#include "DisplaySDL.hpp"

#include <stdexcept>

DisplaySDL::DisplaySDL(int w, int h, uint32_t fgColor, uint32_t bgColor) {
  // Create SDL Window
  mpWindow = SDL_CreateWindow(
    "ChocoChip-8",
    SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
    w, h,
    0
  );
  if(mpWindow == NULL) {
    throw std::runtime_error(SDL_GetError());
  }

  // Convert our foreground/background colors to the format expected by SDL
  SDL_PixelFormat *fmt = SDL_AllocFormat(SDL_GetWindowPixelFormat(mpWindow));
  mFgColor = SDL_MapRGB(
      fmt,
      (fgColor & 0x00FF0000) >> 16,
      (fgColor & 0x0000FF00) >> 8,
      (fgColor & 0x000000FF)
  );
  mBgColor = SDL_MapRGB(
      fmt,
      (bgColor & 0x00FF0000) >> 16,
      (bgColor & 0x0000FF00) >> 8,
      (bgColor & 0x000000FF)
  );
  SDL_FreeFormat(fmt);
};

DisplaySDL::~DisplaySDL() {
  SDL_DestroyWindow(mpWindow);
}

void DisplaySDL::clear() {
  Display::clear();
  SDL_FillRect(SDL_GetWindowSurface(mpWindow), nullptr, mBgColor);
  SDL_UpdateWindowSurface(mpWindow);
  miTopDirtyScanline = chocochip8::gcHeight - 1;
  miBottomDirtyScanline = 0;
}

void DisplaySDL::updateWindow() const {
  if(miTopDirtyScanline > miBottomDirtyScanline) {
    // No changes since the last update
    return;
  }

  SDL_Surface *pSurface = SDL_GetWindowSurface(mpWindow);
  for(int y = 0; y < chocochip8::gcHeight; y++) {
    if(y < miTopDirtyScanline || miBottomDirtyScanline < y) {
      // Skip scanlines that haven't changed since the last update
      continue;
    }

    for(int x = 0; x < chocochip8::gcWidth; x++) {
      // Map framebuffer pixel to SDL surface rectangle
      int x1 = (      x * pSurface->w) / chocochip8::gcWidth;
      int x2 = ((x + 1) * pSurface->w) / chocochip8::gcWidth;
      int y1 = (      y * pSurface->h) / chocochip8::gcHeight;
      int y2 = ((y + 1) * pSurface->h) / chocochip8::gcHeight;
      SDL_Rect rect;
      rect.x = x1;
      rect.y = y1;
      rect.w = x2 - x1;
      rect.h = y2 - y1;

      // Read Chocochip8 Framebuffer and choose appropriate color,
      // note that the MSB of an scanline's bitset is the leftmost pixel.
      Uint32 color = (mpFramebuffer->at(y)[(chocochip8::gcWidth - 1) - x] ? mFgColor : mBgColor);
      SDL_FillRect(pSurface, &rect, color);
    }
  }

  miTopDirtyScanline = chocochip8::gcHeight - 1;
  miBottomDirtyScanline = 0;
  SDL_UpdateWindowSurface(mpWindow);
}