""" Command line interface to difflib.py providing diffs in four formats:

* ndiff: lists every line and highlights interline changes.
* context: highlights clusters of changes in a before/after format.
* unified: highlights clusters of changes in an inline format.
* html: generates side by side comparison with change highlights.

"""

import sys, os, time, difflib, optparse

def main():

 usage = "usage: %prog [options] fromfile tofile"
 parser = optparse.OptionParser(usage)
 parser.add_option("-c", action="store_true", default=False, help='Produce a context format diff (default)')
 parser.add_option("-u", action="store_true", default=False, help='Produce a unified format diff')
 parser.add_option("-m", action="store_true", default=False, help='Produce HTML side by side diff (can use -c and -l in conjunction)')
 parser.add_option("-n", action="store_true", default=False, help='Produce a ndiff format diff')
 parser.add_option("-l", "--lines", type="int", default=3, help='Set number of context lines (default 3)')
 (options, args) = parser.parse_args()

 if len(args) == 0:
 parser.print_help()
 sys.exit(1)
 if len(args) != 2:
 parser.error("need to specify both a fromfile and tofile")

 n = options.lines
 fromfile, tofile = args

 fromdate = time.ctime(os.stat(fromfile).st_mtime)
 todate = time.ctime(os.stat(tofile).st_mtime)
 fromlines = open(fromfile, 'U').readlines()
 tolines = open(tofile, 'U').readlines()

 if options.u:
 diff = difflib.unified_diff(fromlines, tolines, fromfile, tofile, fromdate, todate, n=n)
 elif options.n:
 diff = difflib.ndiff(fromlines, tolines)
 elif options.m:
 diff = difflib.HtmlDiff().make_file(fromlines,tolines,fromfile,tofile,context=options.c,numlines=n)
 else:
 diff = difflib.context_diff(fromlines, tolines, fromfile, tofile, fromdate, todate, n=n)

 sys.stdout.writelines(diff)

if __name__ == '__main__':
 main()