/* -*-c++-*- */
/* osgEarth - Geospatial SDK for OpenSceneGraph
 * Copyright 2020 Pelican Mapping
 * http://osgearth.org
 *
 * osgEarth 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 of the License, or
 * (at your option) any later version.
 *
 * This program 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 program.  If not, see <http://www.gnu.org/licenses/>
 */

#ifndef OSGEARTH_TILE_KEY_H
#define OSGEARTH_TILE_KEY_H 1

#include <osgEarth/Common>
#include <osgEarth/Profile>
#include <osg/ref_ptr>
#include <osg/Version>
#include <string>

namespace osgEarth
{
    /**
     * Uniquely identifies a single tile on the map, relative to a Profile.
     * Profiles have an origin of 0,0 at the top left.
     */
    class OSGEARTH_EXPORT TileKey
    {
    public:     
        /**
         * Constructs an invalid TileKey.
         */
        TileKey() : _lod(0), _x(0), _y(0), _hash(0) { }

        /**
         * Creates a new TileKey with the given tile xy at the specified level of detail
         * 
         * @param lod
         *       The level of detail (subdivision recursion level) of the tile
         * @param tile_x
         *       The x index of the tile
         * @param tile_y
         *       The y index of the tile
         * @param profile
         *       The profile for the tile
         */
        TileKey(
            unsigned int lod,
            unsigned int tile_x,
            unsigned int tile_y,
            const Profile* profile );

        /** Copy constructor. */
        TileKey( const TileKey& rhs );

        /** dtor */
        virtual ~TileKey() { }

        /** Compare two tilekeys for equality. */
        inline bool operator == (const TileKey& rhs) const {
            return
                valid() == rhs.valid() &&
                _lod == rhs._lod &&
                _x == rhs._x &&
                _y == rhs._y &&
                (_profile.valid() ? _profile->isHorizEquivalentTo(rhs._profile.get()) : true);
        }

        /** Compare two tilekeys for inequality */
        inline bool operator != (const TileKey& rhs) const {
            return
                valid() != rhs.valid() ||
                _lod != rhs._lod ||
                _x != rhs._x ||
                _y != rhs._y ||
                (_profile.valid() ? !_profile->isEquivalentTo(rhs._profile.get()) : false);
        }

        /** Sorts tilekeys, ignoring profiles */
        inline bool operator < (const TileKey& rhs) const {
            if (!rhs.valid()) return false;
            if (!valid()) return true;
            if (_lod < rhs._lod) return true;
            if (_lod > rhs._lod) return false;
            if (_x < rhs._x) return true;
            if (_x > rhs._x) return false;
            if (_y < rhs._y) return true;
            if (_y > rhs._y) return false;
            return _profile->getHorizSignature() < rhs._profile->getHorizSignature();
        }

        /**
         * Canonical invalid tile key.
         */
        static TileKey INVALID;

        /**
         * Gets the string representation of the key, formatted like:
         * "lod_x_y"
         */
        const std::string str() const;

        /**
         * Gets the profile within which this key is interpreted.
         */
        const osgEarth::Profile* getProfile() const;

        /**
         * Whether this is a valid key.
         */
        bool valid() const { return _profile.valid(); }

        /**
         * Get the quadrant relative to this key's parent.
         */
        unsigned getQuadrant() const;

        /**
         * Gets a reference to the child key of this key in the specified
         * quadrant (0, 1, 2, or 3).
         */
        TileKey createChildKey( unsigned int quadrant ) const;

        /**
         * Creates and returns a key that represents the parent tile of this key.
         */
        TileKey createParentKey() const;

        //! Convert this key to its parent
        //! @return true upon success, false if invalid
        bool makeParent();

        /**
         * Creates and returns a key that represents an ancestor tile corresponding to
         * the specified LOD.
         */
        TileKey createAncestorKey( int ancestorLod ) const;

        /**
         * Creates a key that represents this tile's neighbor at the same LOD. Wraps
         * around in X and Y automatically. For example, xoffset=-1 yoffset=1 will
         * give you the key for the tile SW of this tile.
         */
        TileKey createNeighborKey( int xoffset, int yoffset ) const;

        /**
         * Gets the level of detail of the tile represented by this key.
         */
        unsigned getLevelOfDetail() const { return _lod; }
        unsigned getLOD() const { return _lod; }

        /**
         * Gets the geospatial extents of the tile represented by this key.
         */
        const GeoExtent getExtent() const;

        /**
         * Gets the extents of this key's tile, in pixels
         */
        void getPixelExtents(
            unsigned int& out_minx,
            unsigned int& out_miny,
            unsigned int& out_maxx,
            unsigned int& out_maxy,
            const unsigned int& tile_size) const;

        /**
         * Gets the X and Y indexes of this tile at its level of detail.
         */
        void getTileXY(
            unsigned int& out_tile_x,
            unsigned int& out_tile_y) const;

        unsigned int getTileX() const { return _x; }
        unsigned int getTileY() const { return _y; }

        /**
         * Maps this tile key to another tile key in order to account in
         * a resolution difference. For example: we are requesting data for
         * a TileKey at LOD 4, at a tile size of 32. The source data's tile
         * size if 256. That means the source data at LOD 1 will contain the
         * data necessary to build the tile.
         *
         *   usage: TileKey tk = mapResolution(31, 256);
         *
         * We want a 31x31 tile. The source data is 256x256. This will return
         * a TileKey that access the appropriate source data, which we will then
         * need to crop to populate our tile.
         *
         * You can set "minimumLOD" if you don't want a key below a certain LOD.
         */
        TileKey mapResolution(
            unsigned targetSize,
            unsigned sourceDataSize,
            unsigned minimumLOD =0) const;

        //! X and Y resolution (in profile units) for the given tile size
        std::pair<double,double> getResolution(
            unsigned tileSize) const;

        //! Convenience method to match this key.
        bool is(unsigned lod, unsigned x, unsigned y) const {
            return _lod == lod && _x == x && _y == y;
        }

    protected:
        unsigned int _lod;
        unsigned int _x;
        unsigned int _y;
        osg::ref_ptr<const Profile> _profile;
        size_t _hash;
        void rehash();

    public:
        size_t hash() const { return _hash; }
    };
}

namespace std {
    // std::hash specialization for TileKey
    template<> struct hash<osgEarth::TileKey> {
        inline size_t operator()(const osgEarth::TileKey& value) const {
            return value.hash();
        }
    };
}

#endif // OSGEARTH_TILE_KEY_H