# Nick's web site: scour filter.  Run scour to reduce the size of SVG images.
#
# Copyright © 2021 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 ScourFilter < Nanoc::Filter
    identifier :scour

    def run(content, params = {})
        defaults = { quiet: true, id_stripping: true, shorten_ids: true }
        args = []
        defaults.merge(params).each do |key, val|
            prefix = nil

            # Normalize some argument names for consistency
            case key
            when :comment_stripping, :viewboxing, :id_stripping
                prefix = :enable
            when :simplify_colors, :style_to_xml, :group_collapsing,
                 :embed_rasters
                prefix = :disable
            when :renderer_workaround, :line_breaks
                prefix = :no if not val
            end

            # scour does not generally have inverse options, so drop
            # some nonsense combinations.
            next if val and prefix == :disable
            next if val and key == :line_breaks
            next if !val

            arg = "--"
            if prefix then arg << "#{prefix}-" end
            arg << key.to_s.gsub("_", "-")
            if val != true then arg << "=#{val}" end

            args << arg
        end

        content, status = Open3.capture2("scour", *args, stdin_data: content)
        raise "scour failed" if status != 0

        return content
    end
end