build xml with ox

[notezen]

May be my changes will be interesting for you:

i moved library dependent code that builds xml data into one place,
changed syntax for building xml to library independent and used fast xml library ox

I marked with "TODO xml builder" places where i did not change old code.

[crapooze]

Thanks! This is very interesting.
I don't have prior experience with ox hence I'll have a look to it.
Also, I'm very interested in the "Component" login, thanks for patching it out.
Give me some more days :).

[crapooze]

Ok, I've browsed through it quickly. You've done interesting work.
Before accepting the merge I'd like to know two things:

1. Do you think there's an easy way to get a "builder" interface close to nokogiri's xml_builder? my point is that when there are deeply nested nodes (e.g., file-transfer negotiations), the block-passing style of nokogiri's xml_builder allows to capture the XML structure. Something I'm not ready to lose is the ability(see https://github.com/crapooze/em-xmpp/blob/master/lib/em-xmpp/helpers.rb#L200-L220 )

2. Do you know if there will be some support or API-compatible interface to JRuby with ox? This point is less important that point (1) but I think we should not move too far from being able to port em-xmpp to JRuby

Ideally, we would have an abstraction that can then enable someone to pick between ox and nokogiri interchangeably. What's your take on that?

[notezen]

1. As you can see in https://github.com/notezen/em-xmpp/blob/ox/lib/em-xmpp/helpers.rb#L198-L218
   porting to new interface is very easy. Deeply nested nodes are done with recursive calls to x and x_if methods.
   Also see https://github.com/ohler55/ox/blob/master/contrib/builder_test.rb as an example of usage.
   The reason why I against nokogiri's style is use of "method_missing" . It is relatively slow and I think can not be used in fast environments.
2. According to homepage https://github.com/ohler55/ox Ox is compatible with Ruby 1.8.7, 1.9.2, JRuby, and RBX.
   You can ask author about details.
3. I thought about it, it is rational and can be done easy. https://github.com/notezen/em-xmpp/blob/ox/lib/em-xmpp/xml_builder.rb (x and x_if methods)
   and https://github.com/notezen/em-xmpp/blob/ox/lib/em-xmpp/xml_parser.rb are points of change for different xml libraries (not only Nokogiri and Ox)

Author of Ox have planed to write SAX push parser (ohler55/ox#50). After that Ox support in em-xmpp will be complete.

[crapooze]

Really good work!
I agree that the method_missing approach is not great (i even warn in the README).
I'm merging it, let's say that the next effort will be to port all entities to your xml_builder approach (plus bin/xmig, which is my debugging swiss-knife for now).