#--
# Copyright (c) 2008 Ryan Grove <ryan@wonko.com>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
#   * Redistributions of source code must retain the above copyright notice,
#     this list of conditions and the following disclaimer.
#   * Redistributions in binary form must reproduce the above copyright notice,
#     this list of conditions and the following disclaimer in the documentation
#     and/or other materials provided with the distribution.
#   * Neither the name of this project nor the names of its contributors may be
#     used to endorse or promote products derived from this software without
#     specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#++

# = CSSMin
#
# Minifies CSS using a fast, safe routine adapted from Julien Lecomte's YUI
# Compressor, which was in turn adapted from Isaac Schlueter's cssmin PHP
# script.
#
# Author::    Ryan Grove (mailto:ryan@wonko.com)
# Version::   1.0.2 (2008-08-23)
# Copyright:: Copyright (c) 2008 Ryan Grove. All rights reserved.
# License::   New BSD License (http://opensource.org/licenses/bsd-license.php)
# Website::   http://github.com/rgrove/cssmin/
#
# == Example
#
#   require 'rubygems'
#   require 'cssmin'
#
#   File.open('example.css', 'r') {|file| puts CSSMin.minify(file) }
#
class Shoebox::Minifiers::CSS

  def initialize(data)
    @data = data
  end

  # Reads CSS from +input+ (which can be a String or an IO object) and
  # returns a String containing minified CSS.
  def minify
    input = @data

    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)/i, '\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])\3([0-9a-f])\4([0-9a-f])\5/i, '\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

end
