/* =============================================================================
 * B05_Profile/logic/B05_Profile_Sections_Stations.ts
 * 측점 한 벌(PLAN 344-3 뼈대 · 346-1) — 그린 노선 + 관 · 구조물 → 측점(지반 null). 계산 묶음 stations
 * 단계(`A00_Common/design/logic/design_pipeline_stations.ts`)가 부름. 측점 열쇠 규칙 한 곳(`stationKey` ·
 * 계약 = `A00_Common/design/logic/design_pipeline_types.ts` 머리).
 *
 * ⚠ 파이썬·TS 짝 — `B05_Profile_Engine_Sections_Core.py` `generate_sections` 의 측점 부분
 *   (격자 · 스냅 · 구조물 측점 병합 · 종류 · 틀 · 방위각) ↔ `buildStations` ·
 *   `_plan_radii` · `_curve_widenings` · `_design_curve_widenings` ↔ `planRadii` · `curveWidenings` ·
 *   `designCurveWidenings` · `curve_widening_m` · `CURVE_WIDENING_TABLE_M` 등(config_system_design) ↔
 *   같은 이름 상수 · `circumradius_2d`(Engine_Geometry) ↔ `circumradius`.
 *   거울 시험 `resources/tester/test_344_3_pipeline_stations_mirror.py`.
 * 이미 있는 짝을 그대로 씀 — 격자 · 스냅 · 틀(`B05_Profile_UI_RouteEdit_Frame`) · 심는 측점
 *   (`common_util_structure_station.planStations`).
 * 화면 · fetch · 세션 없음(순수).
 * ========================================================================== */

import {
  curveSpans,
  snapCurveStations,
  stationFrameAt,
  stationsAlong,
} from "./B05_Profile_UI_RouteEdit_Frame";
import {
  planStations,
  type PlanPipe,
  type PlanStructure,
  type PlanType,
} from "../../common_util/common_util_structure_station";
import { stationKey as commonStationKey } from "../../common_util/common_util_station_key";
import type {
  DesignCurve,
  PipelineStation,
  StationKind,
  Vertex,
} from "../../A00_Common/design/logic/design_pipeline_types";

/** 짝: `config_system_design.py` 같은 이름. */
export const SECTION_STATION_INTERVAL_M = 20.0;
export const SECTION_INCLUDE_ENDPOINT = true;
export const CURVE_WIDENING_TAPER_M = 10.0;
export const CURVE_WIDENING_TABLE_M: ReadonlyArray<readonly [number, number, number]> = [
  [10.0, 13.0, 2.25],
  [13.0, 14.0, 2.0],
  [14.0, 15.0, 1.75],
  [15.0, 18.0, 1.5],
  [18.0, 20.0, 1.25],
  [20.0, 25.0, 1.0],
  [25.0, 30.0, 0.75],
  [30.0, 40.0, 0.5],
  [40.0, 45.0, 0.25],
];
/** 짝: `Engine_Sections_Core.py` 같은 이름. */
export const PLAN_RADIUS_ARM_M = 10.0;
export const PLAN_RADIUS_STRAIGHT_M = 10000.0;
/** 같은 측점으로 볼 거리(m) — 서버 격자 붙임 폭 · `SAME_STATION_M` 과 같은 값. */
const SNAP_M = 0.005;
/** 범위 밖 측점을 앞 값 그대로 쓸 때 범위 앞뒤 여유(m) — 반경 팔 10 + 확폭 테이퍼 10. */
export const REUSE_MARGIN_M = PLAN_RADIUS_ARM_M + CURVE_WIDENING_TAPER_M;

type Side = "left" | "right";
type Span = [number, number, number, Side];

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

/** 누가거리를 글로 쓸 때(열쇠 · 초안 칸) — 자릿수 0.01 m 하나. */
export const stationText = (chainageM: number): string => chainageM.toFixed(2);

