class PostVersion < ActiveRecord::Base
  belongs_to :post
  belongs_to :updater, :class_name => "User"
  before_validation :initialize_updater
  scope :for_user, lambda {|user_id| where("updater_id = ?", user_id)}
  scope :updater_name_matches, lambda {|name| where("updater_id = (select _.id from users _ where lower(_.name) = ?)", name.downcase)}
  
  def self.create_from_post(post)
    if post.created_at == post.updated_at
      create_from_created_post(post)
    else
      create_from_updated_post(post)
    end
  end
  
  def initialize_updater
    self.updater_id = CurrentUser.id
    self.updater_ip_addr = CurrentUser.ip_addr
  end
  
  def tag_array
    @tag_array ||= tags.scan(/\S+/)
  end
  
  def presenter
    PostVersionPresenter.new(self)
  end
  
  def reload
    @tag_array = nil
    super
  end

  def sequence_for_post
    versions = PostVersion.where(:post_id => post_id).order("id desc").all
    diffs = []
    versions.each_index do |i|
      if i < versions.size - 1
        diffs << versions[i].diff(versions[i + 1])
      end
    end
    return diffs
  end
  
  def diff(version)
    latest_tags = post.tag_array
    new_tags = tag_array
    new_tags << "rating:#{rating}" if rating.present?
    new_tags << "parent:#{parent_id}" if parent_id.present?
    new_tags << "source:#{source}" if source.present?
    old_tags = version.present? ? version.tag_array : []
    if version.present?
      old_tags << "rating:#{version.rating}" if version.rating.present?
      old_tags << "parent:#{version.parent_id}" if version.parent_id.present?
      old_tags << "source:#{version.source}" if version.source.present?
    end

    return {
      :added_tags => new_tags - old_tags,
      :removed_tags => old_tags - new_tags,
      :unchanged_tags => new_tags & old_tags,
      :obsolete_added_tags => new_tags - latest_tags,
      :obsolete_removed_tags => old_tags & latest_tags,
    }
  end
  
  def previous
    PostVersion.where("post_id = ? and id < ?", post_id, id).order("id desc").first
  end
  
end