/* =============================================================================
 * common_util_cross_design.ts
 * B06 측점 표준횡단 설계 계산 — **브라우저 판**.
 *
 * ⚠⚠ 파이썬 짝 파일과 **한 벌**이다 — 한쪽만 고치면 두 화면 값이 갈린다 ⚠⚠
 *   짝: `B06_Section/B06_Section_Engine_Design.py` (`compute_cross_design`)
 *   면적 적분은 `common_util_cross_design_areas.ts` ↔ `B06_Section_Engine_Areas.py`.
 *   회귀 테스트가 두 구현을 같은 입력으로 실제 비교한다:
 *   `tmp/tests/test_b06_cross_design_mirror.py` — 어느 쪽을 고치든 반드시 같이 돌릴 것.
 *
 * ── 왜 같은 계산이 두 벌인가 (2026-09-03 사용자 확정) ────────────────
 * 사용자가 계획선을 만지는 동안의 계산은 **브라우저 안에서 끝나야 한다**. 조작은 세션
 * 캐시에 쌓이고 화면은 즉시 따라오며, 서버는 [저장]·[확정]에서만 부른다. 계획고가 바뀔
 * 때마다 서버에 전 측점 횡단을 물으면 왕복이 조작 속도를 지배한다(2026-09-03 실측 보고).
 * 계획선 선형(`B05_Profile_Engine_Grade_Alignment.py` ↔ `B05_Profile_UI_Profile_Alignment.ts`)
 * 이 이미 같은 이유로 1:1 미러다.
 *
 * ── 갈라지지 않게 하는 규칙 ──────────────────────────────────────────
 *   1. **config 상수를 여기에 복제하지 않는다.** 표준단면 수치는 서버가 config 에서 내려
 *      주는 `sections/context.standard_cross_section` 을 입력으로 받는다. 아래 상수는
 *      config 의 *열거값*(지반유형→프리셋 등)뿐이며 그마저 짝 파일과 나란히 둔다.
 *   2. 반올림·경계 판정 상수까지 파이썬과 같은 값을 쓴다.
 *   3. 새 필드를 더하면 양쪽 다 더하고 테스트 비교 목록에도 넣는다.
 * ========================================================================== */

import { splitCutAreas, trapezoidAreas } from "./common_util_cross_design_areas";

/** 지반유형 → 표준단면 프리셋 키. 짝: config `SECTION_GROUND_TYPE_PRESET`. */
const GROUND_TYPE_PRESET: Record<string, string> = {
  soil: "soil",
  ripping_rock: "rock",
  blasting_rock: "rock",
};
/** 단면유형. 짝: config `SECTION_MODES`. 좌=양(+)offset, 우=음(-)offset. */
const SECTION_MODES = ["left_cut", "right_cut", "both_cut", "both_fill"];
/** 짝: config `SECTION_DITCH_SIDES` / `SECTION_DITCH_TYPES`. */
const DITCH_SIDES = ["left", "right"];
const DITCH_TYPES = ["standard", "l_type"];

/** 사면이 원지반과 만났다고 볼 높이차(m). 짝: `_SLOPE_CLOSE_TOLERANCE_M`. */
const SLOPE_CLOSE_TOLERANCE_M = 0.01;
/** 사면·경계 교차 탐색 행진 간격(m)과 최대 거리. 짝: 파이썬 `step`/`max_dist`. */
const MARCH_STEP_M = 0.05;
const KNEE_MAX_M = 200;
const CROSS_MAX_M = 500;

export interface CrossGroundSample {
  offset_m?: number | null;
  elevation_m?: number | null;
  valid?: boolean;
}

/** `sections/context.standard_cross_section` 한 그룹의 모양(서버가 config 에서 내려 준다). */
export interface StandardGroupSpec {
  road_width_m?: number;
  shoulder_left_m?: number;
  shoulder_right_m?: number;
  ditch?: { top_width_m?: number; bottom_width_m?: number; depth_m?: number };
  ditch_l_type?: { width_m?: number; depth_m?: number };
  cross_slope_pct?: { min?: number; max?: number };
  fill_slope_ratio?: number;
  cut_slope_ratio?: number;
  pavement_thickness_m?: number;
}

