//! Day 01 of 2021.

use crate::prelude::*;

/// Get the solution for day 01 of 2021.
pub fn solution() -> Solution {
  Solution::new(Day::new(1, 2021), part_1, part_2).with_expected(1451, 1395)
}

/// The logic to solve part one.
fn part_1(input: &str) -> Result<String> {
  Ok(
    parse_measurements(input)?
      .into_iter()
      .tuple_windows()
      .filter(|(previous, next)| next > previous)
      .count()
      .to_string(),
  )
}

/// The logic to solve part two.
fn part_2(input: &str) -> Result<String> {
  Ok(
    parse_measurements(input)?
      .into_iter()
      .tuple_windows()
      .filter(|(a, b, c, d)| b + c + d > a + b + c)
      .count()
      .to_string(),
  )
}

/// Parse the measurements from the puzzle input.
fn parse_measurements(input: &str) -> Result<Vec<i32>> {
  input
    .lines()
    .map(|line| line.parse::<i32>())
    .collect::<Result<_, _>>()
    .map_err(Into::into)
}