assembler · October 13, 2014 11:06 · Oct 13, 2014
diff --git a/monads.rb b/monads.rb
@@ -0,0 +1,283 @@
+# https://www.youtube.com/watch?v=uTR__8RvgvM
+# ---------------------------------------------------------------------------- #
+
+Project = Struct.new(:creator)
+Person  = Struct.new(:address)
+Address = Struct.new(:country)
+Country = Struct.new(:capital)
+City    = Struct.new(:weather)
+
+class Optional
+  attr_accessor :value
+
+  def initialize(value)
+    @value = value
+  end
+
+  def self.from_value(value)
+    new(value)
+  end
+
+  def and_then(&block)
+    if value.nil?
+      Optional.new(nil)
+    else
+      block.call(value)
+    end
+  end
+
+  def method_missing(*args, &block)
+    and_then do |value|
+      Optional.new(value.public_send(*args, &block))
+    end
+  end
+end
+
+def get_project_weather(project)
+  # Optional.new(project)
+  #   .and_then { |project| Optional.new(project.creator) }
+  #   .and_then { |creator| Optional.new(creator.address) }
+  #   .and_then { |address| Optional.new(address.country) }
+  #   .and_then { |country| Optional.new(country.capital) }
+  #   .and_then { |capital| Optional.new(capital.weather) }
+  #   .value
+  Optional.new(project).creator.address.country.capital.weather.value
+end
+
+
+project = Project.new(Person.new(Address.new(Country.new(City.new("sunny")))))
+p get_project_weather(project)
+
+project = Project.new(Person.new)
+p get_project_weather(project)
+
+
+# ---------------------------------------------------------------------------- #
+
+Blog     = Struct.new(:categories)
+Category = Struct.new(:posts)
+Post     = Struct.new(:comments)
+
+class Many
+  attr_accessor :values
+
+  def initialize(values)
+    @values = values
+  end
+
+  def self.from_value(value)
+    new([value])
+  end
+
+  def and_then(&block)
+    Many.new(values.map(&block).flat_map(&:values))
+  end
+
+  def method_missing(*args, &block)
+    and_then do |value|
+      Many.new(value.public_send(*args, &block))
+    end
+  end
+end
+
+def words_in(blogs)
+  # Many.new(blogs)
+  #   .and_then { |blog|     Many.new(blog.categories) }
+  #   .and_then { |category| Many.new(category.posts) }
+  #   .and_then { |post|     Many.new(post.comments) }
+  #   .and_then { |comment|  Many.new(comment.split(/\s+/)) }
+  #   .values
+  Many.new(blogs).categories.posts.comments.split(/\s+/).values
+end
+
+blogs = [
+  Blog.new([
+    Category.new([
+      Post.new(['I love cats', 'I love dogs']),
+      Post.new(['I love mice', 'I love pigs']),
+    ]),
+    Category.new([
+      Post.new(['I hate cats', 'I hate dogs']),
+      Post.new(['I hate mice', 'I hate pigs']),
+    ]),
+  ]),
+  Blog.new([
+    Category.new([
+      Post.new(['Red is better than blue']),
+    ]),
+    Category.new([
+      Post.new(['Blue is better than red']),
+    ]),
+  ]),
+]
+
+p words_in(blogs)
+
+# ---------------------------------------------------------------------------- #
+
+Thread.abort_on_exception = true
+
+require "rubygems"
+gem "uri_template"
+
+require "uri"
+require "net/http"
+require "json"
+require "uri_template"
+
+def get_json(url, &success)
+  Thread.new do
+    puts "[GET] #{url}..."