/** 측점 열쇠 — 격자 = `grid:k`(k = 원래 격자 번호 · 노선 모양이 바뀌어도 같은 번호) · 관 = `pipe:<id>` ·
 *  구조물 = `structure:<id>`(구간형 시작 · 끝은 `:start` · `:end`) · 시종점 = `end:BP` · `end:EP`.
 *  규칙 한 벌 = `common_util_station_key`(파이썬 짝) — 여기는 꼴만 옮김. */
export function stationKey(
  kind: StationKind,
  ref: number | string,
  role: "start" | "anchor" | "end" = "anchor",
): string {
  if (kind === "end") return commonStationKey(ref === "BP" ? "bp" : "ep", 0, null);
  if (kind === "grid") return commonStationKey("regular", Number(ref), 1); // ref = 격자 번호(간격 1)
  const base = commonStationKey(kind, 0, null, String(ref));
  // ponytail: 구간형 꼬리 — sub2 가 공용 함수에 넣으면 그 인자로 옮김
  return role === "anchor" ? base : `${base}:${role}`;
}

/** 짝: `curve_widening_m` — 직선 · 45 m 이상 · 값 없음은 0. */
export function curveWideningM(radiusM: number | null): number {
  if (radiusM === null) return 0;
  for (const [low, high, widening] of CURVE_WIDENING_TABLE_M)
    if (low <= radiusM && radiusM < high) return widening;
  return 0;
}

/** 짝: `circumradius_2d`. */
function circumradius(p0: Vertex, p1: Vertex, p2: Vertex): number {
  const a = Math.hypot(p1[0] - p2[0], p1[1] - p2[1]);
  const b = Math.hypot(p0[0] - p2[0], p0[1] - p2[1]);
  const c = Math.hypot(p0[0] - p1[0], p0[1] - p1[1]);
  if (a < 0.01 || b < 0.01 || c < 0.01) return Infinity;
  const area2 = Math.abs((p1[0] - p0[0]) * (p2[1] - p0[1]) - (p2[0] - p0[0]) * (p1[1] - p0[1]));
  if (area2 < 1e-9) return Infinity;
  return (a * b * c) / (2 * area2);
}

const pointAt = (line: ReadonlyArray<Vertex>, chainageM: number): Vertex =>
  stationFrameAt(line, chainageM)?.origin ?? line[0];

/** 짝: `_design_curve_spans` — [BC, EC, 반경, 바깥쪽]. */
export function designSpans(
  line: ReadonlyArray<Vertex>,
  curves: ReadonlyArray<DesignCurve>,
): Span[] {
  const spans: Span[] = [];
  for (const curve of curves) {
    const [span] = curveSpans(line, [curve]);
    if (!span) continue;
    const { start, apex, end } = curve;
    const cross =
      (apex[0] - start[0]) * (end[1] - apex[1]) - (apex[1] - start[1]) * (end[0] - apex[0]);
    spans.push([span[0], span[1], curve.radius_m, cross > 0 ? "right" : "left"]);
  }
  return spans.sort((a, b) => a[0] - b[0] || a[1] - b[1] || a[2] - b[2]);
}

/** 짝: `_design_curve_widenings` — 곡선 안 = 설계 반경 · 표값 · 앞뒤 테이퍼 · 겹치면 큰 확폭 · 작은 반경. */
export function designCurveWidenings(
  stations: ReadonlyArray<number>,
  spans: ReadonlyArray<Span>,
): { radii: Array<number | null>; sides: Array<Side | null>; widenings: number[] } {
  const radii: Array<number | null> = stations.map(() => null);
  const sides: Array<Side | null> = stations.map(() => null);
  const widenings = stations.map(() => 0);
  for (const [start, end, radius, side] of spans) {
    const table = curveWideningM(radius);
    stations.forEach((chainage, index) => {
      const inside = start - 1e-9 <= chainage && chainage <= end + 1e-9;
      const current = radii[index];
      if (inside && (current === null || radius < current)) radii[index] = round(radius, 3);
      if (table <= 0) return;
      let amount = table;
      if (!inside) {
        const distance = chainage < start ? start - chainage : chainage - end;
        if (distance > CURVE_WIDENING_TAPER_M) return;
        amount = round(table * (1 - distance / CURVE_WIDENING_TAPER_M), 4);
      }
      if (amount > widenings[index]) {
        widenings[index] = amount;
        sides[index] = side;
      }
    });
  }
  return { radii, sides, widenings };
}

