import { buildAxis, copingSpan, fromAxis, kinkArc, nearKink, toAxis } from './axis';
import { buildIntegratedBlocks, type IntegratedBlock } from './integrated-block';
import { type BlockRebarSettings, DEFAULT_BLOCK_REBAR } from './rebar/bearing-block';
import { type CopingRebarSettings, copingDefaults, DEFAULT_TOP_SPLICE, type TopSpliceSettings } from './rebar/coping-settings';
import { type ColumnRebarSettings, DEFAULT_COLUMN_REBAR } from './rebar/column-settings';
import { type FootingRebarSettings, DEFAULT_FOOTING_REBAR } from './rebar/footing-settings';
import { layoutText, resolveRowCounts, rowLayout, type PileGeometry } from './piles';
import type { PierInput, Row, SolplatePlan } from './types';
import type { BearingPair } from './bearing-pair';
import { type BearingSole, SOLE_DEFAULTS, structureSoles } from './sole-plate';
import { type CopingGeom, P1_COPING_GEOM } from './coping-geom';
import { castShape } from './cast-in-place-shape';

/** Default Level width (mm) when no input: T형 2100 (P1), 2·3주형 D + 200 (spec §3, 2주형 DWG 2026-11-06). */
export function defaultLevelWidthMm(type: PierInput['type'], columnDiameterMm: number): number {
  return type === 'T형' ? P1_COPING_GEOM.levelWidth : columnDiameterMm + DIM.multiLevelExtra * 1000;
}

/** Dimensions in m. Sources: intent.PR sheet (P1 rules) and spec.md §3 defaults. */
export const DIM = {
  columnDiameter: 2.0,
  copingH1: 1.0,
  copingH2: 1.5,
  levelWidth: 2.1,
  /**
   * Multi-column coping, 오목형 underside (spec §4.4, 3주형형상배근.md §2.2, 2주형 DWG 2026-11-06):
   * from each Level end it rises concaveRise over the horizontal haunch length concaveHaunch, stays flat, and comes back down.
   */
  concaveRise: 0.5,
  concaveHaunch: 1.5,
  /** Multi-column Level width = D + this (spec §3, 2주형 DWG). T형 keeps levelWidth (= D + 100 for P1). */
  multiLevelExtra: 0.2,
  padThickness: 0.05,
  padSize: 1.0,
  blockSize: 1.2,
  /** W11 (제안 2026-11-10): 받침블럭 콘크리트(패드 제외) 최소 높이 = 피복 50 + D13 = 63 mm (교대 I01과 같은 기준). */
  blockMinHeight: 0.063,
  footingL: 10.4,
  footingW: 8.15,
  footingH: 2.0,
  blindingMargin: 0.2,
  blindingT: 0.1,
  /** 강관 609.6 × 12 (spec §4.5 강관 type, Q5 추천안 적용). */
  pileDiameter: 0.6096,
  pileEnd: 0.7,
  pileSpacing: 2.25,
  /** Front/back EL difference below this is treated as no lateral step (spec §4.3, Q2). */
  lateralTolerance: 0.005,
} as const;

export interface Vec2 {
  e: number;
  n: number;
}

export interface Segment {
  s0: number;
  s1: number;
  top: number;
}

/** Stretch k, local s from that stretch's base, g = coping-relative arc length, n = lateral offset. */
export interface BearingLocal {
  no: number;
  row: Row;
  k: number;
  s: number;
  g: number;
  n: number;
  z: number;
}

export interface Stretch {
  origin: Vec2;
  u: Vec2;
  nrm: Vec2;
  /** Coping-relative arc length where this stretch starts (0 for k = 0, the kink for k = 1). */
  base: number;
}

export interface BlockModel {
  no: number;
  row: Row;
  k: number;
  s: number;
  g: number;
  n: number;
  bottom: number;
  top: number;
  padTop: number;
  /** Skew (deg, −90…90] of the bearing row against the perpendicular of the stretch axis; the block sides follow the row. */
  rowSkewDeg: number;
  /** Solplate of this bearing (2026-11-06): S from the girder pair, T per row, T1 on the 오르막 쪽. */
  plan: SolplatePlan;
  /** Block bottom from the 두부보 상면 slope (before any 교좌면 EL input), for the check against the input (2026-11-03). */
  seatCalc: number;
}

