use aoc_runner_derive::{aoc, aoc_generator};
use std::io::{BufRead, Lines};

#[aoc_generator(day4)]
pub fn get_input(input: &[u8]) -> WordSearch {
    WordSearch::from(input.lines())
}

pub struct WordSearch {
    rows: Vec<String>,
}

impl<T: BufRead> From<Lines<T>> for WordSearch {
    fn from(input: Lines<T>) -> Self {
        let mut rows = Vec::new();
        for line in input.map(|i| i.unwrap()) {
            rows.push(line);
        }
        Self { rows }
    }
}

impl WordSearch {
    fn count_occurences(haystack: &str, needle: &str) -> u64 {
        let mut count = 0;
        for start in 0..haystack.len() - needle.len() + 1 {
            if &haystack[start..start + needle.len()] == needle {
                count += 1;
            }
        }
        count
    }
    fn count_forward(&self, needle: &str) -> u64 {
        let mut count = 0;
        for row in &self.rows {
            count += Self::count_occurences(row, needle)
        }
        count
    }
    fn count_vertical(&self, needle: &str) -> u64 {
        let mut count = 0;
        for col in 0..self.rows[0].len() {
            let s: String = self.rows.iter().map(|row| row.as_bytes()[col] as char).collect();
            count += Self::count_occurences(&s, needle)
        }
        count
    }
    fn count_diagonal(&self, needle: &str) -> u64 {
        let width = self.rows[0].len();
        let height = self.rows.len();

        let mut count = 0;
        for x in 0..width {
            for y in 0..height {
                // check down-right
                if x <= width - needle.len()
                    && y <= height - needle.len()
                    && (0..needle.len()).all(|i| self.get(x + i, y + i) == needle.as_bytes()[i].into())
                {
                    count += 1
                }
                // check down-left
                if x >= needle.len() - 1
                    && y <= height - needle.len()
                    && (0..needle.len()).all(|i| self.get(x - i, y + i) == needle.as_bytes()[i].into())
                {
                    count += 1
                }
            }
        }
        count
    }

    fn get(&self, x: usize, y: usize) -> char {
        self.rows[y].as_bytes()[x].into()
    }

    fn count_x_mas(&self) -> u64 {
        // M.M M.S S.M S.S
        // .A. .A. .A. .A.
        // S.S M.S S.M M.M
        let searches: [[char; 5]; 4] =
            ["MMASS", "MSAMS", "SMASM", "SSAMM"].map(|s| s.chars().collect::<Vec<char>>().try_into().unwrap());
        let width = self.rows[0].len();
        let height = self.rows.len();

        let mut count = 0;
        for x in 0..width - 2 {
            for y in 0..height - 2 {
                let s = [
                    self.get(x, y),
                    self.get(x + 2, y),
                    self.get(x + 1, y + 1),
                    self.get(x, y + 2),
                    self.get(x + 2, y + 2),
                ];
                for needle in &searches {
                    if needle == &s {
                        count += 1
                    }
                }
            }
        }
        count
    }
}

// PROBLEM 1 solution
#[aoc(day4, part1)]
pub fn part1(ws: &WordSearch) -> u64 {
    let needle = "XMAS";
    let needle_rev: String = needle.chars().rev().collect();
    ws.count_forward(needle)
        + ws.count_forward(&needle_rev)
        + ws.count_vertical(needle)
        + ws.count_vertical(&needle_rev)
        + ws.count_diagonal(needle)
        + ws.count_diagonal(&needle_rev)
}

// PROBLEM 2 solution
#[aoc(day4, part2)]
pub fn part2(ws: &WordSearch) -> u64 {
    ws.count_x_mas()
}

#[cfg(test)]
mod tests {
    use crate::day4::*;

    const EXAMPLE: &[u8] = b"MMMSXXMASM
MSAMXMSMSA
AMXSXMAAMM
MSAMASMSMX
XMASAMXAMM
XXAMMXXAMA
SMSMSASXSS
SAXAMASAAA
MAMMMXMMMM
MXMXAXMASX";

    #[test]
    fn part1_example() {
        assert_eq!(part1(&get_input(EXAMPLE)), 18);
    }

    #[test]
    fn part2_example() {
        assert_eq!(part2(&get_input(EXAMPLE)), 9);
    }
}