Greeklish file names for uploads

<?php

// Greek letters in the names of uploaded files become Latin letters
// (φωτογραφία.jpg → fotografia.jpg). Only uploads change, and only their
// Greek letters: WordPress then cleans up the name as usual.
$greeklish = static function ( string $text ): string {
	return (string) preg_replace_callback(
		'/\p{Greek}+/u',
		static function ( array $m ): string {
			$word = strtr( mb_strtolower( $m[0], 'UTF-8' ), array( 'ου' => 'ou', 'ού' => 'ou' ) );
			return strtr(
				$word,
				array(
					'α' => 'a', 'ά' => 'a', 'β' => 'v', 'γ' => 'g', 'δ' => 'd', 'ε' => 'e', 'έ' => 'e',
					'ζ' => 'z', 'η' => 'i', 'ή' => 'i', 'θ' => 'th', 'ι' => 'i', 'ί' => 'i', 'ϊ' => 'i',
					'ΐ' => 'i', 'κ' => 'k', 'λ' => 'l', 'μ' => 'm', 'ν' => 'n', 'ξ' => 'x', 'ο' => 'o',
					'ό' => 'o', 'π' => 'p', 'ρ' => 'r', 'σ' => 's', 'ς' => 's', 'τ' => 't', 'υ' => 'y',
					'ύ' => 'y', 'ϋ' => 'y', 'ΰ' => 'y', 'φ' => 'f', 'χ' => 'ch', 'ψ' => 'ps', 'ω' => 'o',
					'ώ' => 'o',
				)
			);
		},
		$text
	);
};

$rename = static function ( $file ) use ( $greeklish ) {
	if ( is_array( $file ) && isset( $file['name'] ) && preg_match( '/\p{Greek}/u', (string) $file['name'] ) ) {
		$file['name'] = $greeklish( (string) $file['name'] );
	}
	return $file;
};
add_filter( 'wp_handle_upload_prefilter', $rename );
add_filter( 'wp_handle_sideload_prefilter', $rename );