/** 프리셋 키(soil/rock/paved) → 그룹 값. 세션 편집값도 같은 모양이다. */
export type StandardCrossSectionSpec = Record<string, StandardGroupSpec | undefined>;

export interface CrossDesignOptions {
  groundType: string;
  sectionMode: string;
  ditchSide?: string | null;
  ditchType?: string;
  paved?: boolean;
  /** 표준단면 수치(필수) — config 기본값 또는 그 위에 얹은 세션 편집값. */
  standard: StandardCrossSectionSpec;
  rockBoundaryOffsetM?: number | null;
  twoStageSlope?: boolean;
  ditchEnabled?: boolean | null;
  /** 세월교 월류 높이만큼 노면을 통째로 내린다(m). */
  surfaceDropM?: number;
}

export interface CrossDesignEdge {
  offset_m: number;
  elevation_m: number;
}

export interface CrossDesignResult {
  ground_type: string;
  geometry_preset: string;
  section_mode: string;
  ditch_side: string;
  ditch_type: string | null;
  cut_slope_ratio: number;
  soil_cut_slope_ratio: number;
  two_stage_slope: boolean;
  fill_slope_ratio: number;
  roadbed_width_m: number;
  carriageway_width_m: number;
  cross_slope_pct: number;
  ditch: Record<string, unknown>;
  ditch_enabled: boolean;
  paved: boolean;
  road_edges: { left: CrossDesignEdge; right: CrossDesignEdge };
  carriageway_edges: { left: CrossDesignEdge; right: CrossDesignEdge };
  design_elevation_m: number;
  cut_area_m2: number;
  cut_soil_area_m2: number;
  cut_rock_area_m2: number;
  cut_rock_kind: string | null;
  fill_area_m2: number;
  slope_unclosed: boolean;
  fill_ground_slope: number | null;
  ditch_area_m2: number;
  design_line: CrossDesignEdge[];
  surface_drop_m?: number;
  pavement_thickness_m?: number;
  rock_boundary_offset_m?: number;
}

/** 짝: 파이썬 `round(value, 4)`. */
function round4(value: number): number {
  return Math.round(value * 1e4) / 1e4;
}

/** 짝: `_as_float` — 손상값·음수면 fallback. */
function asFloat(value: unknown, fallback: number): number {
  const parsed = typeof value === "number" ? value : Number(value);
  if (!Number.isFinite(parsed)) return fallback;
  return parsed >= 0 ? parsed : fallback;
}

interface ResolvedGroup {
  road_width_m: number;
  shoulder_left_m: number;
  shoulder_right_m: number;
  ditch_top_width_m: number;
  ditch_bottom_width_m: number;
  ditch_depth_m: number;
  l_ditch_width_m: number;
  l_ditch_depth_m: number;
  cross_slope_pct: number;
  fill_slope_ratio: number;
  cut_slope_ratio: number;
  pavement_thickness_m: number;
}

/**
 * 짝: `_resolve_group`. 파이썬은 config 위에 패널 편집값을 덮지만, 여기서는 이미 그렇게
 * 합쳐진 한 벌(`standard`)을 받는다 — config 수치를 프론트에 복제하지 않기 위함이다.
 */
function resolveGroup(presetKey: string, standard: StandardCrossSectionSpec): ResolvedGroup {
  const group = standard[presetKey];
  if (!group) {
    throw new Error(`표준횡단 설정에 '${presetKey}' 그룹이 없어 횡단 설계를 계산할 수 없습니다.`);
  }
  const ditch = group.ditch ?? {};
  const lDitch = group.ditch_l_type ?? {};
  const slope = group.cross_slope_pct ?? {};
  return {
    road_width_m: asFloat(group.road_width_m, 0),
    shoulder_left_m: asFloat(group.shoulder_left_m, 0),
    shoulder_right_m: asFloat(group.shoulder_right_m, 0),
    ditch_top_width_m: asFloat(ditch.top_width_m, 0),
    ditch_bottom_width_m: asFloat(ditch.bottom_width_m, 0),
    ditch_depth_m: asFloat(ditch.depth_m, 0),
    // 짝 파일의 `base.get("width_m", 0.5)`와 같은 최후 기본값.
    l_ditch_width_m: asFloat(lDitch.width_m, 0.5),
    l_ditch_depth_m: asFloat(lDitch.depth_m, 0.1),
    // 횡단경사는 범위(min~max) 중 하한을 기본 채택한다(도면 표기 앞값).
    cross_slope_pct: asFloat(slope.min, 0),
    fill_slope_ratio: asFloat(group.fill_slope_ratio, 0),
    cut_slope_ratio: asFloat(group.cut_slope_ratio, 0),
    pavement_thickness_m: asFloat(group.pavement_thickness_m, 0.2),
  };
}

