static DAY: u8 = 2;

fn main() {
    let input = advent::read_lines(DAY);
    println!("{DAY}a: {}", safe_reports(&input, false));
    println!("{DAY}b: {}", safe_reports(&input, true));
}

fn is_report_safe(report: &[i32]) -> bool {
    let increasing = report[1] - report[0] > 0;
    for number in report.iter().as_slice().windows(2) {
        let diff = number[1] - number[0];
        if diff.abs() < 1 || diff.abs() > 3 {
            return false;
        }
        if (diff > 0) != increasing {
            return false;
        }
    }
    true
}

fn safe_reports(input: &[String], with_dampener: bool) -> usize {
    let mut reports = Vec::new();
    for line in input {
        let numbers = line.split(" ")
                          .map(|x| x.parse::<i32>().unwrap())
                          .collect::<Vec<_>>();
        reports.push(numbers);
    }
    let mut count = 0;
    for report in reports {
        if is_report_safe(&report) {
            count += 1;
        } else if with_dampener {
            for i in 0 .. report.len() {
                let mut dampened = report.clone();
                dampened.remove(i);
                if is_report_safe(&dampened) {
                    count += 1;
                    break;
                }
            }
        }
    }
    count
}

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

    #[test]
    fn test() {
        let input = [
            "7 6 4 2 1",
            "1 2 7 8 9",
            "9 7 6 2 1",
            "1 3 2 4 5",
            "8 6 4 4 1",
            "1 3 6 7 9",
        ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
        assert_eq!(safe_reports(&input, false), 2);
        assert_eq!(safe_reports(&input, true), 4);
    }
}