// Copyright 2009-2020 Intel Corporation
// SPDX-License-Identifier: Apache-2.0

#pragma once

#include "atomic.h"

namespace embree
{
  struct NullTy {
  };

  extern MAYBE_UNUSED NullTy null;
  
  class RefCount
  {
  public:
    RefCount(int val = 0) : refCounter(val) {}
    virtual ~RefCount() {};
  
    virtual RefCount* refInc() { refCounter.fetch_add(1); return this; }
    virtual void refDec() { if (refCounter.fetch_add(-1) == 1) delete this; }
  private:
    std::atomic<size_t> refCounter;
  };
  
  ////////////////////////////////////////////////////////////////////////////////
  /// Reference to single object
  ////////////////////////////////////////////////////////////////////////////////

  template<typename Type>
  class Ref
  {
  public:
    Type* ptr;

    ////////////////////////////////////////////////////////////////////////////////
    /// Constructors, Assignment & Cast Operators
    ////////////////////////////////////////////////////////////////////////////////

    __forceinline Ref() : ptr(nullptr) {}
    __forceinline Ref(NullTy) : ptr(nullptr) {}
    __forceinline Ref(const Ref& input) : ptr(input.ptr) { if (ptr) ptr->refInc(); }
    __forceinline Ref(Ref&& input) : ptr(input.ptr) { input.ptr = nullptr; }

    __forceinline Ref(Type* const input) : ptr(input)
    {
      if (ptr)
        ptr->refInc();
    }

    __forceinline ~Ref()
    {
      if (ptr)
        ptr->refDec();
    }

    __forceinline Ref& operator =(const Ref& input)
    {
      if (input.ptr)
        input.ptr->refInc();
      if (ptr)
        ptr->refDec();
      ptr = input.ptr;
      return *this;
    }

    __forceinline Ref& operator =(Ref&& input)
    {
      if (ptr)
        ptr->refDec();
      ptr = input.ptr;
      input.ptr = nullptr;
      return *this;
    }

    __forceinline Ref& operator =(Type* const input)
    {
      if (input)
        input->refInc();
      if (ptr)
        ptr->refDec();
      ptr = input;
      return *this;
    }

    __forceinline Ref& operator =(NullTy)
    {
      if (ptr)
        ptr->refDec();
      ptr = nullptr;
      return *this;
    }

    __forceinline operator bool() const { return ptr != nullptr; }

    __forceinline const Type& operator  *() const { return *ptr; }
    __forceinline       Type& operator  *()       { return *ptr; }
    __forceinline const Type* operator ->() const { return  ptr; }
    __forceinline       Type* operator ->()       { return  ptr; }

    template<typename TypeOut>
    __forceinline       Ref<TypeOut> cast()       { return Ref<TypeOut>(static_cast<TypeOut*>(ptr)); }
    template<typename TypeOut>
    __forceinline const Ref<TypeOut> cast() const { return Ref<TypeOut>(static_cast<TypeOut*>(ptr)); }

    template<typename TypeOut>
    __forceinline       Ref<TypeOut> dynamicCast()       { return Ref<TypeOut>(dynamic_cast<TypeOut*>(ptr)); }
    template<typename TypeOut>
    __forceinline const Ref<TypeOut> dynamicCast() const { return Ref<TypeOut>(dynamic_cast<TypeOut*>(ptr)); }
  };

  template<typename Type> __forceinline bool operator < (const Ref<Type>& a, const Ref<Type>& b) { return a.ptr   <  b.ptr;   }

  template<typename Type> __forceinline bool operator ==(const Ref<Type>& a, NullTy            ) { return a.ptr   == nullptr; }
  template<typename Type> __forceinline bool operator ==(NullTy            , const Ref<Type>& b) { return nullptr == b.ptr;   }
  template<typename Type> __forceinline bool operator ==(const Ref<Type>& a, const Ref<Type>& b) { return a.ptr   == b.ptr;   }

  template<typename Type> __forceinline bool operator !=(const Ref<Type>& a, NullTy            ) { return a.ptr   != nullptr; }
  template<typename Type> __forceinline bool operator !=(NullTy            , const Ref<Type>& b) { return nullptr != b.ptr;   }
  template<typename Type> __forceinline bool operator !=(const Ref<Type>& a, const Ref<Type>& b) { return a.ptr   != b.ptr;   }
}