/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2006 Refractions Research Inc.
 * Copyright (C) 2001-2002 Vivid Solutions Inc.
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU Lesser General Public Licence as published
 * by the Free Software Foundation.
 * See the COPYING file for more information.
 *
 **********************************************************************/

#include <geos/index/sweepline/SweepLineIndex.h>
#include <geos/index/sweepline/SweepLineEvent.h>
#include <geos/index/sweepline/SweepLineInterval.h>
#include <geos/index/sweepline/SweepLineOverlapAction.h>

#include <algorithm>

using namespace std;

namespace geos {
namespace index { // geos.index
namespace sweepline { // geos.index.sweepline

SweepLineIndex::SweepLineIndex()
    :
    indexBuilt(false),
    nOverlaps(0)
{
}

SweepLineIndex::~SweepLineIndex() = default;

void
SweepLineIndex::add(SweepLineInterval* sweepInt)
{
    // FIXME: who's going to delete the newly-created events ?
    SweepLineEvent* insertEvent = new SweepLineEvent(sweepInt->getMin(), nullptr, sweepInt);
    events.push_back(insertEvent);
    events.push_back(new SweepLineEvent(sweepInt->getMax(), insertEvent, sweepInt));
}

/*private*/
void
SweepLineIndex::buildIndex()
{
    if(!indexBuilt) {
        sort(events.begin(), events.end(), SweepLineEventLessThen());
        const std::vector<SweepLineEvent*>::size_type n = events.size();
        for(std::vector<SweepLineEvent*>::size_type i = 0; i < n; i++) {
            SweepLineEvent* ev = events[i];
            if(ev->isDelete()) {
                ev->getInsertEvent()->setDeleteEventIndex(i);
            }
        }
        indexBuilt = true;
    }
}

void
SweepLineIndex::computeOverlaps(SweepLineOverlapAction* action)
{
    nOverlaps = 0;

    buildIndex();

    const std::vector<SweepLineEvent*>::size_type n = events.size();
    for(size_t i = 0; i < n; i++) {
        SweepLineEvent* ev = events[i];
        if(ev->isInsert()) {
            processOverlaps(i,
                            ev->getDeleteEventIndex(),
                            ev->getInterval(), action);
        }
    }
}

void
SweepLineIndex::processOverlaps(size_t start, size_t end,
                                SweepLineInterval* s0, SweepLineOverlapAction* action)
{
    /**
     * Since we might need to test for self-intersections,
     * include current insert event object in list of event objects to test.
     * Last index can be skipped, because it must be a Delete event.
     */
    for(auto i = start; i < end; i++) {
        SweepLineEvent* ev = events[i];
        if(ev->isInsert()) {
            SweepLineInterval* s1 = ev->getInterval();
            action->overlap(s0, s1);
            nOverlaps++;
        }
    }
}

} // namespace geos.index.sweepline
} // namespace geos.index
} // namespace geos