/* =============================================================================
 * B05_Profile_Pipeline_RouteGround.ts
 * 실시간 계산 묶음(PLAN 346-1)의 **route · ground 단계** — 계약 = `design_pipeline_types.ts`.
 *
 *   route  — 노선 초안(RouteDraft) → 그린 노선(원호 포함) · 누가거리. 선은 이미 있는 짝
 *            `buildEditedPolyline`(↔ `common_util_route_polyline.py`) 그대로.
 *   ground — 측점(지반 null) → 지반 채운 측점 · 종단 지반선(1 m). 표본 = 지형 격자 짝
 *            (`common_util_surface_sampler.ts` · `B05_Profile_Sections_Ground.ts`) · 격자가 없거나
 *            (아직 못 받음 · DTM 아님) 분석 지형 ≠ 설계 지형이면 주입받은 서버 표본(`remote`).
 *            바뀐 범위 밖 측점 · 종단은 앞 출력 재사용(국부 연산) — 자리 · 축 · 지형이 같을 때만.
 *
 * 화면 · fetch · 세션 안 씀 — 격자 · 서버 길은 부르는 쪽이 넣음(`B05_Profile_Api_TerrainGrid.ts`).
 * ========================================================================== */

import type {
  DesignCurve,
  GroundOutput,
  GroundSample,
  PipelineStation,
  RouteDraft,
  RouteLine,
  StageFn,
  StationGround,
  Vertex,
} from "../../A00_Common/design/logic/design_pipeline_types";
import { type DtmGrid, heightAt } from "../../common_util/common_util_surface_sampler";
import { buildEditedPolyline } from "./B05_Profile_UI_RouteEdit_Curve";
import { applyArcLocks } from "./B05_Profile_UI_RouteEdit_Edits";
import {
  crossOffsets,
  longitudinalPoints,
  round6,
  SECTION_CROSS_HALF_WIDTH_M,
  SECTION_CROSS_SAMPLE_INTERVAL_M,
} from "./B05_Profile_Sections_Ground";

/* ── route ─────────────────────────────────────────────────────────────── */

export interface RouteStageDeps {
  /** 곡선 기본 반지름(m) — 편집기 `minRadiusM`(계획 기준 · 0 = 없음). */
  minRadiusM(): number;
  /** 초안이 없을 때(= 저장분 그대로) 그릴 노선 · 곡선표 — 없으면 null. */
  savedLine(): { line: Vertex[]; curves: DesignCurve[] } | null;
}

/** 정점마다 누가거리 — 첫 점 0. */
export function routeLineOf(line: Vertex[], curves: DesignCurve[] = []): RouteLine {
  const chainage = [0];
  for (let i = 1; i < line.length; i += 1) {
    chainage.push(
      chainage[i - 1] + Math.hypot(line[i][0] - line[i - 1][0], line[i][1] - line[i - 1][1]),
    );
  }
  return { line, curves, chainage, lengthM: chainage[chainage.length - 1] };
}

/** 초안 → 그린 노선 · 곡선표(계약 꼴). 길이를 붙든 곡선은 교각에 맞춰 R 을 다시 잡음(편집기
 *  `markEdited` 와 같은 차례). */
export function draftLine(
  draft: RouteDraft,
  minRadiusM: number,
): { line: Vertex[]; curves: DesignCurve[] } {
  const nodes = draft.nodes.map((node): Vertex => [node[0], node[1]]);
  const radius = [...draft.curveRadius];
  applyArcLocks(nodes, [...draft.curveLock], [...draft.curveArc], radius);
  const built = buildEditedPolyline(nodes, draft.curveOn, radius, minRadiusM);
  return {
    line: built.vertices,
    curves: built.curves.map(({ start, apex, end, radius_m }) => ({ start, apex, end, radius_m })),
  };
}

export function createRouteStage(deps: RouteStageDeps): StageFn<"route"> {
  return (ctx) => {
    const draft = ctx.inputs.route;
    const drawn = draft ? draftLine(draft, deps.minRadiusM()) : deps.savedLine();
    if (!drawn || drawn.line.length < 2) throw new Error("그릴 노선이 없습니다.");
    return routeLineOf(drawn.line, drawn.curves);
  };
}

