#ifndef __JSUPPORT__JTREESCANNERINTERFACE__
#define __JSUPPORT__JTREESCANNERINTERFACE__

#include "JLang/JObjectIterator.hh"
#include "JLang/JNullType.hh"
#include "JLang/JEquals.hh"
#include "JLang/JBidirectionalIterator.hh"
#include "JSupport/JMultipleFileScanner.hh"
#include "JSupport/JLimit.hh"


/**
 * \author mdejong
 */

namespace JSUPPORT {}
namespace JPP { using namespace JSUPPORT; }

namespace JSUPPORT {

  using JLANG::JEquals;
  using JLANG::JBidirectionalIterator;
  using JLANG::JRewindableObjectIterator;
  using JLANG::JNullType;


  /**
   * Auxiliary interface for direct access of elements in ROOT TChain.
   *
   * The optional second template argument is used to the determine the value of an element
   * which defines the apparent order the elements in the TChain.
   */
  template<class T, class JEvaluator_t = JNullType>
  struct JTreeScannerInterface;

  
  /**
   * Specialiation of interface JTreeScannerInterface for unordered direct access of elements in ROOT TChain.
   * 
   * This interface provives for STD compatible iterators.\n
   * Note that a pointer to the parent JTreeScannerInterface is used for the iteration.
   * The user should therefore make separate copies of the read data when data are modified or multiple iterators are simultaneously used.
   *
   * This interface extends the JLANG::JRewindableObjectIterator interface and the JSUPPORT::JLimit class.
   */
  template<class JClass_t>
  struct JTreeScannerInterface<JClass_t, JNullType> :
    public JRewindableObjectIterator<JClass_t>,
    public JLimit
  {
  private:
    /**
     * Base class for STD compatible iterator. 
     */
    template<class T>
    struct basic_iterator :
      public JEquals<T>,
      public JBidirectionalIterator<T>
    {
      /**
       * Equality of iterator.
       *
       * \param  cursor          iterator
       * \return                 true if equal; else false
       */
      virtual bool equals(const T& cursor) const
      {
        return index == cursor.index;
      }


      /**
       * Increment iterator.
       *
       * \return                 true if valid; else false
       */
      virtual bool increment() override 
      {
	return ++index < pTreeScanner->getEntries();
      }


      /**
       * Decrement iterator.
       *
       * \return                 true if valid; else false
       */
      virtual bool decrement() override 
      {
	return --index >= 0;
      }


      /**
       * Increment iterator.
       *
       * \param  offset          offset
       * \return                 true if incremented; else false
       */
      virtual bool increment(const size_t offset) override 
      {
        return (index += offset) < pTreeScanner->getEntries();
      }


      /**
       * Decrement iterator.
       *
       * \param  offset          offset
       * \return                 true if decremented; else false
       */
      virtual bool decrement(const size_t offset) override 
      {
        return (index -= offset) >= 0;
      }


      /**
       * Get index.
       *
       * \return                 index
       */
      counter_type get() const
      {
	return index;
      }

    protected:
      /**
       * Default constructor.
       */
      basic_iterator() :
	pTreeScanner(NULL),
	index(-1)
      {}

      
      /**
       * Constructor.
       *
       * \param  p               pointer to tree scanner interface
       * \param  i               start index
       */
      basic_iterator(JTreeScannerInterface* p, const counter_type i) :
	pTreeScanner(p),
	index(i)
      {}
      
      JTreeScannerInterface* pTreeScanner;
      counter_type           index;
    };

  public:

    typedef JClass_t                                                    data_type;
    typedef typename JRewindableObjectIterator<JClass_t>::pointer_type  pointer_type;


    /**
     * Configure.
     *
     * \param  file_list         file list
     * \param  limit             limit
     */
    virtual void configure(const JMultipleFileScanner_t& file_list, const JLimit& limit) = 0;

      
    /**
     * Configure.
     *
     * \param  file_list         file list
     */
    void configure(const JMultipleFileScanner_t& file_list)
    {
      this->configure(file_list, JLimit());
    }

      
    /**
     * Get number of entries.
     *
     * \return                   number of entries
     */
    virtual Long64_t getEntries() const = 0;


    /**
     * Get entry at given index.
     *
     * \param  index             index
     * \return                   pointer to object (may be NULL)
     */
    virtual JClass_t* getEntry(Long64_t index) = 0;


    /**
     * Get internal counter.
     *
     * \return            counter
     */
    virtual counter_type getCounter() const = 0;
    

    /**
     * Get actual class name.
     *
     * \return                   class name
     */
    virtual const char* getClassName() const 
    {
      return JClass_t::Class_Name();
    }


    /**
     * STD compatible iterator. 
     */
    struct iterator :
      public basic_iterator<iterator>
    { 
      typedef counter_type  difference_type;

      friend class JTreeScannerInterface;

