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//---------------------------------------------------------------------
// Provide an non-intersive reference counting smart pointer template 
// Copyright (C) 2007  Charles S. Wilson
// This file is part of the OptionParse library.
// 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
// 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//---------------------------------------------------------------------
#ifndef OptionParse__ExternalCountedPtr_HEADER
#define OptionParse__ExternalCountedPtr_HEADER

#include <OptionParse/OptionParseVisibility.h>
#include <stdexcept>

namespace OptionParse {

// forward declaration
class OPTIONPARSE_IMPEXP ExternalCountedPtrBase;

class OPTIONPARSE_IMPEXP ExternalCounter
{
private:
    unsigned count;
public:
    ExternalCounter(unsigned c = 1) : count(c) {}
    friend class ExternalCountedPtrBase;
};

class OPTIONPARSE_IMPEXP ExternalCountedPtrBase
{
protected:
    ExternalCounter* theCounter; // managed by derived class

    virtual void deleteTarget(void ) throw() = 0;
    virtual void assignTarget(void*) throw() = 0;

    const unsigned countVal(void) const { return (theCounter ? theCounter->count : 0); }

    // derived class should only call this method immediately
    // after calling release(), or in constructor
    void acquire(ExternalCounter* c, void* p) throw()
    { // increment the count
        theCounter = c;
        if (c)
        {
            ++c->count;
            assignTarget(p);
        }
    }

    void release()
    { // decrement the count, delete if it is 0
        if (theCounter) {
            if (--theCounter->count == 0) {
                deleteTarget();
                delete theCounter;
            }
            theCounter = 0;
        }
    }

    // no default constructor
    ExternalCountedPtrBase(ExternalCounter* c)
    : theCounter(c)
    {}
};

template <typename X>
class ExternalCountedPtr : public ExternalCountedPtrBase
{
private:
    X* thePtr;
protected:
    // this should only be called by the release() method
    // in the base class.
    virtual void deleteTarget(void) throw()
    {
        if (thePtr)
            delete thePtr;
        thePtr = NULL;
    }
    virtual void assignTarget(void* p) throw()
    {
        thePtr = static_cast<X*>(p);
    }

public:
    typedef X element_type;

    explicit ExternalCountedPtr(X* p = 0) // allocate a new counter
    :
        ExternalCountedPtrBase(0),
        thePtr(p)
    {
        if (p)
            theCounter = new ExternalCounter();
    }

    virtual ~ExternalCountedPtr()
    {
        release();
    }

    ExternalCountedPtr(const ExternalCountedPtr& r)
    :
        ExternalCountedPtrBase(0),
        thePtr(NULL)
    {
        acquire(r.theCounter, r.thePtr);
    }

    ExternalCountedPtr& operator=(const ExternalCountedPtr& r)
    {
        if (this != &r)
        {
            release();
            acquire(r.theCounter, r.thePtr);
        }
        return *this;
    }
    bool operator==(const ExternalCountedPtr& rhs) const { return (thePtr == rhs.thePtr); }
    bool operator!=(const ExternalCountedPtr& rhs) const { return (thePtr != rhs.thePtr); }
    bool operator <(const ExternalCountedPtr& rhs) const { return (thePtr  < rhs.thePtr); }

    template <typename Y> friend class ExternalCountedPtr;
    template <typename Y> ExternalCountedPtr(const ExternalCountedPtr<Y>& r)
    :
        ExternalCountedPtrBase(0),
        thePtr(NULL) // do NOT want to assign here, before count incremented
    {
        X* ptr = dynamic_cast<X*>(r.thePtr);
	if (ptr)
        {
            acquire(r.theCounter, ptr);
        }
    }
    template <class Y> ExternalCountedPtr& operator=(const ExternalCountedPtr<Y>& r)
    {
        if (this != &r)
        {
            release();
            X* ptr = dynamic_cast<X*>(r.thePtr);
	    if (ptr)
            {
                acquire(r.theCounter, ptr);
            }
        }
        return *this;
    }

    X& operator*()  const
    {
        if (isNotNull())
            return *thePtr;
        else
            throw std::range_error("Operator* access to a null pointer is not allowed.");
    }
    X* operator->() const
    {
        if (isNotNull())
            return thePtr;
        else
            throw std::range_error("Operator-> access to a null pointer is not allowed.");
    }
    X* get()        const throw()   {return thePtr; }
    bool unique()   const throw()   {return (countVal() == 1 || countVal() == 0); }
    bool isNull()    const throw()  {return (!theCounter || !thePtr); }
    bool isNotNull() const throw()  {return !isNull(); }
    void nullify() throw()          { release(); assignTarget(NULL); }
};

} // namespace OptionParse

#endif // OptionParse__ExternalCountedPtr_HEADER