// Copyright (c) 2007,2008,2009,2010,2011 Max-Planck-Institute Saarbruecken (Germany),
// and Tel-Aviv University (Israel).  All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v5.4/Arrangement_on_surface_2/include/CGAL/Curved_kernel_via_analysis_2/Curve_interval_arcno_cache.h $
// $Id: Curve_interval_arcno_cache.h 0779373 2020-03-26T13:31:46+01:00 Sébastien Loriot
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Pavel Emeliyanenko <asm@mpi-sb.mpg.de>

#ifndef CGAL_CURVED_KERNEL_VIA_ANALYSIS_2_CURVE_INTERVAL_ARCNO_CACHE_H
#define CGAL_CURVED_KERNEL_VIA_ANALYSIS_2_CURVE_INTERVAL_ARCNO_CACHE_H

/*!\file include/CGAL/Curved_kernel_via_analysis_2/Curve_interval_arcno_cache.h
 * \brief defines \c Curve_interval_arcno_cache functor
 */

#include <CGAL/config.h>
#include <CGAL/Handle_with_policy.h>

namespace CGAL {

namespace internal {

/*!\brief
 * Given an arc number over an interval \c i this functor computes a
 * corresponding event arcno (and asymptotic tendency) over a certain vertical
 * line which lies on the given side w.r.t. the interval \c i.
 *
 * For caching issues for each accessed \c Curve_2 object we store
 * \c Interval_arcno_map structure. In its turn, \c Interval_arcno_map
 * for each \c Status_line_1 object stores the precomputed mapping
 * from interval arcnos (on left and right sides) to event arcnos
 */
template <class CurveKernel_2>
struct Curve_interval_arcno_cache {

    //!\name Public types
    //!@{

    //! this instance's first template parameter
    typedef CurveKernel_2 Curve_kernel_2;

    //! type of curve analysis
    typedef typename Curve_kernel_2::Curve_analysis_2 Curve_analysis_2;

    //! type of x-coordinate
    typedef typename Curve_kernel_2::Coordinate_1 Coordinate_1;

    //! type of status line
    typedef typename Curve_analysis_2::Status_line_1 Status_line_1;

    //! event arc number descriptor: stores an arc number along with curve's
    //! end type (+/-oo or \c ARR_INTERIOR )
    typedef std::pair<int, CGAL::Arr_parameter_space> Arcno_desc;

    //! type of first argument
    typedef Status_line_1         first_argument_type;

    //! type of second argument
    typedef bool                  second_argument_type;

    //! type of third arguent
    typedef int                   third_argument_type;

    //! the result type
    typedef Arcno_desc            result_type;

    //! the arity of the functor

    //!@}

    //!\name Constructors
    //!@{

    /*!\brief
     * Standard constructor
     */
    Curve_interval_arcno_cache() :
            _m_last_curve_id(-1) {
    }

    //!@}

    //!\name Functor invokation
    //!@{

    /*!\brief
     * Given arcno over an interval, this computes a corresponding event
     * arcno on status line \c cv_line lying on the given \c side w.r.t. the
     * interval
     *
     * \param cv_line Status line
     * \param side side = \c true: left side; \c side = \c false: right side
     * \param interval_arcno Arcnumber of interval
     * \return Arcnumber information at event line
     */
    result_type operator()(const Status_line_1& cv_line, bool side,
        int interval_arcno) const {

        CGAL_precondition(interval_arcno >= 0);
        if(!cv_line.is_event()) // # of arcs over interval is constant
            return std::make_pair(interval_arcno, CGAL::ARR_INTERIOR);

        Curve_analysis_2 ca_2 = cv_line.curve_analysis_2();
        ///////////////////////////////// polynomial or curve id ?
        int curve_id = static_cast<int>(ca_2.polynomial_2().id());
        /////////////////////////////////
        if(_m_last_curve_id != curve_id) {
            typename Curve_to_interval_arcno_map::iterator it;
            if(_m_last_curve_id != -1) {
            // commit the last changes to the global curve arcno map
                it = _m_curve_arcno_map.find(_m_last_curve_id);
                CGAL_precondition(it != _m_curve_arcno_map.end());
                it->second = _m_last_interval_map;
            }
            // modify _m_last_interval_map to be pointing to the
            // Interval_arcno_map  corresponding to the given curve_id
            it = _m_curve_arcno_map.insert(std::make_pair(curve_id,
                    Interval_arcno_map())).first;
            _m_last_interval_map = it->second;
            _m_last_curve_id = curve_id;
        }
        // cache status lines by id(); shall we use x-coordinate instead of
        // id to ensure uniqueness ?
        // TODO: shall we use cv_line.index() ?
        typename Interval_arcno_map::const_iterator it =
            _m_last_interval_map.find(cv_line.x().id());
        if(it != _m_last_interval_map.end()) {
            const Arcno_vector_pair& tmp = it->second;
            // note: side index must be reversed
            CGAL_precondition(interval_arcno < static_cast<int>(side == 1 ?
                tmp.first.size() : tmp.second.size()));
            return (side == 1 ? tmp.first[interval_arcno] :
                tmp.second[interval_arcno]);
        }

