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//! # Day 21: Fractal Art
//!
//! You find a program trying to generate some art. It uses a strange process that involves
//! repeatedly enhancing the detail of an image through a set of rules.
//!
//! The image consists of a two-dimensional square grid of pixels that are either on (`#`) or off
//! (`.`). The program always begins with this pattern:
//!
//! ```txt
//! .#.
//! ..#
//! ###
//! ```
//!
//! Because the pattern is both `3` pixels wide and `3` pixels tall, it is said to have a **size**
//! of `3`.
//!
//! Then, the program repeats the following process:
//!
//! - If the size is evenly divisible by `2`, break the pixels up into `2x2` squares, and convert
//!   each `2x2` square into a `3x3` square by following the corresponding **enhancement rule**.
//! - Otherwise, the size is evenly divisible by `3`; break the pixels up into `3x3` squares, and
//!   convert each `3x3` square into a `4x4` square by following the corresponding **enhancement
//!   rule**.
//!
//! Because each square of pixels is replaced by a larger one, the image gains pixels and so its
//! **size** increases.
//!
//! The artist's book of enhancement rules is nearby (your puzzle input); however, it seems to be
//! missing rules. The artist explains that sometimes, one must **rotate** or **flip** the input
//! pattern to find a match. (Never rotate or flip the output pattern, though.) Each pattern is
//! written concisely: rows are listed as single units, ordered top-down, and separated by slashes.
//! For example, the following rules correspond to the adjacent patterns:
//!
//! ```txt
//! ../.#  =  ..
//!           .#
//!
//!                 .#.
//! .#./..#/###  =  ..#
//!                 ###
//!
//!                         #..#
//! #..#/..../#..#/.##.  =  ....
//!                         #..#
//!                         .##.
//! ```
//!
//! When searching for a rule to use, rotate and flip the pattern as necessary. For example, all of
//! the following patterns match the same rule:
//!
//! ```txt
//! .#.   .#.   #..   ###
//! ..#   #..   #.#   ..#
//! ###   ###   ##.   .#.
//! ```
//!
//! Suppose the book contained the following two rules:
//!
//! ```txt
//! ../.# => ##./#../...
//! .#./..#/### => #..#/..../..../#..#
//! ```
//!
//! As before, the program begins with this pattern:
//!
//! ```txt
//! .#.
//! ..#
//! ###
//! ```
//!
//! The size of the grid (`3`) is not divisible by `2`, but it is divisible by `3`. It divides
//! evenly into a single square; the square matches the second rule, which produces:
//!
//! ```txt
//! #..#
//! ....
//! ....
//! #..#
//! ```
//!
//! The size of this enhanced grid (`4`) is evenly divisible by `2`, so that rule is used. It
//! divides evenly into four squares:
//!
//! ```txt
//! #.|.#
//! ..|..
//! --+--
//! ..|..
//! #.|.#
//! ```
//!
//! Each of these squares matches the same rule (`../.# => ##./#../...`), three of which require
//! some flipping and rotation to line up with the rule. The output for the rule is the same in all
//! four cases:
//!
//! ```txt
//! ##.|##.
//! #..|#..
//! ...|...
//! ---+---
//! ##.|##.
//! #..|#..
//! ...|...
//! ```
//!
//! Finally, the squares are joined into a new grid:
//!
//! ```txt
//! ##.##.
//! #..#..
//! ......
//! ##.##.
//! #..#..
//! ......
//! ```
//!
//! Thus, after `2` iterations, the grid contains `12` pixels that are on.
//!
//! **How many pixels stay on** after `5` iterations?

use anyhow::Result;

pub const INPUT: &str = include_str!("d21.txt");

pub fn solve_part_one(input: &str) -> Result<i64> {
    Ok(0)
}

pub fn solve_part_two(input: &str) -> Result<i64> {
    Ok(0)
}

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

    #[test]
    fn part_one() {}

    #[test]
    fn part_two() {}
}