/** 짝: `_plan_radii` — 곡선표 없는 옛 노선 · 앞뒤 팔 세 점 외접원 · 바깥쪽. */
export function planRadii(
  line: ReadonlyArray<Vertex>,
  stations: ReadonlyArray<number>,
  total: number,
): { radii: Array<number | null>; sides: Array<Side | null> } {
  const arm = Math.min(PLAN_RADIUS_ARM_M, Math.max(total / 2, 0));
  const radii: Array<number | null> = [];
  const sides: Array<Side | null> = [];
  for (const center of stations) {
    const back = Math.max(0, center - arm);
    const ahead = Math.min(total, center + arm);
    if (arm < 0.5 || center - back < arm * 0.5 || ahead - center < arm * 0.5) {
      radii.push(null);
      sides.push(null);
      continue;
    }
    const trio = [back, center, ahead].map((value) => pointAt(line, value));
    const radius = circumradius(trio[0], trio[1], trio[2]);
    if (!Number.isFinite(radius) || radius >= PLAN_RADIUS_STRAIGHT_M) {
      radii.push(null);
      sides.push(null);
      continue;
    }
    radii.push(round(radius, 3));
    const cross =
      (trio[1][0] - trio[0][0]) * (trio[2][1] - trio[1][1]) -
      (trio[1][1] - trio[0][1]) * (trio[2][0] - trio[1][0]);
    sides.push(cross > 0 ? "right" : cross < 0 ? "left" : null);
  }
  return { radii, sides };
}

/** 짝: `_curve_widenings` — 확폭 측점 덩어리 바깥으로 테이퍼(이웃 측점을 봄). */
export function curveWidenings(
  stations: ReadonlyArray<number>,
  radii: ReadonlyArray<number | null>,
  outerSides: ReadonlyArray<Side | null>,
): { widenings: number[]; sides: Array<Side | null> } {
  const base = radii.map(curveWideningM);
  const widenings = [...base];
  const sides = [...outerSides];
  const runs: Array<[number, number]> = [];
  let start: number | null = null;
  base.forEach((value, index) => {
    if (value > 0 && outerSides[index] !== null) {
      if (start === null) start = index;
    } else if (start !== null) {
      runs.push([start, index - 1]);
      start = null;
    }
  });
  if (start !== null) runs.push([start, base.length - 1]);
  for (const [first, last] of runs) {
    for (const [edge, step] of [
      [first, -1],
      [last, 1],
    ]) {
      for (let index = edge + step; index >= 0 && index < base.length; index += step) {
        const distance = Math.abs(stations[index] - stations[edge]);
        if (distance > CURVE_WIDENING_TAPER_M || base[index] > 0) break;
        const tapered = round(base[edge] * Math.max(0, 1 - distance / CURVE_WIDENING_TAPER_M), 4);
        if (tapered > widenings[index]) {
          widenings[index] = tapered;
          sides[index] = outerSides[edge];
        }
      }
    }
  }
  return { widenings, sides };
}

export interface StationsOptions {
  intervalM?: number;
  includeEndpoint?: boolean;
  stationSnap?: boolean;
  /** 구조물 정의(종류 · 군 · 자리꼴) — 심는 측점 판정. */
  types: ReadonlyArray<PlanType>;
  /** 종류 → 옵션 기본값(카드 이름) — `planStations` 그대로. */
  registry?: Readonly<Record<string, Record<string, unknown>>>;
}

/** 원래 격자 번호 — 스냅으로 옮긴 측점은 사라진 원래 격자 자리 중 가장 가까운 번호를 이어받음. */
function gridIndices(
  original: number[],
  snapped: number[],
  intervalM: number,
): Map<number, number> {
  const has = (list: number[], value: number): boolean =>
    list.some((other) => Math.abs(other - value) < 1e-9);
  const gone = original
    .map((value, index) => ({ value, index }))
    .filter((o) => !has(snapped, o.value));
  const out = new Map<number, number>();
  for (const value of snapped) {
    const same = original.findIndex((other) => Math.abs(other - value) < 1e-9);
    if (same >= 0) {
      out.set(value, same);
      continue;
    }
    const near = gone.sort((a, b) => Math.abs(a.value - value) - Math.abs(b.value - value))[0];
    out.set(value, near ? near.index : Math.round(value / intervalM));
    if (near) gone.splice(gone.indexOf(near), 1);
  }
  return out;
}

