pagination-args.ts

export interface PaginationArgs {
  cursorName?: string;
  cursor?: number;
  forward?: number;
  backward?: number;
  skipPage?: number;
}

export const loadNewPageArgs = (
  totalPage: number,
  rowsPerPage: number,
  cursorName: string,
  pageStart: number,
  pageEnd: number,
  currentPage: number,
  newPage: number,
): PaginationArgs => {
  const firstPage = newPage === 1;
  const lastPage = newPage === totalPage;

  const pageOffset = newPage - currentPage;
  const skipPage = Math.abs(pageOffset) - 1;

  let direction = 'forward';
  if ((!firstPage && pageOffset < 0) || lastPage) {
    direction = 'backward';
  }

  let requestArgs = {};
  if (direction === 'forward') {
    // forward
    requestArgs = {
      forward: rowsPerPage,
    };

    if (!firstPage) {
      requestArgs = {
        ...requestArgs,
        cursorName,
        cursor: pageEnd,
      };
    }
  } else {
    // backward
    requestArgs = {
      backward: rowsPerPage,
    };

    if (!lastPage) {
      requestArgs = {
        ...requestArgs,
        cursorName,
        cursor: pageStart,
      };
    }
  }

  if (skipPage && !firstPage && !lastPage)
    requestArgs = { ...requestArgs, skipPage };

  return requestArgs;
};