defmodule Tz.WatchPeriodically do
@moduledoc """
A process watching for IANA data updates periodically.
"""
use GenServer
require Logger
alias Tz.HTTP
alias Tz.PeriodsProvider
alias Tz.Updater
# Logger.warn/1 is deprecated on Elixir 1.15 but since its
# a macro we can replace it without performance penalty by
# selecting the available Logger macro at compile time.
defmacrop logger_warning(message) do
if Code.ensure_loaded?(Logger) && function_exported?(Logger, :"MACRO-warning", 2) do
quote do
Logger.warning(unquote(message))
end
else
quote do
Logger.warn(unquote(message))
end
end
end
defp watch(on_update_callback) do
Logger.debug("Tz is checking for IANA time zone database updates")
case Updater.fetch_latest_iana_tz_version() do
{:ok, latest_version} ->
if latest_version != PeriodsProvider.iana_version() do
link = "https://data.iana.org/time-zones/releases/tzdata#{latest_version}.tar.gz"
logger_warning("Tz found a more recent time zone database available for download at #{link}")
on_update_callback && on_update_callback.(latest_version)
end
:error ->
Logger.error("Tz failed to read the latest version of the IANA time zone database")
end
end
@doc false
def start_link(opts) do
HTTP.get_http_client!()
GenServer.start_link(__MODULE__, opts)
end
@doc false
def init(opts) do
watch(opts[:on_update])
schedule_work(opts[:interval_in_days])
{:ok, %{opts: opts}}
end
@doc false
def handle_info(:work, %{opts: opts}) do
watch(opts[:on_update])
schedule_work(opts[:interval_in_days])
{:noreply, %{opts: opts}}
end
defp schedule_work(interval_in_days) do
interval_in_days = interval_in_days || 1
Process.send_after(self(), :work, interval_in_days * 24 * 60 * 60 * 1000)
end
end