Recursivly Iterates a directory finding MP3s and then loading the ID3 info via 'mediainfo' for each. it then builds a list of genre popularity by artist (how many songs for each artist use which genre) working with genre beingset to multiple genres and split with either a semicolon (;) or foreslash (/)

set_genre_by_artist_genre_frequency.php

<?php
/**
* Recursivly Iterates a directory finding MP3s and then loading the ID3 info via 'mediainfo' for each.  
* it then builds a list of genre popularity by artist (how many songs for each artist use which genre) 
* working with genre  beingset to multiple genres and split with either a semicolon (;) or foreslash (/)
* 
* - Automatic Backups every 120 seconds (configurable) 
*     @see $backupSeconds
* - Intelligent Reprocessing of MP3s only updating when the "Last Modified Time" is newer than what we stored in the db
* - Commands Optimization drastically cutting back on the number of times "mediainfo" is ran 
*     say for 2500 files to update updates (originally 2500 calls to update them) it grouped 
*     them into a single call per Genre so for me it went down from around 2500 to 80.
* - Automatic handling of removed files without having to specificly check for them.
* 
* @author Joe Huss <detain@interserver.net>
* @copyright 2020
* * 
*/


$mp3Base = __DIR__;
$found = 0;
$badGenres = ['Other', '!', 'Unknown', 'Miscellaneous'];
$toFix = [];
$artistCounts = [];
$backupSeconds = 120;
exec('which mediainfo', $out, $missingMediaInfo);
unset($out);
exec('which mp3info2', $out, $missingMp3Info2);
unset($out);
if ($missingMediaInfo + $missingMp3Info2 > 0) {
	if ($missingMediaInfo == 1) {
		echo '[ERROR] Missing "mediainfo" !   Get it from https://mediaarea.net/en/MediaInfo or "apt install mediainfo"'.PHP_EOL;
	}
	if ($missingMp3Info2 == 1) {
		echo '[ERROR] Missing "mp3info2" !   Get it from perl MP3::Tag module at https://metacpan.org/release/MP3-Tag or "apt install libmp3-tag-perl"'.PHP_EOL;
	}
	exit;
}
if (file_exists('mp3s.json')) {
	$mp3s = json_decode(file_get_contents('mp3s.json'), true);
	echo "Loaded Stored Data for ".count($mp3s)." MP3s\n";
} else {
	$mp3s = [];
}
echo "Scanning Path '{$mp3Base}'...";
$cmd = 'find '.escapeshellarg($mp3Base).' -type f -name "*.mp3"';
$scanTime = time();
$lastBackup = $scanTime;
$files = explode("\n", trim(`$cmd`));
$total = count($files);	
echo $total.' files'.PHP_EOL;
foreach ($files as $file) {
	$modified = filemtime($file);
	$needsUpdate = true;
	if (array_key_exists($file, $mp3s)) {
		if ($modified <= $mp3s[$file]['modified']) {
			$needsUpdate = false;
		}
	}
	if ($needsUpdate === true) {
		$cmd = 'mediainfo --Output=JSON '.escapeshellarg($file);
		$data = json_decode(trim(`$cmd`), true);
		//echo "[$found/$total] Loading Media Info for {$file}\n";
	}
	$data['modified'] = $modified;
	$data['seen'] = $scanTime;
	$mp3s[$file] = $data;
	$found++;
	if (time() - $lastBackup > $backupSeconds) {
		echo '['.$found.'/'.$total.'] Backup Interval triggered saving the current data...';
		$bytes = file_put_contents('mp3s.json', json_encode($mp3s, JSON_PRETTY_PRINT));
		echo $bytes.' bytes written to "mp3s.json"'.PHP_EOL;
		$lastBackup = time();			
	}
}
echo "File Info Loaded from ".count($mp3s)." MP3s\n";
$bytes = file_put_contents('mp3s.json', json_encode($mp3s, JSON_PRETTY_PRINT));
echo $bytes.' bytes written to "mp3s.json"'.PHP_EOL;
echo "Examining the MP3s for Genres and generating some mapping info".PHP_EOL;
foreach ($mp3s as $mp3 => $data) {
	$types = [];
	foreach ($data['media']['track'] as $idx => $track) {
		$types[$track['@type']] = $idx;
	}
	if (!isset($data['media']['track'][$types['General']]['Performer'])) {
		continue;
	}
	if (!isset($data['media']['track'][$types['General']]['Genre'])) {
		$toFix[] = $mp3;
		continue;
	}
	//echo "MP3: $mp3\n";
	//print_r($data['media']['track'][$types['General']]);
	$artist = $data['media']['track'][$types['General']]['Performer'];
	$genres = $data['media']['track'][$types['General']]['Genre'];
	if (!array_key_exists($artist, $artistCounts)) {
		$artistCounts[$artist] = [];
	}
	if (in_array($genres, $badGenres)) {
		$toFix[] = $mp3;
	} elseif (strpos($genres, ';') !== false) {
		$genres = explode(';', $genres);
		$toFix[] = $mp3;
	} elseif (strpos($genres, '/') !== false) {
		$genres = explode('/', $genres);
		$toFix[] = $mp3;
	} else {
		$genres = [$genres];
	}
	foreach ($genres as $genre) {
		$genre = trim($genre);
		if (!array_key_exists($genre, $artistCounts[$artist])) {
			$artistCounts[$artist][$genre] = 0;
		}
		$artistCounts[$artist][$genre]++;		
	}
}
echo count($toFix)." mp3 files found with multiple genres to fix\n";
foreach ($artistCounts as $artist => $genres) {
	$highestCount = 0;
	$highestGenre = false;
	foreach ($genres as $genre => $count) {
		if ($count > $highestCount) {
			$highestGenre = $genre;
			$highestCount = $count;
		}
	}
	echo 'Found artist '.$artist.' to most likely be "'.$highestGenre.'" with a frequency of '.$highestCount.' among '.count($genres).' detected genres'.PHP_EOL;
	$artistCounts[$artist] = $highestGenre;
}
$updates = [];
foreach ($toFix as $mp3) {
	$data = $mp3s[$mp3];
	$types = [];
	foreach ($data['media']['track'] as $idx => $track) {
		$types[$track['@type']] = $idx;
	}
	$artist = $data['media']['track'][$types['General']]['Performer'];
	if (!array_key_exists($artist, $artistCounts)) {
		//echo "Artist $artist had no genres for MP3 $mp3\n";
		continue;
	}
	$updates[$mp3] = $artistCounts[$artist];
}
//file_put_contents('updates.json', json_encode($updates, JSON_PRETTY_PRINT));
//echo "wrote updates.json with ".count($updates)." fixs\n";
$mp3s = $updates;
echo "Grouping ".count($mp3s)." MP3s to update by Genres\n";
$genres = [];
foreach ($mp3s as $mp3 => $genre) {
	if (!isset($genres[$genre])) {  
		$genres[$genre] = [];  
	}                                  
	$genres[$genre][] = $mp3;                      
} 
echo "Sorted them down to ".count($genres)." genres to update\n";
$cmds = [];
foreach ($genres as $genre => $files) {               
	$cmd = 'mp3info2 -g '.escapeshellarg($genre);     
	foreach ($files as $file) {                    
		$cmd .= ' '.escapeshellarg($file);       
	}                                                 
	$cmds[] = $cmd;                                         
} 
file_put_contents('update_mp3s.sh', implode("\n", $cmds));
echo "Done Updating ".count($updates)." MP3s\n";