/** Skew of a bearing row (deg) from the bearing azimuth and the stretch axis direction u (see {@link BlockModel.rowSkewDeg}). */
export function rowSkewDeg(bearingAzimuthDeg: number, u: Vec2): number {
  if (Number.isNaN(bearingAzimuthDeg)) return 0;
  const axisAz = (Math.atan2(u.e, u.n) * 180) / Math.PI;
  const d = (((bearingAzimuthDeg - (axisAz + 90)) % 180) + 540) % 180; // 0…180
  return d > 90 ? d - 180 : d;
}

/**
 * (s, n) of a point (a along the block's s side, c along its n side) measured from the block centre, after the block turns
 * by its row skew. Same turn as the 3D geometry (rotateY(−skew)).
 */
export function blockFramePoint(b: Pick<BlockModel, 's' | 'n' | 'rowSkewDeg'>, a: number, c: number): [number, number] {
  const d = (b.rowSkewDeg * Math.PI) / 180;
  return [b.s + a * Math.cos(d) - c * Math.sin(d), b.n + a * Math.sin(d) + c * Math.cos(d)];
}

export interface ColumnModel {
  s: number;
  k: number;
  top: number;
  bottom: number;
  diameter: number;
}

export interface FootingModel {
  s: number;
  k: number;
  top: number;
  bottom: number;
  length: number;
  width: number;
}

export interface BlindingModel {
  s: number;
  k: number;
  top: number;
  length: number;
  width: number;
  thickness: number;
}

export interface PileModel {
  s: number;
  k: number;
  n: number;
  top: number;
  bottom: number;
  diameter: number;
}

/** One coping slab across [nFrom, nTo]; profile is its (s, EL) outline, closed. */
export interface CopingPart {
  k: number;
  nFrom: number;
  nTo: number;
  profile: [number, number][];
}

export interface PierModel {
  name: string;
  lengthIp: number;
  azimuthDeg: number;
  /** Unit vector along the pier axis (east, north). */
  u: Vec2;
  /** Unit vector across the axis: (u.n, -u.e). Front row is negative, back row positive. */
  nrm: Vec2;
  ip1: Vec2;
  ip2Input: Vec2;
  ip2Calc: Vec2;
  dIp2: number;
  bp1: Vec2;
  bp2: Vec2;
  /** Horizontal centre of the drawing frame: the centre of the first column. */
  pivot: Vec2;
  copingL: number;
  copingB: number;
  copingRefTop: number;
  h1: number;
  h2: number;
  segments: Segment[];
  /** Rear-row steps. Unequal rows use their own coordinate-based boundaries. */
  backSegments?: Segment[];
  /** Coping parts per stretch, split across the width by the lateral step line (one part per stretch without a step). */
  copingParts: CopingPart[];
  stretches: Stretch[];
  /** Bend point IP4, or null for a straight axis. */
  kink: Vec2 | null;
  /** Mitre normal at the kink (unit). A point is on stretch 0 when (p − kink)·mitre ≤ 0. */
  mitre: Vec2 | null;
  levelBottom: number;
  endBottom: number;
  /** Coping heights and Level width in mm, as used by the coping rebar (1단계). */
  copingGeom: CopingGeom;
  /** Column diameter D (mm) used by the model and the column rebar. */
  columnDiameterMm: number;
  bearings: BearingLocal[];
  blocks: BlockModel[];
  /** 일체 블록 (승인 2026-10-26): empty unless 일체 is chosen and allowed. The per-bearing blocks stay for the solplate and pads. */
  integratedBlocks: IntegratedBlock[];
  /** 받침블럭 철근 설정 used by the rebar (승인 2026-10-26). */
  blockRebar: BlockRebarSettings;
  /** 코핑 배근 입력 used by the coping rebar (승인 2026-10-26). */
  copingRebar: CopingRebarSettings;
  /** 상면 주철근 이음 used by the coping rebar (승인 2026-10-26). */
  topSplice: TopSpliceSettings;
  /** 기둥 배근 입력 used by the column rebar (승인 2026-10-26). */
  columnRebar: ColumnRebarSettings;
  /** 확대기초 배근 입력 used by the footing rebar (승인 2026-10-26). */
  footingRebar: FootingRebarSettings;
  columns: ColumnModel[];
  footings: FootingModel[];
  blindings: BlindingModel[];
  piles: PileModel[];
  groundEl: number;
  derived: {
    columnHeight: number;
    soilCover: number;
    pileCount: number;
    pileLayout: string | null;
    pileTipEl: number | null;
    blockHeightFront: number;
    blockHeightBack: number;
    frontBackDiffSpread: number;
  };
  /** Dedicated rebar source; never substitute footing-anchored column inputs. */
  castInput?: PierInput;
  /** Solplate of every bearing with its S source, pair and warnings (2026-11-06), for the ② card and checks. */
  soles: BearingSole[];
}

