/**
 * 솔플레이트 기하 (1단계, 승인 2026-10-23). Pure: the solplate of one bearing, from its block (position, rowSkew) and the
 * 공통 규칙 values. The solplate sits on the bearing (h3) and tapers along the 교축 방향 (s): the thick end T1 is on the
 * 시점 side (s = −L/2), the thin end T2 on the 종점 side (s = +L/2). Lengths in m, as in the model.
 */
import { blockFramePoint, type BlockModel } from './geometry';

export interface SolplateParams {
  /** 받침 평면 A (mm, along 교축 s) and B (mm, along the 교각축 직각 n). */
  A: number;
  B: number;
  /** 솔플 여유 (mm): L = A + margin, W = B + margin. */
  margin: number;
  /** 중심 두께 T (mm). */
  T: number;
  /** 기울기 S (%), negative as drawn: thickness changes by L·|S|/2 from the centre. */
  slopePct: number;
}

export interface SolplateGeometry {
  /** Length along 교축 (m) and width along 교각축 직각 (m). */
  L: number;
  W: number;
  /** Thickness at the 시점 end (T1) and the 종점 end (T2) (m). */
  T1: number;
  T2: number;
  /** Underside (EL m): the bearing top = block top (EL.X) + h3. */
  bottom: number;
  /** Eight corners: [s, y, n] in the model's local frame (EL m). */
  corners: [number, number, number][];
  /** Volume (m³): L·W·(T1 + T2)/2. */
  volume: number;
}

/** Solplate of the bearing at `block`, with the bearing height h3 (mm) and the 공통 규칙 parameters. */
export function solplateGeometry(block: BlockModel, h3: number, p: SolplateParams): SolplateGeometry {
  const L = (p.A + p.margin) / 1000;
  const W = (p.B + p.margin) / 1000;
  // Thickness change from the centre to each end: L·|S|/2, with S in % (mm).
  const drop = ((p.A + p.margin) * Math.abs(p.slopePct)) / 200 / 1000;
  const T = p.T / 1000;
  const T1 = T + drop;
  const T2 = T - drop;
  const bottom = block.padTop + h3 / 1000;
  const thickAt = (a: number) => T1 + ((T2 - T1) * (a + L / 2)) / L;
  const corners: [number, number, number][] = [];
  for (const a of [-L / 2, L / 2]) {
    for (const c of [-W / 2, W / 2]) {
      const [s, n] = blockFramePoint(block, a, c);
      corners.push([s, bottom, n]);
      corners.push([s, bottom + thickAt(a), n]);
    }
  }
  return { L, W, T1, T2, bottom, corners, volume: (L * W * (T1 + T2)) / 2 };
}