/** 짝: `_side_role`. 단면유형 → [좌측 역할, 우측 역할]. */
function sideRole(sectionMode: string): [string, string] {
  if (sectionMode === "left_cut") return ["cut", "fill"];
  if (sectionMode === "right_cut") return ["fill", "cut"];
  if (sectionMode === "both_cut") return ["cut", "cut"];
  if (sectionMode === "both_fill") return ["fill", "fill"];
  throw new Error(`지원하지 않는 단면유형입니다: ${sectionMode}`);
}

/** 짝: `_resolve_ditch_side`. */
function resolveDitchSide(sectionMode: string, ditchSide: string | null | undefined): string {
  if (sectionMode === "left_cut") return "left";
  if (sectionMode === "right_cut") return "right";
  if (ditchSide && DITCH_SIDES.includes(ditchSide)) return ditchSide;
  return "left";
}

/** 짝: `_ground_interpolator`. 정렬된 (offset, 지반고) 선형 보간(범위 밖 끝값 클램프). */
function groundInterpolator(valid: Array<[number, number]>): (offsetM: number) => number {
  return (offsetM: number): number => {
    if (offsetM <= valid[0][0]) return valid[0][1];
    if (offsetM >= valid[valid.length - 1][0]) return valid[valid.length - 1][1];
    for (let index = 1; index < valid.length; index += 1) {
      const [x1, z1] = valid[index];
      if (offsetM > x1) continue;
      const [x0, z0] = valid[index - 1];
      const span = x1 - x0;
      if (span <= 0) return z1;
      return z0 + (z1 - z0) * ((offsetM - x0) / span);
    }
    return valid[valid.length - 1][1];
  };
}

/** 짝: `_SectionGeometry`. 노면 → 측구 → 사면 순으로 offset 의 설계고를 계산한다. */
class SectionGeometry {
  halfRoad: number;
  leftExtent: number;
  rightExtent: number;
  zCenter: number;
  cutRatio: number;
  fillRatio: number;
  leftRole: string;
  rightRole: string;
  ditchSide: string;
  soilCutRatio: number;
  twoStage: boolean;
  ditchType: string;
  slopePerOffset: number;
  hasDitch: boolean;
  ditchPoints: Array<[number, number]> = [];
  private groundAt: ((offsetM: number) => number) | null;
  private rockOffset: number;
  private rockKnee = new Map<string, [number, number] | null>();
  private cutCross = new Map<string, number | null>();
  private fillCross = new Map<string, number | null>();

  constructor(params: {
    designElevationM: number;
    group: ResolvedGroup;
    sectionMode: string;
    ditchSide: string;
    ditchType: string;
    crossSlopePct: number;
    groundAt: ((offsetM: number) => number) | null;
    soilCutRatio: number | null;
    rockBoundaryOffsetM: number | null;
    twoStageSlope: boolean;
    ditchEnabled: boolean | null;
  }) {
    const { group } = params;
    const halfRoad = group.road_width_m / 2;
    this.halfRoad = halfRoad;
    this.leftExtent = halfRoad + group.shoulder_left_m;
    this.rightExtent = halfRoad + group.shoulder_right_m;
    this.zCenter = params.designElevationM;
    this.cutRatio = Math.max(group.cut_slope_ratio, 1e-6);
    this.fillRatio = Math.max(group.fill_slope_ratio, 1e-6);
    [this.leftRole, this.rightRole] = sideRole(params.sectionMode);
    this.ditchSide = params.ditchSide;
    this.soilCutRatio = Math.max(params.soilCutRatio ?? group.cut_slope_ratio, 1e-6);
    this.twoStage = Boolean(
      params.twoStageSlope && params.groundAt !== null && params.rockBoundaryOffsetM !== null,
    );
    this.groundAt = params.groundAt;
    this.rockOffset = params.rockBoundaryOffsetM ?? 0;
    this.ditchType = params.ditchType;
    // 횡단경사: 측구 방향으로 내려가는 단일 사면 (좌=+offset 규약).
    const slope = params.crossSlopePct / 100;
    this.slopePerOffset = params.ditchSide === "left" ? -slope : slope;

