""" Command line interface to difflib.py providing diffs in three 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.

"""

import sys, os, time, difflib, optparse

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("-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).readlines()
tolines = open(tofile).readlines()

if options.u:
    diff = difflib.unified_diff(fromlines, tolines, fromfile, tofile, fromdate, todate, n=n)
elif options.n:
    diff = difflib.ndiff(fromlines, tolines)
else:
    diff = difflib.context_diff(fromlines, tolines, fromfile, tofile, fromdate, todate, n=n)

sys.stdout.writelines(diff)