# --- Day 18: Operation Order ---

# As you look out the window and notice a heavily-forested continent slowly
# appear over the horizon, you are interrupted by the child sitting next to
# you. They're curious if you could help them with their math homework.

# Unfortunately, it seems like this "math" follows different rules than you
# remember.

# The homework (your puzzle input) consists of a series of expressions that
# consist of addition (+), multiplication (*), and parentheses ((...)). Just
# like normal math, parentheses indicate that the expression inside must be
# evaluated before it can be used by the surrounding expression. Addition still
# finds the sum of the numbers on both sides of the operator, and
# multiplication still finds the product.

# However, the rules of operator precedence have changed. Rather than
# evaluating multiplication before addition, the operators have the same
# precedence, and are evaluated left-to-right regardless of the order in which
# they appear.

# For example, the steps to evaluate the expression 1 + 2 * 3 + 4 * 5 + 6 are
# as follows:

# 1 + 2 * 3 + 4 * 5 + 6
#   3   * 3 + 4 * 5 + 6
#       9   + 4 * 5 + 6
#          13   * 5 + 6
#              65   + 6
#                  71

# Parentheses can override this order; for example, here is what happens if
# parentheses are added to form 1 + (2 * 3) + (4 * (5 + 6)):

# 1 + (2 * 3) + (4 * (5 + 6))
# 1 +    6    + (4 * (5 + 6))
#      7      + (4 * (5 + 6))
#      7      + (4 *   11   )
#      7      +     44
#             51

# Here are a few more examples:

#     2 * 3 + (4 * 5) becomes 26.
#     5 + (8 * 3 + 9 + 3 * 4 * 3) becomes 437.
#     5 * 9 * (7 * 3 * 3 + 9 * 3 + (8 + 6 * 4)) becomes 12240.
#     ((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2 becomes 13632.

# Before you can help with the homework, you need to understand it yourself.
# Evaluate the expression on each line of the homework; what is the sum of the
# resulting values?

with open("files/P18.txt", "r") as f:
    homework = [line for line in f.read().strip().split("\n")]


def eval(n1, n2, op) -> int:
    if op == "+":
        return n1 + n2
    elif op == "*":
        return n1 * n2


def simplify(expr) -> str:
    while len(expr) > 1:
        n1 = int(expr.pop())
        op = expr.pop()
        n2 = int(expr.pop())
        result = eval(n1, n2, op)
        expr.append(str(result))

    return expr[0]


def part_1() -> None:
    total = 0
    for line in homework:
        line = line.replace("(", "( ")
        line = line.replace(")", " )")
        expr = line.split()

        stack = []
        for char in expr:
            if char.isdigit() or char in ["+", "*", "("]:
                stack.append(char)
            elif char == ")":
                ordered_stack = []
                while stack[len(stack) - 1] != "(":
                    ordered_stack.append(stack.pop())
                stack.pop()

                result = simplify(ordered_stack)
                stack.append(result)
        stack.reverse()
        result = simplify(stack)
        total += int(result)

    print(f"The result of evaluating my homework is {total}")


# --- Part Two ---

# You manage to answer the child's questions and they finish part 1 of their
# homework, but get stuck when they reach the next section: advanced math.

# Now, addition and multiplication have different precedence levels, but
# they're not the ones you're familiar with. Instead, addition is evaluated
# before multiplication.

# For example, the steps to evaluate the expression 1 + 2 * 3 + 4 * 5 + 6 are
# now as follows:

# 1 + 2 * 3 + 4 * 5 + 6
#   3   * 3 + 4 * 5 + 6
#   3   *   7   * 5 + 6
#   3   *   7   *  11
#      21       *  11
#          231

# Here are the other examples from above:

#     1 + (2 * 3) + (4 * (5 + 6)) still becomes 51.
#     2 * 3 + (4 * 5) becomes 46.
#     5 + (8 * 3 + 9 + 3 * 4 * 3) becomes 1445.
#     5 * 9 * (7 * 3 * 3 + 9 * 3 + (8 + 6 * 4)) becomes 669060.
#     ((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2 becomes 23340.

# What do you get if you add up the results of evaluating the homework problems
# using these new rules?


def simplify_rules(expr) -> str:
    while len(expr) > 1:
        ordered_stack, hold = [], []
        done = False

        while not done and len(expr) > 0:
            char = expr.pop()
            if char == "+":
                done = True
            hold.append(char)

        if not done and len(expr) == 0:
            result = simplify(hold)
            expr.append(result)
        else:
            ordered_stack.append(expr.pop())
            for _ in range(2):
                ordered_stack.append(hold.pop())

            result = simplify(ordered_stack)
            hold.append(result)

            while len(hold) > 0:
                expr.append(hold.pop())

    return expr[0]


def part_2() -> None:
    total = 0
    for line in homework:
        line = line.replace("(", "( ")
        line = line.replace(")", " )")
        expr = line.split()

        stack = []
        for char in expr:
            if char.isdigit() or char in ["+", "*", "("]:
                stack.append(char)
            elif char == ")":
                ordered_stack = []
                while stack[len(stack) - 1] != "(":
                    ordered_stack.append(stack.pop())
                stack.pop()

                result = simplify_rules(ordered_stack)
                stack.append(result)
        stack.reverse()
        result = simplify_rules(stack)
        total += int(result)

    print(f"The result of evaluating my homework is {total}")


if __name__ == "__main__":
    part_1()
    part_2()