+
+    uri = URI.parse(url)
+    json = Net::HTTP.get(uri)
+    value = JSON.parse(json)
+    success.call(value)
+  end
+end
+
+# get_json("https://api.github.com") do |urls|
+#   org_url_template = URITemplate.new(urls["organization_url"])
+#   org_url = org_url_template.expand(org: "ruby")
+#   get_json(org_url) do |org|
+#     repos_url = org["repos_url"]
+
+#     get_json(repos_url) do |repos|
+#       most_popular_repo = repos.max_by { |repo| repo["watchers_count"] }
+#       repo_url = most_popular_repo["url"]
+
+#       get_json(repo_url) do |repo|
+#         contributors_url = repo["contributors_url"]
+
+#         get_json(contributors_url) do |users|
+#           most_profilic_user = users.max_by { |user| user["contributions"] }
+#           user_url = most_profilic_user["url"]
+
+#           get_json(user_url) do |user|
+#             puts "The most influential Rubyist is #{user["name"]} (#{user["login"]})"
+#           end
+#         end
+#       end
+#     end
+#   end
+# end
+
+class Eventually
+  attr_accessor :block
+
+  def initialize(&block)
+    @block = block
+  end
+
+  def self.from_value(value)
+    new { |s| s.call(value) }
+  end
+
+  def and_then(&block)
+    Eventually.new do |success|
+      run do |value|
+        block.call(value).run(&success)
+      end
+    end
+  end
+
+  def run(&success)
+    block.call(success)
+  end
+end
+
+def get_github_api_urls
+  github_root_url = "https://api.github.com"
+  Eventually.new{ |success| get_json(github_root_url, &success) }
+end
+
+def get_org(urls, name)
+  org_url_template = URITemplate.new(urls["organization_url"])
+  org_url = org_url_template.expand(org: name)
+
+  Eventually.new{ |success| get_json(org_url, &success) }
+end
+
+def get_repos(org)
+  repos_url = org["repos_url"]
+
+  Eventually.new { |success| get_json(repos_url, &success) }
+end
+
+def get_most_popular_repo(repos)
+  most_popular_repo = repos.max_by { |repo| repo["watchers_count"] }
+  repo_url = most_popular_repo["url"]
+
+  Eventually.new { |success| get_json(repo_url, &success) }
+end
+
+def get_contributors(repo)
+  contributors_url = repo["contributors_url"]
+
+  Eventually.new { |success| get_json(contributors_url, &success) }
+end
+
+def get_most_profilic_user(users)
+  most_profilic_user = users.max_by { |user| user["contributions"] }
+  user_url = most_profilic_user["url"]
+
+  Eventually.new { |success| get_json(user_url, &success) }
+end
+
+
+get_github_api_urls
+  .and_then { |urls | get_org(urls, 'ruby') }
+  .and_then { |org  | get_repos(org) }
+  .and_then { |repos| get_most_popular_repo(repos) }
+  .and_then { |repo | get_contributors(repo) }
+  .and_then { |users| get_most_profilic_user(users) }
+  .run do |user|
+    puts "The most influential Rubyist is #{user["name"]} (#{user["login"]})"
+  end
+
+# ---------------------------------------------------------------------------- #
+
+module Monad
+  def within(&block)
+    and_then do |value|
+      self.class.from_value(block.call(value))
+    end
+  end
+end
+
+Optional.include Monad
+Many.include Monad
+Eventually.include Monad
+
+
+def description_from(containing_json)
+  containing_json.within do |json|
+    JSON.parse(json)
+  end.within do |hash|
+    "%s (%s)" % hash.values_at("name", "login")
+  end
+end
+
+optional_nil = Optional.new(nil)
+p description_from(optional_nil)
+
+optional_json = Optional.new(%|{ "login": "nobu", "name": "Nobuyoshi Nakada" }|)
+p description_from(optional_json)
+
+many_jsons = Many.new([
+  %|{ "login": "nobu", "name": "Nobuyoshi Nakada" }|,
+  %|{ "login": "matz", "name": "Yukihiro Matsumoto" }|,
+])
+p description_from(many_jsons)
+
+eventually_json = Eventually.new do |success|
+  Thread.new do
+    uri = URI.parse("https://api.github.com/users/nobu")
+    json = Net::HTTP.get(uri)
+    success.call(json)
+  end
+end
+description_from(eventually_json).run { |description| p(description) }
+
+puts "\n press any key to exit \n"
+gets