Sew with Hypertext DSL (.rb extension on templates only for syntax highlighting)

_footer.ht.rb

footer do
  text "You put your foot-er in it."
end

_layout.ht.rb

html lang: "en-GB" do
  head do
    title do
      text @page.title
    end
  end
  body do
    render @page.body
  end
  partial "_footer.ht"
end

build.rb

require_relative './sew'
Sew.clean
Sew.build

index.ht.rb

---
title: Sew Me
---
h1 do
  text "Welcome"
end
p do
  text "A paragraph sewn together."
end

sew.rb

require "hypertext"
require "hypertext/dsl"
require "fileutils"
require "ostruct"
require "webrick"
require "json"
require "yaml"

class Sew
  VERSION = "0.0.4"
  BUILD_DIR = ENV["SITE_DIR"] || "build"
  FILE_REGEX = /\A---\n(.+?)\n---\n(.*)/m
  PATH_MAP = Hash.new do |hash, key|
    key == "index" ? "/" : "/%s/" % key.tr(".", "/")
  end

  def self.version
    puts VERSION
  end

  def self.build
    clean
    pages = Dir["[^_]*.ht"].map do |template|
      Hash.new.tap do |page|
        parts = File.basename(template, ".ht").split(".")
        page[:locale] = parts.pop.intern
        page[:id] = parts.join(".")
        frontmatter, page[:body] = File.read(template).match(FILE_REGEX)[1..2]
        page.merge!(YAML.load(frontmatter))
        page[:path] = PATH_MAP[(page.delete("path") || page[:id])]
        page[:destination_dir] = ("./%s/%s" % [BUILD_DIR, page[:locale]]) + page[:path]
        page[:destination] = page[:destination_dir] + "index.html"
      end
    end
    data = Hash.new.tap do |dat|
      Dir["*.yml"].map do |file|
        dat[File.basename(file, ".yml")] = YAML.load_file(file)
      end
    end
    site = OpenStruct.new(JSON.parse({ pages: pages, data: data }.to_json, object_class: OpenStruct))
    site.pages.map(&:destination_dir).uniq.each(&FileUtils.method(:mkpath))
    site.layout = File.read("_layout.ht")
    site.pages.each do |page|
      File.open(page.destination, "w") do |file|
        site.page = page
        file.write Template.new(site).to_s
      end
    end
  end

  def self.clean
    FileUtils.rm_rf(BUILD_DIR)
  end

  def self.serve
    build
    root = File.expand_path(BUILD_DIR)
    server = WEBrick::HTTPServer.new(:Port => 4567, :DocumentRoot => root)
    trap('INT') { server.shutdown }
    server.start
  end

  class Template < Hypertext::DSL
    def initialize(site)
      site.each_pair do |key, val|
        instance_variable_set(sprintf("@%s", key), val)
      end

      @ht = Hypertext.new
      render @layout
    end

    def render(string)
      instance_eval string
    end

    def partial(filename)
      render File.read(filename)
    end
  end
end