1 files changed, 66 insertions, 0 deletions
diff --git a/forum/diff.py b/forum/diff.py
new file mode 100644
index 00000000..d741d788
--- /dev/null
+++ b/forum/diff.py
@@ -0,0 +1,66 @@
+#!/usr/bin/python2.2
+"""HTML Diff: http://www.aaronsw.com/2002/diff
+Rough code, badly documented. Send me comments and patches."""
+
+__author__ = 'Aaron Swartz <me@aaronsw.com>'
+__copyright__ = '(C) 2003 Aaron Swartz. GNU GPL 2.'
+__version__ = '0.22'
+
+import difflib, string
+
+def isTag(x): return x[0] == "<" and x[-1] == ">"
+
+def textDiff(a, b):
+	"""Takes in strings a and b and returns a human-readable HTML diff."""
+
+	out = []
+	a, b = html2list(a), html2list(b)
+	s = difflib.SequenceMatcher(None, a, b)
+	for e in s.get_opcodes():
+		if e[0] == "replace":
+			# @@ need to do something more complicated here
+			# call textDiff but not for html, but for some html... ugh
+			# gonna cop-out for now
+			out.append('<del>'+''.join(a[e[1]:e[2]]) + '</del><ins>'+''.join(b[e[3]:e[4]])+"</ins>")
+		elif e[0] == "delete":
+			out.append('<del >'+ ''.join(a[e[1]:e[2]]) + "</del>")
+		elif e[0] == "insert":
+			out.append('<ins >'+''.join(b[e[3]:e[4]]) + "</ins>")
+		elif e[0] == "equal":
+			out.append(''.join(b[e[3]:e[4]]))
+		else: 
+			raise "Um, something's broken. I didn't expect a '" + `e[0]` + "'."
+	return ''.join(out)
+
+def html2list(x, b=0):
+	mode = 'char'
+	cur = ''
+	out = []
+	for c in x:
+		if mode == 'tag':
+			if c == '>': 
+				if b: cur += ']'
+				else: cur += c
+				out.append(cur); cur = ''; mode = 'char'
+			else: cur += c
+		elif mode == 'char':
+			if c == '<': 
+				out.append(cur)
+				if b: cur = '['
+				else: cur = c
+				mode = 'tag'
+			elif c in string.whitespace: out.append(cur+c); cur = ''
+			else: cur += c
+	out.append(cur)
+	return filter(lambda x: x is not '', out)
+
+if __name__ == '__main__':
+	import sys
+	try:
+		a, b = sys.argv[1:3]
+	except ValueError:
+		print "htmldiff: highlight the differences between two html files"
+		print "usage: " + sys.argv[0] + " a b"
+		sys.exit(1)
+	print textDiff(open(a).read(), open(b).read())
+