How to write a latex macro to reference a particular time in a set of youtube videos?

Question

I have a set of educational youtube videos that I want to reference in a document, with links to a particular time in the video. In Python, the code I want would do something like this:

links = {
    "first": "https://www.youtube.com/watch?v=3anNG7TfHSQ",
    "second": "https://www.youtube.com/watch?v=cfudXO_vzWk"
}


def youTubeRef(text:str, ref:str h:int, min:int, sec:int):
    link = f"{links[ref]}&t=h{h}m{min}s{sec}"
    return '<a href="{link}">{text}</a>'  # though in latex it would just be a href

Then, in a latex document, I would like to use this like so:

Here is \youTubeRef{my text}{first}{0}{12}{13}

And the final rendered document would show:

Here is my text

Answer 1

In your command you are using mandatory arguments to your command. I would advise against it, since sometimes it might be the case that you don't want to specify a particular time. For this, using optional arguments is a better choice.

\documentclass{article}
\usepackage{hyperref}
\def\first{https://www.youtube.com/watch?v=3anNG7TfHSQ&t}
\NewDocumentCommand{ \ytref }{ m m O{00} O{00} O{00} }{%
  \href{#2=#3h#4m#5s}{%
    #1%
  }%
}

\begin{document}
\ytref{This}{\first}[0][12][13] video will start from 12
minutes 13 seconds.

\ytref{This}{\first} video will start from the beginning.
\end{document}

Also remember that variables can't be used on the fly like you have done it in your code. You will have to define them with \def command and then you can use it like a variable (and there too, they should start with a \).

Answer 2

Code:

\documentclass[11pt]{article}
\usepackage{hyperref}
\newcommand{\youTubeRef}[5]{\href{\csname#2\endcsname\&t=#3h#4m#5s}{#1}}

\newcommand{\first}{https://www.youtube.com/watch?v=3anNG7TfHSQ}
\newcommand{\second}{https://www.youtube.com/watch?v=cfudXO_vzWk}
\begin{document}
Here is \youTubeRef{my text}{first}{0}{12}{13}. % link to https://www.youtube.com/watch?v=3anNG7TfHSQ&t=00h12m13s
\end{document}

Answer 3

With the assumption that hours are quite rare in your links, the following makes them an optional argument defaulting to 0. Else this is pretty similar to the other answers, I've opted for a two-step solution with two document-level macros, one to add new links, the other to use them.

\documentclass{article}

\usepackage{hyperref}

\ExplSyntaxOn
\msg_new:nnn { cirian } { unknown-link }
  { The~ link~ named~ "#1"~ is~ unknown. }
\tl_new:N \l_cirian_link_tl
\prop_new:N \l_cirian_links_prop
\NewDocumentCommand \addyoutubelink { m m }
  { \prop_put:Nnn \l_cirian_links_prop {#1} {#2} }
\NewDocumentCommand \youtuberef { m m O{0} m m }
  {
    \prop_get:NnNTF \l_cirian_links_prop {#2} \l_cirian_link_tl
      { \exp_args:No \href { \l_cirian_link_tl  &=h#3m#4s#5 } {#1} }
      { \msg_error:nnn { cirian } { unknown-link } {#2} }
  }
\ExplSyntaxOff

\addyoutubelink{first}{https://www.youtube.com/watch?v=3anNG7TfHSQ}
\addyoutubelink{second}{https://www.youtube.com/watch?v=cfudXO_vzWk}

\begin{document}
\youtuberef{Cool video}{first}{1}{20}.

And the really long video is only worth it \youtuberef{after an hour}{second}[1]{0}{0}.
\end{document}