/**
 * Bend point IP4 (spec §4.1-2): the point where the IP1→IP2 line meets the line through IP3 whose
 * direction is IP1→IP2 turned by the bend angle. Positive angle = right (clockwise) turn when travelling IP1→IP2.
 * Returns null for a zero angle, where IP4 is not defined.
 */
export function solveIp4(ip1: Vec2, ip2: Vec2, ip3: Vec2, angleDeg: number): Vec2 | null {
  if (angleDeg === 0) return null;
  const cross = (a: Vec2, b: Vec2) => a.e * b.n - a.n * b.e;
  const len = Math.hypot(ip2.e - ip1.e, ip2.n - ip1.n);
  const d1: Vec2 = { e: (ip2.e - ip1.e) / len, n: (ip2.n - ip1.n) / len };
  const rad = (-angleDeg * Math.PI) / 180; // clockwise is positive, so the counter-clockwise rotation uses −θ
  const d2: Vec2 = { e: d1.e * Math.cos(rad) - d1.n * Math.sin(rad), n: d1.e * Math.sin(rad) + d1.n * Math.cos(rad) };
  const t = cross({ e: ip3.e - ip1.e, n: ip3.n - ip1.n }, d2) / cross(d1, d2);
  return { e: ip1.e + t * d1.e, n: ip1.n + t * d1.n };
}

/**
 * Builds the first-stage model of a T-type pier from one input record. Pure function.
 * Coordinates: g = arc length from the coping start (BP1), so g = 0 at BP1 and g = L at BP2.
 * Each object carries its stretch k and a local s measured from that stretch's base (k = 0: BP1, k = 1: IP4).
 * A bent coping (IP4 angle ≠ 0) puts each footing in its stretch's frame; footings that would cross the kink are not combined.
 */
/** Bridge context for one pier: the girder pairs over A1, P1 … Pn, A2 (girderPairs), for the solplate slope S. */
export interface PierContext { pairs?: BearingPair[] }

export function buildPier(input: PierInput, ctx: PierContext = {}): PierModel {
  const ip = (name: string) => {
    const p = input.ips.find((q) => q.name === name);
    if (!p) throw new Error(`IP 누락: ${name}`);
    return p;
  };
  const ip1 = ip('IP1');
  const ip2 = ip('IP2');
  const ip3 = ip('IP3');
  const ip4 = ip('IP4');
  const bent = ip4.angleDeg !== 0;

  const L = input.copingLengthMm / 1000;
  const B = input.copingWidthMm / 1000;
  // Coping heights and Level width (m): inputs, with the P1 values when absent (1단계).
  const copingH1 = (input.copingH1Mm ?? P1_COPING_GEOM.h1) / 1000;
  const copingH2 = (input.copingH2Mm ?? P1_COPING_GEOM.h2) / 1000;
  // Column diameter (m): the input, with 2.0 m when absent (승인 2026-10-23).
  const colD = (input.columnDiameterMm ?? DIM.columnDiameter * 1000) / 1000;
  const levelW = (input.levelWidthMm ?? defaultLevelWidthMm(input.type, colD * 1000)) / 1000;
  const planHalfB = B / 2;
  const ip1v: Vec2 = { e: ip1.x, n: ip1.y };
  const ip2v: Vec2 = { e: ip2.x, n: ip2.y };
  const ip3v: Vec2 = { e: ip3.x, n: ip3.y };
  const kink = bent ? solveIp4(ip1v, ip2v, ip3v, ip4.angleDeg) : null;
  const axis = buildAxis(ip1v, ip3v, kink);
  if (kink) {
    // The bend must move the axis forward: the kink ahead of IP1 along IP1→IP2, and IP3 ahead of the kink along the turned direction.
    const d1 = { e: ip2v.e - ip1v.e, n: ip2v.n - ip1v.n };
    const len1 = Math.hypot(d1.e, d1.n);
    const rad = (-ip4.angleDeg * Math.PI) / 180;
    const d2 = { e: (d1.e * Math.cos(rad) - d1.n * Math.sin(rad)) / len1, n: (d1.e * Math.sin(rad) + d1.n * Math.cos(rad)) / len1 };
    const kinkAhead = (kink.e - ip1v.e) * d1.e + (kink.n - ip1v.n) * d1.n > 0;
    const ip3Ahead = (ip3v.e - kink.e) * d2.e + (ip3v.n - kink.n) * d2.n > 0;
    if (!kinkAhead || !ip3Ahead) {
      throw new Error('꺾임각과 IP 배치가 맞지 않습니다. IP4가 축 뒤로 넘어갑니다. IP3이 꺾인 방향의 앞쪽에 있는지 확인하세요.');
    }
  }
  const lengthIp = axis.length;
  const sStart = copingSpan(axis, L).sStart;
  const arcA = kinkArc(axis);
  const kinkG = arcA === null ? null : arcA - sStart;
  if (kinkG !== null && (kinkG <= 0 || kinkG >= L)) {
    throw new Error('꺾임점이 코핑 범위 밖에 있습니다. 코핑 길이를 확인하세요.');
  }
  const base = [0, kinkG ?? 0];
  const { u, nrm } = axis.segments[0];
  const azimuthDeg = (((Math.atan2(u.e, u.n) * 180) / Math.PI) + 360) % 360;

