#!/usr/bin/env ruby
# encoding: utf-8

require 'time'
require 'rubygems'
require 'bundler/setup'
require 'builder'
require 'json'
require 'rdiscount'
require 'mustache'

def main
  dir = ARGV.shift.to_s
  unless File.directory? dir
    puts 'usage: rss.rb <dir>'
    exit 1
  end
  b = Blag.new dir
  b.generate!
end

class Blag

  def self.go! dir
    self.new(dir).generate!
  end

  def initialize dir, num_posts = 10
    @dir = dir
    @num_posts = num_posts
  end

  def generate!
    generate_latest_post_json
    generate_rss
  end

  def generate_latest_post_json
    post = latest_post
    data['latest'] = {
      title: post['title'],
      date: post['date'],
      timestamp: post['timestamp'],
      tags: post['tags'],
      author: post['author'],
      url: post['relative_url'],
      link: post['link'],
      styles: post['styles'],
      body: post['body']
    }.delete_if { |k, v| v.nil? }
    json = JSON.pretty_generate data
    File.open(data_file, 'w') { |f| f.puts json }
  end

  def generate_rss
    File.open(rss_file, 'w') { |f| f.puts feed_xml.target! }
  end

  def latest_post
    posts.first
  end

  def find_post dir, slug
    # technically should look for slug.md, slug.html.md, etc.
    File.join dir, slug + '.html.md'
  end

  def posts
    @posts ||= begin
      Dir[File.join(@dir, 'posts/20*/*')].map do |dir|
        json = File.read File.join(dir, '_data.json')
        data = JSON.parse json
        prefix = dir.sub(@dir, '')
        data.map do |slug, post|
          filename = find_post dir, slug
          content = File.read filename
          relative_url = File.join(prefix, slug)
          post['slug'] = slug
          post['type'] = post['link'] ? :link : :post
          post['title'] = "→ #{post['title']}" if post['type'] == :link
          post['relative_url'] = relative_url
          post['url'] = root_url + post['relative_url']
          post['content'] = content
          post['body'] = RDiscount.new(post['content'], :smart).to_html
          post['rfc822'] = Time.at(post['timestamp']).rfc822
          post
        end
      end.flatten.sort_by { |p| -p['timestamp'] }.first(@num_posts)
    end
  end

  def title
    data['title']
  end

  def subtitle
    data['subtitle']
  end

  def root_url
    data['url']
  end


private

  def data_file
    File.join @dir, '_data.json'
  end

  def data
    @data ||= JSON.parse File.read(data_file)
  end

  def rss_template(type)
    if type == :post
      @post_rss_template ||= File.read(File.join('templates', 'post.rss.html'))
    elsif type == :link
      @link_rss_template ||= File.read(File.join('templates', 'link.rss.html'))
    else
      raise 'unknown post type: ' + type
    end
  end

  def rss_file
    File.join @dir, 'feed.xml'
  end

  def rss_html post
    Mustache.render rss_template(post['type']), post: post
  end

  def feed_xml
    xml = Builder::XmlMarkup.new
    xml.instruct! :xml, version: '1.0'
    xml.instruct! 'xml-stylesheet', href: root_url + '/css/normalize.css', type: 'text/css'
    xml.instruct! 'xml-stylesheet', href: root_url + '/css/style.css', type: 'text/css'

    xml.rss version: '2.0' do
      xml.channel do
        xml.title title
        xml.description subtitle
        xml.link root_url
        xml.pubDate posts.first['rfc822']

        posts.each do |post|
          xml.item do
            xml.title post['title']
            xml.description rss_html(post)
            xml.pubDate post['rfc822']
            xml.author post['author']
            xml.link post['link'] || post['url']
            xml.guid post['url']
          end
        end
      end
    end
    xml
  end

end

main if $0 == __FILE__