Handlebars.registerHelper('pagination', function(currentPage, totalPage, size, options) {
  var startPage, endPage, context;

  if (arguments.length === 3) {
    options = size;
    size = 5;
  }

  startPage = currentPage - Math.floor(size / 2);
  endPage = currentPage + Math.floor(size / 2);

  if (startPage <= 0) {
    endPage -= (startPage - 1);
    startPage = 1;
  }

  if (endPage > totalPage) {
    endPage = totalPage;
    if (endPage - size + 1 > 0) {
      startPage = endPage - size + 1;
    } else {
      startPage = 1;
    }
  }

  context = {
    startFromFirstPage: false,
    pages: [],
    endAtLastPage: false,
  };
  if (startPage === 1) {
    context.startFromFirstPage = true;
  }
  for (var i = startPage; i <= endPage; i++) {
    context.pages.push({
      page: i,
      isCurrent: i === currentPage,
    });
  }
  if (endPage === totalPage) {
    context.endAtLastPage = true;
  }

  return options.fn(context);
});