/**
 * Stone of Orthanc
 * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
 * Department, University Hospital of Liege, Belgium
 * Copyright (C) 2017-2020 Osimis S.A., Belgium
 *
 * This program is free software: you can redistribute it and/or
 * modify it under the terms of the GNU Affero 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
 * Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 **/


#include "WebAssemblyCairoViewport.h"

#include "../Scene2D/CairoCompositor.h"

#include <Core/Images/Image.h>

namespace OrthancStone
{
  void WebAssemblyCairoViewport::GetCanvasSize(unsigned int& width,
                                               unsigned int& height)
  {
    double w, h;
    emscripten_get_element_css_size(GetCanvasCssSelector().c_str(), &w, &h);

    /**
     * Emscripten has the function emscripten_get_element_css_size()
     * to query the width and height of a named HTML element. I'm
     * calling this first to get the initial size of the canvas DOM
     * element, and then call emscripten_set_canvas_size() to
     * initialize the framebuffer size of the canvas to the same
     * size as its DOM element.
     * https://floooh.github.io/2017/02/22/emsc-html.html
     **/
    if (w > 0 &&
        h > 0)
    {
      width = static_cast<unsigned int>(boost::math::iround(w));
      height = static_cast<unsigned int>(boost::math::iround(h));
    }
    else
    {
      width = 0;
      height = 0;
    }
  }


  void WebAssemblyCairoViewport::Paint(ICompositor& compositor,
                                       ViewportController& controller)
  {
    compositor.Refresh(controller.GetScene());

    // Create a temporary memory buffer for the canvas in JavaScript
    Orthanc::ImageAccessor cairo;
    dynamic_cast<CairoCompositor&>(compositor).GetCanvas().GetReadOnlyAccessor(cairo);

    const unsigned int width = cairo.GetWidth();
    const unsigned int height = cairo.GetHeight();

    if (javascript_.get() == NULL ||
        javascript_->GetWidth() != width ||
        javascript_->GetHeight() != height)
    {
      javascript_.reset(new Orthanc::Image(Orthanc::PixelFormat_RGBA32, width, height,
                                           true /* force minimal pitch */));
    }
      
    // Convert from BGRA32 memory layout (only color mode supported
    // by Cairo, which corresponds to CAIRO_FORMAT_ARGB32) to RGBA32
    // (as expected by HTML5 canvas). This simply amounts to
    // swapping the B and R channels. Alpha channel is also set to
    // full opacity (255).
    uint8_t* q = reinterpret_cast<uint8_t*>(javascript_->GetBuffer());
    for (unsigned int y = 0; y < height; y++)
    {
      const uint8_t* p = reinterpret_cast<const uint8_t*>(cairo.GetConstRow(y));
      for (unsigned int x = 0; x < width; x++)
      {
        q[0] = p[2];  // R
        q[1] = p[1];  // G
        q[2] = p[0];  // B
        q[3] = 255;   // A

        p += 4;
        q += 4;
      }
    }

    // Execute JavaScript commands to blit the image buffer onto the
    // 2D drawing context of the HTML5 canvas
    EM_ASM({
        const data = new Uint8ClampedArray(Module.HEAP8.buffer, $1, 4 * $2 * $3);
        const img = new ImageData(data, $2, $3);
        const ctx = document.getElementById(UTF8ToString($0)).getContext('2d');
        ctx.putImageData(img, 0, 0);
      },
      GetCanvasId().c_str(), // $0
      javascript_->GetBuffer(),   // $1
      javascript_->GetWidth(),    // $2
      javascript_->GetHeight());  // $3
  }
    

  void WebAssemblyCairoViewport::UpdateSize(ICompositor& compositor)
  {
    unsigned int width, height;
    GetCanvasSize(width, height);
    emscripten_set_canvas_element_size(GetCanvasCssSelector().c_str(), width, height);

    dynamic_cast<CairoCompositor&>(compositor).UpdateSize(width, height);
  }


  WebAssemblyCairoViewport::WebAssemblyCairoViewport(
    const std::string& canvasId) :
    WebAssemblyViewport(canvasId)
  {
    unsigned int width, height;
    GetCanvasSize(width, height);
    emscripten_set_canvas_element_size(GetCanvasCssSelector().c_str(), 
                                       width, 
                                       height);

    AcquireCompositor(new CairoCompositor(width, height));
  }
}