// SPDX-License-Identifier: LGPL-2.1-or-later
//
// SPDX-FileCopyrightText: 2011 Niko Sams <niko.sams@gmail.com>
//

#include "ElevationModel.h"
#include "GeoSceneHead.h"
#include "GeoSceneLayer.h"
#include "GeoSceneMap.h"
#include "GeoSceneDocument.h"
#include "GeoSceneTextureTileDataset.h"
#include "HttpDownloadManager.h"
#include "Tile.h"
#include "TileLoader.h"
#include "TileLoaderHelper.h"
#include "MarbleDebug.h"
#include "MapThemeManager.h"
#include "TileId.h"
#include "PluginManager.h"

#include <QCache>
#include <QImage>
#include <qmath.h>

namespace Marble
{

class ElevationModelPrivate
{
public:
    ElevationModelPrivate( ElevationModel *_q, HttpDownloadManager *downloadManager, PluginManager* pluginManager )
        : q( _q ),
          m_tileLoader( downloadManager, pluginManager ),
          m_textureLayer( nullptr ),
          m_srtmTheme(nullptr)
    {
        m_cache.setMaxCost( 10 ); //keep 10 tiles in memory (~17MB)

        m_srtmTheme = MapThemeManager::loadMapTheme( "earth/srtm2/srtm2.dgml" );
        if ( !m_srtmTheme ) {
            mDebug() << "Failed to load map theme earth/srtm2/srtm2.dgml. Check your installation. No elevation will be returned.";
            return;
        }

        const GeoSceneHead *head = m_srtmTheme->head();
        Q_ASSERT( head );

        const GeoSceneMap *map = m_srtmTheme->map();
        Q_ASSERT( map );

        const GeoSceneLayer *sceneLayer = map->layer( head->theme() );
        if (!sceneLayer) {
            mDebug() << "Failed to instantiate elevation map. No elevation will be returned.";
            return;
        }
        Q_ASSERT( sceneLayer );

        m_textureLayer = dynamic_cast<GeoSceneTextureTileDataset*>( sceneLayer->datasets().first() );
        Q_ASSERT( m_textureLayer );
    }

    ~ElevationModelPrivate()
    {
       delete m_srtmTheme;
    }

    void tileCompleted( const TileId & tileId, const QImage &image )
    {
        m_cache.insert( tileId, new QImage( image ) );
        emit q->updateAvailable();
    }

public:
    ElevationModel *q;

    TileLoader m_tileLoader;
    const GeoSceneTextureTileDataset *m_textureLayer;
    QCache<TileId, const QImage> m_cache;
    GeoSceneDocument *m_srtmTheme;
};

ElevationModel::ElevationModel( HttpDownloadManager *downloadManager, PluginManager* pluginManager, QObject *parent ) :
    QObject( parent ),
    d( new ElevationModelPrivate( this, downloadManager, pluginManager ) )
{
    connect( &d->m_tileLoader, SIGNAL(tileCompleted(TileId,QImage)),
             this, SLOT(tileCompleted(TileId,QImage)) );
}

ElevationModel::~ElevationModel()
{
    delete d;
}


qreal ElevationModel::height( qreal lon, qreal lat ) const
{
    if ( !d->m_textureLayer ) {
        return invalidElevationData;
    }

    const int tileZoomLevel = TileLoader::maximumTileLevel( *( d->m_textureLayer ) );
    Q_ASSERT( tileZoomLevel == 9 );

    const int width = d->m_textureLayer->tileSize().width();
    const int height = d->m_textureLayer->tileSize().height();

    const int numTilesX = TileLoaderHelper::levelToColumn( d->m_textureLayer->levelZeroColumns(), tileZoomLevel );
    const int numTilesY = TileLoaderHelper::levelToRow( d->m_textureLayer->levelZeroRows(), tileZoomLevel );
    Q_ASSERT( numTilesX > 0 );
    Q_ASSERT( numTilesY > 0 );

    qreal textureX = 180 + lon;
    textureX *= numTilesX * width / 360;

    qreal textureY = 90 - lat;
    textureY *= numTilesY * height / 180;

    qreal ret = 0;
    bool hasHeight = false;
    qreal noData = 0;

    for ( int i = 0; i < 4; ++i ) {
        const int x = static_cast<int>( textureX + ( i % 2 ) );
        const int y = static_cast<int>( textureY + ( i / 2 ) );