/** 노선 길이(m) — 길이 0 선분은 0(서버 `_clean_polyline`). */
const lineLength = (line: ReadonlyArray<Vertex>): number =>
  line.reduce(
    (sum, vertex, index) =>
      index ? sum + Math.hypot(vertex[0] - line[index - 1][0], vertex[1] - line[index - 1][1]) : 0,
    0,
  );

/** 측점 한 벌 — 서버 `generate_sections` 측점 목록과 같은 자리 · 종류 · 틀 · 반경 · 확폭(지반 null). */
export function buildStations(
  line: ReadonlyArray<Vertex>,
  curves: ReadonlyArray<DesignCurve>,
  pipes: ReadonlyArray<PlanPipe>,
  structures: ReadonlyArray<PlanStructure>,
  options: StationsOptions,
): PipelineStation[] {
  if (line.length < 2) return [];
  const intervalM = options.intervalM ?? SECTION_STATION_INTERVAL_M;
  const total = lineLength(line);
  const original = stationsAlong(
    line,
    intervalM,
    options.includeEndpoint ?? SECTION_INCLUDE_ENDPOINT,
  );
  const spans = designSpans(line, curves);
  const grid = options.stationSnap
    ? snapCurveStations(
        original,
        spans.map(([bc, ec]) => [bc, ec] as const),
      )
    : original;
  const gridIndex = gridIndices(original, grid, intervalM);

  // 심는 측점(관 · 구조물) — 격자 0.005 m 안이면 격자 자리에 얹고 서로 겹치면 앞선 것만(서버 `extras`).
  const pipeIds = new Set(pipes.map((pipe) => pipe.id ?? `pipe-${pipe.chainage_m.toFixed(2)}`));
  const planted = new Map<number, { kind: "pipe" | "structure"; id: string; role: string }>();
  for (const station of planStations(pipes, structures, options.types, options.registry)) {
    if (station.chainage_m < 0 || station.chainage_m > total) continue;
    const near = grid.find((value) => Math.abs(value - station.chainage_m) < SNAP_M);
    const at = near ?? station.chainage_m;
    if ([...planted.keys()].some((taken) => Math.abs(taken - at) < SNAP_M)) continue;
    const owner = station.owners.find((id) => pipeIds.has(id)) ?? station.owners[0];
    planted.set(at, {
      kind: pipeIds.has(owner) ? "pipe" : "structure",
      id: owner,
      role: station.role,
    });
  }
  const chainages = [...new Set([...grid, ...planted.keys()])].sort((a, b) => a - b);

  const fromSpans = spans.length ? designCurveWidenings(chainages, spans) : null;
  const measured = fromSpans ? null : planRadii(line, chainages, total);
  const tapered = measured ? curveWidenings(chainages, measured.radii, measured.sides) : null;
  const radii = fromSpans?.radii ?? measured!.radii;
  const sides = fromSpans?.sides ?? tapered!.sides;
  const widenings = fromSpans?.widenings ?? tapered!.widenings;

  return chainages.map((chainage, index) => {
    const frame = stationFrameAt(line, chainage)!;
    const tangent: Vertex = [frame.left[1], -frame.left[0]];
    const mark = planted.get(chainage);
    let kind: StationKind = "grid";
    let key = stationKey("grid", gridIndex.get(chainage) ?? Math.round(chainage / intervalM));
    if (index === 0 || Math.abs(chainage - total) <= 1e-6) {
      kind = "end";
      key = stationKey("end", index === 0 ? "BP" : "EP");
    } else if (mark) {
      kind = mark.kind;
      key = stationKey(mark.kind, mark.id, mark.role as "start" | "anchor" | "end");
    }
    return {
      key,
      chainageM: round(chainage, 6),
      x: round(frame.origin[0], 6),
      y: round(frame.origin[1], 6),
      azimuthDeg: round(
        (((Math.atan2(tangent[0], tangent[1]) * 180) / Math.PI + 360) % 360) as number,
        6,
      ),
      left: [round(frame.left[0], 9), round(frame.left[1], 9)],
      kind,
      id: mark?.id ?? null,
      ground: null,
      planRadiusM: radii[index],
      curveOuterSide: sides[index],
      curveWideningM: widenings[index],
    };
  });
}