additionals/app/models/additionals_chart.rb

class AdditionalsChart
  include ActiveRecord::Sanitization
  include Redmine::I18n

  CHART_DEFAULT_HEIGHT = 350
  CHART_DEFAULT_WIDTH = 400

  class << self
    def color_schema
      Redmine::Plugin.installed?('redmine_reporting') ? RedmineReporting.setting(:chart_color_schema) : 'tableau.Classic20'
    end

    def data
      raise 'overwrite it!'
    end

    # build return value
    def build_chart_data(datasets, options = {})
      cached_labels = labels
      data = { datasets: datasets.to_json,
               labels: cached_labels.keys,
               label_ids: cached_labels.values }

      required_labels = options.key?(:required_labels) ? options.delete(:required_labels) : 2

      data[:valid] = cached_labels.any? && cached_labels.count >= required_labels unless options.key?(:valid)
      data[:width] = self::CHART_DEFAULT_WIDTH unless options.key?(:width)
      data[:height] = self::CHART_DEFAULT_HEIGHT unless options.key?(:height)
      data[:value_link_method] = '_project_issues_path' unless options.key?(:value_link_method)
      data[:color_schema] = color_schema

      data.merge(options)
    end

    private

    def build_values_without_gaps(data, gap_value = 0)
      values = []
      labels.each do |label, _label_id|
        values << if data.key?(label)
                    data[label]
                  else
                    gap_value
                  end
      end

      values
    end

    def init_labels
      @labels = {}
    end

    def labels
      # NOTE: do not sort it, because color changes if user switch language
      @labels.to_h
    end

    def add_label(label, id)
      return if @labels.key? label

      @labels[label] = id
    end
  end
end