module Gematria
  class English < Struct.new(:text)
    # applies "mispar hechrachi" method to English alphabet (http://www.inner.org/gematria/fourways.php)
    CORRESPONDENCE_TABLE = {
      :a => 1,   :b => 2,   :c => 3,   :d => 4,   :e => 5,   :f => 6,   :g => 7,   :h => 8,   :i => 9,
      :j => 10,  :k => 20,  :l => 30,  :m => 40,  :n => 50,  :o => 60,  :p => 70,  :q => 80,  :r => 90,
      :s => 100, :t => 200, :u => 300, :v => 400, :w => 500, :x => 600, :y => 700, :z => 800
    }

    # Gets an array of the values for each character of text.
    #
    #   name = Gematria::English.new("Adam")
    #   name.mapped # => [1, 4, 1, 40]
    #
    # @return [Array<Number>] numerical values attributed to each character of the original text
    def mapped
      text.each_char.map { |c| lookup_char c }
    end

    # Gets the summed gematria number of text.
    #
    #   name = Gematria::English.new("Adam")
    #   name.converted # => 46
    #
    # This uses <tt>mapped</tt> internally and sums the results.
    # @return [Number] sum of the values of each character
    def converted
      mapped.inject(:+)
    end

    # Recursively reduces the <tt>converted</tt> value to a single digit mispar katan mispari style.
    #
    #   name = Gematria::English.new("Adam")
    #   name.reduced # => 1
    #
    # For example: "Adam" -> 46 -> 10 -> 1
    # @return [Number] single digit from reduction of <tt>converted</tt> value
    def reduced
      do_reduction_on converted
    end

    private
    def lookup_char(char)
      CORRESPONDENCE_TABLE.fetch(char.downcase.to_sym, 0)
    end

    def do_reduction_on(number)
      if number < 10
        number
      else
        do_reduction_on number.to_s.each_char.map(&:to_i).inject(:+)
      end
    end

  end
end