  // IP2 is a 1:9 reference point on a straight axis (intent.PR, spec §2.2). On a bent axis IP2 is on the first stretch, so no check.
  const ip2Calc: Vec2 = kink ? ip2v : { e: ip1.x + 0.1 * (ip3.x - ip1.x), n: ip1.y + 0.1 * (ip3.y - ip1.y) };
  const ip2Input: Vec2 = ip2v;

  const pointAt = (g: number, n: number): Vec2 => {
    const arc = sStart + g;
    const k = kinkG !== null && g > kinkG ? 1 : 0;
    return fromAxis(axis, { k, s: arc, n });
  };
  const bp1 = pointAt(0, 0);
  const bp2 = pointAt(L, 0);
  const pivot = pointAt(L / 2, 0);

  const front = input.bearings.filter((b) => b.row === '전열').sort((a, b) => a.no - b.no);
  const back = input.bearings.filter((b) => b.row === '후열').sort((a, b) => a.no - b.no);
  if (!front.length || !back.length) throw new Error('전열과 후열에 각각 받침이 1개 이상 필요합니다.');
  const unequalRows = front.length !== back.length;

  // Bearing block heights (spec §4.3 h1OshoeBlock / h2, pad 50 included). Not the coping end heights (DIM.copingH1/H2).
  const h1 = front[0].z - input.copingTopEl;
  const h2 = h1 + (back[0].z - front[0].z);

  const place = (b: { x: number; y: number }) => {
    const q = toAxis(axis, { e: b.x, n: b.y });
    const g = q.s - sStart;
    return { k: q.k, g, s: g - base[q.k], n: q.n };
  };
  const frontPlaced = front.map((b) => ({ no: b.no, row: '전열' as Row, z: b.z, ...place(b) }));
  const backPlaced = back.map((b) => ({ no: b.no, row: '후열' as Row, z: b.z, ...place(b) }));
  if (unequalRows) { frontPlaced.sort((a,b)=>a.g-b.g); backPlaced.sort((a,b)=>a.g-b.g); }

  // Step boundaries sit midway between consecutive front bearings in coping coordinates (spec §4.3).
  const bounds = [0];
  for (let k = 0; k < frontPlaced.length - 1; k++) {
    bounds.push((frontPlaced[k].g + frontPlaced[k + 1].g) / 2);
  }
  bounds.push(L);
  // 교좌면 EL per bearing (2026-11-10): when given, it is the coping top of that bearing's step; otherwise z − h1 (z − h2 behind).
  const seatOf = new Map(input.bearings.map((r) => [r.no, r.seatEl]));
  const segments: Segment[] = frontPlaced.map((b, k) => ({ s0: bounds[k], s1: bounds[k + 1], top: seatOf.get(b.no) ?? b.z - h1 }));

  // Lateral step (spec §4.3, Q1·Q2 추천안): front and back tops differ by 5 mm or more in some segment.
  // The back steps break midway between consecutive back bearings (2026-11-10), as the front ones do: back bearings need
  // not sit opposite the front ones (산외교 P11 ⑥ ↔ ⑦). With equal counts, a back bound less than half a block from the
  // front bound snaps to it, so slightly staggered rows (P1, ≈ 0.09 m) keep one boundary and no sliver step.
  const backBound = (k: number) => {
    const own = (backPlaced[k-1].g + backPlaced[k].g) / 2;
    return !unequalRows && Math.abs(own - bounds[k]) < DIM.blockSize / 2 ? bounds[k] : own;
  };
  const backSegments: Segment[] = backPlaced.map((b,k) => ({
    s0: k === 0 ? 0 : backBound(k),
    s1: k === backPlaced.length-1 ? L : backBound(k + 1),
    top: seatOf.get(b.no) ?? b.z-h2,
  }));
  const stepBounds = [...new Set([0,L,...segments.slice(1).map(s=>s.s0),...backSegments.slice(1).map(s=>s.s0)])].sort((a,b)=>a-b);
  const stepSamples = stepBounds.slice(1).map((end,k)=>(stepBounds[k]+end)/2);
  const lateralStep = stepSamples.some(s => Math.abs(segmentTop(segments,s)-segmentTop(backSegments,s)) >= DIM.lateralTolerance);

