# Nick's web site: css_clean_selectors filter.  Remove unnecessary whitespace
# from CSS selectors as this improves compatibility with old versions of IE.
#
# Copyright © 2020 Nick Bowler
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

class CssCleanSelectorsFilter < Nanoc::Filter
    identifier :css_clean_selectors

    require 'crass'

    def run(content, params = {})
        tree = Crass.parse(content, params)

        queue = Array.new(tree)
        while i = queue.shift do
          if i[:node] == :at_rule
            case i[:name]
            when "media", "supports"
              # Re-parse the block as a list of rules.
              s = Crass::Parser.stringify(i[:block])
              i[:block] = Crass::Parser.parse_rules(s, params)
              queue += i[:block]
            end
          end

          if i[:selector]
            ts = i[:selector][:tokens]
            ts.each_index do |i|
                next if ts[i].nil? or ts[i][:node] != :delim
                next if ts[i][:value] == '*'

                if ts[i-1]
                    # keep whitespace before class selectors
                    next if ts[i][:value] == '.' and ts[i-1][:node] == :whitespace
                end

                ts[i-1] = nil if ts[i-1] and ts[i-1][:node] == :whitespace
                ts[i+1] = nil if ts[i+1] and ts[i+1][:node] == :whitespace
            end
          end
        end

        return Crass::Parser.stringify(tree)
    end
end