/**
 * 거더 짝 받침 · 종단경사 S · 솔플레이트 열 두께 (결정 2026-11-06, RAG/받침방위각_솔플레이트검토.md §3, Q-SH1·4·8·9).
 * Pure. Used by src/core/sole-plate.ts (pier solplates, 2026-11-06) through src/core/bridge-pairs.ts.
 *
 * Frame: (E, N) in m as in the model (x = E, y = N). Azimuth: the model's 진북 방위각 (deg, clockwise from north), i.e. the
 * workbook CAD angle θ_CAD converted by 90 − θ_CAD. A girder at azimuth θ runs along (sin θ, cos θ).
 */

export interface PairBearing {
  no: number;
  x: number;
  y: number;
  /** z (EL m). Q-SH5: both ends on the 받침블럭 상면 basis; the pier z definition is still spec Q16. */
  z: number;
  azimuthDeg: number;
}

export interface PairStructure {
  name: string;
  bearings: PairBearing[];
}

/** Q-SH1 tolerances and the Q-SH4 azimuth check. */
export const PAIR_AZIMUTH_TOL_DEG = 0.1;
export const PAIR_OFFSET_TOL_M = 0.1;
export const AZIMUTH_CHECK_SEC = 10;
/** Two candidates nearer than this along the girder are ambiguous (WS04). Less than the row spacing (block 1.2 m). */
export const PAIR_ALONG_TOL_M = 0.5;

export type PairWarning = 'WS01' | 'WS04';

export interface BearingPair {
  /** The bearing on structure k and its partner on structure k + 1 (structure order A1, P1 … Pn, A2). */
  from: { structure: string; no: number };
  to: { structure: string; no: number };
  /** Horizontal distance (m), distance off the girder line of `from` (m), azimuth difference |θ_to − θ_from| (deg). */
  distanceM: number;
  offsetM: number;
  azimuthDiffDeg: number;
  /** Direction from → to as an azimuth (deg), and its difference from each input azimuth (arc seconds). */
  directionDeg: number;
  fromCheckSec: number;
  toCheckSec: number;
  /** S = (z_to − z_from) / distance × 100 (%), sign along the structure order (− = lower towards the later structure). */
  slopePct: number;
  /** The structure on the higher end: the 오르막 쪽 where T1 sits for both bearings. */
  uphill: string;
  /** girder = the two ends of one girder; chord = A1 ↔ A2 of a bridge loaded without piers (현, chordPairs). */
  kind: 'girder' | 'chord';
  warnings: PairWarning[];
}

const DEG = Math.PI / 180;
const angleDiffDeg = (a: number, b: number) => Math.abs(((a - b + 540) % 360) - 180);

/**
 * Girder pairs over the bridge (Q-SH1, Q-SH4). For each bearing b the candidates on the other structures lie
 * ahead along b's azimuth, within 0.1° of its azimuth and 0.1 m of its girder line. The pair is the first one reached along
 * the girder: on a straight bridge the next span's bearing (후열) lies on the same line further on, so "closest to the line"
 * alone would be a tie (2026-11-06 review). WS04 when another candidate is within 0.5 m of it along the girder.
 * WS01 when either input azimuth is more than 10″ from the pair direction.
 */
export function girderPairs(structures: PairStructure[]): BearingPair[] {
  const pairs: BearingPair[] = [];
  // Every other structure is searched, not only the next one in the list: with two lines (광주 · 완도) the list order
  // A1-광주, A1-완도, P1-완도 … mixes the lines, and the geometry alone tells which bearing ends the girder (2026-11-06).
  for (const here of structures) {
    const others = structures.filter((s) => s !== here).flatMap((s) => s.bearings.map((c) => ({ ...c, structure: s.name })));
    for (const b of here.bearings) {
      const u = { e: Math.sin(b.azimuthDeg * DEG), n: Math.cos(b.azimuthDeg * DEG) };
      const candidates = others.map((c) => {
        const d = { e: c.x - b.x, n: c.y - b.y };
        return { c, along: d.e * u.e + d.n * u.n, offset: Math.abs(d.e * u.n - d.n * u.e), dAz: angleDiffDeg(c.azimuthDeg, b.azimuthDeg), d };
      }).filter((t) => t.along > 0 && t.dAz <= PAIR_AZIMUTH_TOL_DEG && t.offset <= PAIR_OFFSET_TOL_M)
        .sort((p, q) => p.along - q.along);
      if (!candidates.length) continue;
      // The nearest along the girder, and among those about as near (ambiguous, WS04) the one closest to the line.
      const near = candidates.filter((t) => t.along - candidates[0].along < PAIR_ALONG_TOL_M).sort((p, q) => p.offset - q.offset);
      const best = near[0];
      const ambiguous = near.length > 1;
      const distanceM = Math.hypot(best.d.e, best.d.n);
      const directionDeg = (Math.atan2(best.d.e, best.d.n) / DEG + 360) % 360;
      const fromCheckSec = angleDiffDeg(directionDeg, b.azimuthDeg) * 3600;
      const toCheckSec = angleDiffDeg(directionDeg, best.c.azimuthDeg) * 3600;
      const slopePct = ((best.c.z - b.z) / distanceM) * 100;
      const warnings: PairWarning[] = [];
      if (fromCheckSec > AZIMUTH_CHECK_SEC || toCheckSec > AZIMUTH_CHECK_SEC) warnings.push('WS01');
      if (ambiguous) warnings.push('WS04');
      pairs.push({
        from: { structure: here.name, no: b.no }, to: { structure: best.c.structure, no: best.c.no },
        distanceM, offsetM: best.offset, azimuthDiffDeg: best.dAz, directionDeg, fromCheckSec, toCheckSec,
        slopePct, uphill: best.c.z > b.z ? best.c.structure : here.name, warnings, kind: 'girder',
      });
    }
  }
  return pairs;
}

