random: Return random tracks by time constraint

[bearcatsandor]

It would be really cool to have a random by time function. Such that when you had 30 minutes before you raced out the door, you could give the random command a time and it would pick tracks that would fit within that time constraint.

Then the resulting tracks could be piped to other commands, and utilized for the "play" command as well.

One could do:

beet random -t 37
to return 37 minutes of random tracks

beet random -t 45 "Metallica"
to return 40 minutes of random Metallica

beet random -t 120 title:cats
to return 2 hours of random tracks with the word "cats" in the title.

If one didn't have 2 hours worth of tracks with the word "cats" in them, it would just return as much as it can.

Random could be set up to return a defined number of tracks as well, but that's another Issue.

[diomekes]

I've made changes to the random plugin to implement this. I won't open a pull request because it has other changes that I made for #2304, but here's a pastebin of it:

https://ptpb.pw/tJ4N

[bearcatsandor]

That looks awesome and better than i'd dreamed! Thank you!!!

[sampsyo]

Nice work, @diomekes! This looks awesome. I'd love to merge the new feature separately if you're amenable to splitting up the patches.

[diomekes]

Yes, I can do that. I'll add the code to the current random plugin (which does not define several functions, just the main one, so I'll add the code under that function).

Can I run the tests that github runs on pull-requests on my end (either off-line or through github) so I can fix small issues before requesting a pull?

Also, do you want me to add the extra documentation or do you usually do that?

[sampsyo]

Yes, awesome! Thank you!

Here are some tips on running tests: https://github.com/beetbox/beets/wiki/Testing

And yes, please do add some docs (even just a draft is good).

[diomekes]

OK, I'm almost done with the plugin code. Quick question: Should I make -e and -t mutually exclusive or should I add a if opts.time into the if opts.equal_chance? Here are pastebins to see the two options:
https://ptpb.pw/_238
https://ptpb.pw/Z09i

[sampsyo]

Huh—interesting question. Can you explain intuitively how things work if -e and -t are used together?

[diomekes]

I'll try, if I understand -e correctly.

-e chooses a song by first making a list of artists and choosing a random artist from that list (instead of a list of songs, and choosing a random song). That way, it doesn't matter how many songs from each artist you have, all artists are treated equal and once it chooses all the songs from one artist, that artist is deleted from the list.

With -n, it does that N times.

With -t, it does it until it reaches -t minutes, or more exact it stops if it can't find any song that would keep it under the minutes.

I like to use -e because it seems more random to me than without it, but the code looks kludgier to me (once again, I'm new at this, so there is a more elegant way I'm sure).

[sampsyo]

OK, thank you for explaining!

It sounds like the combination of the two would be good to keep. Feel free to open the PR as is; maybe we can sort out a simpler version of the code afterward.