/**
 * 교대 부재 · AA3 (2026-11-03, spec_abut §4.3–4.6): 벽체, 흉벽 상단, 저판, 말뚝의 치수와 위치. Pure.
 *
 * - 교대축 기준 t: 전면 쪽이 +. 벽체 전면 +1.6 m (교좌면 끝), 배면 −0.8 m (브라켓 배면). 두께 2.4 m.
 * - 흉벽: t −0.5 ~ 0 m. 상단 EL(s) = 받침 ① 교좌면 EL + 벽체 높이 H_w (받침 ① 기준 연직, 기본 3.326 m) + i_b × (s − s_1), i_b = 받침 z의 축 방향 경사.
 * - 저판: 하면 = 기초 하단 EL, 두께 1.1 m. 폭은 t −1.8 ~ +2.8 m (앞굽 1.2, 뒷굽 1.0, 벽체 2.4). 길이 = 교좌면 길이 L.
 * - 말뚝: 열 위치 t = −1.15 / +0.85 / +2.15 m. 열 안 본수 = int((L − 1.3)/2.0) + 1, 양끝 0.65 m 띄움, 균등 간격.
 *   말뚝 선단 EL = 기초 하단 EL − 말뚝길이. (skew 평행사변형에서 열 끝이 밀리는 보정은 아직 없다 — QA-5 이후.)
 * - 벽체 높이 = 구간 교좌면 EL − (기초 하단 EL + 저판 두께).
 */
import type { AbutModel } from './geometry';
import { resolveShape, type AbutShape, type ResolvedShape } from './shape';

export interface WallSegment {
  /** 축 위 구간 범위 (IP1에서 m). */
  sFrom: number;
  sTo: number;
  /** 구간의 교좌면 EL (구간 i). */
  seatEl: number;
  /** 벽체 높이 (m) = seat − (footing bottom + footing thickness). */
  heightM: number;
}

export interface PileRow {
  /** 횡방향 위치 t (m, 전면 +). */
  t: number;
  /** 축 위 말뚝 위치 (IP1에서 m). */
  s: number[];
}

export interface AbutMembers {
  /** The shape values in use (defaults merged with the user's changes), in m. */
  shape: ResolvedShape;
  wallSegments: WallSegment[];
  /** 흉벽 상단 EL: s = 0 (IP1 끝)과 s = L (IP3 끝), 축 방향 경사 i_b (소수, + = IP3 쪽으로 올라감). */
  parapetTopStartEl: number;
  parapetTopEndEl: number;
  parapetSlope: number;
  footingTopEl: number;
  footingBottomEl: number | undefined;
  piles: PileRow[];
  pileBottomEl: number | undefined;
}

/** 흉벽 상단 EL at axial position s (m). */
export function parapetTopEl(seatFirst: number, bearingSFirst: number, slope: number, s: number, parapetHeightM: number): number {
  return seatFirst + parapetHeightM + slope * (s - bearingSFirst);
}

export function buildMembers(model: AbutModel, foundation: { bottomEl?: number; pileLengthMm?: number } = {}, shapeChanges?: Partial<AbutShape>): AbutMembers {
  const L = model.length;
  const shape = resolveShape(shapeChanges);
  const sorted = [...model.bearings].sort((a, b) => a.s - b.s);
  const bounds = [0, ...model.stepBounds, L];
  const footingBottomEl = foundation.bottomEl;
  const footingTopEl = footingBottomEl === undefined ? NaN : footingBottomEl + shape.footingThicknessM;

  // 인접 무시 기준 (2026-11-03): a step smaller than shape.seatStepIgnoreM joins the segment before it (one 교좌면 EL).
  const wallSegments: WallSegment[] = [];
  sorted.forEach((b, k) => {
    const prev = wallSegments[wallSegments.length - 1];
    // Compared with the neighbouring bearing (인접), not with the first step of the joined run.
    if (prev && k > 0 && Math.abs(b.seatEl - sorted[k - 1].seatEl) < shape.seatStepIgnoreM) {
      prev.sTo = bounds[k + 1];
      return;
    }
    wallSegments.push({ sFrom: bounds[k], sTo: bounds[k + 1], seatEl: b.seatEl, heightM: b.seatEl - footingTopEl });
  });

  // 받침 ①(첫 입력)과 마지막 입력 받침이 흉벽 상단선을 정한다 (spec §4.4).
  const first = model.bearings[0];
  const last = model.bearings[model.bearings.length - 1];
  const slope = (last.z - first.z) / (last.s - first.s);
  const parapetTopStartEl = parapetTopEl(first.seatEl, first.s, slope, 0, shape.parapetHeightM);
  const parapetTopEndEl = parapetTopEl(first.seatEl, first.s, slope, L, shape.parapetHeightM);

  // 본수 규칙 int((L − 2·연단)/간격) + 1; 열별 본수가 0이 아니면 그 값 (2026-11-04, 시안 열별 말뚝 본수).
  const ruleCount = Math.floor((L - 2 * shape.pileEdgeM) / shape.pileSpacingM) + 1;
  const piles: PileRow[] = shape.pileRowsT.map((t, r) => {
    const count = shape.pileCounts[r] > 0 ? shape.pileCounts[r] : ruleCount;
    const spacing = count > 1 ? (L - 2 * shape.pileEdgeM) / (count - 1) : 0;
    return { t, s: Array.from({ length: count }, (_, k) => shape.pileEdgeM + k * spacing) };
  });
  const pileBottomEl = footingBottomEl === undefined || foundation.pileLengthMm === undefined ? undefined : footingBottomEl - foundation.pileLengthMm / 1000;

  return {
    shape,
    wallSegments,
    parapetTopStartEl,
    parapetTopEndEl,
    parapetSlope: slope,
    footingTopEl,
    footingBottomEl,
    piles,
    pileBottomEl,
  };
}