require 'planet/fido'
require 'planet/transmogrify'
require 'planet/sift'
require 'fileutils'

module Planet

  # Fetch a set of feeds, normalize, and write each as a set of entries into a
  # cache directory.
  def Planet.spider
    config = Planet.config['Planet']
    cache = config['cache_directory']
    http_cache = File.join(cache,'http')
    entry_cache = File.join(cache,'entry')
    source_cache = File.join(cache,'source')

    # make output directories
    FileUtils.mkdir_p http_cache, :mode => 0700
    FileUtils.mkdir_p entry_cache, :mode => 0700
    FileUtils.mkdir_p source_cache, :mode => 0700

    # prep fetcher
    fido = Planet::Fido.new(http_cache)
    fido.threads = config['spider_threads'].to_i if config['spider_threads']
    fido.timeout = config['feed_timeout'].to_f if config['feed_timeout']

    # process subscriptions: for each updated feed, updated the cache with
    # the set of canonicalized entries augmented with source information.
    subs = Planet.config.keys.grep(/^https?:\/\//)
    fido.each(subs) do |sub, resp|
      next unless resp.code == '200'
      uri = resp.header['Content-Location'] || sub

      # first set of filters: xml parsing and element names
      doc = Planet::Transmogrify.parse(resp.body)
      feed = doc.root || doc

      # add in self information
      if not feed.elements['link[@rel="self"]']
        link = feed.add_element('link',{'rel'=>'self', 'href'=>uri})
        if doc.version[0..2] == 'rss'
          link.attributes['type'] == 'application/rss+xml'
        elsif doc.version[0..3] == 'atom'
          link.attributes['type'] == 'application/atom+xml'
        else
          Planet.log.error "Not a feed - #{uri}"
          next
        end
        feed.add_text("\n  ")
      end

      # second set of filters: cardinality, sanitization, dates, and uris
      doc.attributes['xml:base'] = uri
      Planet.sift feed, fido

      # process feed attributes: xml* (xml:lang, xml:base, xmlns) will need
      # need to be transplanted to each entry.  The rest will simply be
      # placed on the source element
      root_attrs = {}
      source = REXML::Element.new('source')
      feed.attributes.each_attribute do |attrib|
        if attrib.expanded_name[0..2] == 'xml'
          root_attrs[attrib.expanded_name] = attrib.value
        else
          source.attributes[attrib.expanded_name] = attrib.value
        end
      end

      # add in configuration information (names, hackergotchi icons...)
      source.add_namespace 'planet', 'http://planet.intertwingly.net/'
      Planet.source(sub, source)

      # process feed elements: entries will be captured for later processing,
      # other elements will be transplanted to the source element.
      entries = []
      feed.elements.each do |element|
        if element.name == 'entry'
          entries << element
        else
          source.add_element(element)
        end
      end

      entries.each do |entry|
        # try to find a unique id (TODO: try harder)
        id = entry.elements['id'].text rescue nil
        id ||= entry.elements['link[@rel="alternate"]/@href'] rescue nil
        next unless id

        # determine output file name for this entry
        entry_file = File.join(entry_cache, Planet.filename(id))

        # determine updated date
        updated = entry.elements['updated']
        if not updated
          updated = entry.add_element('updated')
          if entry.elements['published']
            updated.text = entry.elements['published'].text
          elsif File.exist? entry_file
            updated.text=File.stat(entry_file).mtime.iso8601
          else
            updated.text=DateTime.now.to_s
          end
        end

        # augment with feed xml* attributes and source information
        root_attrs.each_pair {|name,value| entry.attributes[name]=value}
        entry.add(source) if not entry.elements['source']

        # output the entry, with a timestamp reflecting the update time
        File.open(entry_file, 'w') { |file| file.write(entry.to_s) }
        updated = Time.parse(updated.text)
        File.utime updated, updated, entry_file
      end

      # write source information out to the cache
      if feed.name == 'feed'
        source.name = 'planet:source'
        root_attrs.each_pair {|name,value| source.attributes[name]=value}
        source_file = File.join(source_cache, Planet.filename(sub))
        File.open(source_file, 'w') { |file| file.write(source.to_s) }
      end
    end
  end

  # add configuration information to a source element
  def Planet.source sub, element
    Planet.config[sub].each do |name,value|
      next if name[0..1] == '__'
      child = element.add_element("planet:#{name}")
      child.text = value
    end
  end
end