    // 단면유형 자동 판정(D-2) — 노면 끝 지반이 설계면보다 높으면 절토, 낮으면 성토.
    const groundAt = params.groundAt;
    if (groundAt !== null) {
      this.leftRole =
        groundAt(this.leftExtent) > this.roadZ(this.leftExtent) + 1e-3 ? "cut" : "fill";
      this.rightRole =
        groundAt(-this.rightExtent) > this.roadZ(-this.rightExtent) + 1e-3 ? "cut" : "fill";
    }

    // 측구 생성 여부(D-1).
    if (params.sectionMode === "both_fill") {
      this.hasDitch = false;
    } else if (params.ditchEnabled !== null && params.ditchEnabled !== undefined) {
      this.hasDitch = params.ditchEnabled;
    } else if (groundAt !== null) {
      const ditchEdge = params.ditchSide === "left" ? this.leftExtent : -this.rightExtent;
      this.hasDitch = groundAt(ditchEdge) > this.roadZ(ditchEdge) + 1e-3;
    } else {
      this.hasDitch = true;
    }

    // 측구 꼭짓점(측구측 노면 끝 기준, 바깥 방향 부호 적용).
    const edgeOffset = params.ditchSide === "left" ? this.leftExtent : -this.rightExtent;
    const outward = params.ditchSide === "left" ? 1 : -1;
    const edgeZ = this.roadZ(edgeOffset);
    if (this.hasDitch) {
      if (params.ditchType === "l_type") {
        // L형: 노면 끝에서 폭 W 동안 깊이 D로 내려가는 경사 바닥 + 바깥 수직벽.
        const width = group.l_ditch_width_m;
        const depth = group.l_ditch_depth_m;
        this.ditchPoints = [
          [edgeOffset, edgeZ],
          [edgeOffset + outward * width, edgeZ - depth],
          [edgeOffset + outward * width, edgeZ],
        ];
      } else {
        // 일반: 상단폭/저폭/깊이 사다리꼴.
        const top = group.ditch_top_width_m;
        const bottom = Math.min(group.ditch_bottom_width_m, top);
        const depth = group.ditch_depth_m;
        const inset = (top - bottom) / 2;
        this.ditchPoints = [
          [edgeOffset, edgeZ],
          [edgeOffset + outward * inset, edgeZ - depth],
          [edgeOffset + outward * (inset + bottom), edgeZ - depth],
          [edgeOffset + outward * top, edgeZ],
        ];
      }
    }
  }

  /** 노면(노견 포함) 설계고 — 중심 계획고에서 횡단경사로 기운 단일 평면. */
  roadZ(offsetM: number): number {
    return this.zCenter + this.slopePerOffset * offsetM;
  }

  /** 짝: `_slope_start`. 사면 시작점 [오프셋 절대값 거리, 표고]. */
  private slopeStart(side: string): [number, number] {
    const edgeOffset = side === "left" ? this.leftExtent : this.rightExtent;
    const edgeZ = side === "left" ? this.roadZ(this.leftExtent) : this.roadZ(-this.rightExtent);
    if (side === this.ditchSide && this.ditchPoints.length) {
      const outer = this.ditchPoints[this.ditchPoints.length - 1];
      return [Math.abs(outer[0]), outer[1]];
    }
    return [edgeOffset, edgeZ];
  }

  /** 짝: `_rock_boundary_z`. 암반 경계선 표고 = 지반선 + 오프셋(음수=하향). */
  private rockBoundaryZ(side: string, dist: number): number {
    const signed = side === "left" ? dist : -dist;
    return (this.groundAt as (offsetM: number) => number)(signed) + this.rockOffset;
  }

