/****************************************************************************

    AstroMenace
    Hardcore 3D space scroll-shooter with spaceship upgrade possibilities.
    Copyright (c) 2006-2019 Mikhail Kurinnoi, Viewizard


    AstroMenace 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.

    AstroMenace 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 AstroMenace. If not, see <https://www.gnu.org/licenses/>.


    Website: https://viewizard.com/
    Project: https://github.com/viewizard/astromenace
    E-mail: viewizard@viewizard.com

*****************************************************************************/

// NOTE GL_EXT_direct_state_access (since OpenGL 4.5)
//      glGetTextureLevelParameterfv()
//      could be used to replace glGetTexLevelParameterfv()

#include "../math/math.h"
#include "../texture/texture.h"
#include "graphics.h"

namespace viewizard {

namespace {

float DrawBuffer[16]; // RI_2f_XY | RI_2f_TEX = (2 + 2) * 4 vertices = 16
unsigned int DrawBufferCurrentPosition{0};

} // unnamed namespace


/*
 * Switch to 2D rendering mode. Origin is upper left corner.
 */
void vw_Start2DMode(GLdouble zNear, GLdouble zFar)
{
    glPushAttrib(GL_ENABLE_BIT);
    glDisable(GL_CULL_FACE);
    glDisable(GL_DEPTH_TEST);

    // get current viewport start point and size
    float tmpViewportX, tmpViewportY, tmpViewportWidth, tmpViewportHeight;
    vw_GetViewport(&tmpViewportX, &tmpViewportY, &tmpViewportWidth, &tmpViewportHeight);

    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();

    float tmpInternalWidth{0.0f};
    float tmpInternalHeight{0.0f};

    // care about fixed internal resolution, that could be setted up
    // change origin to upper left corner
    if (vw_GetInternalResolution(&tmpInternalWidth, &tmpInternalHeight)) {
        glOrtho(tmpViewportX * tmpInternalWidth / tmpViewportWidth,
                (tmpViewportX + tmpViewportWidth) * tmpInternalWidth / tmpViewportWidth,
                (tmpViewportY + tmpViewportHeight) * tmpInternalHeight / tmpViewportHeight,
                tmpViewportY * tmpInternalHeight / tmpViewportHeight,
                zNear, zFar);
    } else {
        glOrtho(0, tmpViewportWidth, tmpViewportHeight, 0, zNear, zFar);
    }

    // change textures origin to upper left corner
    vw_SelectActiveTextureUnit(0); // switch to 0 unit, for proper texture matrix
    glMatrixMode(GL_TEXTURE);
    glPushMatrix();
    glLoadIdentity();
    glScalef(1.0, -1.0, 1.0);
    glTranslatef(0.0f, -1.0f, 0.0f);

    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glLoadIdentity();
}

/*
 * Switch back to 3D rendering mode.
 * Restore matrices and attributes in reverse to vw_Start2DMode() sequence.
 */
void vw_End2DMode()
{
    // we don't switch to 0 unit, in 2D mode only 0 unit should be used
    glMatrixMode(GL_TEXTURE);
    glPopMatrix();

    glMatrixMode(GL_PROJECTION);
    glPopMatrix();

    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();

    glPopAttrib();
}

/*
 * Add data to local draw buffer.
 */
static inline void AddToDrawBuffer(float CoordX, float CoordY, float TextureU, float TextureV)
{
    DrawBuffer[DrawBufferCurrentPosition++] = CoordX;
    DrawBuffer[DrawBufferCurrentPosition++] = CoordY;
    DrawBuffer[DrawBufferCurrentPosition++] = TextureU;
    DrawBuffer[DrawBufferCurrentPosition++] = TextureV;
}

/*
 * Draw transparent. Origin is upper left corner.
 */
void vw_Draw2D(const sRECT &DstRect, const sRECT &SrcRect, GLtexture Texture, bool Alpha,
               float Transp, float RotateAngle, const sRGBCOLOR &Color)
{
    if (!Texture || Transp <= 0.0f) {
        return;
    }

    // bind texture before glGetTexLevelParameterfv() call
    vw_BindTexture(0, Texture);

    float ImageHeight{0.0f};
    float ImageWidth{0.0f};
    // if texture loaded via textures manager, get data from it
    if (!vw_FindTextureSizeByID(Texture, &ImageWidth, &ImageHeight)) {
        // get Width and Height for 0 mipmap level
        // call glGetTexLevelParameterfv() is generally not recommended,
        // since it could stall the OpenGL pipeline
        glGetTexLevelParameterfv(GL_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &ImageWidth);
        glGetTexLevelParameterfv(GL_TEXTURE_2D, 0, GL_TEXTURE_HEIGHT, &ImageHeight);
    }
    if (!ImageHeight || !ImageWidth) {
        std::cerr << __func__ << "(): " << "zero image height or width not allowed.\n";
        return;
    }

    // texture's UV coordinates
    // WARNING performance issue, remove conversion (blocked by sRECT)
    float U_left = static_cast<float>(SrcRect.left) / ImageWidth;
    float V_top = static_cast<float>(SrcRect.top) / ImageHeight;
    float U_right = static_cast<float>(SrcRect.right) / ImageWidth;
    float V_bottom = static_cast<float>(SrcRect.bottom) / ImageHeight;

    // 'reset' buffer
    DrawBufferCurrentPosition = 0;

    // TRIANGLE_STRIP (2 triangles)
    // WARNING performance issue, remove conversion (blocked by sRECT)
    AddToDrawBuffer(static_cast<float>(DstRect.left), static_cast<float>(DstRect.top), U_left, V_top);
    AddToDrawBuffer(static_cast<float>(DstRect.left), static_cast<float>(DstRect.bottom), U_left, V_bottom);
    AddToDrawBuffer(static_cast<float>(DstRect.right), static_cast<float>(DstRect.top), U_right, V_top);
    AddToDrawBuffer(static_cast<float>(DstRect.right), static_cast<float>(DstRect.bottom), U_right, V_bottom);

    // setup OpenGL
    vw_SetTextureBlend(Alpha, eTextureBlendFactor::SRC_ALPHA, eTextureBlendFactor::ONE_MINUS_SRC_ALPHA);
    vw_Clamp(Transp, 0.0f, 1.0f);
    vw_SetColor(Color.r, Color.g, Color.b, Transp);
    glPushMatrix();
    glRotatef(RotateAngle, 0, 0, 1);

    vw_Draw3D(ePrimitiveType::TRIANGLE_STRIP, 4, RI_2f_XY | RI_1_TEX, DrawBuffer, 4 * sizeof(DrawBuffer[0]));

    // restore previous OpenGL states
    glPopMatrix();
    vw_SetTextureBlend(false, eTextureBlendFactor::ONE, eTextureBlendFactor::ZERO);
    vw_SetColor(1.0f, 1.0f, 1.0f, 1.0f);
    vw_BindTexture(0, 0);
}

} // viewizard namespace
