class MailchimpTemplate

# File lib/mailchimp_template.rb, line 6
def initialize(template)
  @template = template
end

# File lib/mailchimp_template.rb, line 18
def merge_tags
  @template.scan(/\*\|(?<tag_name>.+?)\|\*/).flatten
end

# File lib/mailchimp_template.rb, line 10
def render(options = {})
  merge_tags = options.delete(:merge_tags)
  regions = options.delete(:regions)
  result = @template
  result = render_regions(result, regions)
  return render_merge_tags(result, merge_tags)
end

# File lib/mailchimp_template.rb, line 31
def render_merge_tags(template, merge_tags = {})
  # | is %7C when escaped by Nokogiri
  template.gsub! /\*(?:\||%7C)(?<tag_name>.+?)(?:\||%7C)\*/ do |match|
    tag_name = $~[:tag_name]
    case tag_name
    when /^IF:(?<cond>.+)/, /^IFNOT:(?<cond>.+)/, /^ELSEIF:(?<cond>.+)/, "ELSE:", "END:IF"
      #TODO: handle conditional merge tags
      match
    when "MC:TOC"
      #TODO: generate TOC of h1 and h2 tags
      match
    when "MC:TOC_TEXT"
      #TODO: generate TOC of h1 and h2 tags, render as text
      match
    when /^DATE:(?<format>.+)/
      #TODO: render with PHP date format (nontrivial, requires a custom parser)
      match
    when "CURRENT_YEAR"
      Date.today.year
    else
      merge_tags[tag_name] || match
    end
  end
end

# File lib/mailchimp_template.rb, line 22
def render_regions(template, regions = {})
  html = Nokogiri::HTML::DocumentFragment.parse(template)
  html.css("*").select { |n| n.attr("mc:edit") }.each do |editable_region|
    editable_region.children = Nokogiri::HTML::DocumentFragment.parse(regions[editable_region.attr("mc:edit")])
    editable_region.remove_attribute("mc:edit")
  end
  result = html.to_s
end