  /** 짝: `knee`. 절토 사면이 암반 경계선을 지나는 전환점(무릎). */
  knee(side: string): [number, number] | null {
    if (!this.twoStage) return null;
    const cached = this.rockKnee.get(side);
    if (cached !== undefined) return cached;
    const [startDist, startZ] = this.slopeStart(side);
    let diffPrev = startZ - this.rockBoundaryZ(side, startDist);
    let result: [number, number] | null;
    if (diffPrev >= 0) {
      result = [startDist, startZ]; // 시작부터 토사(경계 위)
    } else {
      result = null;
      let distPrev = startDist;
      let dist = startDist + MARCH_STEP_M;
      while (dist <= startDist + KNEE_MAX_M) {
        const zRock = startZ + (dist - startDist) / this.cutRatio;
        const diff = zRock - this.rockBoundaryZ(side, dist);
        if (diff >= 0) {
          const span = diff - diffPrev;
          const ratio = Math.abs(span) > 1e-9 ? -diffPrev / span : 0;
          const kneeDist = distPrev + (dist - distPrev) * ratio;
          const kneeZ = startZ + (kneeDist - startDist) / this.cutRatio;
          result = [kneeDist, kneeZ];
          break;
        }
        distPrev = dist;
        diffPrev = diff;
        dist += MARCH_STEP_M;
      }
    }
    this.rockKnee.set(side, result);
    return result;
  }

  /** 짝: `_cut_slope_z`. 절토 사면선 표고(2단계 무릎 반영, 지반 클램프 없음). */
  private cutSlopeZ(side: string, dist: number): number {
    const [startDist, startZ] = this.slopeStart(side);
    const knee = this.twoStage ? this.knee(side) : null;
    if (knee !== null) {
      const [kneeDist, kneeZ] = knee;
      if (dist <= kneeDist) return startZ + (dist - startDist) / this.cutRatio;
      return kneeZ + (dist - kneeDist) / this.soilCutRatio;
    }
    return startZ + (dist - startDist) / this.cutRatio;
  }

  /** 짝: `cut_cross_dist`. 절토 사면이 지반선과 처음 만나는 거리(N-2-4). */
  cutCrossDist(side: string): number | null {
    const cached = this.cutCross.get(side);
    if (cached !== undefined) return cached;
    let result: number | null = null;
    if (this.groundAt !== null) {
      const [startDist] = this.slopeStart(side);
      let dist = startDist;
      const maxDist = startDist + CROSS_MAX_M;
      while (dist <= maxDist) {
        const signed = side === "left" ? dist : -dist;
        if (this.cutSlopeZ(side, dist) - this.groundAt(signed) >= 0) {
          result = dist;
          break;
        }
        dist += MARCH_STEP_M;
      }
    }
    this.cutCross.set(side, result);
    return result;
  }

  /** 짝: `fill_cross_dist`. 성토 사면이 지반선과 처음 만나는 거리. */
  fillCrossDist(side: string): number | null {
    const cached = this.fillCross.get(side);
    if (cached !== undefined) return cached;
    let result: number | null = null;
    if (this.groundAt !== null) {
      const [startDist, startZ] = this.slopeStart(side);
      let dist = startDist;
      const maxDist = startDist + CROSS_MAX_M;
      while (dist <= maxDist) {
        const signed = side === "left" ? dist : -dist;
        const fillLine = startZ - (dist - startDist) / this.fillRatio;
        if (fillLine - this.groundAt(signed) <= 0) {
          result = dist;
          break;
        }
        dist += MARCH_STEP_M;
      }
    }
    this.fillCross.set(side, result);
    return result;
  }

  /** 짝: `fill_ground_slope`. 성토측 자연 지반 평균 경사(rise/run). */
  fillGroundSlope(): number | null {
    if (this.groundAt === null) return null;
    const slopes: number[] = [];
    for (const side of ["left", "right"]) {
      const role = side === "left" ? this.leftRole : this.rightRole;
      if (role !== "fill") continue;
      const [startDist] = this.slopeStart(side);
      const endDist = this.fillCrossDist(side) ?? startDist + 10;
      const run = endDist - startDist;
      if (run <= 1e-6) continue;
      const sign = side === "left" ? 1 : -1;
      const rise = Math.abs(this.groundAt(sign * endDist) - this.groundAt(sign * startDist));
      slopes.push(rise / run);
    }
    return slopes.length ? Math.min(...slopes) : null;
  }