      /**
       * Default constructor.
       */
      iterator()
      {}


      /**
       * Smart pointer operator.
       *
       * \return                 pointer to object
       */
      const data_type* operator->()
      { 
        return this->pTreeScanner->getEntry(this->index);
      }


      /**
       * Dereference operator.
       *
       * \return                 reference to object
       */
      const data_type& operator*()
      {
        return *(this->pTreeScanner->getEntry(this->index));
      }


      /**
       * Get distance between two iterators.
       *
       * \param  first           first  iterator
       * \param  second          second iterator
       * \return                 distance
       */
      friend inline difference_type distance(const iterator& first,
					     const iterator& second)
      {
	return second.index - first.index;
      }
      

    private:
      /**
       * Constructor.
       *
       * \param  p               pointer to tree scanner interface
       * \param  i               start index
       */
      iterator(JTreeScannerInterface* p, const counter_type i) :
	basic_iterator<iterator>(p, i)
      {}
    };
    

    /**
     * STD compatible reverse iterator. 
     */
    struct reverse_iterator :
      public basic_iterator<reverse_iterator>
    {
      typedef counter_type  difference_type;

      friend class JTreeScannerInterface;

      /**
       * Default constructor.
       */
      reverse_iterator()
      {}


      /**
       * Smart pointer operator.
       *
       * \return                 pointer to object
       */
      const data_type* operator->()
      { 
        return  (this->pTreeScanner->getEntry(this->pTreeScanner->getEntries() - this->index - 1));
      }


      /**
       * Dereference operator.
       *
       * \return                 reference to object
       */
      const data_type& operator*()
      {
        return *(this->pTreeScanner->getEntry(this->pTreeScanner->getEntries() - this->index - 1));
      }


      /**
       * Get distance between two iterators.
       *
       * \param  first           first  iterator
       * \param  second          second iterator
       * \return                 distance
       */
      friend inline difference_type distance(const reverse_iterator& first,
					     const reverse_iterator& second)
      {
	return second.index - first.index;
      }
      
      
    private:
      /**
       * Constructor.
       *
       * \param  p               pointer to tree scanner interface
       * \param  i               start index
       */
      reverse_iterator(JTreeScannerInterface* p, const counter_type i) :
	basic_iterator<reverse_iterator>(p, i)
      {}
    };


    /**
     * Check emptyness.
     *
     * \return                 true if empty; else false
     */
    bool empty() const
    {
      return getEntries() == 0;
    }

    
    /**
     * Get iterator to begin of data.
     * 
     * \return                 iterator
     */
    iterator begin()
    {
      return iterator(this, this->getLowerLimit());
    }
 
   
    /**
     * Get iterator to end of data.
     *
     * \return                 iterator
     */
    iterator end()
    {
      return iterator(this, this->getUpperLimit() < this->getEntries() ? this->getUpperLimit() : this->getEntries());
    }

    
    /**
     * Get reverse iterator to begin of data.
     * 
     * \return                 reverse iterator
     */
    reverse_iterator rbegin()
    {
      return reverse_iterator(this, this->getLowerLimit());
    }
 
   
    /**
     * Get reverse iterator to end of data.
     *
     * \return                 reverse iterator
     */
    reverse_iterator rend()
    {
      return reverse_iterator(this, this->getUpperLimit() < this->getEntries() ? this->getUpperLimit() : this->getEntries());
    }
  };

  
  /**
   * Specialiation of interface JTreeScannerInterface for ordered direct access of elements in ROOT TChain.
   * 
   * This interface extends the JTreeScannerInterface<JClass_t, JNullType> interface 
   * with the additional interface method to find a corresponding entry in the ROOT TChain.
   */
  template<class JClass_t, class JEvaluator_t>
  struct JTreeScannerInterface :
    public virtual JTreeScannerInterface<JClass_t>
  {
    /**
     * Constructor.
     *
     * \param  evaluator         evaluator
     */
    JTreeScannerInterface(const JEvaluator_t& evaluator = JEvaluator_t()) :
      getValue(evaluator)
    {}


    /**
     * Find index of element that is closest in value to given value.
     *
     * \param  value             value
     * \return                   index (-1 in case of error)
     */
    virtual Long64_t find(const double value) const = 0;


    /**
     * Find index of element that is closest in value to given object.
     *
     * \param  object            object
     * \return                   index (-1 in case of error)
     */
    template<class T>
    Long64_t find(const T& object) const
    {
      return this->find(getValue(object));
    }


    /**
     * Get evaluator.
     *
     * \return                   evaluator
     */
    const JEvaluator_t& getEvaluator() const
    {
      return getValue;
    }

    
  protected:
    JEvaluator_t getValue;
  };
}

#endif