# frozen_string_literal: true

module Versionaire
  VERSION_ATTRIBUTES = %i[major minor maintenance].freeze
  VERSION_DELIMITER = "."

  # An immutable, semantic version value object.
  # rubocop:disable Metrics/BlockLength
  Version = Struct.new :major, :minor, :maintenance, keyword_init: true do
    include Comparable

    def self.regex
      /
        \A                    # Start of string.
        \d{1,}                # Major version.
        #{VERSION_DELIMITER}  # Delimiter.
        \d{1,}                # Minor version.
        #{VERSION_DELIMITER}  # Delimiter.
        \d{1,}                # Maintenance version.
        \z                    # End of string.
      /x
    end

    def self.arguments major, minor, maintenance
      Hash[VERSION_ATTRIBUTES.zip [major, minor, maintenance]]
    end

    def initialize major: 0, minor: 0, maintenance: 0
      super
      validate
      freeze
    end

    def + other
      klass = self.class
      klass.new klass.arguments(*reduce(other, :+))
    end

    def - other
      klass = self.class
      klass.new klass.arguments(*reduce(other, :-))
    end

    def == other
      hash == other.hash
    end

    alias_method :eql?, :==

    def <=> other
      to_s <=> other.to_s
    end

    def to_s
      to_a.join VERSION_DELIMITER
    end

    alias_method :to_str, :to_s

    def to_a
      [major, minor, maintenance]
    end

    private

    def validate
      fail(Errors::InvalidNumber) if to_a.any? { |number| !number.is_a? Integer }
      fail(Errors::NegativeNumber) if to_a.any?(&:negative?)
    end

    def reduce other, action
      to_a.zip(other.to_a).map { |pair| pair.reduce(action) }
    end
  end
  # rubocop:enable Metrics/BlockLength
end