        //mDebug() << "x" << x << ( x / width );
        //mDebug() << "y" << y << ( y / height );

        const TileId id( 0, tileZoomLevel, ( x % ( numTilesX * width ) ) / width, ( y % ( numTilesY * height ) ) / height );
        //mDebug() << "LAT" << lat << "LON" << lon << "tile" << ( x % ( numTilesX * width ) ) / width << ( y % ( numTilesY * height ) ) / height;

        const QImage *image = d->m_cache[id];
        if ( image == nullptr ) {
            image = new QImage( d->m_tileLoader.loadTileImage( d->m_textureLayer, id, DownloadBrowse ) );
            d->m_cache.insert( id, image );
        }
        Q_ASSERT( image );
        Q_ASSERT( !image->isNull() );
        Q_ASSERT( width == image->width() );
        Q_ASSERT( height == image->height() );

        const qreal dx = ( textureX > ( qreal )x ) ? textureX - ( qreal )x : ( qreal )x - textureX;
        const qreal dy = ( textureY > ( qreal )y ) ? textureY - ( qreal )y : ( qreal )y - textureY;

        Q_ASSERT( 0 <= dx && dx <= 1 );
        Q_ASSERT( 0 <= dy && dy <= 1 );
        unsigned int pixel = image->pixel( x % width, y % height ) & 0xffff; // 16 valid bits
        short int elevation = (short int) pixel; // and signed type, so just cast it
        //mDebug() << "(1-dx)" << (1-dx) << "(1-dy)" << (1-dy);
        if ( pixel != invalidElevationData ) { //no data?
            //mDebug() << "got at x" << x % width << "y" << y % height << "a height of" << pixel << "** RGB" << qRed(pixel) << qGreen(pixel) << qBlue(pixel);
            ret += ( qreal )elevation * ( 1 - dx ) * ( 1 - dy );
            hasHeight = true;
        } else {
            //mDebug() << "no data at" <<  x % width << "y" << y % height;
            noData += ( 1 - dx ) * ( 1 - dy );
        }
    }

    if ( !hasHeight ) {
        ret = invalidElevationData; //no data
    } else {
        if ( noData ) {
            //mDebug() << "NO DATA" << noData;
            ret += ( ret / ( 1 - noData ) ) * noData;
        }
    }

    //mDebug() << ">>>" << lat << lon << "returning an elevation of" << ret;
    return ret;
}

QVector<GeoDataCoordinates> ElevationModel::heightProfile( qreal fromLon, qreal fromLat, qreal toLon, qreal toLat ) const
{
    if ( !d->m_textureLayer ) {
        return QVector<GeoDataCoordinates>();
    }

    const int tileZoomLevel = TileLoader::maximumTileLevel( *( d->m_textureLayer ) );
    const int width = d->m_textureLayer->tileSize().width();
    const int numTilesX = TileLoaderHelper::levelToColumn( d->m_textureLayer->levelZeroColumns(), tileZoomLevel );

    qreal distPerPixel = ( qreal )360 / ( width * numTilesX );
    //mDebug() << "heightProfile" << fromLat << fromLon << toLat << toLon << "distPerPixel" << distPerPixel;

    qreal lat = fromLat;
    qreal lon = fromLon;
    char dirLat = fromLat < toLat ? 1 : -1;
    char dirLon = fromLon < toLon ? 1 : -1;
    qreal k = qAbs( ( fromLat - toLat ) / ( fromLon - toLon ) );
    //mDebug() << "fromLon" << fromLon << "fromLat" << fromLat;
    //mDebug() << "diff lon" << ( fromLon - toLon ) << "diff lat" << ( fromLat - toLat );
    //mDebug() << "dirLon" << QString::number(dirLon) << "dirLat" << QString::number(dirLat) << "k" << k;
    QVector<GeoDataCoordinates> ret;
    while ( lat*dirLat <= toLat*dirLat && lon*dirLon <= toLon * dirLon ) {
        //mDebug() << lat << lon;
        qreal h = height( lon, lat );
        if ( h < 32000 ) {
            ret << GeoDataCoordinates( lon, lat, h, GeoDataCoordinates::Degree );
        }
        if ( k < 0.5 ) {
            //mDebug() << "lon(x) += distPerPixel";
            lat += distPerPixel * k * dirLat;
            lon += distPerPixel * dirLon;
        } else {
            //mDebug() << "lat(y) += distPerPixel";
            lat += distPerPixel * dirLat;
            lon += distPerPixel / k * dirLon;
        }
    }
    //mDebug() << ret;
    return ret;
}

}



#include "moc_ElevationModel.cpp"
