class ImageSize

# File lib/image_size.rb, line 39
def self.dpi
  @dpi || 72
end

# File lib/image_size.rb, line 44
def self.dpi=(dpi)
  @dpi = dpi.to_f
end

# File lib/image_size.rb, line 49
def initialize(data)
  Reader.open(data) do |ir|
    @format = detect_format(ir)
    @width, @height = send("size_of_#{@format}", ir) if @format
  end
end

# File lib/image_size.rb, line 34
def self.path(path)
  new(Pathname.new(path))
end

# File lib/image_size/uri_reader.rb, line 87
def self.url(url)
  new(url.is_a?(URI) ? url : URI(url))
end

# File lib/image_size.rb, line 68
def size
  Size.new([width, height]) if format
end

# File lib/image_size.rb, line 76
def detect_format(ir)
  head = ir[0, 1024]
  case
  when head.nil? || head.empty?                                 then nil
  when head[0, 6] =~ /GIF8[79]a/                                then :gif
  when head[0, 8] == "\211PNG\r\n\032\n"                        then detect_png_type(ir)
  when head[0, 8] == "\212MNG\r\n\032\n"                        then :mng
  when head[0, 2] == "\377\330"                                 then :jpeg
  when head[0, 2] == 'BM'                                       then :bmp
  when head[0, 3] =~ /P[1-6]\s|P7\n/                            then detect_pnm_type(ir)
  when head =~ /\#define\s+\S+\s+\d+/                           then :xbm
  when %W[II*\0 MM\0*].include?(head[0, 4])                     then :tiff
  when head =~ %r{/\* XPM \*/}                                  then :xpm
  when head[0, 4] == '8BPS'                                     then :psd
  when head[0, 3] =~ /[FC]WS/                                   then :swf
  when head =~ SVG_R || (head =~ XML_R && ir[0, 4096] =~ SVG_R) then :svg
  when head[0, 2] =~ /\n[\0-\5]/                                then :pcx
  when head[0, 12] =~ /RIFF(?m:....)WEBP/                       then :webp
  when head[0, 4] == "\0\0\1\0"                                 then :ico
  when head[0, 4] == "\0\0\2\0"                                 then :cur
  when head[0, 12] == "\0\0\0\fjP  \r\n\207\n"                  then detect_jpeg2000_type(ir)
  when head[0, 4] == "\377O\377Q"                               then :j2c
  end
end

# File lib/image_size.rb, line 123
def detect_jpeg2000_type(ir)
  return unless ir[16, 4] == 'ftyp'

  # using xl-box would be weird, but doesn't seem to contradict specification
  skip = ir[12, 4] == "\0\0\0\1" ? 16 : 8
  case ir[12 + skip, 4]
  when 'jp2 ' then :jp2
  when 'jpx ' then :jpx
  end
end

# File lib/image_size.rb, line 101
def detect_png_type(ir)
  offset = 8
  loop do
    type = ir[offset + 4, 4]
    break if ['IDAT', 'IEND', nil].include?(type)
    return :apng if type == 'acTL'

    length = ir.unpack1(offset, 4, 'N')
    offset += 8 + length + 4
  end
  :png
end

# File lib/image_size.rb, line 114
def detect_pnm_type(ir)
  case ir[0, 2]
  when 'P1', 'P4' then :pbm
  when 'P2', 'P5' then :pgm
  when 'P3', 'P6' then :ppm
  when 'P7'       then :pam
  end
end

# File lib/image_size.rb, line 180
def size_of_bmp(ir)
  header_size = ir.unpack1(14, 4, 'V')
  if header_size == 12
    ir.unpack(18, 4, 'vv')
  else
    ir.unpack(18, 8, 'VV').map do |n|
      if n > 0x7fff_ffff
        0x1_0000_0000 - n # absolute value of converted to signed
      else
        n
      end
    end
  end
end

# File lib/image_size.rb, line 134
def size_of_gif(ir)
  ir.unpack(6, 4, 'vv')
end

# File lib/image_size.rb, line 320
def size_of_ico(ir)
  ir.unpack(6, 2, 'CC').map{ |v| v.zero? ? 256 : v }
end

# File lib/image_size.rb, line 374
def size_of_j2c(ir)
  ir.unpack(8, 8, 'NN')
end

# File lib/image_size.rb, line 338
def size_of_jp2(ir)
  offset = 12
  stop = nil
  in_header = false
  loop do
    break if stop && offset >= stop
    break if ir[offset, 4] == '' || ir[offset, 4].nil?

    size = ir.unpack1(offset, 4, 'N')
    type = ir.fetch(offset + 4, 4)

    data_offset = 8
    case size
    when 1
      size = ir.unpack1(offset, 8, 'Q>')
      data_offset = 16
      raise FormatError, "Unexpected xl-box size #{size}" if (1..15).include?(size)
    when 2..7
      raise FormatError, "Reserved box size #{size}"
    end

    if type == 'jp2h'
      stop = offset + size unless size.zero?
      offset += data_offset
      in_header = true
    elsif in_header && type == 'ihdr'
      return ir.unpack(offset + data_offset, 8, 'NN').reverse
    else
      break if size.zero? # box to the end of file

      offset += size
    end
  end
end

# File lib/image_size.rb, line 161
def size_of_jpeg(ir)
  section_marker = "\xFF"
  offset = 2
  loop do
    offset += 1 until [nil, section_marker].include? ir[offset, 1]
    offset += 1 until section_marker != ir[offset + 1, 1]
    raise FormatError, 'EOF in JPEG' if ir[offset, 1].nil?

