# frozen_string_literal: true

require_relative "cpf_cnpj_tools/version"

module CpfCnpjTools
  ##
  # Class responsible for generating and
  # validating CPF and CNPJ numbers
  class Generator
    CPF1DIGIT = [10, 9, 8, 7, 6, 5, 4, 3, 2].freeze
    CPF2DIGIT = [11, 10, 9, 8, 7, 6, 5, 4, 3, 2].freeze
    CNPJ1DIGIT = [5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2].freeze
    CNPJ2DIGIT = [6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2].freeze

    ##
    # Method for generating valid CPF numbers
    # @return String
    def generate_cpf
      base = generate_base
      base << generate_identifier(base, true)
      base << generate_identifier(base, false)
      base.join
    end

    ##
    # Method for generating valid CNPJ numbers
    # @return String
    def generate_cnpj
      base = generate_base(cnpj: true)
      base << generate_identifier(base, true, cpf: false)
      base << generate_identifier(base, false, cpf: false)
      base.join
    end

    ##
    # Method for validating CPF numbers.
    # @param cpf (String, Integer)
    # @return Boolean
    def validate_cpf(cpf)
      cpf_array = cpf.to_s.split('').map!(&:to_i)
      first_digit = cpf_array[-2]
      second_digit = cpf_array[-1]
      base_cpf = cpf_array[0..8]
      calculated_first_digit = generate_identifier(base_cpf, true)
      calculated_second_digit = generate_identifier(base_cpf << calculated_first_digit, false)
      return false if (first_digit != calculated_first_digit) || (second_digit != calculated_second_digit)

      true
    end

    ##
    # Method for validating CNPJ numbers.
    # @param cnpj (String, Integer)
    # @return Boolean
    def validate_cnpj(cnpj)
      cnpj_array = cnpj.to_s.split('').map!(&:to_i)
      first_digit = cnpj_array[-2]
      second_digit = cnpj_array[-1]
      base_cnpj = cnpj_array[0..11]
      calculated_first_digit = generate_identifier(base_cnpj, true, cpf: false)
      calculated_second_digit = generate_identifier(base_cnpj << calculated_first_digit, false, cpf: false)
      return false if (first_digit != calculated_first_digit) || (second_digit != calculated_second_digit)

      true
    end

    private

    ##
    # Generate the first numbers of CPF/CNPJ
    # randomly.
    # @param cnpj (Boolean)
    # @return (Array)
    def generate_base(cnpj: false)
      base_number = []
      9.times do
        base_number << rand(10)
      end
      if cnpj
        base_number.delete_at(-1)
        base_number.push 0, 0, 0, 1
      end
      base_number
    end

    ##
    # Generate the first and second identifier numbers
    # of the CPF/CNPJ.
    # @param first_numbers (Array)
    # @param first (Boolean)
    # @param cpf (Boolean)
    # @return Integer
    def generate_identifier(first_numbers, first, cpf: true)
      multipliers = if cpf
                      first ? CPF1DIGIT : CPF2DIGIT
                    else
                      first ? CNPJ1DIGIT : CNPJ2DIGIT
                    end
      product = []
      first_numbers.length.times do |index|
        product << first_numbers[index] * multipliers[index]
      end
      generate_valid_digit(product)
    end

    ##
    # Calculates the value of a valid identifier digit.
    # @param digits (Array)
    # @return Integer
    def generate_valid_digit(digits)
      sum = 0
      digits.each do |item|
        sum += item
      end
      remainder = sum % 11
      if remainder < 2
        0
      else
        11 - remainder
      end
    end
  end
end