module Feedzirra
  module FeedUtilities
    UPDATABLE_ATTRIBUTES = %w(title feed_url url last_modified)
    
    attr_writer :updated, :last_modified, :entries
    attr_accessor :etag

    def initialize
      @entries = []
      super
    end

    def last_modified
      @last_modified ||= begin
        entry = entries.reject {|e| e.published.nil? }.sort_by { |entry| entry.published if entry.published }.last
        entry ? entry.published : nil
      end
    end
    
    [ :old, :new ].each do |flag| 
      define_method("mark_all_entries_#{flag}!") do         # def mark_all_entries_new!
        @entries.each{ |e| e.__send__(:"mark_#{flag}!") }   #   @entries.each {|e| e.mark_new! }
      end                                                   # end
    end
        
    def updated?
      @updated
    end
    
    def new_entries
      @entries.select{ |e| e.new_entry? }
    end
    
    def has_new_entries?
      new_entries.size > 0
    end
    
    def update_from_feed(feed)
      # Mark all existing entries as old, then add new entries, which are
      # marked as new by default.
      self.entries.each{|e| e.mark_old! }

      find_new_entries_for(feed).each do |e|
        self.entries << e
      end
      
      updated! if UPDATABLE_ATTRIBUTES.any? { |name| update_attribute(feed, name) }
    end
    
    def update_attribute(feed, name)
      old_value, new_value = send(name), feed.send(name)
      
      if old_value != new_value
        send("#{name}=", new_value)
      end
    end
    
    def sanitize_entries!
      entries.each {|entry| entry.sanitize!}
    end
    
    private
    
    def updated!
      @updated = true
    end
    
    def find_new_entries_for(feed)
      # This implementation is a hack to get around the fact that not all feeds 
      # have a published date - we exploit the fact that feeds are always 
      # ordered with newest element first to work backwards until we reach feed urls 
      # that we've already seen.      
      feed.entries.reverse.inject([]) do |res, entry| 
        break res if entry.url == self.entries.first.url
        res << entry
      end
    end
    
    def existing_entry?(test_entry)
      entries.any? { |entry| entry.url == test_entry.url }
    end
  end
end