#!/usr/bin/env perl

use strict;
use warnings;

use JSON;

my $ENDPOINT = "https://www.googleapis.com/youtube/v3";
my $YT_API_KEY = $ENV{'YOUTUBE_API_KEY'}
    || die "Error: You need to define the env variable 'YOUTUBE_API_KEY'\n";

sub decode_json_utf8 {
    my $json = join "", @_;
    utf8::encode($json);
    return decode_json($json);
}

sub api_playlist_videos {
    my $id = shift;
    my $videos = (decode_json_utf8 `curl -s '$ENDPOINT/playlistItems?part=snippet&maxResults=1000&playlistId=$id&key=$YT_API_KEY'`)->{items};
    return map { $_->{snippet}{resourceId}{videoId} } @$videos;
}

@ARGV == 1 or die "Usage: $0 <playlist_id>\n";
my $pl_id = $ARGV[0];
my @videos = map { "https://www.youtube.com/watch?v=" . $_ } api_playlist_videos($pl_id);

`mkdir $pl_id && cd $pl_id && youtube-dl @videos\n`;