#!/usr/bin/env python3
""" 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, difflib, argparse
from datetime import datetime, timezone

def file_mtime(path):
 t = datetime.fromtimestamp(os.stat(path).st_mtime,
 timezone.utc)
 return t.astimezone().isoformat()

def main():

 parser = argparse.ArgumentParser()
 parser.add_argument('-c', action='store_true', default=False,
 help='Produce a context format diff (default)')
 parser.add_argument('-u', action='store_true', default=False,
 help='Produce a unified format diff')
 parser.add_argument('-m', action='store_true', default=False,
 help='Produce HTML side by side diff '
 '(can use -c and -l in conjunction)')
 parser.add_argument('-n', action='store_true', default=False,
 help='Produce a ndiff format diff')
 parser.add_argument('-l', '--lines', type=int, default=3,
 help='Set number of context lines (default 3)')
 parser.add_argument('fromfile')
 parser.add_argument('tofile')
 options = parser.parse_args()

 n = options.lines
 fromfile = options.fromfile
 tofile = options.tofile

 fromdate = file_mtime(fromfile)
 todate = file_mtime(tofile)
 with open(fromfile) as ff:
 fromlines = ff.readlines()
 with open(tofile) as tf:
 tolines = tf.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()