Validating youtube link

YouTube links can easily be matched with regular expressions.

Check out this introduction to regular expressions if you’re not familiar with them yet:

If you want to learn how to use regular expressions in Elixir, take a look at the documentation of the Regex module which has a nice introduction to using them and detailed information about the individual methods:

If the video IDs are guaranteed to be at the end, you can do a pattern match, which is probably a lot faster:

def get_video_id("http://youtu.be/" <> id), do: id
def get_video_id("http://www.youtube.com/watch?v=" <> id), do: id
def get_video_id("http://www.youtube.com/?v=" <> id), do: id

How you can append that video ID to the string "http://www.youtube.com/embed/" is left as an exercise.

I’d prefer to make it HTTPS ready and solve it via meta programming, roughly like this:

Enum.each(["http", "https"], fn protocol ->
  Enum.each(["youtu.be/", "www.youtube.com/watch?v=", "www.youtube.com/?v="], fn prefix ->
    def get_video_id(unquote(protocol <> "://" <> prefix) <> id), do: id
  end)
end)

But probably the best version is to properly parse the URL and extract the video ID from the parsed URL. Pattern matching as shown by me will not work correctly when there are other parameters in the query string, and regular expressions that cover those possibilities tend to grow into an unreadable and slow monstrosity.

Also Erlang has a handy module http_uri, here’s how you use it

 case url |> String.to_char_list() |> :http_uri.parse() do
    {:ok, {scheme, user_info, host, port, path, query}} -> # check the host, extract id from query etc
    {:error, msg} -> # incorrect url - handle error
 end

In elixir we have the URI module, it has a parse/1 function as well.

It’s not quite the same:

Note this function expects a well-formed URI and does not perform any validation.

Erlangs function does perform validation and returns helpful messages, useful if these urls come from external source or user input.

You can’t expect YouTube URLs to have the id at the end since they can also take additional parameters.

Then an RegEx will be totally unreadable and absolutely not easy to get it right as well. Proper parsing of the URL is the only option then.

This is not a valid YouTube URL, by the way: http://www.youtube.com/?v=dQw4w9WgXckQ

But its one of the OPs examples, so he seems to allow it as a valid one… He must have got it from somewhere to list it up.

Can any one get me regEx to replace https://youtu.be/64XLNqIlY00 to https://www.youtube.com/watch?v=64XLNqIlY00??