14.zote

include!("stdlib");
include!("aoc.zote");

input := read("input");
lines := input >> split("\n");

cubes := set();
rocks := set();

rows := len(lines);
cols := len(lines[0]);

for (row, line) in lines >> enumerate for (col, char) in line >> enumerate {
	if char == '#' {
		[row, col] >> insert(cubes);
	} else if char == 'O' {
		[row, col] >> insert(rocks);
	}
}

// Four almost identical functions for moving. Could be one, but don't know the performance penalty for the extra if, and I wanted speed
fn move_up() -> {
	next := set();
	move := false;
	for (i, rock) in rocks >> keys >>  enumerate {
		(row, col) := rock;

		if row != 0 {
			up := [row - 1, col];
			if !(up >> in(cubes)) and !(up >> in(rocks)) {
				up >> insert(next);
				move = true;
			} else {
				rock >> insert(next);
			}
		} else {
			rock >> insert(next);
		}
	}
	rocks = next;
	move
}

fn move_left() -> {
	next := set();
	move := false;
	for (i, rock) in rocks >> keys >>  enumerate {
		(row, col) := rock;

		if col != 0 {
			left := [row, col-1];
			if !(left >> in(cubes)) and !(left >> in(rocks)) {
				left >> insert(next);
				move = true;
			} else {
				rock >> insert(next);
			}
		} else {
			rock >> insert(next);
		}
	}
	rocks = next;
	move
}

fn move_down() -> {
	next := set();
	move := false;
	for (i, rock) in rocks >> keys >>  enumerate {
		(row, col) := rock;

		if row != rows-1 {
			down := [row + 1, col];
			if !(down >> in(cubes)) and !(down >> in(rocks)) {
				down >> insert(next);
				move = true;
			} else {
				rock >> insert(next);
			}
		} else {
			rock >> insert(next);
		}
	}
	rocks = next;
	move
}

fn move_right() -> {
	next := set();
	move := false;
	for (i, rock) in rocks >> keys >>  enumerate {
		(row, col) := rock;

		if col != cols-1 {
			right := [row, col+1];
			if !(right >> in(cubes)) and !(right >> in(rocks)) {
				right >> insert(next);
				move = true;
			} else {
				rock >> insert(next);
			}
		} else {
			rock >> insert(next);
		}
	}
	rocks = next;
	move
}

fn load() -> rocks >> keys >> map(\>> [0] >> sub(rows) >> neg) >> sum;

start := 0;
pattern := [];
for i in [0:1000] {
	while move_up() {};
	if i == 0 print(load());
	while move_left() {};
	while move_down() {};
	while move_right() {};

	load() >> push(pattern);

	// Try to find a pattern (of sufficient length) repeating twice.
	if i%2 == 1 and i > 100 for l in [25:i/2] {
		if pattern[-l:] == pattern[-2*l:-l] {
			// Extrapolate the answer from the pattern repeating to infinity
			free := (1000000000 - i - 2) % l;
			print(pattern[-l:][free]);
			return
		}
	}
}