  /** 짝: `design_z`. offset 하나의 설계 표고(사면은 지반 교차점 이후 지반 추종). */
  designZ(offsetM: number, groundM: number): number {
    const side = offsetM >= 0 ? "left" : "right";
    const extent = side === "left" ? this.leftExtent : this.rightExtent;
    if (Math.abs(offsetM) <= extent + 1e-9) return this.roadZ(offsetM);
    // 측구 구간: 꼭짓점 사이 선형 보간(지반 무관 강제 굴착).
    if (side === this.ditchSide && this.ditchPoints.length) {
      const inner = Math.abs(this.ditchPoints[0][0]);
      const outer = Math.abs(this.ditchPoints[this.ditchPoints.length - 1][0]);
      if (Math.abs(offsetM) >= inner - 1e-9 && Math.abs(offsetM) <= outer + 1e-9) {
        const points = this.ditchPoints;
        for (let index = 1; index < points.length; index += 1) {
          const x0 = Math.abs(points[index - 1][0]);
          const z0 = points[index - 1][1];
          const x1 = Math.abs(points[index][0]);
          const z1 = points[index][1];
          if (Math.abs(offsetM) > x1 + 1e-9) continue;
          const span = x1 - x0;
          if (span <= 1e-9) return z1;
          return z0 + (z1 - z0) * ((Math.abs(offsetM) - x0) / span);
        }
        return points[points.length - 1][1];
      }
    }
    const role = side === "left" ? this.leftRole : this.rightRole;
    const [startDist, startZ] = this.slopeStart(side);
    const dist = Math.abs(offsetM);
    const run = dist - startDist;
    if (role === "cut") {
      const cross = this.cutCrossDist(side);
      if (cross !== null && dist >= cross) return groundM;
      return Math.min(this.cutSlopeZ(side, dist), groundM);
    }
    const cross = this.fillCrossDist(side);
    if (cross !== null && dist >= cross) return groundM;
    return Math.max(startZ - run / this.fillRatio, groundM);
  }

  /** 짝: `breakpoints`. 적분·설계선에 반드시 넣을 설계 꼭짓점 오프셋. */
  breakpoints(): number[] {
    const points = [0, this.leftExtent, -this.rightExtent];
    for (const [offset] of this.ditchPoints) points.push(offset);
    if (this.twoStage) {
      for (const side of ["left", "right"]) {
        const role = side === "left" ? this.leftRole : this.rightRole;
        const knee = role === "cut" ? this.knee(side) : null;
        if (knee !== null) points.push(side === "left" ? knee[0] : -knee[0]);
      }
    }
    for (const side of ["left", "right"]) {
      const role = side === "left" ? this.leftRole : this.rightRole;
      const cross = role === "cut" ? this.cutCrossDist(side) : this.fillCrossDist(side);
      if (cross !== null) points.push(side === "left" ? cross : -cross);
    }
    return points;
  }
}

/**
 * 짝: `compute_cross_design`. 측점 하나의 표준횡단 설계선과 절·성토 단면적을 낸다.
 *
 * `samples` 는 지반선 원시 샘플, `designElevationM` 은 중심선 계획고(노면고)다.
 * 계산 불가(계획고 없음·샘플 부족·잘못된 유형)면 던진다 — 호출부가 그 측점을 건너뛴다.
 */
export function computeCrossDesign(
  samples: CrossGroundSample[],
  designElevationM: number | null | undefined,
  options: CrossDesignOptions,
): CrossDesignResult {
  const groundType = options.groundType;
  const sectionMode = options.sectionMode;
  const ditchType = options.ditchType ?? "standard";
  const paved = Boolean(options.paved);
  if (!(groundType in GROUND_TYPE_PRESET)) {
    throw new Error(`지원하지 않는 지반유형입니다: ${groundType}`);
  }
  if (!SECTION_MODES.includes(sectionMode)) {
    throw new Error(`지원하지 않는 단면유형입니다: ${sectionMode}`);
  }
  if (!DITCH_TYPES.includes(ditchType)) {
    throw new Error(`지원하지 않는 측구 형식입니다: ${ditchType}`);
  }
  if (designElevationM === null || designElevationM === undefined) {
    throw new Error("계획고(design_elevation_m)가 없어 횡단 설계를 계산할 수 없습니다.");
  }
  const drop = Math.max(options.surfaceDropM ?? 0, 0);
  const centerElevation = designElevationM - drop;

