const isMissingPositionColumn = (error) =>
  error &&
  error.code === "ER_BAD_FIELD_ERROR" &&
  String(error.sqlMessage || "").includes("position");

const moveByPosition = async ({
  db,
  table,
  id,
  direction,
  selectQuery,
  missingColumnMessage,
  notFoundMessage,
}) => {
  if (direction !== "up" && direction !== "down") {
    return { status: 400, body: { error: "Ungueltige Richtung" } };
  }

  let rows;

  try {
    await db.query(
      `UPDATE ${table} SET position = id WHERE position IS NULL`
    );

    ;[rows] = await db.query(selectQuery);
  } catch (error) {
    if (isMissingPositionColumn(error)) {
      return { status: 400, body: { error: missingColumnMessage } };
    }

    throw error;
  }

  const index = rows.findIndex((row) => row.id == id);

  if (index === -1) {
    return { status: 404, body: { error: notFoundMessage } };
  }

  const swapIndex = direction === "up" ? index - 1 : index + 1;

  if (swapIndex < 0 || swapIndex >= rows.length) {
    return { status: 200, body: { success: true } };
  }

  const moved = rows.splice(index, 1)[0];
  rows.splice(swapIndex, 0, moved);

  for (let i = 0; i < rows.length; i++) {
    await db.query(
      `UPDATE ${table} SET position = ? WHERE id = ?`,
      [i + 1, rows[i].id]
    );
  }

  return { status: 200, body: { success: true } };
};

module.exports = {
  moveByPosition,
  isMissingPositionColumn,
};