"""
REX/Python

Based on Robert D. Cameron's REX/Perl 1.0.

Original copyright notice follows:

REX/Perl 1.0

Robert D. Cameron "REX: XML Shallow Parsing with Regular Expressions",
Technical Report TR 1998-17, School of Computing Science, Simon Fraser 
University, November, 1998.
Copyright (c) 1998, Robert D. Cameron. 
The following code may be freely used and distributed provided that
this copyright and citation notice remains intact and that modifications
or additions are clearly identified.

"""

import re

# See the original article if you want to demysticize what follows. ;)
# ftp://fas.sfu.ca/pub/cs/TR/1998/CMPT1998-17.html

# Here's a key to the naming conventions used for variable names.
# SE: scanning expression
# CE: continuation expression
# RSB: right square bracket
# QM: question mark
# DT: DOCTYPE
# SPE: shallow parsing expression
# RE: regular expression

TextSE = "[^<]+"
UntilHyphen = "[^-]*-"
Until2Hyphens = UntilHyphen + "(?:[^-]" + UntilHyphen + ")*-"
CommentCE = Until2Hyphens + ">?"
UntilRSBs = "[^\\]]*](?:[^\\]]+])*]+"
CDATA_CE = UntilRSBs + "(?:[^\\]>]" + UntilRSBs + ")*>"
S = "[ \\n\\t\\r]+"
NameStrt = "[A-Za-z_:]|[^\\x00-\\x7F]"
NameChar = "[A-Za-z0-9_:.-]|[^\\x00-\\x7F]"
Name = "(?:" + NameStrt + ")(?:" + NameChar + ")*"
QuoteSE = "\"[^\"]*\"|'[^']*'"
DT_IdentSE = S + Name + "(?:" + S + "(?:" + Name + "|" + QuoteSE + "))*"
MarkupDeclCE = "(?:[^\\]\"'><]+|" + QuoteSE + ")*>"
S1 = "[\\n\\r\\t ]"
UntilQMs = "[^?]*\\?+"
PI_Tail = "\\?>|" + S1 + UntilQMs + "(?:[^>?]" + UntilQMs + ")*>"
DT_ItemSE = "<(?:!(?:--" + Until2Hyphens + ">|[^-]" + MarkupDeclCE + ")|\\?" + Name + "(?:" + PI_Tail + "))|%" + Name + ";|" + S
DocTypeCE = DT_IdentSE + "(?:" + S + ")?(?:\\[(?:" + DT_ItemSE + ")*](?:" + S + ")?)?>?"
DeclCE = "--(?:" + CommentCE + ")?|\\[CDATA\\[(?:" + CDATA_CE + ")?|DOCTYPE(?:" + DocTypeCE + ")?"
PI_CE = Name + "(?:" + PI_Tail + ")?"
EndTagCE = Name + "(?:" + S + ")?>?"
AttValSE = "\"[^<\"]*\"|'[^<']*'"
ElemTagCE = Name + "(?:" + S + Name + "(?:" + S + ")?=(?:" + S + ")?(?:" + AttValSE + "))*(?:" + S + ")?/?>?"
MarkupSPE = "<(?:!(?:" + DeclCE + ")?|\\?(?:" + PI_CE + ")?|/(?:" + EndTagCE + ")?|(?:" + ElemTagCE + ")?)"
XML_SPE = TextSE + "|" + MarkupSPE

XML_SPE_ = re.compile(XML_SPE)

def shallow_parse(s):
    return re.findall(XML_SPE, s)