Grokdown

require "grokdown"

class Text < String
  include Grokdown

  def consumes?(*) = false

  def self.matches_node?(node) = node.type == :text

  def self.arguments_from_node(node) = node.string_content
end

class Link < Struct.new(:href, :title, :text, keyword_init: true)
  include Grokdown

  def self.matches_node?(node) = node.type == :link

  def self.arguments_from_node(node) = {href: node.url, title: node.title}

  consumes Text => :text=

  def on_text( &block)
    @text_callback = block
  end

  def text=(new_text)
    return if self[:text]

    @text_callback&.call(new_text)

    self[:text] = new_text
  end
end

class License < Struct.new(:text, :href, :name, :link, keyword_init: true)
  include Grokdown

  def self.matches_node?(node) = node.type == :header && node.header_level == 2 && node.first_child.string_content == "License"

  consumes Text => :text=, Link => :link=

  extend Forwardable

  def_delegator :link, :href

  def link=(link)
    self[:link] = link
    license = self
    link.on_text do |value|
      license.name = value
    end
  end
end

Struct.new(:text, :link, :keyword_init) do
  include described_module

  def self.matches_node?(node) = node.type == :header && node.header_level == 2

  consumes Text => :text=, Link => :link=
end

class Readme < Struct.new(:license)
  include Grokdown

  def self.matches_node?(node) = node.type == :document

  consumes License => :license=
end

readme = Grokdown::Document.new(File.read("README.md")).first

puts readme.license.name
# fetch license at url
readme.license.href