use std::error::Error;
use std::fs::File;
use std::io::{self, BufRead};
use std::vec::Vec;

enum SyntaxPoints {
    Corrupted(u64),
    Incomplete(u64),
}

fn check_syntax(line: &str) -> SyntaxPoints {
    let mut stack: Vec<char> = Vec::new();

    for c in line.chars() {
        match c {
            '[' => stack.push('['),
            '(' => stack.push('('),
            '{' => stack.push('{'),
            '<' => stack.push('<'),
            ']' => {
                if stack.pop() != Some('[') {
                    return SyntaxPoints::Corrupted(57);
                }
            }
            ')' => {
                if stack.pop() != Some('(') {
                    return SyntaxPoints::Corrupted(3);
                }
            }
            '}' => {
                if stack.pop() != Some('{') {
                    return SyntaxPoints::Corrupted(1197);
                }
            }
            '>' => {
                if stack.pop() != Some('<') {
                    return SyntaxPoints::Corrupted(25137);
                }
            }
            _ => panic!("Unknown char {}", c),
        }
    }

    let mut points = 0;
    for c in stack.iter().rev() {
        match c {
            '(' => points = points * 5 + 1,
            '[' => points = points * 5 + 2,
            '{' => points = points * 5 + 3,
            '<' => points = points * 5 + 4,
            _ => panic!("Unknown char {}", c),
        }
    }

    SyntaxPoints::Incomplete(points)
}

fn main() -> Result<(), Box<dyn Error>> {
    let file = File::open("inputs/day10.txt")?;
    let lines: Vec<String> = io::BufReader::new(file)
        .lines()
        .map(|l| l.unwrap())
        .collect();

    let mut answer1 = 0;

    let mut incompletes: Vec<u64> = Vec::new();

    for line in lines.iter() {
        match check_syntax(line) {
            SyntaxPoints::Corrupted(p) => answer1 += p,
            SyntaxPoints::Incomplete(p) => incompletes.push(p),
        }
    }

    println!("Answer1: {}", answer1);

    incompletes.sort();

    println!("Answer2: {}", incompletes[incompletes.len() / 2]);

    Ok(())
}