# encoding: utf-8

require 'sass'
require 'set'

module Nanoc3::Filters
  class Sass < Nanoc3::Filter

    class << self
      # The current filter. This is definitely going to bite me if I ever get
      # to multithreading nanoc.
      attr_accessor :current
    end

    # Essentially the {Sass::Importers::Filesystem} but registering each
    # import file path.
    class SassFilesystemImporter < ::Sass::Importers::Filesystem

      private

      def _find(dir, name, options)
        full_filename, syntax = find_real_file(dir, name)
        return unless full_filename && File.readable?(full_filename)

        filter = Nanoc3::Filters::Sass.current
        item = filter.imported_filename_to_item(full_filename)
        filter.depend_on([ item ]) unless item.nil?

        options[:syntax] = syntax
        options[:filename] = full_filename
        options[:importer] = self
        ::Sass::Engine.new(File.read(full_filename), options)
      end
    end

    # Runs the content through [Sass](http://sass-lang.com/).
    # Parameters passed to this filter will be passed on to Sass.
    #
    # @param [String] content The content to filter
    #
    # @return [String] The filtered content
    def run(content, params={})
      # Build options
      options = params.dup
      sass_filename = options[:filename] ||
        (@item && @item[:content_filename])
      options[:filename] ||= sass_filename
      options[:filesystem_importer] ||=
        Nanoc3::Filters::Sass::SassFilesystemImporter

      # Render
      engine = ::Sass::Engine.new(content, options)
      self.class.current = self
      engine.render
    end

    def imported_filename_to_item(filename)
      path = Pathname.new(filename).realpath
      @items.find do |i|
        next if i[:content_filename].nil?
        Pathname.new(i[:content_filename]).realpath == path
      end
    end

    # @todo Remove me in nanoc 3.2.x
    def depend_on(items)
      # Notify
      items.each do |item|
        Nanoc3::NotificationCenter.post(:visit_started, item)
        Nanoc3::NotificationCenter.post(:visit_ended,   item)
      end

      # Raise unmet dependency error if necessary
      items.each do |item|
        rep = item.reps.find { |r| !r.compiled? }
        raise Nanoc3::Errors::UnmetDependency.new(rep) if rep
      end
    end

  end
end