#include <assert.h>
#include <kandinsky/context.h>
#include <kandinsky/font.h>
#include <ion/unicode/utf8_decoder.h>
#include <ion/display.h>

constexpr static int k_tabCharacterWidth = 4;

KDPoint KDContext::drawString(const char * text, KDPoint p, const KDFont * font, KDColor textColor, KDColor backgroundColor, int maxByteLength) {
  return pushOrPullString(text, p, font, textColor, backgroundColor, maxByteLength, true);
}

int KDContext::checkDrawnString(const char * text, KDPoint p, const KDFont * font, KDColor textColor, KDColor backgroundColor, int maxLength) {
  int numberOfFailedPixels = 0;
  pushOrPullString(text, p, font, textColor, backgroundColor, maxLength, false, &numberOfFailedPixels);
  return numberOfFailedPixels;
}

KDPoint KDContext::pushOrPullString(const char * text, KDPoint p, const KDFont * font, KDColor textColor, KDColor backgroundColor, int maxByteLength, bool push, int * result) {
  KDPoint position = p;
  KDSize glyphSize = font->glyphSize();
  KDFont::RenderPalette palette = font->renderPalette(textColor, backgroundColor);
  KDFont::GlyphBuffer glyphBuffer;

  UTF8Decoder decoder(text);
  const char * codePointPointer = decoder.stringPosition();
  CodePoint codePoint = decoder.nextCodePoint();
  while (codePoint != UCodePointNull && (maxByteLength < 0 || codePointPointer < text + maxByteLength)) {
    codePointPointer = decoder.stringPosition();
    if (codePoint == UCodePointLineFeed) {
      position = KDPoint(0, position.y() + glyphSize.height());
      codePoint = decoder.nextCodePoint();
    } else if (codePoint == UCodePointTabulation) {
      position = position.translatedBy(KDPoint(k_tabCharacterWidth * glyphSize.width(), 0));
      codePoint = decoder.nextCodePoint();
    } else {
      assert(!codePoint.isCombining());
      font->setGlyphGreyscalesForCodePoint(codePoint, &glyphBuffer);
      codePoint = decoder.nextCodePoint();
      while (codePoint.isCombining()) {
        font->accumulateGlyphGreyscalesForCodePoint(codePoint, &glyphBuffer);
        codePointPointer = decoder.stringPosition();
        codePoint = decoder.nextCodePoint();
      }
      font->colorizeGlyphBuffer(&palette, &glyphBuffer);
      if (push) {
        // Push the character on the screen
        fillRectWithPixels(
            KDRect(position, glyphSize),
            glyphBuffer.colorBuffer(),
            glyphBuffer.colorBuffer() // It's OK to trash the content of the color buffer since we'll re-fetch it for the next char anyway
            );
      } else {
        // Pull and compare the character from the screen
        assert(result != nullptr);
        *result = 0;
        KDFont::GlyphBuffer workingGlyphBuffer;
        KDColor * workingColorBuffer = workingGlyphBuffer.colorBuffer();
        KDColor * colorBuffer = glyphBuffer.colorBuffer();
        for (int i = 0; i < glyphSize.height() * glyphSize.width(); i++) {
          workingColorBuffer[i] = KDColorRed;
        }
        /* Caution: Unlike fillRectWithPixels, pullRect accesses outside (0, 0,
         * Ion::Display::Width, Ion::Display::Height) might give weird data. */
        Ion::Display::pullRect(KDRect(position, glyphSize), workingColorBuffer);
        for (int k = 0; k < glyphSize.height() * glyphSize.width(); k++) {
          if (colorBuffer[k] != workingColorBuffer[k]) {
            *result = (*result)+1;
            break;
          }
        }
      }
      position = position.translatedBy(KDPoint(glyphSize.width(), 0));
    }
  }

  return position;
}