#ifndef COMPONENTS_TERRAIN_STORAGE_H
#define COMPONENTS_TERRAIN_STORAGE_H

#include <vector>

#include <osg/Array>
#include <osg/Vec2f>
#include <osg/Vec3f>
#include <osg/ref_ptr>

#include <components/esm/exteriorcelllocation.hpp>
#include <components/esm/refid.hpp>

#include "defs.hpp"

namespace osg
{
    class Image;
}

namespace Terrain
{
    /// We keep storage of terrain data abstract here since we need different implementations for game and editor
    /// @note The implementation must be thread safe.
    class Storage
    {
    public:
        virtual ~Storage() {}

    public:
        /// Get bounds of the whole terrain in cell units
        virtual void getBounds(float& minX, float& maxX, float& minY, float& maxY, ESM::RefId worldspace) = 0;

        /// Return true if there is land data for this cell
        /// May be overriden for a faster implementation
        virtual bool hasData(ESM::ExteriorCellLocation cellLocation)
        {
            float dummy;
            return getMinMaxHeights(
                1, osg::Vec2f(cellLocation.mX + 0.5, cellLocation.mY + 0.5), cellLocation.mWorldspace, dummy, dummy);
        }

        /// Get the minimum and maximum heights of a terrain region.
        /// @note Will only be called for chunks with size = minBatchSize, i.e. leafs of the quad tree.
        ///        Larger chunks can simply merge AABB of children.
        /// @param size size of the chunk in cell units
        /// @param center center of the chunk in cell units
        /// @param min min height will be stored here
        /// @param max max height will be stored here
        /// @return true if there was data available for this terrain chunk
        virtual bool getMinMaxHeights(
            float size, const osg::Vec2f& center, ESM::RefId worldspace, float& min, float& max)
            = 0;

        /// Fill vertex buffers for a terrain chunk.
        /// @note May be called from background threads. Make sure to only call thread-safe functions from here!
        /// @note returned colors need to be in render-system specific format! Use RenderSystem::convertColourValue.
        /// @note Vertices should be written in row-major order (a row is defined as parallel to the x-axis).
        ///       The specified positions should be in local space, i.e. relative to the center of the terrain chunk.
        /// @param lodLevel LOD level, 0 = most detailed
        /// @param size size of the terrain chunk in cell units
        /// @param center center of the chunk in cell units
        /// @param positions buffer to write vertices
        /// @param normals buffer to write vertex normals
        /// @param colours buffer to write vertex colours
        virtual void fillVertexBuffers(int lodLevel, float size, const osg::Vec2f& center, ESM::RefId worldspace,
            osg::Vec3Array& positions, osg::Vec3Array& normals, osg::Vec4ubArray& colours)
            = 0;

        typedef std::vector<osg::ref_ptr<osg::Image>> ImageVector;
        /// Create textures holding layer blend values for a terrain chunk.
        /// @note The terrain chunk shouldn't be larger than one cell since otherwise we might
        ///       have to do a ridiculous amount of different layers. For larger chunks, composite maps should be used.
        /// @note May be called from background threads. Make sure to only call thread-safe functions from here!
        /// @param chunkSize size of the terrain chunk in cell units
        /// @param chunkCenter center of the chunk in cell units
        /// @param blendmaps created blendmaps will be written here
        /// @param layerList names of the layer textures used will be written here
        virtual void getBlendmaps(float chunkSize, const osg::Vec2f& chunkCenter, ImageVector& blendmaps,
            std::vector<LayerInfo>& layerList, ESM::RefId worldspace)
            = 0;

        virtual float getHeightAt(const osg::Vec3f& worldPos, ESM::RefId worldspace) = 0;

        /// Get the transformation factor for mapping cell units to world units.
        virtual float getCellWorldSize(ESM::RefId worldspace) = 0;

        /// Get the number of vertices on one side for each cell. Should be (power of two)+1
        virtual int getCellVertices(ESM::RefId worldspace) = 0;

        virtual int getBlendmapScale(float chunkSize) = 0;
    };

}

#endif
