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RSS-aware ATOM feed helper

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rss_aware_atom_feed_helper.rb
Ruby
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##
# RSS-aware patched helper. See http://www.zephyros-systems.co.uk/blog/?p=179
#
require 'set'
 
module ActionView
# = Action View Atom Feed Helpers
module Helpers #:nodoc:
module AtomFeedHelper
# Adds easy defaults to writing Atom feeds with the Builder template engine (this does not work on ERb or any other
# template languages).
#
# Full usage example:
#
# config/routes.rb:
# Basecamp::Application.routes.draw do
# resources :posts
# root :to => "posts#index"
# end
#
# app/controllers/posts_controller.rb:
# class PostsController < ApplicationController::Base
# # GET /posts.html
# # GET /posts.atom
# def index
# @posts = Post.find(:all)
#
# respond_to do |format|
# format.html
# format.atom
# end
# end
# end
#
# app/views/posts/index.atom.builder:
# atom_feed do |feed|
# feed.title("My great blog!")
# feed.updated(@posts.first.created_at)
#
# for post in @posts
# feed.entry(post) do |entry|
# entry.title(post.title)
# entry.content(post.body, :type => 'html')
#
# entry.author do |author|
# author.name("DHH")
# end
# end
# end
# end
#
# The options for atom_feed are:
#
# * <tt>:language</tt>: Defaults to "en-US".
# * <tt>:root_url</tt>: The HTML alternative that this feed is doubling for. Defaults to / on the current host.
# * <tt>:url</tt>: The URL for this feed. Defaults to the current URL.
# * <tt>:id</tt>: The id for this feed. Defaults to "tag:#{request.host},#{options[:schema_date]}:#{request.request_uri.split(".")[0]}"
# * <tt>:schema_date</tt>: The date at which the tag scheme for the feed was first used. A good default is the year you
# created the feed. See http://feedvalidator.org/docs/error/InvalidTAG.html for more information. If not specified,
# 2005 is used (as an "I don't care" value).
# * <tt>:instruct</tt>: Hash of XML processing instructions in the form {target => {attribute => value, }} or {target => [{attribute => value, }, ]}
#
# Other namespaces can be added to the root element:
#
# app/views/posts/index.atom.builder:
# atom_feed({'xmlns:app' => 'http://www.w3.org/2007/app',
# 'xmlns:openSearch' => 'http://a9.com/-/spec/opensearch/1.1/'}) do |feed|
# feed.title("My great blog!")
# feed.updated((@posts.first.created_at))
# feed.tag!(openSearch:totalResults, 10)
#
# for post in @posts
# feed.entry(post) do |entry|
# entry.title(post.title)
# entry.content(post.body, :type => 'html')
# entry.tag!('app:edited', Time.now)
#
# entry.author do |author|
# author.name("DHH")
# end
# end
# end
# end
#
# The Atom spec defines five elements (content rights title subtitle
# summary) which may directly contain xhtml content if :type => 'xhtml'
# is specified as an attribute. If so, this helper will take care of
# the enclosing div and xhtml namespace declaration. Example usage:
#
# entry.summary :type => 'xhtml' do |xhtml|
# xhtml.p pluralize(order.line_items.count, "line item")
# xhtml.p "Shipped to #{order.address}"
# xhtml.p "Paid by #{order.pay_type}"
# end
#
#
# atom_feed yields an AtomFeedBuilder instance. Nested elements yield
# an AtomBuilder instance.
def atom_feed(options = {}, &block)
if options[:schema_date]
options[:schema_date] = options[:schema_date].strftime("%Y-%m-%d") if options[:schema_date].respond_to?(:strftime)
else
options[:schema_date] = "2005" # The Atom spec copyright date
end
 
xml = options.delete(:xml) || eval("xml", block.binding)
xml = rssify(xml) if (rssify = options.delete(:rssify))
 
xml.instruct!
if options[:instruct]
options[:instruct].each do |target, attrs|
if attrs.respond_to?(:keys)
xml.instruct!(target, attrs)
elsif attrs.respond_to?(:each)
attrs.each { |attr_group| xml.instruct!(target, attr_group) }
end
end
end
 
feed_opts = {
"xml:lang" => options[:language] || "en-US",
"xmlns#{':a' if rssify}" => 'http://www.w3.org/2005/Atom'
}
feed_opts.merge!(options).reject! { |k, v| !k.to_s.match(/^xml/) }
 
xml.feed(feed_opts) do
xml.id(options[:id] || "tag:#{request.host},#{options[:schema_date]}:#{request.fullpath.split(".")[0]}")
xml.link(:rel => 'alternate', :type => 'text/html', :href => options[:root_url] || (request.protocol + request.host_with_port))
xml.link(:rel => 'self', :type => 'application/atom+xml', :href => options[:url] || request.url)
 
