module JekyllSupport
  # Attribution aspect of JekyllPluginHelper
  class JekyllPluginHelper
    # @param file must be a fully qualified file name that points to a file within a gem.
    # @return Gem::Specification of gem that file points into, or nil if not called from a gem
    # See https://stackoverflow.com/a/75890279/553865
    def self.current_spec(file)
      abort 'JekyllPluginHelper::current_spec: file is nil' if file.nil?
      return nil unless File.exist?(file)

      searcher = if Gem::Specification.respond_to?(:find)
                   Gem::Specification
                 elsif Gem.respond_to?(:searcher)
                   Gem.searcher.init_gemspecs
                 end

      searcher&.find do |spec|
        file.start_with? spec.full_gem_path
      end
    end

    def attribute
      return unless @current_gem

      <<~END_OUTPUT
        <div id="jps_attribute_#{rand(999_999)}" class="jps_attribute">
          <div>
            <a href="#{@homepage}" target="_blank" rel="nofollow">
              #{attribution_string}
            </a>
          </div>
        </div>
      END_OUTPUT
    end

    def default_attribution
      authors = @authors&.join(', ')
      result = "Generated by the \#{@name} v\#{@version} Jekyll plugin"
      result << ", written by #{authors}" if authors
      result << " \#{@published_date}" if @published_date
      result << '.'
      result
    end

    # Sets @current_gem if file points at a uniquely named file within a gem.
    # @param file must be a fully qualified file name in a gem, for example: __FILE__
    def gem_file(file)
      @current_gem = JekyllPluginHelper.current_spec file
      @logger.debug "No gem found for '#{file} was found." unless @current_gem
      annotate_globals if @attribution && @current_gem
    end

    private

    def annotate_globals
      return unless @current_gem

      @name           = @current_gem.name
      @authors        = @current_gem.authors
      @homepage       = @current_gem.homepage
      @published_date = @current_gem.date.to_date.to_s
      @version        = @current_gem.version
    end

    def attribution_string
      string = if @attribution == true
                 default_attribution
               else
                 @attribution
               end
      String.interpolate { string }
    end
  end
end