    code, length = ir.unpack(offset, 4, 'xCn')
    offset += 4

    if JPEG_CODE_CHECK.include?(code)
      return ir.unpack(offset + 1, 4, 'nn').reverse
    end

    offset += length - 2
  end
end

# File lib/image_size.rb, line 138
def size_of_mng(ir)
  unless ir[12, 4] == 'MHDR'
    raise FormatError, 'MHDR not in place for MNG'
  end

  ir.unpack(16, 8, 'NN')
end

# File lib/image_size.rb, line 204
def size_of_pam(ir)
  width = height = nil
  offset = 3
  until width && height
    if ir[offset, 1] == '#'
      offset += 1 until ["\n", '', nil].include?(ir[offset, 1])
      offset += 1
    else
      chunk = ir[offset, 32]
      case chunk
      when /\AWIDTH (\d+)\n/
        width = $1.to_i
      when /\AHEIGHT (\d+)\n/
        height = $1.to_i
      when /\AENDHDR\n/
        break
      when /\A(?:DEPTH|MAXVAL) \d+\n/, /\ATUPLTYPE \S+\n/
        # ignore
      else
        raise FormatError, "Unexpected data in PAM header: #{chunk.inspect}"
      end
      offset += $&.length
    end
  end
  [width, height]
end

# File lib/image_size.rb, line 283
def size_of_pcx(ir)
  parts = ir.unpack(4, 8, 'v4')
  [parts[2] - parts[0] + 1, parts[3] - parts[1] + 1]
end

# File lib/image_size.rb, line 146
def size_of_png(ir)
  unless ir[12, 4] == 'IHDR'
    raise FormatError, 'IHDR not in place for PNG'
  end

  ir.unpack(16, 8, 'NN')
end

# File lib/image_size.rb, line 195
def size_of_ppm(ir)
  header = ir[0, 1024]
  header.gsub!(/^\#[^\n\r]*/m, '')
  header =~ /^(P[1-6])\s+?(\d+)\s+?(\d+)/m
  [$2.to_i, $3.to_i]
end

# File lib/image_size.rb, line 248
def size_of_psd(ir)
  ir.unpack(14, 8, 'NN').reverse
end

# File lib/image_size.rb, line 297
def size_of_svg(ir)
  attributes = {}
  svg_tag = ir[0, 1024][SVG_R, 1] || ir[0, 4096][SVG_R, 1]
  svg_tag.scan(/(\S+)=(?:'([^']*)'|"([^"]*)"|([^'"\s]*))/) do |name, v0, v1, v2|
    attributes[name] = v0 || v1 || v2
  end
  dpi = self.class.dpi
  [attributes['width'], attributes['height']].map do |length|
    next unless length

    pixels = case length.downcase.strip[/(?:em|ex|px|in|cm|mm|pt|pc|%)\z/]
    when 'em', 'ex', '%' then nil
    when 'in' then length.to_f * dpi
    when 'cm' then length.to_f * dpi / 2.54
    when 'mm' then length.to_f * dpi / 25.4
    when 'pt' then length.to_f * dpi / 72
    when 'pc' then length.to_f * dpi / 6
    else length.to_f
    end
    pixels.round if pixels
  end
end

# File lib/image_size.rb, line 288
def size_of_swf(ir)
  value_bit_length = ir.unpack1(8, 1, 'B5').to_i(2)
  bit_length = 5 + (value_bit_length * 4)
  rect_bits = ir.unpack1(8, (bit_length / 8) + 1, "B#{bit_length}")
  values = rect_bits[5..-1].unpack("a#{value_bit_length}" * 4).map{ |bits| bits.to_i(2) }
  x_min, x_max, y_min, y_max = values
  [(x_max - x_min) / 20, (y_max - y_min) / 20]
end

# File lib/image_size.rb, line 252
def size_of_tiff(ir)
  endian2b = ir.fetch(0, 4) == "II*\000" ? 'v' : 'n'
  endian4b = endian2b.upcase
  packspec = [nil, 'C', nil, endian2b, endian4b, nil, 'c', nil, endian2b, endian4b]

  offset = ir.unpack1(4, 4, endian4b)
  num_dirent = ir.unpack1(offset, 2, endian2b)
  offset += 2
  num_dirent = offset + (num_dirent * 12)

  width = height = nil
  until width && height
    ifd = ir.fetch(offset, 12)
    raise FormatError, 'Reached end of directory entries in TIFF' if offset > num_dirent

    tag, type = ifd.unpack(endian2b * 2)
    offset += 12

    next if packspec[type].nil?

    value = ifd[8, 4].unpack(packspec[type])[0]
    case tag
    when 0x0100
      width = value
    when 0x0101
      height = value
    end
  end
  [width, height]
end

# File lib/image_size.rb, line 325
def size_of_webp(ir)
  case ir.fetch(12, 4)
  when 'VP8 '
    ir.unpack(26, 4, 'vv').map{ |v| v & 0x3fff }
  when 'VP8L'
    n = ir.unpack1(21, 4, 'V')
    [(n & 0x3fff) + 1, ((n >> 14) & 0x3fff) + 1]
  when 'VP8X'
    w16, w8, h16, h8 = ir.unpack(24, 6, 'vCvC')
    [(w16 | (w8 << 16)) + 1, (h16 | (h8 << 16)) + 1]
  end
end

# File lib/image_size.rb, line 231
def size_of_xbm(ir)
  ir[0, 1024] =~ /^\#define\s*\S*\s*(\d+)\s*\n\#define\s*\S*\s*(\d+)/mi
  [$1.to_i, $2.to_i]
end

# File lib/image_size.rb, line 236
def size_of_xpm(ir)
  length = 1024
  until (data = ir[0, length]) =~ /"\s*(\d+)\s+(\d+)(\s+\d+\s+\d+){1,2}\s*"/m
    if data.length != length
      raise FormatError, 'XPM size not found'
    end

    length += 1024
  end
  [$1.to_i, $2.to_i]
end