cbrfilter.rb

# Store CBRFilter objects
#
class CBRFilters
  include Enumerable
  extend Forwardable

  attr_accessor :filters

  def_delegators :@filters, :each, :size, :<<, :push

  def initialize
    @filters ||= []
  end

  # Compile Elastic Search query (as hash)
  def query
    query = {
      size: 0,
      aggs: {}
    }

    @filters.each do |filter|
      query[:aggs].update(filter.query)
    end

    return query
  end
end

# Filter object
#
class CBRFilter
  attr_accessor :type, :defaults, :selected

  def initialize(opts = {})
    opts.each do |key, val|
      instance_variable_set("@#{key}", opts[key])
    end
  end

  # Factory: create new filter
  def self.create type
    begin
      name = "CBRFilter" + (type.classify)
      name.constantize.new
    rescue NameError
      raise(NameError, "Filter class #{name} doesn't exist.")
    end
  end

  def query
    {}
  end

  def option_query
    query = {
      @type.to_sym => {
        terms: {
          field: @field
        }
      }
    }
  end

  def min_max_query
    query = {
      (@type + '_min').to_sym => {
        min: {
          field: @field
        }
      },
      (@type + '_max').to_sym => {
        max: {
          field: @field
        },
      }
    }
  end
end

# Date range filter
#
class CBRFilterDateRange < CBRFilter
  def initialize
    super :type => 'date_range',
          :defaults => nil,
          :selected => nil,
          :field => 'timestamp'
  end

  def query
    min_max_query
  end
end

# PFI filter
#
class CBRFilterPfi < CBRFilter
  def initialize
    super :type => 'pfi',
          :defaults => nil,
          :selected => nil,
          :field => 'pfi'
  end

  def query
    option_query
  end
end

# Typ DO filter
#
class CBRFilterTypDo < CBRFilter
  def initialize
    super :type => 'typ_do',
          :defaults => nil,
          :selected => nil,
          :field => 'typ_do'
  end

  def query
    option_query
  end
end

### usage

filters = CBRFilters.new

filters << CBRFilter.create('date_range')
filters << CBRFilter.create('pfi')
filters << CBRFilter.create('typ_do')

puts filters.query.to_json

# output:
# {"size":0,"aggs":{"date_range_min":{"min":{"field":"timestamp"}},"date_range_max":{"max":{"field":"timestamp"}},"pfi":{"terms":{"field":"pfi"}},"typ_do":{"terms":{"field":"typ_do"}}}}