require "yaml"

module RateCenter
  class DataLoader
    attr_reader :data_directory, :cities, :rate_centers

    def initialize(**options)
      @data_directory = options.fetch(:data_directory) { Pathname(File.expand_path("../../data/", __dir__)) }
    end

    def load(type, ...)
      case type.to_sym
      when :all
        @cities = load_data("cities", :all)
        @rate_centers = load_data("rate_centers", :all)
      when :cities
        @cities = load_data("cities", ...)
      when :rate_centers
        @rate_centers = load_data("rate_centers", ...)
      else
        raise ArgumentError, "Invalid type: #{type}"
      end

      nil
    end

    private

    def load_data(type, all = nil, **options)
      if all
        load_data_from(data_directory.join(type).glob("**/*.yml"), type:)
      else
        load_data_with_filter(options.fetch(:only), type:)
      end
    end

    def load_data_with_filter(filter, type:)
      unless filter.is_a?(Hash)
        return Array(filter).each_with_object([]) do |country, result|
          result.concat(load_country_data(type:, country:))
        end
      end

      filter.each_with_object([]) do |(country, regions), result|
        if regions.is_a?(Hash)
          regions.each do |region, keys|
            data = load_region_data(type:, country:, region:)
            result.concat(data.select { |d| Array(keys).include?(d.fetch("name")) })
          end
        else
          Array(regions).each do |region|
            result.concat(load_region_data(type:, country:, region:))
          end
        end
      end
    end

    def load_data_from(files, type:)
      Array(files).each_with_object([]) do |file, result|
        result.concat(YAML.load(file.read).fetch(type))
      end
    end

    def load_country_data(type:, country:)
      load_data_from(data_directory.join(type.to_s, country.to_s.downcase).glob("**/*.yml"), type:)
    end

    def load_region_data(type:, country:, region:)
      load_data_from(
        data_directory.join(type.to_s, country.to_s.downcase, "#{region.to_s.downcase}.yml"),
        type:
      )
    end
  end
end