#! /usr/bin/env python3
from copy import copy

sample = [
    "nop +0",
    "acc +1",
    "jmp +4",
    "acc +3",
    "jmp -3",
    "acc -99",
    "acc +1",
    "jmp -4",
    "acc +6",
]


def parse_lines(lines):
    def parse_line(line):
        inst, _, num = line.partition(" ")
        return (inst, int(num))

    return [
        parse_line(line)
        for line in lines
    ]


def run_line(instructions, index):
    inst, num = instructions[index]
    if inst == "nop":
        return index+1, 0
    elif inst == "acc":
        return index+1, num
    elif inst == "jmp":
        return index+num, 0


def part1():
    with open("input.txt") as f:
        instructions = parse_lines(f)
    _, acc = run_until_loop(instructions, 0)
    print("Total accumulated:", acc)


def run_until_loop(instructions, line, seen_lines=None):
    if seen_lines is None:
        seen_lines = set()
    acc = 0
    while line < len(instructions):
        seen_lines.add(line)
        # print(f"Inner: {line}:{instructions[line]}")
        line, num = run_line(instructions, line)
        acc += num
        if line in seen_lines:
            # print(f"Inner loop, break out")
            return True, acc
    return False, acc


def part2():
    with open("input.txt") as f:
        instructions = parse_lines(f)

    accum = 0
    line = 0
    seen_lines = set()

    while line < len(instructions):
        if line in seen_lines:
            print(f"Ugh, looping")
            return

        # print(f"{line}:{instructions[line]}")
        inst, num = instructions[line]
        if inst != "acc":
            # print(f"Found an alternate, check for loop")
            # Possible change
            new_inst = copy(instructions)
            new_seen = copy(seen_lines)
            new_inst[line] = ("nop" if inst == "jmp" else "jmp", num)
            has_loop, acc_d = run_until_loop(new_inst, line, new_seen)
            if not has_loop:
                accum += acc_d
                print(f"Found solution! Changing {line}: Total {accum}")
                return

        seen_lines.add(line)
        line, num = run_line(instructions, line)
        accum += num


if __name__ == "__main__":
    part1()
    part2()