#!/bin/python3.9
import re
import hashlib
import os
from sys import argv, stderr
from os.path import basename
from colorama import init, Fore, Back, Style

init(autoreset=True)

if len(argv) <= 3:
    print('usage: {0} [REGEX] [SUB] [FILES...]'.format(basename(__file__)), file=stderr)
    exit(1)

regex = argv[1]
sub = argv[2]
files = argv[3:]
replace_all = False
quit_loop = False
sub_count = 0
match_count = 0

def prompt(matchobj, line, line_n, file):
    global replace_all
    global quit_loop
    global sub_count
    global match_count

    if quit_loop:
        return matchobj.group(0)


    replaced_match = re.sub(regex, sub, matchobj.group(0))

    if replaced_match == matchobj.group(0):
        return replaced_match

    match_count += 1

    if replace_all:
        sub_count += 1
        return replaced_match

    highlighted = line.replace(matchobj.group(0),
            Back.RED + matchobj.group(0) + Back.RESET)
    replaced = line.replace(matchobj.group(0),
            Back.YELLOW + Fore.BLACK + replaced_match + Back.RESET + Fore.RESET)

    print(Fore.GREEN + Style.BRIGHT + file)

    print(Fore.YELLOW + Style.BRIGHT + str(line_n), end='')
    print(':{0}'.format(highlighted))

    print('Becomes the following:')

    print(Fore.YELLOW + Style.BRIGHT + str(line_n), end='')
    print(':{0}'.format(replaced))

    print()

    while True:
        answer = input('Confirm the change? [Y/n/a/q] ').lower()

        if answer in ['y', 'yes', '']:
            sub_count += 1
            print()
            return replaced_match
        elif answer in ['n', 'no']:
            print()
            return matchobj.group(0)
        elif answer in ['a', 'all']:
            sub_count += 1
            replace_all = True
            return replaced_match
        elif answer in ['q', 'quit']:
            quit_loop = True
            return matchobj.group(0)

        print('Invalid answer. Please type again.')

def filter_file(fname):
    with open(fname, 'r') as file:
        contents = file.read()

    lines = contents.splitlines()

    lines = [
            re.sub(regex,
                lambda matchobj: prompt(matchobj, line, line_n, fname),
                line)
            for (line_n, line) in enumerate(lines)
            ]

    new_contents = '\n'.join(lines)

    hash_old = hashlib.md5(contents.encode())
    hash_new = hashlib.md5(new_contents.encode())

    if hash_old.digest() != hash_new.digest():
        with open(fname, 'w') as file:
            file.write(new_contents)
            file.write('\n')

for file in files:
    if os.access(file, os.W_OK):
        filter_file(file)

        if quit_loop:
            break

if match_count == 0:
    print(Fore.RED + Style.BRIGHT + 'No matches found.')
else:
    print(Fore.YELLOW + Style.BRIGHT + 'Made {0} of {1} substitutions.'.
            format(Fore.WHITE + str(sub_count) + Fore.YELLOW,
                Fore.WHITE + str(match_count) + Fore.YELLOW))