  // Columns (spec §4.5). Positions are coping coordinates; a column must stay a Level half-width away from the kink.
  const colG = columnPositions(input.type, L, input.columnEndOffsetMm, input.columnSpacingMm);
  if (kinkG !== null) {
    const near = nearKink(axis, colG.map((g) => sStart + g), levelW / 2);
    if (near.length) throw new Error('미실시: 꺾임점 근처(Level 반폭 이내)에 기둥이 있습니다. 기둥 위치를 확인하세요.');
  }
  const colK = colG.map((g) => (kinkG !== null && g > kinkG ? 1 : 0));
  // Coping underside: ends at (top − end height h1 = 1000), Level zone at (top − h1 − h2 taper height = 1500).
  const levelBottom = input.copingTopEl - copingH1 - copingH2;
  const endBottom = input.copingTopEl - copingH1;
  const levelStart = Math.min(...colG) - levelW / 2;
  const levelEnd = Math.max(...colG) + levelW / 2;
  if (levelStart < 0 || levelEnd > L) throw new Error('코핑 길이가 Level 구간보다 짧습니다.');

  // Underside from the right end to the left end. Between columns (2·3주형) it is 오목형: from each Level end it rises
  // h_r (500) over the horizontal haunch l_h (1500), stays flat, and comes back down (spec §4.4, 3주형형상배근.md §2.2).
  const underside: [number, number][] = [[L, endBottom]];
  const levelZones = [...colG].sort((a, b) => b - a).map((s) => [s - levelW / 2, s + levelW / 2] as const);
  levelZones.forEach(([zoneStart, zoneEnd], k) => {
    underside.push([zoneEnd, levelBottom], [zoneStart, levelBottom]);
    const next = levelZones[k + 1];
    if (!next) return;
    const gap = zoneStart - next[1];
    // RB-M01: no flat part left between the two haunches.
    if (gap <= 2 * DIM.concaveHaunch + 1e-9) {
      throw new Error(`기둥 사이 간격 ${Math.round(gap * 1000)} mm가 오목형 헌치(${DIM.concaveHaunch * 1000} × 2)보다 짧아 코핑 하면을 만들 수 없습니다 (RB-M01).`);
    }
    const raisedEl = levelBottom + DIM.concaveRise;
    underside.push([zoneStart - DIM.concaveHaunch, raisedEl], [next[1] + DIM.concaveHaunch, raisedEl], [next[1], levelBottom]);
  });

  // Elevation outline in coping coordinates for one row of tops, closed by the shared underside.
  const outline = (steps: Segment[]): [number, number][] => {
    const pts: [number, number][] = [[0, endBottom]];
    steps.forEach(seg => pts.push([seg.s0, seg.top], [seg.s1, seg.top]));
    pts.push(...underside);
    return pts;
  };
  // Each stretch uses the same outline shifted to its own base; the mitre plane trims the overlap at the kink.
  const shifted = (pts: [number, number][], b: number): [number, number][] => pts.map(([s, z]) => [s - b, z]);

  const meanN = (rows: { n: number }[]) => rows.reduce((sum, r) => sum + r.n, 0) / rows.length;
  const copingParts: CopingPart[] = [];
  const stretchCount = kinkG === null ? 1 : 2;
  for (let k = 0; k < stretchCount; k++) {
    const fRows = frontPlaced.filter((b) => b.k === k);
    const bRows = backPlaced.filter((b) => b.k === k);
    const nStep = fRows.length && bRows.length
      ? (meanN(fRows) + meanN(bRows)) / 2
      : (meanN(frontPlaced) + meanN(backPlaced)) / 2;
    if (lateralStep) {
      // The front row may lie on either side of the axis (it depends on the IP1 → IP3 direction), so each part takes the
      // side of its own row; the order stays [front, back].
      const frontLow = (fRows.length && bRows.length ? meanN(fRows) - meanN(bRows) : meanN(frontPlaced) - meanN(backPlaced)) <= 0;
      copingParts.push(
        { k, nFrom: frontLow ? -planHalfB : nStep, nTo: frontLow ? nStep : planHalfB, profile: shifted(outline(segments), base[k]) },
        { k, nFrom: frontLow ? nStep : -planHalfB, nTo: frontLow ? planHalfB : nStep, profile: shifted(outline(backSegments), base[k]) },
      );
    } else {
      copingParts.push({ k, nFrom: -planHalfB, nTo: planHalfB, profile: shifted(outline(segments), base[k]) });
    }
  }

