/* =============================================================================
 * B05_Profile_Structure_Follow.ts
 * 노선 초안 동안 종단 알약 자리(PLAN 346-2 덧 3) — 계산 묶음 follow 가 좌표로 따라간 관 · 구조물의 새
 * 누가거리를 알약 목록에 얹음. 구조물 = structure_id 로 짝 · 관 알약 id = 세션 id(`pipeIdAt`) 라 묶음 관 id
 * (서버 고정 id)와 다르면 누가거리 차례로 짝.
 *
 * 순수 — 화면 · fetch · 세션 없음.
 * ========================================================================== */

interface Placed {
  chainage_m?: number | null;
  start_m?: number | null;
  end_m?: number | null;
}

interface Mark extends Placed {
  structure_id?: string | null;
}

interface Moved extends Placed {
  id?: string | null;
  structure_id?: string | null;
}

const list = (value: unknown): Moved[] => (Array.isArray(value) ? (value as Moved[]) : []);
const at = (item: Placed): number => item.chainage_m ?? item.start_m ?? 0;

/** 알약 목록 → 따라간 자리를 얹은 사본 · 짝 없는 알약은 그대로. `structures` · `pipes` = 묶음 입력(follow 뒤). */
export function followedMarks<T extends Mark>(
  marks: ReadonlyArray<T>,
  structures: unknown,
  pipes: unknown,
): T[] {
  const byId = new Map<string, Moved>();
  for (const item of list(structures)) if (item.structure_id) byId.set(item.structure_id, item);
  const movedPipes = list(pipes).filter((pipe) => typeof pipe.chainage_m === "number");
  for (const pipe of movedPipes) if (pipe.id) byId.set(pipe.id, pipe);
  // ponytail: 차례 짝 — 노선을 고쳐 관 차례가 뒤바뀌면 틀림 · 알약이 서버 관 id 를 들면 id 짝으로
  const loose = marks
    .filter((mark) => mark.structure_id?.startsWith("pipe-") && !byId.has(mark.structure_id))
    .sort((a, b) => at(a) - at(b));
  const ids = new Set(marks.map((mark) => mark.structure_id));
  const free = movedPipes.filter((pipe) => !ids.has(pipe.id)).sort((a, b) => at(a) - at(b));
  const paired = new Map<T, Moved>();
  if (loose.length === free.length) loose.forEach((mark, index) => paired.set(mark, free[index]));
  return marks.map((mark) => {
    const moved = (mark.structure_id ? byId.get(mark.structure_id) : undefined) ?? paired.get(mark);
    if (!moved) return mark;
    const shift = at(moved) - at(mark);
    const move = (value: number | null | undefined, next: number | null | undefined) =>
      value == null ? value : (next ?? value + shift);
    return {
      ...mark,
      chainage_m: move(mark.chainage_m, moved.chainage_m),
      start_m: move(mark.start_m, moved.start_m),
      end_m: move(mark.end_m, moved.end_m),
    };
  });
}