use std::collections::HashSet;
use std::fs;
use std::{cmp::Ordering, ops::RangeInclusive as Range};

use anyhow::Error;
use chrono::{Datelike, Local};
use pico_args::Arguments;

fn main() -> Result<(), Error> {
    let mut args = Arguments::from_env();
    let small = args.contains("--small");
    let part = args.opt_free_from_str()?.unwrap_or(1);
    let day = args
        .opt_free_from_str()?
        .unwrap_or_else(|| Local::now().day());
    let small = if small { ".small" } else { "" };
    let path = format!("inputs/{day}{small}.txt");
    let input = fs::read_to_string(path)?;
    println!("running day {day} part {part}");
    let result = SOLNS[day as usize - 1][part as usize - 1](input);
    println!("{result}");
    Ok(())
}

type Part = fn(String) -> u64;
type Day = [Part; 2];
const DAYS: usize = 4;
const SOLNS: [Day; DAYS] = [
    [
        // day 1 part 1
        |input| {
            let lines = input.lines();
            let (max, _) = lines.fold((0, 0), |(max, sum), line| {
                if line.is_empty() {
                    (max.max(sum), 0)
                } else {
                    let cal = line.parse::<u64>().expect("Got bad line");
                    (max, sum + cal)
                }
            });
            max
        },
        // day 1 part 2
        |input| {
            let lines = input.lines();
            let (a, b, c, _) = lines.fold((0, 0, 0, 0), |(a, b, c, sum), line| {
                if line.trim().is_empty() {
                    if sum > a {
                        (sum, a, b, 0)
                    } else if sum > b {
                        (a, sum, b, 0)
                    } else if sum > c {
                        (a, b, sum, 0)
                    } else {
                        (a, b, c, 0)
                    }
                } else {
                    let cal = line.trim().parse::<u64>().expect("Got bad line");
                    (a, b, c, sum + cal)
                }
            });
            a + b + c
        },
    ],
    [
        // day 2 part 1
        |input| {
            input
                .lines()
                .map(|line| {
                    let (you, me) = line.split_once(' ').expect("oof");
                    let (you, me) = (RPS::from_str(you), RPS::from_str(me));
                    RPS::score(you, me)
                })
                .sum()
        },
        // day 2 part 2
        |input| {
            input
                .lines()
                .map(|line| {
                    let (you, out) = line.split_once(' ').expect("oof");
                    let (you, out) = (RPS::from_str(you), Outcome::from_str(out));
                    let me = out.requires(you);
                    RPS::score(you, me)
                })
                .sum()
        },
    ],
    [
        // day 3 part 1
        |input| {
            input
                .lines()
                .map(|line| {
                    let line = String::from(line);
                    let rs = Rucksack::new(line);
                    rs.score()
                })
                .sum()
        },
        // day 3 part 2
        |input| {
            let lines: Vec<_> = input.lines().collect();
            lines
                .chunks(3)
                .map(|chunks| match chunks {
                    [f, s, t] => {
                        let rs =
                            Rucksacks::new(String::from(*f), String::from(*s), String::from(*t));
                        rs.score()
                    }
                    _ => unreachable!("fooey"),
                })
                .sum()
        },
    ],
    [
        // day 4 part 1
        |input| {
            make_ranges(input)
                .iter()
                .map(|(first, second)| {
                    range_contains(first, second) || range_contains(second, first)
                })
                .map(|b| if b { 1 } else { 0 })
                .sum()
        },
        // day 4 part 2
        |input| {
            make_ranges(input)
                .iter()
                .map(|(first, second)| {
                    range_overlaps(first, second) || range_overlaps(second, first)
                })
                .map(|b| if b { 1 } else { 0 })
                .sum()
        },
    ],
];

