class Paperclip::ContentTypeDetector

def blank_name?
  @filepath.nil? || @filepath.empty?
end

def calculated_type_matches
  possible_types.select do |content_type|
    content_type == type_from_file_contents
  end
end

def detect
  if blank_name?
    SENSIBLE_DEFAULT
  elsif empty_file?
    EMPTY_TYPE
  elsif calculated_type_matches.any?
    calculated_type_matches.first
  else
    type_from_file_contents || SENSIBLE_DEFAULT
  end.to_s
end

def empty_file?
  File.exist?(@filepath) && File.size(@filepath) == 0
end

def initialize(filepath)
  @filepath = filepath
end

def possible_types
  MIME::Types.type_for(@filepath).collect(&:content_type)
end

def type_from_file_command
  @type_from_file_command ||=
    FileCommandContentTypeDetector.new(@filepath).detect
end

def type_from_file_contents
  type_from_mime_magic || type_from_file_command
rescue Errno::ENOENT => e
  Paperclip.log("Error while determining content type: #{e}")
  SENSIBLE_DEFAULT
end

def type_from_mime_magic
  @type_from_mime_magic ||=
    MimeMagic.by_magic(File.open(@filepath)).try(:type)
end