use std::collections::HashMap;

pub fn process_part1(input: &str) -> String {
    let line_len = input.find("\n").unwrap();
    let mut rows: Vec<HashMap<char, u32>> = vec![HashMap::new(); line_len];
    input.lines().for_each(|line| {
        for (idx, chara) in line.chars().enumerate() {
            rows[idx]
                .entry(chara)
                .and_modify(|count| *count += 1)
                .or_insert(1);
        }
    });
    let mut res = String::new();
    for row in rows {
        let most_common = row.iter().max_by(|a, b| a.1.cmp(b.1)).unwrap().0;
        res.push(*most_common);
    }
    res
}

pub fn process_part2(input: &str) -> String {
    let line_len = input.find("\n").unwrap();
    let mut rows: Vec<HashMap<char, u32>> = vec![HashMap::new(); line_len];
    input.lines().for_each(|line| {
        for (idx, chara) in line.chars().enumerate() {
            rows[idx]
                .entry(chara)
                .and_modify(|count| *count += 1)
                .or_insert(1);
        }
    });
    let mut res = String::new();
    for row in rows {
        let most_common = row.iter().max_by(|a, b| b.1.cmp(a.1)).unwrap().0;
        res.push(*most_common);
    }
    res
}

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

    const INPUT: &str = "eedadn
drvtee
eandsr
raavrd
atevrs
tsrnev
sdttsa
rasrtv
nssdts
ntnada
svetve
tesnvt
vntsnd
vrdear
dvrsen
enarar";

    #[test]
    fn part1() {
        let result = process_part1(INPUT);
        assert_eq!(result, *"easter");
    }

    #[test]
    fn part2() {
        let result = process_part2(INPUT);
        assert_eq!(result, *"advent");
    }
}