Bash Array Script Exclude Duplicates - arrays

Question

So I have written a bash script (named music.sh) for a Raspberry Pi to perform the following functions:
When executed, look into one single directory (Music folder) and select a random folder to look into. (Note: none of these folders here have subdirectories)
Once a folder within "Music" has been selected, then play all mp3 files IN ORDER until the last mp3 file has been reached
At this point, the script would go back to the folders in the "Music" directory and select another random folder
Then it would again play all mp3 files in that folder in order
Loop indefinitely until input from user
I have this code which does all of the above EXCEPT for the following items:
I would like to NOT play any other "album" that has been played before
Once all albums played once, then shutdown the system
Here is my code so far that is working (WITH duplicates allowed):
#!/bin/bash
folderarray=($(ls -d /home/alphekka/Music/*/))
for i in "${folderarray[#]}";
do
folderitems=(${folderarray[RANDOM % ${#folderarray[#]}]})
for j in "${folderitems[#]}";
do
echo `ls $j`
cvlc --play-and-exit "${j[#]}"
done
done
exit 0
Please note that there isn't a single folder or file that has a space in the name. If there is a space, then I face some issues with this code working.
Anyways, I'm getting close, but I'm not quite there with the entire functionality I'm looking for. Any help would be greatly appreciated! Thank you kindly! :)

Answer 1

Use an associative array as a set. Note that this will work for all valid folder and file names.
#!/bin/bash
declare -A folderarray
# Each folder name is a key mapped to an empty string
for d in /home/alphekka/Music/*/; do
folderarray["$d"]=
done
while [[ "${!folderarray[*]}" ]]; do
# Get a list of the remaining folder names
foldernames=( "${!folderarray[#]}" )
# Pick a folder at random
folder=${foldernames[RANDOM%${#foldernames[#]}]}
# Remove the folder from the set
# Must use single quotes; see below
unset folderarray['$folder']
for j in "$folder"/*; do
cvlc --play-and-exit "$j"
done
done
Dealing with keys that contain spaces (and possibly other special characters) is tricky. The quotes shown in the call to unset above are not syntactic quotes in the usual sense. They do not prevent $folder from being expanded, but they do appear to be used by unset itself to quote the resulting string.

Answer 2

Here's another solution: randomize the list of directories first, save the result in an array and then play (my script just prints) the files from each element of the array
MUSIC=/home/alphekka/Music
OLDIFS=$IFS
IFS=$'\n'
folderarray=($(ls -d $MUSIC/*/|while read line; do echo $RANDOM $line; done| sort -n | cut -f2- -d' '))
for folder in ${folderarray[*]};
do
printf "Folder: %s\n" $folder
fileArray=($(find $folder -type f))
for j in ${fileArray[#]};
do
printf "play %s\n" $j
done
done
For the random shuffling I used this answer.

Answer 3

One liner solution with mpv, rl (randomlines), xargs, find:
find /home/alphekka/Music/ -maxdepth 1 -type d -print0 | rl -d \0 | xargs -0 -l1 mpv