Day 06: Probably a Fire Hazard

Now we finally get to use my Space2d class. Having worked on this over multiple Advent of Codes, it is my general purpose Grid class. It will accumulate more and more features as more problems require them. Hopefully by the end of every Advent of Code it is complete with every feature I could want.

Once you have a grid class and a point class this problem is very straightforward. Read the instructions and act on the grid for every instruction.

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day_06.rs

use crate::space::point::Point2d;
use crate::space::space::Space2d;

type Instruction = (Action, Point2d, Point2d);

#[derive(Clone, Copy)]
enum Action {
	Toggle,
	Off,
	On
}

impl Action {
	fn part_1_modify (chosen_action: Action, current_value: isize) -> isize {
		return match chosen_action {
			Action::Off => 0,
			Action::On => 1,
			Action::Toggle => if current_value == 0 { 1 } else { 0 }
		};
	}

	fn part_2_modify (chosen_action: Action, current_value: isize) -> isize {
		let change = match chosen_action {
			Action::Toggle => 2,
			Action::On => 1,
			Action::Off => -1,
		};

		return isize::max(0, current_value + change);
	}
}

fn parse_input (input: &str) -> impl Iterator<Item = Instruction> + '_ {
	return input.lines()
		.map(|line| line.replace("turn", "").replace("through", ""))
		.map(|line| {
			// Couldn't be done in another map because .replace creates a String not a str
			// while .split_whitespace returns an iterator of &str causing ownership issues.
			let mut line = line.split_whitespace();
			let action = match line.next().unwrap() {
				"toggle" => Action::Toggle,
				"off" => Action::Off,
				"on" => Action::On,
				_ => panic!()
			};

			let start = Point2d::new_from_csv(line.next().unwrap());
			let end = Point2d::new_from_csv(line.next().unwrap());

			return (action, start, end);
		});
}

fn solve_problem (input: &str, modify_pixel: fn(Action, isize) -> isize) -> String {
	let instructions = parse_input(input);
	let mut lights = Space2d::new_grid_sized(0, 1000, 1000);
	for instruction in instructions {
		for point in Point2d::points_in_bounding_box(&instruction.1, &instruction.2) {
			let old_value = lights.get(&point).unwrap();
			let new_value = modify_pixel(instruction.0, *old_value);
			lights.set(&point, new_value);
		}
	}
	return lights.indices()
		.fold(0, |acc, x| acc + lights.get(&x).unwrap())
		.to_string();
}

pub fn day_06_1 (input: &str) -> String {
	return solve_problem(input, Action::part_1_modify);
}

pub fn day_06_2 (input: &str) -> String {
	return solve_problem(input, Action::part_2_modify);
}