/* ── ground ────────────────────────────────────────────────────────────── */

export interface GroundStageDeps {
  /** 지금 쓸 수 있는 설계 지형 격자 — 아직 못 받았거나 없으면 null(그동안은 서버 길). */
  grid(): { grid: DtmGrid; design: "las" | "sheet" } | null;
  /** 서버 표본(`/route/elevations`) — 점 차례 그대로 · 무효 null · `signal` 로 끊김. */
  remote(
    points: Vertex[],
    terrain: string | null,
    signal: AbortSignal,
  ): Promise<Array<number | null>>;
  /** 횡단 반폭(m) — 비면 서버 기본(20 m). */
  crossHalfWidthM?(): number | null;
}

const samePlace = (a: PipelineStation, b: PipelineStation): boolean =>
  a.x === b.x && a.y === b.y && a.left[0] === b.left[0] && a.left[1] === b.left[1];

const outside = (chainageM: number, range: { fromM: number; toM: number } | null): boolean =>
  range !== null && (chainageM < range.fromM || chainageM > range.toM);

export function createGroundStage(deps: GroundStageDeps): StageFn<"ground"> {
  /** 앞 출력이 쓴 지형 · 노선 · 반폭 — 다르면 재사용 안 함. */
  let last: { terrain: string; line: Vertex[] | null; halfWidth: number } | null = null;

  return async (ctx) => {
    const stations = ctx.out.stations ?? [];
    const line = ctx.out.route?.line ?? null;
    const terrain = ctx.inputs.route?.terrain ?? null;
    const halfWidth = deps.crossHalfWidthM?.() ?? SECTION_CROSS_HALF_WIDTH_M;
    const offsets = crossOffsets(halfWidth, SECTION_CROSS_SAMPLE_INTERVAL_M);
    const local = deps.grid();
    const useGrid = local !== null && (terrain === null || terrain === local.design);

    const tag = terrain ?? "design";
    const reusable = ctx.prev !== null && last?.terrain === tag && last.halfWidth === halfWidth;
    const range = ctx.range;
    const prevByKey = new Map((reusable ? ctx.prev!.stations : []).map((s) => [s.key, s]));

    // 다시 셀 측점 — 범위 안 · 앞 출력에 없음 · 자리나 축이 바뀜.
    const kept = stations.map((station) => {
      const before = prevByKey.get(station.key);
      return before?.ground && outside(station.chainageM, range) && samePlace(before, station)
        ? before.ground
        : null;
    });

    const long = line ? longitudinalPoints(line) : { chainage: [], xy: [] as Vertex[], lengthM: 0 };
    // 종단 — 노선이 그대로면 통째 · 범위 앞쪽은 같은 노선 위라 그대로.
    const prevLong = reusable ? ctx.prev!.longitudinal : null;
    const longKept: Array<number | null | undefined> = long.chainage.map((c, i) => {
      if (!prevLong || prevLong.chainageM[i] !== round6(c)) return undefined;
      if (last?.line === line || (range !== null && c < range.fromM)) return prevLong.z[i];
      return undefined;
    });

    const points: Vertex[] = [];
    stations.forEach((station, i) => {
      if (kept[i]) return;
      for (const offset of offsets) {
        points.push([station.x + station.left[0] * offset, station.y + station.left[1] * offset]);
      }
    });
    long.xy.forEach((xy, i) => {
      if (longKept[i] === undefined) points.push(xy);
    });

    let heights: Array<number | null>;
    if (useGrid) {
      heights = points.map(([x, y]) => {
        const z = heightAt(local!.grid, x, y);
        return Number.isNaN(z) ? null : round6(z);
      });
    } else {
      heights = points.length ? await deps.remote(points, terrain, ctx.signal) : [];
    }

    let cursor = 0;
    const filled: PipelineStation[] = stations.map((station, i) => {
      if (kept[i]) return { ...station, ground: kept[i] };
      const zs = offsets.map(() => heights[cursor++] ?? null);
      return { ...station, ground: stationGround(offsets, zs) };
    });
    const z = long.chainage.map((_, i) =>
      longKept[i] === undefined ? (heights[cursor++] ?? null) : (longKept[i] as number | null),
    );
    last = { terrain: tag, line, halfWidth };
    const output: GroundOutput = {
      stations: filled,
      longitudinal: { chainageM: long.chainage.map(round6), z },
    };
    return output;
  };
}

/** offset 열 표고 → 계약 꼴(중심 · 좌 · 우 · 중심에서 바깥 차례 · offsetM 양수). */
function stationGround(offsets: number[], zs: Array<number | null>): StationGround {
  const left: GroundSample[] = [];
  const right: GroundSample[] = [];
  let centerZ: number | null = null;
  offsets.forEach((offset, i) => {
    if (Math.abs(offset) <= 1e-9) centerZ = zs[i];
    else if (offset > 0) left.push({ offsetM: round6(offset), z: zs[i] });
    else right.unshift({ offsetM: round6(-offset), z: zs[i] });
  });
  return { centerZ, left, right };
}