/* =============================================================================
 * A00_Common/design/logic/design_pipeline_stations.ts
 * 계산 묶음 stations 단계(PLAN 346-1) — 측점 계산은 `B05_Profile/logic/B05_Profile_Sections_Stations.ts`
 * (서버 `generate_sections` 짝) · 여기는 단계 꼴 · 범위 밖 앞 값 재사용만.
 * ========================================================================== */

import {
  buildStations,
  REUSE_MARGIN_M,
  type StationsOptions,
} from "../../../B05_Profile/logic/B05_Profile_Sections_Stations";
import type {
  PlanPipe,
  PlanStructure,
  PlanType,
} from "../../../common_util/common_util_structure_station";
import type {
  PipelineRunRecord,
  PipelineStation,
  RouteDraft,
  StageContext,
  StageFn,
} from "./design_pipeline_types";
import type { SectionDetailResponse } from "../../../B06_Section/B06_Section_Api_Fetch";

/** 범위 밖 측점은 앞 값(같은 열쇠 · 같은 자리)을 그대로 — 뒤 단계가 같은 객체로 「안 바뀜」을 앎. */
export function reuseOutside(
  next: PipelineStation[],
  prev: ReadonlyArray<PipelineStation> | null,
  range: { fromM: number; toM: number } | null,
): PipelineStation[] {
  if (!prev || !range) return next;
  const old = new Map(prev.map((station) => [station.key, station]));
  return next.map((station) => {
    const inside =
      station.chainageM >= range.fromM - REUSE_MARGIN_M &&
      station.chainageM <= range.toM + REUSE_MARGIN_M;
    const before = old.get(station.key);
    return !inside && before && Math.abs(before.chainageM - station.chainageM) < 1e-9
      ? before
      : station;
  });
}

/** 저장 노선의 측점 스냅 설정(`RoutePlanResponse` 칸). */
export interface SavedSnap {
  station_snap?: boolean;
  station_snap_step?: number | null;
}

/** 측점 스냅 설정 — 노선 초안이 있으면 그 값 · 없으면 저장 노선 값(441 · 저장 스냅 노선 측점 어긋남).
 *  간격 = 10 만 그 값 · 옛 초안 0.1 · 1 m 등 = null — 짝 `B05_Profile_Engine_Sections.py` load_station_snap_step(505-2). */
export function snapOptions(
  draft: RouteDraft | null | undefined,
  saved: SavedSnap | null | undefined,
): Pick<StationsOptions, "stationSnap" | "stationSnapStep"> {
  const step = draft ? draft.stationSnapStep : saved?.station_snap_step;
  return {
    stationSnap: draft ? draft.stationSnap : (saved?.station_snap ?? false),
    stationSnapStep: step === 10 ? 10 : null,
  };
}

/** `buildStations` 인자 한 벌 — 화면 셈 · 서버 셈(계산 자리 「서버」)이 같은 값을 받음. */
export type StationsArgs = Parameters<typeof buildStations>;

/** stations 단계 — 입력 관 · 구조물(follow 뒤 누가거리) · 그린 노선 · 곡선표 · 스냅(초안 · 없으면 저장 노선).
 *  `remote` = 계산 자리 「서버」면 서버 Node 값(같은 `buildStations` · 511-B B-2) · null = 화면 셈 · 서버가
 *  못 내면(끊김 · 실패) 화면 셈. */
export function createStationsStage(
  options: Omit<StationsOptions, "stationSnap" | "stationSnapStep" | "types"> & {
    types: () => ReadonlyArray<PlanType>;
    saved?: () => SavedSnap | null;
    remote?: (
      args: StationsArgs,
      signal: AbortSignal,
    ) => Promise<PipelineStation[] | undefined> | null;
  },
): StageFn<"stations"> {
  const { saved, remote, ...rest } = options;
  return (ctx: StageContext<"stations">) => {
    const route = ctx.out.route;
    if (!route) return [];
    const args: StationsArgs = [
      route.line,
      route.curves,
      (ctx.inputs.pipes as PlanPipe[] | null) ?? [],
      (ctx.inputs.structures as PlanStructure[] | null) ?? [],
      {
        ...rest,
        types: options.types(),
        ...snapOptions(ctx.inputs.route, saved?.()),
        plus: ctx.inputs.plusStations ?? undefined, // follow 가 옮긴 추가 측점(459 · 가게보다 먼저)
      },
    ];
    const done = (next: PipelineStation[] | undefined) =>
      reuseOutside(next ?? buildStations(...args), ctx.prev, ctx.range);
    const asked = remote?.(args, ctx.signal);
    return asked ? asked.then(done) : done(undefined); // 화면 셈 = 동기 그대로
  };
}

/** 상세 측점 대 묶음 측점(1 mm) — 같으면 null · 다르면 첫 다른 자리 · 개수(묶음 기록 `restoreDiff`). */
export function stationDiff(
  detail: SectionDetailResponse,
  stations: ReadonlyArray<PipelineStation>,
): NonNullable<PipelineRunRecord["restoreDiff"]> | null {
  const saved = detail.cross_sections.map((section) => section.chainage_m);
  const n = Math.max(saved.length, stations.length);
  for (let i = 0; i < n; i += 1) {
    const pipelineM = stations[i]?.chainageM ?? null;
    if (saved[i] !== undefined && pipelineM !== null && Math.abs(saved[i] - pipelineM) < 1e-3)
      continue;
    return { savedM: saved[i] ?? null, pipelineM, saved: saved.length, pipeline: stations.length };
  }
  return null;
}