# frozen_string_literal: true

module CnsBrazil
  class Cns
    def initialize(value:)
      @value = value.to_s.gsub(/[^\d]/, '')
    end

    def valid?
      return false if @value.length != 15

      return start_with_1_or_2? if %w[1 2].include?(@value[0])
      return start_with_7_8_or_9? if %w[7 8 9].include?(@value[0])

      false
    end

    def self.generate
      generator = CnsBrazil::Generator.new

      generator.call
    end

    private

    def start_with_1_or_2?
      pis = @value[0, 11]

      sum_result = sum_result(pis)

      rest = sum_result % 11
      verificator_digit = rest.zero? ? 0 : 11 - rest
      result = verificator_digit == 10 ? "#{pis}001#{11 - ((sum_result + 2) % 11)}" : "#{pis}000#{verificator_digit}"

      result == @value
    end

    def start_with_7_8_or_9?
      sum_result = sum_result(@value)

      rest = sum_result % 11

      rest.zero?
    end

    def sum_result(value)
      cns_to_array = value.chars.map(&:to_i)

      cns_to_array.each_with_index.reduce(0) do |sum, (element, index)|
        sum += element * (15 - index)
        sum
      end
    end
  end
end