        int n_left = ca_2.status_line_of_interval(
                cv_line.index()).number_of_events(), // # arcs to the left
            n_right = ca_2.status_line_of_interval( // # arcs to the right
                cv_line.index()+1).number_of_events();
        std::pair<int, int> n_mininf, n_maxinf, ipair;
        n_mininf = cv_line.number_of_branches_approaching_minus_infinity();
        n_maxinf = cv_line.number_of_branches_approaching_plus_infinity();
        // we must also account for the number of asymptotic arcs approaching
        // this status line
        Arcno_vector_pair vpair;
        vpair.first.resize(n_left); //+ n_mininf.first + n_maxinf.first);
        vpair.second.resize(n_right); //+ n_mininf.second + n_maxinf.second);

        int i, _arcno, left_i = 0, right_i = 0;
        // process arcs approaching -oo from left and right
        for(; left_i < n_mininf.first; left_i++)
            vpair.first[left_i] = std::make_pair(left_i,
                CGAL::ARR_BOTTOM_BOUNDARY);

        for(; right_i < n_mininf.second; right_i++)
            vpair.second[right_i] = std::make_pair(right_i,
                CGAL::ARR_BOTTOM_BOUNDARY);

        // process all finite events over this vertical line
        for(_arcno = 0; _arcno < cv_line.number_of_events(); _arcno++) {
            ipair = cv_line.number_of_incident_branches(_arcno);
            for(i = 0; i < ipair.first; i++)
                vpair.first[left_i++] = std::make_pair(_arcno,
                    CGAL::ARR_INTERIOR);

            for(i = 0; i < ipair.second; i++)
            vpair.second[right_i++] = std::make_pair(_arcno,
                CGAL::ARR_INTERIOR);
        }
        // process arcs approaching +oo from left and right
        // this is not clear.. why arcnos at +oo are mapped to the same
        // interval arcnos ?
        for(i = 0; i < n_maxinf.first; i++, left_i++)
            vpair.first[left_i] = std::make_pair(left_i,
                CGAL::ARR_TOP_BOUNDARY);

        for(i = 0; i < n_maxinf.second; i++, right_i++)
            vpair.second[right_i] = std::make_pair(right_i,
                CGAL::ARR_TOP_BOUNDARY);

        CGAL_precondition(left_i == static_cast<int>(vpair.first.size()));
        CGAL_precondition(right_i == static_cast<int>(vpair.second.size()));
        _m_last_interval_map.insert(std::make_pair(cv_line.x().id(), vpair));
        CGAL_precondition(interval_arcno < static_cast<int>(side == 1 ?
                vpair.first.size() : vpair.second.size()));
        return (side == 1 ? vpair.first[interval_arcno] :
               vpair.second[interval_arcno]);
    }

    //!@}
private:

    //!\name Private members
    //!@{

    //! a pair of vectors (right and left side of event-line respectively)
    typedef std::pair<std::vector<Arcno_desc>, std::vector<Arcno_desc> >
        Arcno_vector_pair;

    //! maps from \c Status_line_1 id to a container of interval ->
    //! event arcnos
    // TODO: use hash instead ?? cache status lines by x-coordinate ? (Pavel)
  typedef typename Status_line_1::Algebraic_real_1::Id_type Id_type;
    typedef std::map<Id_type, Arcno_vector_pair> Interval_arcno_map;

    //! maps from \c Curve_2 id to \c Interval_arcno_map
    typedef std::map<int, Interval_arcno_map> Curve_to_interval_arcno_map;

    //! arcno mapping container instance
    mutable Curve_to_interval_arcno_map _m_curve_arcno_map;

    //! an id of the last queried \c Curve_2 object
    mutable int _m_last_curve_id;

    //! stores an address of the last accessed map
    mutable Interval_arcno_map _m_last_interval_map;

    //!@}

};  // struct Curve_interval_arcno_cache

} // namespace internal

} //namespace CGAL

#endif // CGAL_CURVED_KERNEL_VIA_ANALYSIS_2_CURVE_INTERVAL_ARCNO_CACHE_H
// EOF
