I believe such an Elixir-friendly tool would be useful, but does not belong
in the Elixir language itself.
In the spirit of a slim but extensible core, functionality and especially
structs in Elixir stdlib tend to be limited to:
- Things useful to any domain, that can only be realized optimally in the
language itself
- Things required by the language tooling itself
For example, you see general things like Range parsing/structs in stdlib
because their membership tests work with guards and the *in* operator, so
the language itself has to be able to operate on them. And you see things
like the URI parsing and semantic Version structs in the stdlib because
they are required for mix to be able to fetch libraries and resolve version
constraints.
If Elixir needed to deal with this date format to work, or if they were
more general-purpose, there'd be a stronger case for inclusion. As it, it
probably belongs in one of the general-purpose HTTP handling libraries as a
dependency.
On the other hand, you can always go pouring through the erlang stdlib's
much more kitchen-sinky set of tools for these sorts of things to see if
functions that accomplish what you want are already available to you from
erlang itself, without extra dependencies. For example, I knew that erlang
comes with a pretty robust http server/client implementation. I remembered
that it has a module called :httpc, so I found the docs for the application
that contains it, :inets. I noticed an :http_util module in there, and it
seems to have the functionality you want. For Elixir compatibility, you
just need to translate between erlang and Elixir, something like:
defmodule HTTPDate do
def now(calendar \\ Calendar.ISO) do
calendar |> DateTime.utc_now() |> from_date_time()
end
def from_date_time(date_time = %DateTime{}) when date_time.utc_offset == 0
do
{
{date_time.year, date_time.month, date_time.day},
{date_time.hour, date_time.minute, date_time.second}
}
|> :httpd_util.rfc1123_date()
end
def from_date_time(other), do: raise("expected a DateTime in UTC (GMT),
got: #{inspect(other)}")
def to_date_time(string, calendar \\ Calendar.ISO) do
with {{year, month, day}, {hour, minute, second}} <- :httpd_util.
convert_request_date(string),
{:ok, date} <- Date.new(year, month, day, calendar),
{:ok, time} <- Time.new(hour, minute, second, {0, 0}, calendar) do
DateTime.new(date, time, "Etc/UTC")
else
# Normalize :httpd_util.convert_request_date errors
:bad_date -> {:error, :invalid_date}
# Date/Time/DateTime.new errors
{:error, reason} -> {:error, reason}
end
end
end
On Thursday, November 21, 2024 at 6:18:50 PM UTC-6 yordis...@gmail.com
wrote:
> I came across a PR that required parsing
> https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Date, so the
> person reached out for a third-party library.
>
> I wonder if Elixir should handle parsing HTTP Date or allow the
> construction of a Date using the day name (Mon, Tue ...), month name (Jan,
> Feb), and other formatting from HTTP Date.
>
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