// * This file is part of the COLOBOT source code
// * Copyright (C) 2012, Polish Portal of Colobot (PPC)
// *
// * This program is free software: you can redistribute it and/or modify
// * it under the terms of the GNU General Public License as published by
// * the Free Software Foundation, either version 3 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 General Public License for more details.
// *
// * You should have received a copy of the GNU General Public License
// * along with this program. If not, see  http://www.gnu.org/licenses/.

/**
 * \file graphics/core/texture.h
 * \brief Texture struct and related enums
 */

#pragma once


#include "math/intpoint.h"


// Graphics module namespace
namespace Gfx {

/**
 * \enum TexImgFormat
 * \brief Format of image data
 */
enum TexImgFormat
{
    //! Try to determine automatically (may not work)
    TEX_IMG_AUTO,
    //! RGB triplet, 3 bytes
    TEX_IMG_RGB,
    //! BGR triplet, 3 bytes
    TEX_IMG_BGR,
    //! RGBA triplet, 4 bytes
    TEX_IMG_RGBA,
    //! BGRA triplet, 4 bytes
    TEX_IMG_BGRA
};

/**
 * \enum TexMinFilter
 * \brief Texture minification filter
 *
 * Corresponds to OpenGL modes but should translate to DirectX too.
 */
enum TexMinFilter
{
    TEX_MIN_FILTER_NEAREST,
    TEX_MIN_FILTER_LINEAR,
    TEX_MIN_FILTER_NEAREST_MIPMAP_NEAREST,
    TEX_MIN_FILTER_LINEAR_MIPMAP_NEAREST,
    TEX_MIN_FILTER_NEAREST_MIPMAP_LINEAR,
    TEX_MIN_FILTER_LINEAR_MIPMAP_LINEAR
};

/**
 * \enum TexMagFilter
 * \brief Texture magnification filter
 */
enum TexMagFilter
{
    TEX_MAG_FILTER_NEAREST,
    TEX_MAG_FILTER_LINEAR
};

/**
 * \enum TexWrapMode
 * \brief Wrapping mode for texture coords
 */
enum TexWrapMode
{
    TEX_WRAP_CLAMP,
    TEX_WRAP_REPEAT
};

/**
 * \enum TexMixOperation
 * \brief Multitexture mixing operation
 */
enum TexMixOperation
{
    //! Default operation on default params (modulate on computed & texture)
    TEX_MIX_OPER_DEFAULT,
    //! = Arg1
    TEX_MIX_OPER_REPLACE,
    //! = Arg1 * Arg2
    TEX_MIX_OPER_MODULATE,
    //! = Arg1 + Arg2
    TEX_MIX_OPER_ADD,
    //! = Arg1 - Arg2
    TEX_MIX_OPER_SUBTRACT
};

/**
 * \enum TexMixArgument
 * \brief Multitexture mixing argument
 */
enum TexMixArgument
{
    //! Color from current texture
    TEX_MIX_ARG_TEXTURE,
    //! Color computed by previous texture unit (current in DirectX; previous in OpenGL)
    TEX_MIX_ARG_COMPUTED_COLOR,
    //! (Source) color of textured fragment (diffuse in DirectX; primary color in OpenGL)
    TEX_MIX_ARG_SRC_COLOR,
    //! Constant color (texture factor in DirectX; texture env color in OpenGL)
    TEX_MIX_ARG_FACTOR
};

/**
  \struct TextureCreateParams
  \brief Parameters for texture creation

  These params define how particular texture is created and later displayed.
  They must be specified at texture creation time and cannot be changed later. */
struct TextureCreateParams
{
    //! Whether to generate mipmaps
    bool mipmap;
    //! Format of source image data
    TexImgFormat format;
    //! Minification filter
    TexMinFilter minFilter;
    //! Magnification filter
    TexMagFilter magFilter;

    //! Constructor; calls LoadDefault()
    TextureCreateParams()
        { LoadDefault(); }

    //! Loads the default values
    inline void LoadDefault()
    {
        format = TEX_IMG_RGB;
        mipmap = false;

        minFilter = TEX_MIN_FILTER_NEAREST;
        magFilter = TEX_MAG_FILTER_NEAREST;
    }
};

/**
  \struct TextureStageParams
  \brief Parameters for a texture unit

  These params define the behavior of texturing units (stages).
  They can be changed freely and are feature of graphics engine, not any particular texture. */
struct TextureStageParams
{
    //! Mixing operation done on color values
    TexMixOperation colorOperation;
    //! 1st argument of color operations
    TexMixArgument colorArg1;
    //! 2nd argument of color operations
    TexMixArgument colorArg2;
    //! Mixing operation done on alpha values
    TexMixOperation alphaOperation;
    //! 1st argument of alpha operations
    TexMixArgument alphaArg1;
    //! 2nd argument of alpha operations
    TexMixArgument alphaArg2;
    //! Wrap mode for 1st tex coord
    TexWrapMode    wrapS;
    //! Wrap mode for 2nd tex coord
    TexWrapMode    wrapT;

    //! Constructor; calls LoadDefault()
    TextureStageParams()
        { LoadDefault(); }

    //! Loads the default values
    inline void LoadDefault()
    {
        colorOperation = TEX_MIX_OPER_DEFAULT;
        colorArg1 = TEX_MIX_ARG_COMPUTED_COLOR;
        colorArg2 = TEX_MIX_ARG_TEXTURE;

        alphaOperation = TEX_MIX_OPER_DEFAULT;
        alphaArg1 = TEX_MIX_ARG_COMPUTED_COLOR;
        alphaArg2 = TEX_MIX_ARG_TEXTURE;

        wrapS = wrapT = TEX_WRAP_REPEAT;
    }
};

/**
  \struct Texture
  \brief Info about a texture

  Identifies (through id) a texture created in graphics engine.
  Also contains some additional data. */
struct Texture
{
    //! ID of the texture in graphics engine; 0 = invalid texture
    unsigned int id;
    //! Size of texture
    Math::IntPoint size;
    //! Whether the texture has alpha channel
    bool alpha;

    Texture()
    {
        id = 0;
        alpha = false;
    }

    //! Returns whether the texture is valid (ID != 0)
    bool Valid() const
    {
        return id != 0;
    }

    //! Sets the ID to invalid value (0)
    void SetInvalid()
    {
        id = 0;
    }

    //! Comparator for use in texture maps and sets
    inline bool operator<(const Texture &other) const
    {
        // Invalid textures are always "less than" every other texture

        if ( (! Valid()) && (! other.Valid()) )
            return false;

        if (! Valid())
            return true;

        if (! other.Valid())
            return false;

        return id < other.id;
    }

    //! Comparator
    inline bool operator==(const Texture &other) const
    {
        if (Valid() != other.Valid())
            return false;
        if ( (! Valid()) && (! other.Valid()) )
            return true;

        return id == other.id;
    }
};


} // namespace Gfx