yield AtomFeedBuilder.new(xml, self, options)
end
end
 
##
# ATOM elements with their analogues in RSS. Expressed in the form of a hash,
# the LHS is the atom name, RHS is *either* a string with the RSS name, *or*
# a hash of the RSS name to a custom tagger lambda which will call the xml builder itself
#
# Anything that is RSS should appear here, even if it has the same element name in ATOM.
# Things that don't will fall back to the ATOM namespace.
ATOM_RSS_METHOD_MAP = {
'id' => 'guid',
'title' => 'title',
'subtitle' => 'description',
'feed' =>
{
'channel' => lambda do |xml, *options, &block|
xml.tag!("rss", :version => '2.0') do
xml.tag! "channel", *options, &block
end
end
},
'entry' => 'item',
'link' =>
{
'link' => lambda do |xml, *options, &block|
tag_with = 'link'
rel = options.last[:rel]
if rel == 'alternate' && options.last[:type] == 'text/html'
options.last.delete(:rel)
options.last.delete(:type)
options.unshift(options.last.delete(:href))
else
tag_with = 'a:link'
end
xml.tag! tag_with, *options, &block
end
},
'content' =>
{
'description' => lambda do |xml, *options, &block|
# 'description' element has no type="html""
options.last.delete(:type)
xml.tag! 'description', *options, &block
end
},
'published' =>
{
'pubDate' => lambda do |xml, *options, &block|
options[0] = DateTime.parse(options[0]).rfc822
xml.tag! 'pubDate', *options, &block
end
}
}
 
##
# Modify this instance of Builder::XmlMarkup to
# intercept atom calls and patch them to their RSS equivalents
def rssify(xml)
ATOM_RSS_METHOD_MAP.each_pair do |atom_name, handler|
rss_method_name, custom_tagger = *(handler.is_a?(Hash) ?
[handler.keys.first, handler.values.first] : [handler, nil])
 
xml.class_eval do
define_method atom_name do |*options, &block|
if custom_tagger
custom_tagger.call(xml, *options, &block)
else
xml.tag!(rss_method_name, *options, &block)
end
end
end
end
##
# Define the fallback to atom for method_missing
xml.class_eval do
define_method :method_missing_with_fallback_to_atom do |sym, *args, &block|
# Violation of DRY (see ATOM_RSS_METHOD_MAP above). TODO: make it not one.
@@known ||= [:rss, :title, :description, :guid, :channel, :item, :link, :description, :pubDate]
sym_s = sym.to_s
sym = "a:#{sym_s}".to_sym unless @@known.include?(sym) || sym_s.include?(':')
method_missing_without_fallback_to_atom sym, *args, &block
end
alias_method_chain :method_missing, :fallback_to_atom
end
 
xml
end
 
class AtomBuilder
(XHTML_TAG_NAMES = %w(content rights title subtitle summary).to_set) unless defined?(XHTML_TAG_NAMES)
 
def initialize(xml)
@xml = xml
end
 
private
# Delegate to xml builder, first wrapping the element in a xhtml
# namespaced div element if the method and arguments indicate
# that an xhtml_block? is desired.
def method_missing(method, *arguments, &block)
if xhtml_block?(method, arguments)
@xml.__send__(method, *arguments) do
@xml.div(:xmlns => 'http://www.w3.org/1999/xhtml') do |xhtml|
block.call(xhtml)
end
end
else
@xml.__send__(method, *arguments, &block)
end
end
 
# True if the method name matches one of the five elements defined
# in the Atom spec as potentially containing XHTML content and
# if :type => 'xhtml' is, in fact, specified.
def xhtml_block?(method, arguments)
if XHTML_TAG_NAMES.include?(method.to_s)
last = arguments.last
last.is_a?(Hash) && last[:type].to_s == 'xhtml'
end
end
end
 
class AtomFeedBuilder < AtomBuilder
def initialize(xml, view, feed_options = {})
@xml, @view, @feed_options = xml, view, feed_options
end
 
# Accepts a Date or Time object and inserts it in the proper format. If nil is passed, current time in UTC is used.
def updated(date_or_time = nil)
@xml.updated((date_or_time || Time.now.utc).xmlschema)
end
 
# Creates an entry tag for a specific record and prefills the id using class and id.
#
# Options:
#
# * <tt>:published</tt>: Time first published. Defaults to the created_at attribute on the record if one such exists.
# * <tt>:updated</tt>: Time of update. Defaults to the updated_at attribute on the record if one such exists.
# * <tt>:url</tt>: The URL for this entry. Defaults to the polymorphic_url for the record.
# * <tt>:id</tt>: The ID for this entry. Defaults to "tag:#{@view.request.host},#{@feed_options[:schema_date]}:#{record.class}/#{record.id}"
def entry(record, options = {})
@xml.entry do
@xml.id(options[:id] || "tag:#{@view.request.host},#{@feed_options[:schema_date]}:#{record.class}/#{record.id}")
 
if options[:published] || (record.respond_to?(:created_at) && record.created_at)
@xml.published((options[:published] || record.created_at).xmlschema)
end
 
if options[:updated] || (record.respond_to?(:updated_at) && record.updated_at)
@xml.updated((options[:updated] || record.updated_at).xmlschema)
end
 
@xml.link(:rel => 'alternate', :type => 'text/html', :href => options[:url] || @view.polymorphic_url(record))
 
yield AtomBuilder.new(@xml)
end
end
end
 
end
end
end
 
module RssAwareAtomFeedHelper
# Keeps ActiveRecord dependencies quiet. TODO: find a way of removing
end

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