/* =============================================================================
 * B05_Profile/logic/B05_Profile_Grade_Carry.ts
 * 노선이 바뀔 때 계획고 옮김 — 바뀐 구간만 지반에 다시 맞추고 그 밖 편집은 길이 차만큼 밂(344-2).
 *
 * 짝 = 파이썬 `B05_Profile_Engine_Grade_Carry.py`(서버 정본 · 같은 규칙) · 거울 시험 =
 * resources/tester/test_344_2_route_pairs.py.
 *   - 바뀐 구간 = 옛 · 새 노선 정점열의 같은 앞머리 · 꼬리를 뺀 가운데(바뀐 노드 앞 · 뒤 접선점 사이).
 *   - 앞 = 그대로 · 뒤 = 누가거리만 길이 차만큼 밂 · 안 = 새 지반 첫 계획선 꼭짓점(`groundFollowingBasePvi`)
 *     · 안의 편집(계획고 · 종단곡선 R)은 버림.
 *   - 옮기는 것 = base_pvi · station_offsets · curve_radii(누가거리 글자 키).
 * ========================================================================== */

import {
  chainageKey,
  type AlignmentEdits,
  type AlignmentNode,
} from "./B05_Profile_UI_Profile_Alignment";

/** 같은 정점으로 볼 거리(m) — 파이썬 `SAME_VERTEX_M` 짝. */
export const SAME_VERTEX_M = 1e-3;
const EPS = 1e-6;

export interface XY {
  x: number;
  y: number;
}

export interface ChangedSpan {
  start_m: number;
  old_end_m: number;
  new_end_m: number;
  delta_m: number;
  start_fixed: boolean;
  end_fixed: boolean;
}

const roundTo = (value: number, digits: number): number => Number(value.toFixed(digits));

function cumulative(xy: ReadonlyArray<XY>): number[] {
  const total = [0];
  for (let index = 1; index < xy.length; index += 1) {
    const prev = xy[index - 1];
    total.push(total[index - 1] + Math.hypot(xy[index].x - prev.x, xy[index].y - prev.y));
  }
  return total;
}

const same = (a: XY, b: XY): boolean =>
  Math.abs(a.x - b.x) <= SAME_VERTEX_M && Math.abs(a.y - b.y) <= SAME_VERTEX_M;

/** 옛 · 새 노선 정점열 → 바뀐 누가거리 구간 · 같으면 null(파이썬 `changed_span` 짝). */
export function changedSpan(
  oldXy: ReadonlyArray<XY>,
  newXy: ReadonlyArray<XY>,
): ChangedSpan | null {
  const limit = Math.min(oldXy.length, newXy.length);
  let prefix = 0;
  while (prefix < limit && same(oldXy[prefix], newXy[prefix])) prefix += 1;
  if (prefix === oldXy.length && prefix === newXy.length) return null;
  let suffix = 0;
  while (
    suffix < limit - prefix &&
    same(oldXy[oldXy.length - 1 - suffix], newXy[newXy.length - 1 - suffix])
  )
    suffix += 1;
  const oldCum = cumulative(oldXy);
  const newCum = cumulative(newXy);
  return {
    start_m: prefix ? oldCum[prefix - 1] : 0,
    old_end_m: suffix ? oldCum[oldXy.length - suffix] : oldCum[oldCum.length - 1],
    new_end_m: suffix ? newCum[newXy.length - suffix] : newCum[newCum.length - 1],
    delta_m: newCum[newCum.length - 1] - oldCum[oldCum.length - 1],
    start_fixed: prefix > 0,
    end_fixed: suffix > 0,
  };
}

const before = (span: ChangedSpan, s: number): boolean =>
  s < span.start_m - EPS || (span.start_fixed && s <= span.start_m + EPS);

const after = (span: ChangedSpan, s: number, end: number): boolean =>
  s > end + EPS || (span.end_fixed && s >= end - EPS);

/** 옛 꼭짓점 · 편집을 새 노선으로 옮김 — `groundPvi` = 새 노선 지반 첫 계획선(전 구간). */
export function carryProfileEdits(
  basePvi: ReadonlyArray<AlignmentNode>,
  edits: Partial<AlignmentEdits> | null | undefined,
  span: ChangedSpan,
  groundPvi: ReadonlyArray<AlignmentNode>,
): { basePvi: AlignmentNode[]; edits: AlignmentEdits } {
  const moved = (s: number): number | null => {
    if (before(span, s)) return s;
    if (after(span, s, span.old_end_m)) return s + span.delta_m;
    return null; // 바뀐 구간 안 — 버림
  };

  const nodes = new Map<number, AlignmentNode>();
  basePvi.forEach((node) => {
    const at = moved(node.chainage_m);
    if (at !== null)
      nodes.set(roundTo(at, 3), { chainage_m: roundTo(at, 6), elevation_m: node.elevation_m });
  });
  groundPvi.forEach((node) => {
    const s = node.chainage_m;
    if (before(span, s) || after(span, s, span.new_end_m)) return;
    const slot = roundTo(s, 3);
    if (!nodes.has(slot))
      nodes.set(slot, { chainage_m: roundTo(s, 6), elevation_m: node.elevation_m });
  });

  const carry = (values: Record<string, number> | undefined): Record<string, number> => {
    const out: Record<string, number> = {};
    Object.entries(values ?? {}).forEach(([key, value]) => {
      const chainage = Number(key);
      if (!Number.isFinite(chainage) || value == null) return;
      const at = moved(chainage);
      if (at !== null) out[chainageKey(at)] = Number(value);
    });
    return out;
  };

  return {
    basePvi: [...nodes.keys()].sort((a, b) => a - b).map((slot) => nodes.get(slot)!),
    edits: {
      station_offsets: carry(edits?.station_offsets),
      curve_radii: carry(edits?.curve_radii),
    },
  };
}