  const fd = footingDims(input);
  // Footings are grouped per stretch so that a 일체기초 never crosses the kink; each group is aligned with its stretch.
  const footingSets: { s: number; k: number; length: number }[] = [];
  for (let k = 0; k < stretchCount; k++) {
    for (const g of footingGroups(colG.filter((_, i) => colK[i] === k), fd.L)) {
      footingSets.push({ s: g.s - base[k], k, length: g.length });
    }
  }

  const cast = castShape(input);
  if (input.foundationType === '현장타설말뚝' && (!Number.isFinite(cast.pileTopEl) || cast.pileTopEl >= levelBottom || !Number.isFinite(input.pileLengthMm) || input.pileLengthMm <= 0)) throw new Error('현장타설말뚝은 지반고가 코핑 Level 하면보다 낮고 말뚝 길이가 양수여야 합니다.');
  const footingTop = input.foundationType === '현장타설말뚝' ? cast.pileTopEl : input.footingBottomEl + fd.H;
  const columns: ColumnModel[] = colG.map((g, i) => ({
    s: g - base[colK[i]],
    k: colK[i],
    top: levelBottom,
    bottom: footingTop,
    diameter: colD,
  }));

  const footings: FootingModel[] = [];
  const blindings: BlindingModel[] = [];
  const piles: PileModel[] = [];
  const pileLength = input.pileLengthMm / 1000;
  const pileTip = input.foundationType === '현장타설말뚝' ? cast.pileBottomEl : input.footingBottomEl - pileLength;

  if (input.foundationType === '현장타설말뚝') {
    columns.forEach((c) => {
      piles.push({ s: c.s, k: c.k, n: 0, top: cast.pileTopEl, bottom: pileTip, diameter: colD });
    });
  } else {
    for (const f of footingSets) {
      footings.push({ s: f.s, k: f.k, top: footingTop, bottom: input.footingBottomEl, length: f.length, width: fd.W });
      blindings.push({
        s: f.s,
        k: f.k,
        top: input.footingBottomEl,
        length: f.length + fd.blM,
        width: fd.W + fd.blM,
        thickness: fd.blT,
      });
      if (input.foundationType === '말뚝기초') {
        const g = pileGeometry(f.length, fd.W);
        const counts = resolveRowCounts(input.pileRows, g);
        piles.push(...pilesFor(f.s, input.footingBottomEl, pileLength, g, counts, fd.pileD).map((p) => ({ ...p, k: f.k })));
      }
    }
  }

