# File lib/cssmin.rb, line 52
def self.minify(input)
  css = input.is_a?(IO) ? input.read : input.to_s

  # Remove comments.
  css.gsub!(/\/\*[\s\S]*?\*\//, '')

  # Compress all runs of whitespace to a single space to make things easier
  # to work with.
  css.gsub!(/\s+/, ' ')

  # Replace box model hacks with placeholders.
  css.gsub!(/"\\"\}\\""/, '___BMH___')

  # Remove unnecessary spaces, but be careful not to turn "p :link {...}"
  # into "p:link{...}".
  css.gsub!(/(?:^|\})[^\{:]+\s+:+[^\{]*\{/) do |match|
    match.gsub(':', '___PSEUDOCLASSCOLON___')
  end
  css.gsub!(/\s+([!\{\};:>+\(\)\],])/, '\1')
  css.gsub!('___PSEUDOCLASSCOLON___', ':')
  css.gsub!(/([!\{\}:;>+\(\[,])\s+/, '\1')

  # Add missing semicolons.
  css.gsub!(/([^;\}])\}/, '\1;}')

  # Replace 0(%, em, ex, px, in, cm, mm, pt, pc) with just 0.
  css.gsub!(/([\s:])([+-]?0)(?:%|em|ex|px|in|cm|mm|pt|pc)/, '\1\2')

  # Replace 0 0 0 0; with 0.
  css.gsub!(/:(?:0 )+0;/, ':0;')

  # Replace background-position:0; with background-position:0 0;
  css.gsub!('background-position:0;', 'background-position:0 0;')

  # Replace 0.6 with .6, but only when preceded by : or a space.
  css.gsub!(/(:|\s)0+\.(\d+)/, '\1.\2')

  # Convert rgb color values to hex values.
  css.gsub!(/rgb\s*\(\s*([0-9,\s]+)\s*\)/) do |match|
    '#' << $1.scan(/\d+/).map{|n| n.to_i.to_s(16).rjust(2, '0') }.join
  end

  # Compress color hex values, making sure not to touch values used in IE
  # filters, since they would break.
  css.gsub!(/([^"'=\s])(\s?)\s*#([0-9a-f])\33(([0-9a-f])\44(([0-9a-f])\55//, '\1\2#\3\4\5')

  # Remove empty rules.
  css.gsub!(/[^\}]+\{;\}\n/, '')

  # Re-insert box model hacks.
  css.gsub!('___BMH___', '"\"}\""')

  # Prevent redundant semicolons.
  css.gsub!(/;;+/, ';')

  css.strip
end