dflike/server/src/systems/movementSystem.ts

import { Direction, type Movement, type Position } from '@dflike/shared';
import type { World } from '../ecs/World.js';

function directionFromDelta(dx: number, dy: number): number {
  if (Math.abs(dx) > Math.abs(dy)) return dx > 0 ? Direction.RIGHT : Direction.LEFT;
  return dy > 0 ? Direction.DOWN : Direction.UP;
}

export function movementSystem(world: World): void {
  for (const entity of world.query('position', 'movement')) {
    const movement = world.getComponent<Movement>(entity, 'movement')!;
    const pos = world.getComponent<Position>(entity, 'position')!;

    if (movement.state !== 'walking' || movement.path.length === 0) {
      if (movement.state === 'walking' && movement.path.length === 0) {
        movement.state = 'idle';
        movement.target = null;
      }
      continue;
    }

    const next = movement.path.shift()!;
    movement.direction = directionFromDelta(next.x - pos.x, next.y - pos.y);
    pos.x = next.x;
    pos.y = next.y;

    if (movement.path.length === 0) {
      movement.state = 'idle';
      movement.target = null;
    }
  }
}