  const blocks: BlockModel[] = [];
  // 계산 방위각을 적용한 받침 (2026-11-06): that value turns the block, bearing and solplate; the workbook value stays in input.
  const azimuthOf = (r: { no: number; azimuthDeg: number }) => input.azimuthApplied?.[String(r.no)] ?? r.azimuthDeg;
  const bearingAz = new Map(input.bearings.map((r) => [r.no, azimuthOf(r)]));
  const skewOf = (no: number, k: number) => rowSkewDeg(bearingAz.get(no) ?? NaN, axis.segments[k].u);
  // Solplate of every bearing (결정 2026-11-06): S from the girder pair (ctx.pairs over the whole bridge), else the
  // 종단경사 input, else the other row; T per row; the girder underside stays, so the block top drops by T − T_ref.
  // 받침높이 per bearing (2026-11-10): h3 = H − T_ref keeps the girder underside at z + H; a typed h3 still wins.
  const tRef = input.sole?.tRefMm ?? SOLE_DEFAULTS.tRefMm;
  const h3ByNo = Object.fromEntries(input.bearings.filter((b) => b.heightMm !== undefined).map((b) => [String(b.no), b.heightMm! - tRef]));
  const soles = new Map(structureSoles(input.name, input.bearings.map((b) => ({ no: b.no, row: b.row, azimuthDeg: azimuthOf(b), inputAzimuthDeg: b.azimuthDeg })),
    { ...input.sole, h3ByNo }, ctx.pairs ?? [], input.longitudinalSlope === undefined ? undefined : input.longitudinalSlope * 100).map((s) => [s.no, s]));
  const planOf = (no: number, k: number, skewDeg: number): SolplatePlan => {
    const s = soles.get(no)!;
    // The block's c axis in (E, N): (−sin d)·u + (cos d)·nrm; T1 goes to the end of c that points uphill.
    const { u, nrm } = axis.segments[k];
    const d = (skewDeg * Math.PI) / 180;
    const c = { e: -Math.sin(d) * u.e + Math.cos(d) * nrm.e, n: -Math.sin(d) * u.n + Math.cos(d) * nrm.n };
    const t1Side = s.uphill && c.e * s.uphill.e + c.n * s.uphill.n > 0 ? 1 : -1;
    return { L: s.L, W: s.W, slopePct: s.slopePct, T: s.T, T1: s.T1, T2: s.T2, h3: s.h3, t1Side };
  };
  const dropOf = (no: number) => soles.get(no)!.dropMm / 1000;
  // 교좌면 EL (2026-11-03): when the input gives it, the block bottom is that EL; otherwise the 두부보 상면 slope.
  // seatCalc stays the slope value (z − h1, z − h2) as the W10 reference.
  frontPlaced.forEach((b) => {
    const seatCalc = b.z - h1;
    const bottom = seatOf.get(b.no) ?? seatCalc;
    const skew = skewOf(b.no, b.k), drop = dropOf(b.no);
    blocks.push({ no: b.no, row: '전열', k: b.k, s: b.s, g: b.g, n: b.n, bottom, top: b.z - DIM.padThickness - drop, padTop: b.z - drop, rowSkewDeg: skew, plan: planOf(b.no, b.k, skew), seatCalc });
  });
  backPlaced.forEach((b) => {
    const seatCalc = b.z - h2;
    const bottom = seatOf.get(b.no) ?? seatCalc;
    const skew = skewOf(b.no, b.k), drop = dropOf(b.no);
    blocks.push({ no: b.no, row: '후열', k: b.k, s: b.s, g: b.g, n: b.n, bottom, top: b.z - DIM.padThickness - drop, padTop: b.z - drop, rowSkewDeg: skew, plan: planOf(b.no, b.k, skew), seatCalc });
  });

  const blockHeightFront = blocks.find((b) => b.row === '전열')!.top - blocks.find((b) => b.row === '전열')!.bottom;
  const blockHeightBack = blocks.find((b) => b.row === '후열')!.top - blocks.find((b) => b.row === '후열')!.bottom;
  const diffs = unequalRows ? stepSamples.map(s=>segmentTop(segments,s)-segmentTop(backSegments,s)) : frontPlaced.map((f, k) => f.z - backPlaced[k].z);
  const frontBackDiffSpread = Math.max(...diffs) - Math.min(...diffs);

  return {
    name: input.name,
    lengthIp,
    azimuthDeg,
    u,
    nrm,
    ip1: ip1v,
    ip2Input,
    ip2Calc,
    dIp2: (ip2Calc.e - bp1.e) * u.e + (ip2Calc.n - bp1.n) * u.n,
    bp1,
    bp2,
    pivot,
    copingL: L,
    copingB: B,
    copingRefTop: input.copingTopEl,
    h1,
    h2,
    segments,
    backSegments,
    copingParts,
    stretches: axis.segments.map((seg, k) => ({ origin: k === 0 ? bp1 : seg.start, u: seg.u, nrm: seg.nrm, base: base[k] })),
    kink,
    mitre: axis.mitre,
    levelBottom,
    endBottom,
    copingGeom: { h1: copingH1 * 1000, h2: copingH2 * 1000, levelWidth: levelW * 1000 },
    columnDiameterMm: colD * 1000,
    bearings: [...frontPlaced, ...backPlaced].map((b) => ({ no: b.no, row: b.row, k: b.k, s: b.s, g: b.g, n: b.n, z: b.z })),
    blocks,
    integratedBlocks: buildIntegratedBlocks(blocks, input.bearingLayout === '일체'),
    blockRebar: { ...DEFAULT_BLOCK_REBAR, ...input.blockRebar },
    copingRebar: { ...copingDefaults(columns.length), ...input.copingRebar },
    topSplice: { ...DEFAULT_TOP_SPLICE, ...input.topSplice },
    columnRebar: { ...DEFAULT_COLUMN_REBAR, ...input.columnRebar },
    footingRebar: { ...DEFAULT_FOOTING_REBAR, ...input.footingRebar },
    columns,
    footings,
    blindings,
    piles,
    groundEl: input.groundEl,
    derived: {
      columnHeight: levelBottom - columns[0].bottom,
      soilCover: input.foundationType === '현장타설말뚝' ? 0 : input.groundEl - footingTop,
      pileCount: piles.length,
      pileLayout: input.foundationType === '말뚝기초' ? layoutText(resolveRowCounts(input.pileRows, pileGeometry(footings[0].length, fd.W)), pileGeometry(footings[0].length, fd.W)) : null,
      pileTipEl: piles.length ? pileTip : null,
      blockHeightFront,
      blockHeightBack,
      frontBackDiffSpread,
    },
    soles: [...soles.values()],
    ...(input.foundationType === '현장타설말뚝' ? { castInput: { ...input } } : {}),
  };
}