  const presetKey = GROUND_TYPE_PRESET[groundType];
  if (ditchType === "l_type" && presetKey !== "rock") {
    throw new Error("L형 측구는 암(리핑암/발파암) 구간에서만 선택할 수 있습니다.");
  }
  const group = resolveGroup(presetKey, options.standard);
  const pavedGroup = resolveGroup("paved", options.standard);
  // 포장 중첩: 횡단경사와 포장층 두께만 포장 그룹을 따른다.
  const crossSlopePct = paved ? pavedGroup.cross_slope_pct : group.cross_slope_pct;
  const resolvedDitchSide = resolveDitchSide(sectionMode, options.ditchSide);

  const valid: Array<[number, number]> = samples
    .filter(
      (sample) =>
        sample.valid !== false &&
        sample.offset_m !== null &&
        sample.offset_m !== undefined &&
        sample.elevation_m !== null &&
        sample.elevation_m !== undefined,
    )
    .map((sample) => [Number(sample.offset_m), Number(sample.elevation_m)] as [number, number])
    .sort((a, b) => a[0] - b[0]);
  if (valid.length < 2) {
    throw new Error("유효한 지반 샘플이 부족해 횡단 설계를 계산할 수 없습니다.");
  }

  const groundAt = groundInterpolator(valid);
  const rockBoundaryOffsetM = options.rockBoundaryOffsetM ?? null;
  // 2단계 절토는 암 프리셋에서만, 암반 경계 오프셋이 있을 때만 켠다.
  const enableTwoStage =
    presetKey === "rock" && (options.twoStageSlope ?? true) && rockBoundaryOffsetM !== null;
  const geometry = new SectionGeometry({
    designElevationM: centerElevation,
    group,
    sectionMode,
    ditchSide: resolvedDitchSide,
    ditchType,
    crossSlopePct,
    groundAt,
    soilCutRatio: resolveGroup("soil", options.standard).cut_slope_ratio,
    rockBoundaryOffsetM,
    twoStageSlope: enableTwoStage,
    ditchEnabled: options.ditchEnabled ?? null,
  });

  // 적분 오프셋 = 지반 샘플 ∪ 설계 꼭짓점(샘플 범위 안쪽만).
  const minOffset = valid[0][0];
  const maxOffset = valid[valid.length - 1][0];
  const mergedSet = new Set<number>(valid.map(([offset]) => round6(offset)));
  for (const point of geometry.breakpoints()) {
    if (point >= minOffset && point <= maxOffset) mergedSet.add(round6(point));
  }
  const merged = [...mergedSet].sort((a, b) => a - b);

  const offsets: number[] = [];
  const diffs: number[] = [];
  const designLine: CrossDesignEdge[] = [];
  for (const offsetM of merged) {
    const groundM = groundAt(offsetM);
    const designZ = geometry.designZ(offsetM, groundM);
    offsets.push(offsetM);
    diffs.push(groundM - designZ);
    designLine.push({ offset_m: round4(offsetM), elevation_m: round4(designZ) });
  }

  // 측구 굴착은 설계선에 포함돼 절토 면적에 자연 반영된다(별도 가산 없음).
  const [cutArea, fillArea] = trapezoidAreas(offsets, diffs);
  const fillGroundSlope = geometry.fillGroundSlope();
  const slopeUnclosed =
    diffs.length > 0 &&
    (Math.abs(diffs[0]) > SLOPE_CLOSE_TOLERANCE_M ||
      Math.abs(diffs[diffs.length - 1]) > SLOPE_CLOSE_TOLERANCE_M);

  // 절토면적 토사/암반 분리 — 지표면~암반 경계선이 토사, 그 아래가 암.
  let cutSoilArea: number;
  let cutRockArea: number;
  let cutRockKind: string | null;
  if (presetKey !== "rock") {
    cutSoilArea = cutArea;
    cutRockArea = 0;
    cutRockKind = null;
  } else if (rockBoundaryOffsetM === null) {
    cutSoilArea = 0;
    cutRockArea = cutArea;
    cutRockKind = groundType;
  } else {
    [cutSoilArea, cutRockArea] = splitCutAreas(offsets, diffs, Math.abs(rockBoundaryOffsetM));
    cutRockKind = groundType;
  }

