#!/usr/bin/env python3.8
"""
replace stuff in a file or files
"""
# maybe i should just use https://replace.richardlloyd.org.uk/
import argparse
import difflib
import fileinput
import re
import sys

cli = argparse.ArgumentParser(description=__doc__)
cli.add_argument(
    "-v", "--verbose", action="store_true", help="print diffs for every replacement"
)
cli.add_argument(
    "-d", "--dry", action="store_true", help="just print what would have happened"
)
cli.add_argument(
    "-r", "--regex", action="store_true", help="use regex instead of literal replace"
)
cli.add_argument("old", type=str, help="target string")
cli.add_argument("new", type=str, help="replacement string")
cli.add_argument(
    "files",
    nargs="*",
    metavar="FILE",
    help="file(s) to operate on, or omit for stdin",
)
args = cli.parse_args()

differ = difflib.Differ()


def raw(s):
    return r"{}".format(s)


def log(s):
    sys.stderr.write(s)


for line in fileinput.input(files=args.files, inplace=not args.dry):
    if args.regex:
        replacement = re.sub(raw(args.old), args.new, line, flags=re.MULTILINE)
    else:
        replacement = line.replace(args.old, args.new)
    if (args.verbose or args.dry) and (line != replacement):
        diff = list(differ.compare([line], [replacement]))
        sys.stderr.write(f"{fileinput.filename()}:{fileinput.lineno()}:\n")
        sys.stderr.writelines(diff)
    if not args.dry:
        print(replacement, end="")