// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
#pragma once

#include "Luau/DenseHash.h"
#include "Luau/Error.h"
#include "Luau/TypeFwd.h"

#include <utility>

namespace Luau
{
struct InternalErrorReporter;

struct TypeIdPairHash
{
    size_t hashOne(Luau::TypeId key) const
    {
        return (uintptr_t(key) >> 4) ^ (uintptr_t(key) >> 9);
    }

    size_t operator()(const std::pair<Luau::TypeId, Luau::TypeId>& x) const
    {
        return hashOne(x.first) ^ (hashOne(x.second) << 1);
    }
};

struct UnifierCounters
{
    int recursionCount = 0;
    int recursionLimit = 0;
    int iterationCount = 0;
    int iterationLimit = 0;
};

struct UnifierSharedState
{
    UnifierSharedState(InternalErrorReporter* iceHandler)
        : iceHandler(iceHandler)
    {
    }

    InternalErrorReporter* iceHandler;

    DenseHashMap<TypeId, bool> skipCacheForType{nullptr};
    DenseHashSet<std::pair<TypeId, TypeId>, TypeIdPairHash> cachedUnify{{nullptr, nullptr}};
    DenseHashMap<std::pair<TypeId, TypeId>, TypeErrorData, TypeIdPairHash> cachedUnifyError{{nullptr, nullptr}};

    DenseHashSet<TypeId> tempSeenTy{nullptr};
    DenseHashSet<TypePackId> tempSeenTp{nullptr};

    UnifierCounters counters;

    bool reentrantTypeReduction = false;
};

struct TypeReductionRentrancyGuard final
{
    explicit TypeReductionRentrancyGuard(NotNull<UnifierSharedState> sharedState)
        : sharedState{sharedState}
    {
        sharedState->reentrantTypeReduction = true;
    }
    ~TypeReductionRentrancyGuard()
    {
        sharedState->reentrantTypeReduction = false;
    }
    TypeReductionRentrancyGuard(const TypeReductionRentrancyGuard&) = delete;
    TypeReductionRentrancyGuard(TypeReductionRentrancyGuard&&) = delete;

private:
    NotNull<UnifierSharedState> sharedState;
};

} // namespace Luau