Ruby script that copies music files in flat file hierarchy

copy-music.rb

#!/usr/bin/env ruby
require 'fileutils'

VALID_FILE_TYPES = ["mp3", "flac", "waw", "aac"]

def print_usage() 
    puts "music-copy.rb <SOURCE> <DESTINATION>"
end    

def validate_args()
    if ARGV.length != 2
        puts "Invalid usage of script\n"
        print_usage()
        exit 1
    end

    if !Dir.exist?(ARGV[0]) || !Dir.exist?(ARGV[1])
        puts "Source and destination should be valid folders"
        print_usage()
        exit 1
    end    
end

def build_file_search_regex(path, file_type)
    File.join(path, "**", "**", "*.#{file_type}")
end

def collect_music_files(source)
    VALID_FILE_TYPES.collect {|file_type| Dir.glob(build_file_search_regex(source, file_type), File::FNM_CASEFOLD)}.flatten(1)
end

def should_copy(destination, file_name)
    !File.exist?(File.join(DESTINATION, file_name))
end

validate_args()

SOURCE = ARGV[0]
DESTINATION = ARGV[1]

found_music_files = collect_music_files(SOURCE)

found_music_files.each do |file_path|
    file_name = File.basename(file_path)
    if should_copy(DESTINATION, file_name)
        FileUtils.cp(file_path, DESTINATION)
    else
        puts "#{file_name} already exists on #{DESTINATION}"
    end
end