fn make_ranges(input: String) -> Vec<(Range<u64>, Range<u64>)> {
    input
        .lines()
        .map(|line| {
            line.split(',')
                .map(|range| {
                    range
                        .split('-')
                        .map(|num| num.parse::<u64>().expect("bad num :/"))
                })
                .map(|mut nums| {
                    let lo = nums.next().expect("nolo :/");
                    let hi = nums.next().expect("nohi :/");
                    lo..=hi
                })
        })
        .map(|mut ranges| {
            let f = ranges.next().unwrap();
            let s = ranges.next().unwrap();
            (f, s)
        })
        .collect()
}

fn range_contains(r1: &Range<u64>, r2: &Range<u64>) -> bool {
    r1.start() <= r2.start() && r1.end() >= r2.end()
}

fn range_overlaps(r1: &Range<u64>, r2: &Range<u64>) -> bool {
    r1.contains(r2.start())
}

#[derive(Copy, Clone, PartialEq, Eq)]
enum RPS {
    Rock,
    Paper,
    Scissors,
}

impl RPS {
    fn from_str(s: &str) -> Self {
        match s {
            "A" | "X" => RPS::Rock,
            "B" | "Y" => RPS::Paper,
            "C" | "Z" => RPS::Scissors,
            _ => unreachable!("you did a bad thing"),
        }
    }

    fn win(self) -> RPS {
        match self {
            RPS::Rock => RPS::Scissors,
            RPS::Paper => RPS::Rock,
            RPS::Scissors => RPS::Paper,
        }
    }

    fn lose(self) -> RPS {
        match self {
            RPS::Rock => RPS::Paper,
            RPS::Paper => RPS::Scissors,
            RPS::Scissors => RPS::Rock,
        }
    }

    fn cmp(self, other: Self) -> Ordering {
        if self == other {
            Ordering::Equal
        } else if self.win() == other {
            Ordering::Greater
        } else {
            Ordering::Less
        }
    }

    fn score(you: Self, me: Self) -> u64 {
        let base = match me {
            RPS::Rock => 1,
            RPS::Paper => 2,
            RPS::Scissors => 3,
        };
        let win = match RPS::cmp(me, you) {
            Ordering::Less => 0,
            Ordering::Equal => 3,
            Ordering::Greater => 6,
        };
        base + win
    }
}

#[derive(Copy, Clone)]
enum Outcome {
    Win,
    Draw,
    Lose,
}

impl Outcome {
    fn from_str(s: &str) -> Self {
        match s {
            "X" => Outcome::Lose,
            "Y" => Outcome::Draw,
            "Z" => Outcome::Win,
            _ => unreachable!("yikes"),
        }
    }

    fn requires(self, you: RPS) -> RPS {
        match self {
            Outcome::Win => you.lose(),
            Outcome::Draw => you,
            Outcome::Lose => you.win(),
        }
    }
}

struct Rucksack {
    first: HashSet<char>,
    second: HashSet<char>,
}

impl Rucksack {
    fn new(mut input: String) -> Self {
        assert!(input.len() % 2 == 0);
        let second = input.split_off(input.len() / 2).chars().collect();
        Self {
            first: input.chars().collect(),
            second,
        }
    }

    fn overlap(&self) -> HashSet<&char> {
        self.first.intersection(&self.second).collect()
    }

    fn score(&self) -> u64 {
        self.overlap().into_iter().copied().map(score_char).sum()
    }
}

struct Rucksacks {
    first: HashSet<char>,
    second: HashSet<char>,
    third: HashSet<char>,
}

impl Rucksacks {
    fn new(f: String, s: String, t: String) -> Self {
        Rucksacks {
            first: f.chars().collect(),
            second: s.chars().collect(),
            third: t.chars().collect(),
        }
    }

    fn intersection(&self) -> HashSet<char> {
        let start: HashSet<_> = self.first.intersection(&self.second).copied().collect();
        start.intersection(&self.third).copied().collect()
    }

    fn score(&self) -> u64 {
        self.intersection().into_iter().map(score_char).sum()
    }
}

fn score_char(c: char) -> u64 {
    if c.is_lowercase() {
        c as u64 - 96
    } else {
        c as u64 - 38
    }
}