require "identification/parser/parser"

module Identification
  module Parser
    # Represents a passport parser.
    #
    # @private 
    class Passport < Parser
      def self.parse(mrz_line_1, mrz_line_2)
        return { validity: false }  if mrz_line_1.length != 44 || mrz_line_2.length != 44

        doc_data = Hash.new(10)

        # Document will be valid unless an error occurs.
        doc_data[:validity] = true

        # Document may not be valid, but still, continue parsing.
        doc_data[:validity] = false unless mrz_check_line_checksum(mrz_line_2)

        # Read the first line without chevrons
        split = mrz_line_1.split(/<+/)

        doc_data[:date_of_birth] = yymmdd_to_ruby_date(mrz_line_2[13...19])
        doc_data[:expiry_date] = yymmdd_to_ruby_date(mrz_line_2[21...27])

        # In case of an invalid date...
        if doc_data['date_of_birth'] == false || doc_data['expiry_date'] == false
          doc_data[:validity] = false
        end

        doc_data[:issuing_state] = mrz_line_1[2...5].sub(/<+/, '')
        doc_data[:last_name] = split[1][3..-1]
        doc_data[:first_names] = split[2..-1]
        doc_data[:passport_number] = mrz_line_2[0...9]
        doc_data[:nationality] = mrz_line_2[10...13].sub(/<+/, '')
        doc_data[:gender] = mrz_line_2[20].sub(/<+/, '')
        doc_data[:personal_number] = mrz_line_2[28...42].sub(/<+/, '')

        doc_data
      end

      def self.mrz_check_digit_calculate(str)
        str = str.strip.upcase
        values = str.chars.map do |char|
          case char
          when '<'
            0
          when 'A'..'Z'
            char.ord - 65 + 10
          when '0'..'9'
            char.ord - 48
          else
            fail "Unexpected character '#{char}'"
          end
        end
        (values.zip([7, 3, 1].cycle).map { |(v, w)| v * w }.reduce(:+) % 10).to_s
      end

      def self.mrz_check_line_checksum(mrz_line)
        # Grabbing the MRZ's check digits
        doc_check = []
        doc_check[0] = mrz_line[9].to_s
        doc_check[1] = mrz_line[19].to_s
        doc_check[2] = mrz_line[27].to_s
        doc_check[3] = mrz_line[42].to_s
        doc_check[4] = mrz_line[43].to_s

        # Calculating our own check digits...
        our_check = []
        our_check[0] = mrz_check_digit_calculate(mrz_line[0...9])
        our_check[1] = mrz_check_digit_calculate(mrz_line[13...19])
        our_check[2] = mrz_check_digit_calculate(mrz_line[21...27])
        our_check[3] = mrz_check_digit_calculate(mrz_line[28...42])
        our_check[4] = mrz_check_digit_calculate(mrz_line[0...10] + mrz_line[13...20] + mrz_line[21...43])

        # The 4th check digit can be either > or 0, we always return 0 from our CheckDigit calc.
        our_check[3] = '<' if our_check[3] == '0' && doc_check[3] == '<'

        return true if doc_check.uniq.sort == our_check.uniq.sort

        false
      end

      private_class_method :mrz_check_digit_calculate, :mrz_check_line_checksum
    end
  end
end