from itertools import product
import signal
from subprocess import DEVNULL, PIPE, Popen, TimeoutExpired

chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~ '

# Prevent zombie processes
signal.signal(signal.SIGCHLD, signal.SIG_IGN)


def check_pair(script, instr, outstr):
    process = Popen(
        ["/usr/bin/env", "bash", "-c", "--", script],
        stdin=PIPE,
        stdout=PIPE,
        stderr=DEVNULL,
    )

    try:
        stdout, stderr = process.communicate(instr.encode(), timeout=5)
        return process.returncode == 0 and stdout == outstr.encode()
    except TimeoutExpired:
        try:
            process.kill()
            stdout, stderr = process.communicate()
        except ProcessLookupError:
            pass

        return False


def check_pairs(script, pairs):
    for pair in pairs:
        if not check_pair(script, *pair):
            return False
    return True


def find_script(pairs, max_length):
    candidates = []
    chars_count = len(chars)
    total_options = int((chars_count ** (max_length + 1) - 1) / (chars_count - 1))
    current_option = 0

    for length in range(max_length + 1):
        for letters in product(chars, repeat=length):
            current_option += 1

            if current_option % 1000 == 0:
                print(f"Progress: {current_option}/{total_options}")

            script = "".join(letters)

            if check_pairs(script, pairs):
                print("> Found candidate:", script)
                candidates.append(script)

    print("Candidates:", candidates)


if __name__ == '__main__':
    # Identity
    print("\nSearching for identity")
    find_script((
        ("1", "1"),
        ("42", "42"),
        ("1984", "1984"),
    ), max_length=3)

    # Successor
    # print("\nSearching for successor")
    # find_script((
    #     ("1", "2"),
    #     ("2", "3"),
    #     ("3", "4"),
    # ), max_length=5)