fn main() {
    let result = find_largest_palindrome(3);
    println!("Result: {result}");
}

fn find_largest_palindrome(digits: u32) -> i64 {
    let mut largest = 0;
    let lower = 10_i64.pow(digits - 1);
    let upper = 10_i64.pow(digits);
    for i in lower..upper {
        for j in lower..upper {
            let product = i * j;
            if check_palindrome(product) && product > largest {
                largest = product;
            }
        }
    }

    largest
}

fn check_palindrome(number: i64) -> bool {
    let number: Vec<char> = number.to_string().chars().collect();
    let upper = (number.len() as f64 / 2.0).ceil() as usize;
    for pos in 0..upper {
        if number[pos] != number[number.len() - 1 - pos] {
            return false;
        }
    }
    true
}

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

    #[test]
    fn it_works() {
        let result = find_largest_palindrome(2);
        assert_eq!(result, 9009);
    }
}