pixi-demo/src/game/chase/hexGraph.ts

import type { GameGraph, NodeId } from "./types";

export function axialNeighbors(q: number, r: number): Array<[number, number]> {
  return [
    [q + 1, r],
    [q + 1, r - 1],
    [q, r - 1],
    [q - 1, r],
    [q - 1, r + 1],
    [q, r + 1],
  ];
}

export function shortestPathLength(
  graph: GameGraph,
  from: NodeId,
  to: NodeId,
): number {
  if (!graph.nodes[from] || !graph.nodes[to]) {
    return Infinity;
  }

  if (from === to) {
    return 0;
  }

  const queue: Array<[NodeId, number]> = [[from, 0]];
  let head = 0;
  const visited = new Set<NodeId>([from]);

  while (head < queue.length) {
    const [current, distance] = queue[head];
    head += 1;
    const node = graph.nodes[current];

    for (const neighbor of node.neighbors) {
      if (neighbor === to) {
        return distance + 1;
      }
      if (!visited.has(neighbor) && graph.nodes[neighbor]) {
        visited.add(neighbor);
        queue.push([neighbor, distance + 1]);
      }
    }
  }

  return Infinity;
}

export function isConnected(graph: GameGraph): boolean {
  const nodeIds = Object.keys(graph.nodes);
  if (nodeIds.length <= 1) {
    return true;
  }

  const start = nodeIds[0];
  const visited = new Set<NodeId>([start]);
  const queue: NodeId[] = [start];
  let head = 0;

  while (head < queue.length) {
    const current = queue[head];
    head += 1;
    const node = graph.nodes[current];

    for (const neighbor of node.neighbors) {
      if (!visited.has(neighbor) && graph.nodes[neighbor]) {
        visited.add(neighbor);
        queue.push(neighbor);
      }
    }
  }

  return visited.size === nodeIds.length;
}