  // 측구 공칭 단면적(수량 산출 참고용): 일반=사다리꼴, L형=직각삼각형 근사.
  let ditchArea: number;
  let ditchSpec: Record<string, unknown>;
  if (!geometry.hasDitch) {
    ditchArea = 0;
    ditchSpec = { type: "none" };
  } else if (ditchType === "l_type") {
    ditchArea = (group.l_ditch_width_m * group.l_ditch_depth_m) / 2;
    ditchSpec = {
      type: "l_type",
      width_m: group.l_ditch_width_m,
      depth_m: group.l_ditch_depth_m,
    };
  } else {
    ditchArea = ((group.ditch_top_width_m + group.ditch_bottom_width_m) / 2) * group.ditch_depth_m;
    ditchSpec = {
      type: "standard",
      top_width_m: group.ditch_top_width_m,
      bottom_width_m: group.ditch_bottom_width_m,
      depth_m: group.ditch_depth_m,
    };
  }

  // 자동 판정된 절/성토 역할에서 실제 단면 유형을 도출해 echo 한다(D-2).
  let resolvedMode: string;
  if (geometry.leftRole === "cut" && geometry.rightRole === "cut") resolvedMode = "both_cut";
  else if (geometry.leftRole === "fill" && geometry.rightRole === "fill") resolvedMode = "both_fill";
  else if (geometry.leftRole === "cut") resolvedMode = "left_cut";
  else resolvedMode = "right_cut";

  const result: CrossDesignResult = {
    ground_type: groundType,
    geometry_preset: presetKey,
    section_mode: resolvedMode,
    ditch_side: resolvedDitchSide,
    ditch_type: geometry.hasDitch ? ditchType : null,
    cut_slope_ratio: round4(geometry.cutRatio),
    soil_cut_slope_ratio: round4(geometry.soilCutRatio),
    two_stage_slope: geometry.twoStage,
    fill_slope_ratio: round4(geometry.fillRatio),
    roadbed_width_m: round4(geometry.leftExtent + geometry.rightExtent),
    carriageway_width_m: round4(group.road_width_m),
    cross_slope_pct: round4(crossSlopePct),
    ditch: ditchSpec,
    ditch_enabled: geometry.hasDitch,
    paved,
    road_edges: {
      left: {
        offset_m: round4(geometry.leftExtent),
        elevation_m: round4(geometry.roadZ(geometry.leftExtent)),
      },
      right: {
        offset_m: round4(-geometry.rightExtent),
        elevation_m: round4(geometry.roadZ(-geometry.rightExtent)),
      },
    },
    carriageway_edges: {
      left: {
        offset_m: round4(geometry.halfRoad),
        elevation_m: round4(geometry.roadZ(geometry.halfRoad)),
      },
      right: {
        offset_m: round4(-geometry.halfRoad),
        elevation_m: round4(geometry.roadZ(-geometry.halfRoad)),
      },
    },
    design_elevation_m: round4(centerElevation),
    cut_area_m2: round4(cutArea),
    cut_soil_area_m2: round4(cutSoilArea),
    cut_rock_area_m2: round4(cutRockArea),
    cut_rock_kind: cutRockKind,
    fill_area_m2: round4(fillArea),
    slope_unclosed: slopeUnclosed,
    fill_ground_slope: fillGroundSlope === null ? null : round4(fillGroundSlope),
    ditch_area_m2: round4(ditchArea),
    design_line: designLine,
  };
  if (drop > 0) result.surface_drop_m = round4(drop);
  if (paved) result.pavement_thickness_m = round4(pavedGroup.pavement_thickness_m);
  if (presetKey === "rock" && rockBoundaryOffsetM !== null) {
    result.rock_boundary_offset_m = round4(rockBoundaryOffsetM);
  }
  return result;
}

/** 짝: 파이썬 `round(offset, 6)` — 병합 격자 중복 제거 기준. */
function round6(value: number): number {
  return Math.round(value * 1e6) / 1e6;
}