/**
 * A1 ↔ A2 pairs when no pier is loaded (교대만, 검토 2026-11-06). Over several spans the azimuths of the two ends differ
 * (곡선, 운곡교 8°), so the girder test fails; the chord from b to c then runs along the mean of the two azimuths (exact on a
 * circular arc). The partner is the end bearing whose chord is within 0.1° of that mean (WS04 when two are), and S is the
 * whole-bridge average Δz / chord. The check value is chord − mean azimuth, for reference only (no WS01).
 */
export function chordPairs(starts: PairStructure[], ends: PairStructure[]): BearingPair[] {
  const pairs: BearingPair[] = [];
  for (const here of starts) for (const b of here.bearings) {
    const candidates = ends.flatMap((s) => s.bearings.map((c) => {
      const d = { e: c.x - b.x, n: c.y - b.y };
      const directionDeg = (Math.atan2(d.e, d.n) / DEG + 360) % 360;
      const mean = (b.azimuthDeg + c.azimuthDeg + (Math.abs(b.azimuthDeg - c.azimuthDeg) > 180 ? 360 : 0)) / 2 % 360;
      return { c, structure: s.name, d, directionDeg, dev: angleDiffDeg(directionDeg, mean) };
    })).filter((t) => t.dev <= PAIR_AZIMUTH_TOL_DEG).sort((p, q) => p.dev - q.dev);
    if (!candidates.length) continue;
    const best = candidates[0];
    const distanceM = Math.hypot(best.d.e, best.d.n);
    pairs.push({
      from: { structure: here.name, no: b.no }, to: { structure: best.structure, no: best.c.no },
      distanceM, offsetM: 0, azimuthDiffDeg: angleDiffDeg(best.c.azimuthDeg, b.azimuthDeg), directionDeg: best.directionDeg,
      fromCheckSec: best.dev * 3600, toCheckSec: best.dev * 3600, slopePct: ((best.c.z - b.z) / distanceM) * 100,
      uphill: best.c.z > b.z ? best.structure : here.name, warnings: candidates.length > 1 ? ['WS04'] : [], kind: 'chord',
    });
  }
  return pairs;
}

/** The pair a bearing belongs to, on either end; undefined when it has none (then WS03 with a fallback S, not done here). */
export function pairOf(pairs: BearingPair[], structure: string, no: number): BearingPair | undefined {
  return pairs.find((p) => (p.from.structure === structure && p.from.no === no) || (p.to.structure === structure && p.to.no === no));
}

/** Smallest allowed thin-end thickness T_min (mm, Q-SH3). */
export const SOLE_T_MIN_MM = 22;

/** Thickness one bearing needs: T_req = T_min + L·|S|/2 (L mm, S %). */
export function soleRequiredT(lengthMm: number, slopePct: number, tMinMm: number = SOLE_T_MIN_MM): number {
  return tMinMm + (lengthMm * Math.abs(slopePct)) / 200;
}

/**
 * Row thickness and end thicknesses (Q-SH8·9): T_row = max(T_min, ⌈max T_req⌉) over the row; per bearing
 * T1 = round(T_row + L·|S|/2) on the 오르막 쪽 and T2 = round(T_row − L·|S|/2) (≥ T_min by construction).
 */
export function soleRowThickness(items: { lengthMm: number; slopePct: number }[], tMinMm: number = SOLE_T_MIN_MM) {
  const T = Math.max(tMinMm, Math.ceil(Math.max(...items.map((i) => soleRequiredT(i.lengthMm, i.slopePct, tMinMm))) - 1e-9));
  return {
    T,
    ends: items.map((i) => {
      const half = (i.lengthMm * Math.abs(i.slopePct)) / 200;
      return { T1: Math.round(T + half), T2: Math.round(T - half) };
    }),
  };
}