#include "DisplaySDL.hpp"
#include "Peripherals.hpp"

#include <SDL2/SDL_surface.h>
#include <stdexcept>

DisplaySDL::DisplaySDL(int w, int h, uint32_t fgColor, uint32_t bgColor):
  mpFramebuffer{std::make_unique<Framebuffer>()},
  mpDisplayState{std::make_unique<Framebuffer>()},
  mDoClear{true} {
  // 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() {
  for(auto &scanline : *mpFramebuffer) {
    scanline.reset();
  }
  mDoClear = true;
}

int DisplaySDL::blit(const chocochip8::Scanline &spriteScanline, int y) {
  using chocochip8::Scanline;
  Scanline &targetScanline = mpFramebuffer->at(y);
  bool collision = (spriteScanline & targetScanline).any();
  targetScanline ^= spriteScanline;
  return collision;
}

void DisplaySDL::updateWindow(bool doWindowUpdate) const {
  using chocochip8::Scanline;
  SDL_Surface *pSurface = SDL_GetWindowSurface(mpWindow);
  if(mDoClear) {
    for(auto &scanline : *mpDisplayState) {
      scanline.reset();
    }
    SDL_FillRect(pSurface, NULL, mBgColor);
    mDoClear = false;
    doWindowUpdate = true;
  }

  for(int y = 0; y < mpFramebuffer->size(); y++) {
    Scanline &rNewScanline = (*mpFramebuffer)[y];
    Scanline &rOldScanline = (*mpDisplayState)[y];
    if(rNewScanline == rOldScanline) {
      // Skip scanlines that haven't changed since the last update
      continue;
    }

    for(int x = 0; x < rNewScanline.size(); x++) {
      bool isSet = rNewScanline._Unchecked_test(x);
      bool wasSet = rOldScanline._Unchecked_test(x);
      if(isSet == wasSet) {
        continue;
      }

      // Map framebuffer pixel to SDL surface rectangle,
      // note that the MSB of an scanline's bitset is the leftmost pixel.
      int z = (chocochip8::gcWidth - 1) - x;
      int x1 = (      z * pSurface->w) / chocochip8::gcWidth;
      int x2 = ((z + 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;

      Uint32 color = (isSet ? mFgColor : mBgColor);
      SDL_FillRect(pSurface, &rect, color);
      doWindowUpdate = true;
    }
  }

  if(doWindowUpdate) {
    *mpDisplayState = *mpFramebuffer;
    SDL_UpdateWindowSurface(mpWindow);
  }
}