Ruby Regular Expression lookahead to Split at pipe unless contained in brackets

Question

I'm trying to decode the following string:

body = '{type:paragaph|class:red|content:[class:intro|body:This is the introduction paragraph.][body:This is the second paragraph.]}'
body << '{type:image|class:grid|content:[id:1|title:image1][id:2|title:image2][id:3|title:image3]}'

I need the string to split at the pipes but not where a pipe is contained with square brackets, to do this I think I need to perform a lookahead as described here: How to split string by ',' unless ',' is within brackets using Regex?

My attempt(still splits at every pipe):

x = self.body.scan(/\{(.*?)\}/).map {|m| m[0].split(/ *\|(?!\]) */)}
->
[
  ["type:paragaph", "class:red", "content:[class:intro", "body:This is the introduction paragraph.][body:This is the second paragraph.]"]
  ["type:image", "class:grid", "content:[id:1", "title:image1][id:2", "title:image2][id:3", "title:image3]"]
]

Expecting:

   ->
    [
      ["type:paragaph", "class:red", "content:[class:intro|body:This is the introduction paragraph.][body:This is the second paragraph.]"]
      ["type:image", "class:grid", "content:[id:1|title:image1][id:2|title:image2][id:3|title:image3]"]
    ]

---

Does anyone know the regex required here?

Is it possible to match this regex? I can't seem to modify it correctly Regular Expression to match underscores not surrounded by brackets?

---

I modified the answer here Split string in Ruby, ignoring contents of parentheses? to get:

 self.body.scan(/\{(.*?)\}/).map {|m| m[0].split(/\|\s*(?=[^\[\]]*(?:\[|$))/)}

Seems to do the trick. Though I'm sure if there's any shortfalls.

Answer 1

I modified the answer here Split string in Ruby, ignoring contents of parentheses? to get:

 self.body.scan(/\{(.*?)\}/).map {|m| m[0].split(/\|\s*(?=[^\[\]]*(?:\[|$))/)}

Seems to do the trick. If it has any shortfalls please suggest something better.

Answer 2

Dealing with nested structures that have identical syntax is going to make things difficult for you.

You could try a recursive descent parser (a quick Google turned up https://github.com/Ragmaanir/grammy - not sure if any good)

Personally, I'd go for something really hacky - some gsubs that convert your string into JSON, then parse with a JSON parser :-). That's not particularly easy either, though, but here goes:

require 'json'

b1 = body.gsub(/([^\[\|\]\:\}\{]+)/,'"\1"').gsub(':[',':[{').gsub('][','},{').gsub(']','}]').gsub('}{','},{').gsub('|',',')


JSON.parse('[' + b1 + ']')  

It wasn't easy because the string format apparently uses [foo:bar][baz:bam] to represent an array of hashes. If you have a chance to modify the serialised format to make it easier, I would take it.