module Rack::Less

  # Handles configuration for Rack::Less
  # Available config settings:
  # :cache
  #   whether to cache the compilation output to
  #   a corresponding static file. Also determines
  #   what value config#combinations(:key) returns
  # :compress
  #   whether to remove extraneous whitespace from
  #   compilation output
  # :combinations
  #   Rack::Less uses combinations as directives for
  #   combining the output of many stylesheets and
  #   serving them as a single resource.  Combinations
  #   are defined using a hash, where the key is the
  #   resource name and the value is an array of
  #   names specifying the stylesheets to combine
  #   as that resource.  For example:
  #     Rack::Less.config.combinations = {
  #       'web'    => ['reset', 'common', 'app_web'],
  #       'mobile' => ['reset', 'iui', 'common', 'app_mobile']
  #     }
  # :cache_bust
  #   whether to append a timestamp to the sheet requests generated by combinations
  class Config

    ATTRIBUTES = [:cache, :compress, :combinations, :cache_bust]
    attr_accessor *ATTRIBUTES

    DEFAULTS = {
      :cache        => false,
      :compress     => false,
      :combinations => {},
      :cache_bust   => nil
    }

    def initialize(settings={})
      ATTRIBUTES.each do |a|
        instance_variable_set("@#{a}", settings[a].nil? ? DEFAULTS[a] : settings[a])
      end
    end

    def cache?
      !!@cache
    end

    def compress?
      !!@compress
    end

    def combinations(key=nil)
      if key.nil?
        @combinations
      else
        if cache?
          stylesheet_filename(key)
        else
          (@combinations[key] || []).collect do |combo|
            stylesheet_filename(combo)
          end
        end
      end
    end

    def stylesheet(key)
      if @combinations[key]
        combinations(key.to_s)
      else
        stylesheet_filename(key.to_s)
      end
    end

    private

    def stylesheet_filename(key)
      filename = key.strip
      filename += ".css" unless filename.include?('.css')
      if !filename.include?('?') && self.cache_bust != false
        if !(cb = cache_bust_value).empty?
          filename += "?#{cb}"
        end
      end
      filename
    end

    def cache_bust_value
      if self.cache_bust == true
        Time.now.to_i
      else
        self.cache_bust ||= default_cache_bust
      end.to_s
    end

    def default_cache_bust
      if defined?(::Sinatra) && defined?(::Sinatra::Application)
        app_root_cache_bust(::Sinatra::Application)
      elsif defined?(::Rails)
        app_root_cache_bust(::Rails)
      end || ""
    end

    def app_root_cache_bust(app)
      if app.respond_to?(:root)
        mtime_cache_bust(app.root.to_s)
      end
    end

    def mtime_cache_bust(path)
      if File.exists?(path)
        File.mtime(path).to_i
      end
    end

  end
end