require 'net/http'

module Varnish
  def self.included(base)
    base.send :extend,  ClassMethods
    base.send :include, InstanceMethods
  end

  module ClassMethods
    # Enables edge-side-includes for the listed actions
    #   esi :index, :show, :new
    def esi(*actions)
      after_filter lambda { response.headers['X-Varnish-Esi'] = 'true' }, :only => actions
    end
  end

  module InstanceMethods
    # Removes an object from cache
    #   purge("/pages/123")
    def purge(path)
      http = Net::HTTP.new(request.host, request.port)
      http.purge(path).code == "200"
    end

    # Creates a new netry in varnish's ban list
    #   ban("req.http.host == example.com && req.url ~ \.png$")
    def ban(value)
      http = Net::HTTP.new(request.host, request.port)
      http.ban('/', {'X-Varnish-Ban' => value}).code == "200"
    end

    # Sets the time-to-live for an object in varnish.  Can take both a Time or Integer.
    #   cache 1.hour
    #   cache 1.day.from_now
    def cache(value)
      if value.is_a?(Time)
        ttl   = value.utc.to_i - Time.now.utc.to_i
        stale = value.utc + 1.second
      else
        ttl   = value.to_i
        stale = ttl.from_now.utc + 1.second
      end

      response.headers['X-Fresh-Until'] = stale.strftime("%a, %d %b %Y %H:%M:%S GMT")
      response.headers['X-Varnish-Ttl'] = ttl.to_s
    end

    # Sets the Cache-Control header for the response, this was taken from Sinatra.
    #   cache_control :public, :max_age => 1.hour
    #   cache_control :private, :must_revalidate
    def cache_control(*values)
      if values.last.kind_of?(Hash)
        hash = values.pop
        hash.reject! { |k,v| v == false }
        hash.reject! { |k,v| values << k if v == true }
      else
        hash = {}
      end

      values = values.map { |value| value.to_s.tr('_','-') }
      hash.each do |key, value|
        key = key.to_s.tr('_', '-')
        value = value.to_i if key == "max-age"
        values << [key, value].join('=')
      end

      response['Cache-Control'] = values.join(', ') if values.any?
    end
  end
end