Fix SGF parsing regular expressions, fix #36

[neagle]

This was all caused by an emoticon: :/

SGF parsing can currently be broken by an escaped backslash preceding an ending square bracket: ']'

This updates the regular expressions used to parse sequences and properties to account for the possibility that a preceding backslash has been, itself, escaped.

[waltheri]

Thanks for solving this issue (I wasn't at home). I will check it and merge soon.

[neagle]

No problem! It's a pretty understandable oversight since it's such an edge case to have an intended (and escaped) backslash right before a closing bracket, but it managed to break the game to an impressive degree. 😄

[xcombelle]

I have an improvement on @neagle code. It is still to be tested but here it is:

If I understand it is done to detect the between square bracket elements
shouldn't be

  \[([^\\\]]|\\.)*\]

expanded with explanation pcre with /x modifier

  \[ #an opening braquet
   ( # either
      [^\\\]] # not ( an antislash or a closing braquet )
    |  # or
    \\. # an antislash followed by any character
   )* #repeated at least 0 times
   \] # followed by a close bracket

I tested both regexp with regex101 online tool ( https://regex101.com/r/bF0jQ5/4 for compact and js one and https://regex101.com/r/bF0jQ5/2 for pcre and explained one ) It looks that both work

By the way looks like on some cases, your version eat too much
for example
with

 C[\\];C[a]

your version eat both comment and that between: https://regex101.com/r/bF0jQ5/5

while mine take just the first https://regex101.com/r/fB2hF2/1

(originally in in neagle/gokibitz#92 (comment) which is said by @neagle as a clarity improvement and fix bug improvement)

[waltheri]

@xcombelle code looks pretty and works. However I would suggest a little improvement. According to SGF specification you can escape new line characters. Therefore I would use this reg exp:

/\[([^\\\]]|\\(.|\n|\r))*\]/g

and then I would remove these line breaks. Please check it and I will update master branch.

[xcombelle]

You are full right I actually missed that . don't match carriage return in javascript (good catch)

[yewang]

Does this change work for all of these test cases?

(;C[\];B[aa];W[bb])
Two nodes: comment ];B[aa in root node, white move in second node

(;C[\\];B[aa];W[bb])
Three nodes: comment \ in root node, black move in second node, white move in third node

(;C[\\\];B[aa];W[bb])
Two nodes: comment \];B[aa in root node, white move in second node

(;C[\\\\];B[aa];W[bb])
Three nodes: comment \\ in root node, black move in second node, white move in third node

[xcombelle]

@yewang yes it should works for these uses cases you can test it on https://regex101.com/r/bF0jQ5/6 (I tested the four)