custom liquid filter + drop

data.rb

class Data 
  attr_accessor :date_range

  def initialize(type)
    @type = type
  end

  def graph_points
    SomeClass.graph_points( 
      @type,
      date_between: @date_range)
  end

  def to_liquid
    self
  end
end

demo.rb

Liquid::Template.register_filter(StatsFilter)

Liquid::Template.
  parse("$.draw_graph({{stats.users | date_range: options.date_start, options.date_end | compute }})").
  render('stats' => StatsDrop.new, 'options' => OptionsDrop.new(params))

options_drop.rb

class OptionsDrop < Liquid::Drop
  def date_start
    Date.today - 3.month
  end
  
  def date_end
    Date.today
  end
end

stats_drop.rb

class StatsDrop  < Liquid::Drop
  def users
    Data.new("User")
  end
end

stats_filter.rb

module StatsFilter 
  def date_range(input, *options)
    input.date_range = options[0]..options[1]
    input
  end

  def compute(input)
    input.graph_points.to_json
  end
end