class Term::ANSIColor::PPMReader

def initialize(io, options = {})
  @io            = io
  @options       = options
  @buffer        = ''.dup
  if options[:true_coloring]
    @color = -> pixel { on_color Attribute.true_color(pixel, @options) }
  else
    @color = -> pixel { on_color Attribute.nearest_rgb_color(pixel, @options) }
  end
end

def next_line
  while line = @io.gets and line =~ /^#|^\s$/
  end
  line
end

def parse_header
  (line = next_line) =~ /^P([36])$/ or raise "unknown type #{line.to_s.chomp.inspect}"
  @type = $1.to_i
  if next_line =~ /^(\d+)\s+(\d+)$/
    @width, @height = $1.to_i, $2.to_i
  else
    raise "missing dimensions"
  end
  unless next_line =~ /^255$/
    raise "only 255 max color images allowed"
  end
end

def parse_next_pixel
  pixel = nil
  case @type
  when 3
    @buffer.empty? and @buffer << next_line
    @buffer.sub!(/(\d+)\s+(\d+)\s+(\d+)\s*/) do
      pixel = [ $1.to_i, $2.to_i, $3.to_i ]
      ''
    end
  when 6
    @buffer.size < 3 and @buffer << @io.read(8192)
    pixel = @buffer.slice!(0, 3).unpack('C3')
  end
  pixel
end

def parse_row
  @width.times.map { parse_next_pixel }
end

def reset_io
  begin
    @io.rewind
  rescue Errno::ESPIPE
  end
  parse_header
end

def rows
  reset_io
  Enumerator.new do |yielder|
    @height.times do
      yielder.yield parse_row
    end
  end
end

def to_a
  rows.to_a
end

def to_s
  rows.map do |row|
    last_pixel = nil
    row.map do |pixel|
      if pixel != last_pixel
        last_pixel = pixel
        @color.(pixel) << ' '
      else
        ' '
      end
    end.join << reset << ?\n
  end.join
end