/**
 * Column centres along the coping (m). spec §4.5: L/5 · (L/2) · 4L/5. For 2·3주형 the 끝 여유 e_c and 간격 s_c may be typed
 * (Q-M10 미결, 3주형형상배근.md §2.1): e_c + k·s_c, s_c defaulting to the even spacing between e_c and L − e_c.
 */
export function columnPositions(type: PierInput['type'], L: number, endOffsetMm?: number, spacingMm?: number): number[] {
  if (type === 'T형') return [L / 2];
  const n = type === '2주형' ? 2 : 3;
  if (endOffsetMm !== undefined) {
    const e = endOffsetMm / 1000;
    const step = spacingMm !== undefined ? spacingMm / 1000 : (L - 2 * e) / (n - 1);
    return Array.from({ length: n }, (_, k) => e + k * step);
  }
  if (type === '2주형') return [L / 5, L - L / 5];
  return [L / 5, L / 2, L - L / 5];
}

function segmentTop(segments: Segment[], s: number): number {
  const hit = segments.find((seg) => s >= seg.s0 && s < seg.s1) ?? segments[segments.length - 1];
  return hit.top;
}

/**
 * Footings (spec §4.6). Adjacent columns closer than one footing length share a 일체기초 whose length is
 * the distance between its outer columns + DIM.footingL, centred between them. Other columns get their own footing.
 */
export function footingGroups(colS: number[], footL: number = DIM.footingL): { s: number; length: number }[] {
  const groups: number[][] = [];
  for (const s of [...colS].sort((a, b) => a - b)) {
    const last = groups[groups.length - 1];
    if (last && s - last[last.length - 1] < footL) last.push(s);
    else groups.push([s]);
  }
  return groups.map((g) => ({
    s: (g[0] + g[g.length - 1]) / 2,
    length: g[g.length - 1] - g[0] + footL,
  }));
}

/**
 * Piles under one footing (spec §4.6): rows across the footing width, piles along the length,
 * both with an end distance of 0.7 m and an even spacing that never exceeds 2.25 m.
 */
/** Pile geometry of one footing, from the 1단계 constants (spec §4.6). */
export function pileGeometry(footingLength: number, footingWidth: number = DIM.footingW): PileGeometry {
  return { footingLength, footingWidth, end: DIM.pileEnd, minSpacing: DIM.pileSpacing };
}

/** Footing and pile dimensions in m: the input when given, else the 1단계 constants (승인 2026-10-23). */
export function footingDims(input: PierInput): { L: number; W: number; H: number; blM: number; blT: number; pileD: number } {
  return {
    L: (input.footingLengthMm ?? DIM.footingL * 1000) / 1000,
    W: (input.footingWidthMm ?? DIM.footingW * 1000) / 1000,
    H: (input.footingHeightMm ?? DIM.footingH * 1000) / 1000,
    // 비림 여유 is the margin on each side (삽도 한쪽 100); the blinding grows by twice that on each length and width.
    blM: (2 * (input.blindingMarginMm ?? DIM.blindingMargin * 500)) / 1000,
    blT: (input.blindingThicknessMm ?? DIM.blindingT * 1000) / 1000,
    pileD: (input.pileOuterMm ?? DIM.pileDiameter * 1000) / 1000,
  };
}

/**
 * Piles under one footing (spec §4.6): one 열 per row across the width, each with its own count along the length.
 * counts holds the 본수 of each 열 (see core/piles.ts).
 */
export function pilesFor(s: number, topEl: number, length: number, g: PileGeometry, counts: number[], diameter: number = DIM.pileDiameter): PileModel[] {
  const rows = rowLayout(counts, g);
  const spacingN = (g.footingWidth - 2 * g.end) / (counts.length - 1);
  const out: PileModel[] = [];
  rows.forEach((row, j) => {
    for (let i = 0; i < row.count; i++) {
      out.push({
        s: s + (i - (row.count - 1) / 2) * row.spacing,
        k: 0,
        n: (j - (counts.length - 1) / 2) * spacingN,
        top: topEl,
        bottom: topEl - length,
        diameter,
      });
    }
  });
  return out;
}