AlexAegis/advent-of-code

import { Direction, GridGraph, Vec2 } from '@alexaegis/advent-of-code-lib';

export const mirrors: Record<string, Record<string, Direction>> = {
    '\\': {
        [Direction.WEST.toString()]: Direction.SOUTH,
        [Direction.NORTH.toString()]: Direction.EAST,
        [Direction.EAST.toString()]: Direction.NORTH,
        [Direction.SOUTH.toString()]: Direction.WEST,
    },
    '/': {
        [Direction.WEST.toString()]: Direction.NORTH,
        [Direction.NORTH.toString()]: Direction.WEST,
        [Direction.EAST.toString()]: Direction.SOUTH,
        [Direction.SOUTH.toString()]: Direction.EAST,
    },
};

export const splitters: Record<string, Record<string, [Direction, Direction] | undefined>> = {
    '|': {
        [Direction.EAST.toString()]: [Direction.NORTH, Direction.SOUTH],
        [Direction.WEST.toString()]: [Direction.SOUTH, Direction.NORTH],
    },
    '-': {
        [Direction.NORTH.toString()]: [Direction.EAST, Direction.WEST],
        [Direction.SOUTH.toString()]: [Direction.WEST, Direction.EAST],
    },
};

export interface Beam {
    position: Vec2;
    direction: Direction;
}

export const energizeMap = (gg: GridGraph, startingBeam: Beam): number => {
    let beams: Beam[] = [startingBeam];
    const beamPathHistory = new Map<string, Set<string>>();
    while (beams.length > 0) {
        const spawnedBeams: Beam[] = [];
        for (const beam of beams) {
            const node = gg.getNode(beam.position);
            if (node) {
                const pathHistory = beamPathHistory.getOrAdd(
                    node.coordinate.toString(),
                    () => new Set(),
                );

                if (pathHistory.has(beam.direction.toString())) {
                    beam.direction = Direction.ZERO;
                } else {
                    pathHistory.add(beam.direction.toString());
                    const mirroredTo =
                        mirrors[node.value.toString()]?.[beam.direction.reverse().toString()];
                    const splitter =
                        splitters[node.value.toString()]?.[beam.direction.reverse().toString()];
                    if (mirroredTo) {
                        beam.direction = mirroredTo;
                        beam.position = beam.position.add(mirroredTo);
                    } else if (splitter) {
                        const [dirA, dirB] = splitter;
                        beam.direction = dirA;
                        beam.position = beam.position.add(dirA);
                        spawnedBeams.push({ position: beam.position.add(dirB), direction: dirB });
                    } else {
                        beam.position = beam.position.add(beam.direction);
                    }
                }
            } else {
                beam.direction = Direction.ZERO;
            }
        }
        beams.push(...spawnedBeams);
        spawnedBeams.clear();
        beams = beams.filter((beam) => !beam.direction.equals(Direction.ZERO));
    }
    // gg.print((n) => (beamPathHistory.has(n.coordinate.toString()) ? '#' : n.toString()));
    return beamPathHistory.size;
};