class Gem::Package::TarWriter

def self.new(io)
  writer = super
  return writer unless block_given?
  begin
    yield writer
  ensure
    writer.close
  end
  nil
end

def add_file(name, mode, mtime=nil) # :yields: io
  check_closed
  name, prefix = split_name name
  init_pos = @io.pos
  @io.write Gem::Package::TarHeader::EMPTY_HEADER # placeholder for the header
  yield RestrictedStream.new(@io) if block_given?
  size = @io.pos - init_pos - 512
  remainder = (512 - (size % 512)) % 512
  @io.write "\0" * remainder
  final_pos = @io.pos
  @io.pos = init_pos
  header = Gem::Package::TarHeader.new name: name, mode: mode,
                                       size: size, prefix: prefix,
                                       mtime: mtime || Gem.source_date_epoch
  @io.write header
  @io.pos = final_pos
  self
end

def add_file_digest(name, mode, digest_algorithms) # :yields: io
  digests = digest_algorithms.map do |digest_algorithm|
    digest = digest_algorithm.new
    digest_name =
      if digest.respond_to? :name
        digest.name
      else
        digest_algorithm.class.name[/::([^:]+)\z/, 1]
      end
    [digest_name, digest]
  end
  digests = Hash[*digests.flatten]
  add_file name, mode do |io|
    Gem::Package::DigestIO.wrap io, digests do |digest_io|
      yield digest_io
    end
  end
  digests
end

def add_file_signed(name, mode, signer)
  digest_algorithms = [
    signer.digest_algorithm,
    Gem::Security.create_digest("SHA512"),
  ].compact.uniq
  digests = add_file_digest name, mode, digest_algorithms do |io|
    yield io
  end
  signature_digest = digests.values.compact.find do |digest|
    digest_name =
      if digest.respond_to? :name
        digest.name
      else
        digest.class.name[/::([^:]+)\z/, 1]
      end
    digest_name == signer.digest_name
  end
  raise "no #{signer.digest_name} in #{digests.values.compact}" unless signature_digest
  if signer.key
    signature = signer.sign signature_digest.digest
    add_file_simple "#{name}.sig", 0o444, signature.length do |io|
      io.write signature
    end
  end
  digests
end

def add_file_simple(name, mode, size) # :yields: io
  check_closed
  name, prefix = split_name name
  header = Gem::Package::TarHeader.new(name: name, mode: mode,
                                       size: size, prefix: prefix,
                                       mtime: Gem.source_date_epoch).to_s
  @io.write header
  os = BoundedStream.new @io, size
  yield os if block_given?
  min_padding = size - os.written
  @io.write("\0" * min_padding)
  remainder = (512 - (size % 512)) % 512
  @io.write("\0" * remainder)
  self
end

def add_symlink(name, target, mode)
  check_closed
  name, prefix = split_name name
  header = Gem::Package::TarHeader.new(name: name, mode: mode,
                                       size: 0, typeflag: "2",
                                       linkname: target,
                                       prefix: prefix,
                                       mtime: Gem.source_date_epoch).to_s
  @io.write header
  self
end

def check_closed
  raise IOError, "closed #{self.class}" if closed?
end

def close
  check_closed
  @io.write "\0" * 1024
  flush
  @closed = true
end

def closed?
  @closed
end

def flush
  check_closed
  @io.flush if @io.respond_to? :flush
end

def initialize(io)
  @io = io
  @closed = false
end

def mkdir(name, mode)
  check_closed
  name, prefix = split_name(name)
  header = Gem::Package::TarHeader.new name: name, mode: mode,
                                       typeflag: "5", size: 0,
                                       prefix: prefix,
                                       mtime: Gem.source_date_epoch
  @io.write header
  self
end

def split_name(name) # :nodoc:
  if name.bytesize > 256
    raise Gem::Package::TooLongFileName.new("File \"#{name}\" has a too long path (should be 256 or less)")
  end
  prefix = ""
  if name.bytesize > 100
    parts = name.split("/", -1) # parts are never empty here
    name = parts.pop            # initially empty for names with a trailing slash ("foo/.../bar/")
    prefix = parts.join("/")    # if empty, then it's impossible to split (parts is empty too)
    while !parts.empty? && (prefix.bytesize > 155 || name.empty?)
      name = parts.pop + "/" + name
      prefix = parts.join("/")
    end
    if name.bytesize > 100 || prefix.empty?
      raise Gem::Package::TooLongFileName.new("File \"#{prefix}/#{name}\" has a too long name (should be 100 or less)")
    end
    if prefix.bytesize > 155
      raise Gem::Package::TooLongFileName.new("File \"#{prefix}/#{name}\" has a too long base path (should be 155 or less)")
    end
  end
  [name, prefix]
end