it3s/meppit

module Exportable
  extend ActiveSupport::Concern

  included do

    scope :to_geojson, -> do
      features = where('1=1').map { |item| JSON.parse item.to_geojson }
      {type: "FeatureCollection", features: features}.to_json
    end

    def to_geojson
      serialized_as :geojson
    end

    def to_csv
      serialized_as :csv
    end

    def serialized_as(format)
      active_model_serializer.new(self).send(:"to_#{format}")
    end

    def self.serialized_as(format, ids=nil)
      collection = (ids ? where(id: ids) : all).map { |obj| active_model_serializer.new(obj) }
      hashs_collection = collection.map &:serializable_hash
      case format
        when :json    then hashs_collection.to_json
        when :xml     then hashs_collection.to_xml
        when :csv     then ::CSVGenerator.generate hashs_collection
        when :geojson then feature_collection(collection.map &:geojson_feature_hash)
      end
    end

    private

      def self.feature_collection(collection)
        { "type" => "FeatureCollection", "features" => collection }.to_json
      end

  end
end