postland/lib/postland_web/controllers/export_controller.ex

defmodule PostlandWeb.ExportController do
  use PostlandWeb, :controller

  def export(conn, _params) do
    db_path = Postland.Repo.config() |> Keyword.get(:database)
    dirname = Path.dirname(db_path)
    filename = Path.basename(db_path)

    files = [filename, "#{filename}-shm", "#{filename}-wal"] |> Enum.map(&String.to_charlist/1)
    zip_path = Path.join([File.cwd!(), "priv", "tmp", "db-export.zip"])

    :zip.create(String.to_charlist(zip_path), files, cwd: dirname)

    send_download(conn, {:file, zip_path}, filename: "db-export.zip")
  end
end