Types2

module Types
 
  # --------------------------------------------------------------------------- 
  
  module Typenames
    
    CONSTANTS = [
      NUM     = [Integer, Float, Complex, Rational],
      INT     = Integer,
      DEC     = [Float, Rational],
      STR     = String,
      CHR     = String,
      REX     = Regexp,
      BOOL    = [TrueClass, FalseClass],
      ENUM    = Enumerable,
      NIL     = NilClass
    ]
  
    class Unset; end

  end

  # --------------------------------------------------------------------------- 

  class Tp
    attr_reader :vars

    def initialize
      @vars = {}
      @data = Struct.new(:value, :classes, :to, :args)
    end

    def define(&bl) = ( instance_exec(&bl) if bl )

    def method_missing(name, val = nil)
      name[/^(\w+)=/] ?
        @vars.key?($1.to_sym) ? set($1.to_sym, val) : super :
        @vars.key?(name) ? @vars[name].value : super
    end

    private

    def set(name, val)
      # handle to:
      val = ((to = @vars[name].to) && val.respond_to?(to)) ?
        val.send(to, *@vars[name].args) : val

      @vars[name].classes.map { it === val }.any?(true) ?
        (@vars[name].value = val) :
          abort('TypeError: %s => %s (%s)' % [name, val, val.class])
    end

    def →(key, *cls, to: nil, args: [])
      @vars[key] = @data.new(Unset, cls.flatten, to, args)
    end
  end

end

require './types.rb'

# =============================================================================

# NOTE: Default value is `Unset`.. not `nil`.

# NOTE: `to` is used for type conversion (to_s, to_i, to_f, to_a, to_h, to_r)
#   but you can use any method the object responds to and that results in
#   the 'type' required. (ex: :upcase). It uses <value>.send(:method, [*args])
#   args: is used for extra arguments for the method.
#   Ex: to: :tr, args: [' ', '']

tp = Types::Tp.new
include Types::Typenames

tp.define {
  → :name,      STR, to: :tr, args: [' ', '']
  → :age,       INT, Types::Tp::NIL, to: :to_i
  → :employed,  BOOL
  → :list,      ENUM
  → :unset,     STR
}


tp.name = 'Helge'
tp.age = 33
tp.employed = true
tp.list = (1..11)

p %i(name age employed list).map { tp.send(it) }
# => "Helge, 33, true, 1..11"

tp.age = nil # nil (age allows Integer and NilClass)
tp.age = '13' # 13 (testing to: :to_i)

tp.name = 'Pow Wow' # testing to: :tr, args: [' ', '']
p tp.name # => "PowWow"

p tp.unset unless tp.unset == Unset # no output

tp.name = nil # TypeError: name =>  (NilClass)