mimemagic.rb

# frozen_string_literal: true

require 'mimemagic/tables'
require 'mimemagic/version'

require 'stringio'

MimeMagic.parse_database

# Mime type detection
class MimeMagic
  attr_reader :type, :mediatype, :subtype

  # Mime type by type string
  def initialize(type)
    @type = type
    @mediatype, @subtype = type.split('/', 2)
  end

  # Add custom mime type. Arguments:
  # * <i>type</i>: Mime type
  # * <i>options</i>: Options hash
  #
  # Option keys:
  # * <i>:extensions</i>: String list or single string of file extensions
  # * <i>:parents</i>: String list or single string of parent mime types
  # * <i>:magic</i>: Mime magic specification
  # * <i>:comment</i>: Comment string
  def self.add(type, options)
    extensions = [options[:extensions]].flatten.compact
    TYPES[type] = [extensions,
                  [options[:parents]].flatten.compact,
                  options[:comment]]
    extensions.each {|ext| EXTENSIONS[ext] = type }
    MAGIC.unshift [type, options[:magic]] if options[:magic]
  end

  # Removes a mime type from the dictionary.  You might want to do this if
  # you're seeing impossible conflicts (for instance, application/x-gmc-link).
  # * <i>type</i>: The mime type to remove.  All associated extensions and magic are removed too.
  def self.remove(type)
    EXTENSIONS.delete_if {|ext, t| t == type }
    MAGIC.delete_if {|t, m| t == type }
    TYPES.delete(type)
  end

  # Returns true if type is a text format
  def text?; mediatype == 'text' || child_of?('text/plain'); end

  # Mediatype shortcuts
  def image?; mediatype == 'image'; end
  def audio?; mediatype == 'audio'; end
  def video?; mediatype == 'video'; end

  # Returns true if type is child of parent type
  def child_of?(parent)
    MimeMagic.child?(type, parent)
  end

  # Get string list of file extensions
  def extensions
    TYPES.key?(type) ? TYPES[type][0] : []
  end

  # Get mime comment
  def comment
    (TYPES.key?(type) ? TYPES[type][2] : nil).to_s
  end

  # Lookup mime type by file extension
  def self.by_extension(ext)
    ext = ext.to_s.downcase
    mime = ext[0..0] == '.' ? EXTENSIONS[ext[1..-1]] : EXTENSIONS[ext]
    mime && new(mime)
  end

  # Lookup mime type by filename
  def self.by_path(path)
    by_extension(File.extname(path))
  end

  # Lookup mime type by magic content analysis.
  # This is a slow operation.
  def self.by_magic(io)
    mime = magic_match(io, :find)
    mime && new(mime[0])
  end

  # Lookup all mime types by magic content analysis.
  # This is a slower operation.
  def self.all_by_magic(io)
    magic_match(io, :select).map { |mime| new(mime[0]) }
  end

  # Return type as string
  def to_s
    type
  end

  # Allow comparison with string
  def eql?(other)
    type == other.to_s
  end

  def hash
    type.hash
  end

  alias == eql?

  def self.child?(child, parent)
    child == parent || TYPES.key?(child) && TYPES[child][1].any? {|p| child?(p, parent) }
  end

  def self.magic_match(io, method)
    return magic_match(StringIO.new(io.to_s), method) unless io.respond_to?(:read)

    io.binmode if io.respond_to?(:binmode)
    io.set_encoding(Encoding::BINARY) if io.respond_to?(:set_encoding)
    buffer = "".encode(Encoding::BINARY)

    MAGIC.send(method) { |type, matches| magic_match_io(io, matches, buffer) }
  end

  def self.magic_match_io(io, matches, buffer)
    matches.any? do |offset, value, children|
      match =
        if Range === offset
          io.read(offset.begin, buffer)
          x = io.read(offset.end - offset.begin + value.bytesize, buffer)
          x && x.include?(value)
        else
          io.read(offset, buffer)
          io.read(value.bytesize, buffer) == value
        end
      io.rewind
      match && (!children || magic_match_io(io, children, buffer))
    end
  end

  private_class_method :magic_match, :magic_match_io
end