const getNormalizedRangeEndPoint = (direction: number, root: Node, range: Range): CaretPosition => {
  const normalizedRange = normalizeRange(direction, root, range);

  if (direction === -1) {
    return CaretPosition.fromRangeStart(normalizedRange);
  }

  return CaretPosition.fromRangeEnd(normalizedRange);
};

const isAfterInline = (pos: CaretPosition): boolean => {
  const container = pos.container();
  if (!pos || !NodeType.isText(container)) {
    return false;
  }

  // The text nodes may not be normalized, so check the current node and the next one
  return container.data.charAt(pos.offset() - 1) === Zwsp.ZWSP || pos.isAtEnd() && isCaretContainerInline(container.nextSibling);
};

const getChildNodeAtRelativeOffset = (relativeOffset: number, caretPosition: CaretPosition): Node => {
  let container, offset;

  if (!caretPosition) {
    return null;
  }

  container = caretPosition.container();
  offset = caretPosition.offset();

  if (!isElement(container)) {
    return null;
  }

  return container.childNodes[offset + relativeOffset];
};

const getVisualCaretPosition = (walkFn, caretPosition: CaretPosition): CaretPosition => {
  while ((caretPosition = walkFn(caretPosition))) {
    if (caretPosition.isVisible()) {
      return caretPosition;
    }
  }

  return caretPosition;
};

const isMoveInsideSameBlock = (from: CaretPosition, to: CaretPosition): boolean => {
  const inSameBlock = isInSameBlock(from, to);

  // Handle bogus BR <p>abc|<br></p>
  if (!inSameBlock && NodeType.isBr(from.getNode())) {
    return true;
  }

  return inSameBlock;
};

const scrollRangeIntoView = (editor: Editor, rng: Range) => {
  Arr.head(CaretPosition.fromRangeStart(rng).getClientRects()).each((rngRect) => {
    const bodyRect = getViewPortRect(editor);
    const overflow = getOverflow(bodyRect, rngRect);
    const margin = 4;
    const dx = overflow.x > 0 ? overflow.x + margin : overflow.x - margin;
    const dy = overflow.y > 0 ? overflow.y + margin : overflow.y - margin;

    scrollBy(editor, overflow.x !== 0 ? dx : 0, overflow.y !== 0 ? dy : 0);
  });
};

const normalizeSelection = (editor: Editor) => {
  const rng = editor.selection.getRng();
  const startPos = CaretPosition.fromRangeStart(rng);
  const endPos = CaretPosition.fromRangeEnd(rng);

  if (CaretPosition.isElementPosition(startPos)) {
    const container = startPos.container();
    if (isTextBlockNode(container)) {
      CaretFinder.firstPositionIn(container).each((pos) => rng.setStart(pos.container(), pos.offset()));
    }
  }

  if (CaretPosition.isElementPosition(endPos)) {
    const container = startPos.container();
    if (isTextBlockNode(container)) {
      CaretFinder.lastPositionIn(container).each((pos) => rng.setEnd(pos.container(), pos.offset()));
    }
  }

  editor.selection.setRng(RangeNormalizer.normalize(rng));
};

const normalize = (dom: DOMUtils, rng: Range): Option<Range> => {
  const collapsed = rng.collapsed, normRng = rng.cloneRange();
  const startPos = CaretPosition.fromRangeStart(rng);

  normalizeEndPoint(dom, collapsed, true, normRng).each(function (pos) {
    // #TINY-1595: Do not move the caret to previous line
    if (!collapsed || !CaretPosition.isAbove(startPos, pos)) {
      normRng.setStart(pos.container(), pos.offset());
    }
  });

  if (!collapsed) {
    normalizeEndPoint(dom, collapsed, false, normRng).each(function (pos) {
      normRng.setEnd(pos.container(), pos.offset());
    });
  }

  // If it was collapsed then make sure it still is
  if (collapsed) {
    normRng.collapse(true);
  }

  return RangeCompare.isEq(rng, normRng) ? Option.none() : Option.some(normRng);
};

const findClosestPositionInBelowCell = (table: HTMLElement, pos: CaretPosition): Option<CaretPosition> => {
  return Arr.last(pos.getClientRects()).bind((rect) => {
    return getClosestCellBelow(table, rect.left, rect.top);
  }).bind((cell) => findClosestHorizontalPosition(getFirstLinePositions(cell), pos));
};

const isAfterInline = (pos: CaretPosition): boolean => {
  const container = pos.container();
  return pos && NodeType.isText(container) && container.data.charAt(pos.offset() - 1) === Zwsp.ZWSP;
};