class UComponent
  def self.defaults
    {}
  end

  def self.build(_doc, _options)
    raise NotImplementedError
  end

  def self.call(*args)
    fn = args[0].is_a?(Proc) ? args[0] : method(:build)
    options = args[0].is_a?(Hash) ? args[0] : (args[1] || {})

    new.call(options, fn)
  end

  def self.to_proc
    -> (*args) { call(*args) }
  end

  def initialize(fn = nil)
    @fn = fn 
  end

  def call(opt = {}, fn = nil)
    func = @fn || fn
    options = opt.is_a?(Hash) ? self.class.defaults.merge(opt) : opt
    builder = Nokogiri::HTML::Builder.new do |doc|
      func.arity == 1 ? func.(doc) : func.(doc, options)
    end

    builder.to_html.sub!(/<!DOCTYPE.*[^>]/, '')
  end

  def to_proc
    -> (options) { call(options) }
  end
end

class HelloWorld < UComponent
  def self.build(doc)
    doc.span.bold {
      doc.text("Hello world")
    }
  end
end

class HelloWorld2 < UComponent
  def self.build(doc, message:)
    doc.span.bold {
      doc.text(message)
    }
  end
end

class Greet < UComponent
  def self.defaults
    { name: 'John Doe' }
  end

  def self.build(doc, name:)
    doc.span.bar.foo! {
      doc.text("Hello #{name}")
    }
  end
end

# == Examples ==

HelloWorld.call
#=> "<span class=\"bold\">Hello world</span>\n"

HelloWorld2.call message: 'Olá mundo'
#=> "<span class=\"bold\">Ol&aacute; mundo</span>\n"

UComponent.call -> doc { doc.span.bold { doc.text("Hello world") } }
#=> "<span class=\"bold\">Hello world</span>\n"

UComponent.call(
  -> doc, message { doc.span.bold { doc.text(message) } },
  'Olá mundo'
)
#=> "<span class=\"bold\">Ol&aacute; mundo</span>\n"

Greet.call
#=> "<span class=\"bar\" id=\"foo\">Hello John Doe</span>\n"

Greet.call name: 'Serradura'
#=> "<span class=\"bar\" id=\"foo\">Hello Serradura</span>\n"

[{name: 'Rodrigo'}, {name: 'Talita'}, {}].map(&Greet)
#=> ["<span class=\"bar\" id=\"foo\">Hello Rodrigo</span>\n", "<span class=\"bar\" id=\"foo\">Hello Talita</span>\n", "<span class=\"bar\" id=\"foo\">Hello John Doe</span>\n"]

greet = UComponent.new(-> (doc, name:) do
  doc.span.bar.foo! {
    doc.text("Hello #{name}")
  }
end)

greet.call(name: 'Bella')
#=> "<span class=\"bar\" id=\"foo\">Hello Bella</span>\n"

[{name: 'Rodrigo'}, {name: 'Talita'}].map(&greet)
#=> ["<span class=\"bar\" id=\"foo\">Hello Rodrigo</span>\n", "<span class=\"bar\" id=\"foo\">Hello Talita</span>\n"]

number = UComponent.new(-> (doc, n) do
  doc.strong { doc.text(n) }
end)

[1,2,3,4].map(&number)
#=> ["<strong>1</strong>\n", "<strong>2</strong>\n", "<strong>3</strong>\n", "<strong>4</strong>\n"]