ttrpg-tools/src/plotcutter/plotter.ts

import { normalize } from "./normalize";

/**
 * 生成 HPGL 代码，支持指定起点和终点
 * @param pts 路径点数组
 * @param width 页面宽度（mm）
 * @param height 页面高度（mm）
 * @param px2mm 像素到毫米的转换系数
 * @param startPoint 起点坐标（mm），默认为左上角 [0, height]
 * @param endPoint 终点坐标（mm），默认为左上角 [0, height]
 */
export function pts2plotter(
  pts: [number, number][][],
  width: number,
  height: number,
  px2mm = 0.1,
  startPoint?: [number, number],
  endPoint?: [number, number]
) {
  const start = startPoint ?? [0, height];
  const end = endPoint ?? [0, height];

  let str = init(width * px2mm, height * px2mm);

  // 使用最近邻算法排序路径
  const sorted = sortPathsByNearestNeighbor(pts, start);

  // 从起点到第一个路径
  if (sorted.length > 0) {
    const firstPath = sorted[0];
    str += ` U${plu(start[0] * px2mm)},${plu((height - start[1]) * px2mm)}`;
    str += ` D${plu(firstPath[0][0] * px2mm)},${plu((height - firstPath[0][1]) * px2mm)}`;

    // 切割第一个路径
    for (let i = 1; i < firstPath.length; i++) {
      const pt = firstPath[i];
      str += ` D${plu(pt[0] * px2mm)},${plu((height - pt[1]) * px2mm)}`;
    }

    // 如果第一个路径未闭合，添加闭合命令
    if (!isPathClosed(firstPath)) {
      str += ` D${plu(firstPath[0][0] * px2mm)},${plu((height - firstPath[0][1]) * px2mm)}`;
    }

    // 路径之间移动
    for (let i = 1; i < sorted.length; i++) {
      const prevPath = sorted[i - 1];
      const currPath = sorted[i];

      // 抬刀移动到下一个路径起点
      str += ` U${plu(currPath[0][0] * px2mm)},${plu((height - currPath[0][1]) * px2mm)}`;
      // 下刀切割
      str += ` D${plu(currPath[0][0] * px2mm)},${plu((height - currPath[0][1]) * px2mm)}`;

      for (let j = 1; j < currPath.length; j++) {
        const pt = currPath[j];
        str += ` D${plu(pt[0] * px2mm)},${plu((height - pt[1]) * px2mm)}`;
      }

      // 如果当前路径未闭合，添加闭合命令
      if (!isPathClosed(currPath)) {
        str += ` D${plu(currPath[0][0] * px2mm)},${plu((height - currPath[0][1]) * px2mm)}`;
      }
    }
  }

  // 返回终点
  str += ` U${plu(end[0] * px2mm)},${plu((height - end[1]) * px2mm)}`;
  str += endCommand();

  return str;
}

// 兼容旧版本（不使用新参数）
export function pts2plotterLegacy(
  pts: [number, number][][],
  width: number,
  height: number,
  px2mm = 0.1
) {
  return pts2plotter(pts, width, height, px2mm);
}

function topleft(pts: [number, number][]) {
  let minx = NaN;
  let miny = NaN;
  for (const pt of pts) {
    if (isNaN(minx) || minx > pt[0]) minx = pt[0];
    if (isNaN(miny) || miny > pt[1]) miny = pt[1];
  }
  return [minx, miny] as [number, number];
}

/**
 * 检测路径是否已闭合（起点和终点距离小于阈值）
 * @param path 路径点数组
 * @param threshold 距离阈值（像素），默认 0.01
 */
function isPathClosed(path: [number, number][], threshold = 0.01): boolean {
  if (path.length < 2) return true;
  const [sx, sy] = path[0];
  const [ex, ey] = path[path.length - 1];
  const dist = Math.sqrt((sx - ex) ** 2 + (sy - ey) ** 2);
  return dist < threshold;
}

/**
 * 计算点到路径的最近距离
 * @param pt 点坐标
 * @param path 路径点数组
 */
function distanceToPath(pt: [number, number], path: [number, number][]): number {
  let minDist = Infinity;
  for (const p of path) {
    const dist = Math.sqrt((pt[0] - p[0]) ** 2 + (pt[1] - p[1]) ** 2);
    if (dist < minDist) minDist = dist;
  }
  return minDist;
}

/**
 * 使用最近邻算法排序路径
 * @param paths 路径数组
 * @param startPos 起始位置
 */
function sortPathsByNearestNeighbor(
  paths: [number, number][][],
  startPos: [number, number]
): [number, number][][] {
  if (paths.length === 0) return [];

  const result: [number, number][][] = [];
  const remaining = paths.slice();
  let currentPos = startPos;

  while (remaining.length > 0) {
    // 找到距离当前位置最近的路径
    let nearestIndex = 0;
    let nearestDist = Infinity;

    for (let i = 0; i < remaining.length; i++) {
      const dist = distanceToPath(currentPos, remaining[i]);
      if (dist < nearestDist) {
        nearestDist = dist;
        nearestIndex = i;
      }
    }

    // 将最近的路径添加到结果中
    const nearestPath = remaining.splice(nearestIndex, 1)[0];
    result.push(nearestPath);

    // 更新当前位置为该路径的终点
    currentPos = nearestPath[nearestPath.length - 1];
  }

  return result;
}

function init(w: number, h: number) {
  return ` IN TB26,${plu(w)},${plu(h)} CT1`;
}

function endCommand() {
  return ' @ @';
}

function plu(n: number) {
  return Math.round(n / 0.025);
}