
            }
        } else if (t->isEpsilon()) {
            _LOOK(t->target, stopState, ctx, look, lookBusy, calledRuleStack, seeThruPreds, addEOF);
        } else if (t->getSerializationType() == Transition::WILDCARD) {
            look.addAll(misc::IntervalSet::of(
                Token::MIN_USER_TOKEN_TYPE, static_cast<ssize_t>(_atn.maxTokenType)));
        } else {
            misc::IntervalSet set = t->label();
            if (!set.isEmpty()) {
                if (is<NotSetTransition*>(t)) {
                    set = set.complement(misc::IntervalSet::of(
                        Token::MIN_USER_TOKEN_TYPE, static_cast<ssize_t>(_atn.maxTokenType)));
                }
                look.addAll(set);
            }
        }
    }
}
