/* =============================================================================
 * B05_Profile_UI_Profile_Alignment.ts
 * 종단 계획선 선형(직선 + 측점 위 종단곡선) 프론트엔드 기하 계산.
 *
 * 백엔드 `B05_Profile_Engine_Grade_Alignment.py`와 **같은 식**을 쓴다. 사용자가
 * 0.1m 버튼을 누를 때마다 서버를 오가지 않고 즉시 다시 그리기 위한 계산부이며,
 * 확정 시점에는 편집 델타만 서버로 보내 백엔드가 정본을 다시 만든다.
 *
 * 규칙:
 *   - 변화점(PVI)은 기준 측점 위에만 놓인다 → 곡선 중심이 측점 수직선상에 있다.
 *   - 종단곡선은 변화점 대칭이며 좌우에 직선이 반드시 남는다.
 *   - 반경 R이 1차 값이고 곡선길이 L = R × |대수차| 로 따라온다 (편집해도 R은 유지).
 *   - 편집 델타는 항상 **자동 선형(base_pvi) 기준**이라 키를 지우면 정확히 원복된다.
 * ========================================================================== */

export interface AlignmentPolicy {
  station_interval_m: number;
  curve_radius_ratio: number;
  curve_tangent_max_ratio: number;
  curve_skip_legal_exception: boolean;
  default_curve_radius_m: number;
  balance_tolerance_percent: number;
  edit_step_m: number;
  grade_violation_policy: string;
  max_grade_pct: number;
  curve_skip_delta_pct: number;
  paved: boolean;
}

export interface AlignmentNode {
  chainage_m: number;
  elevation_m: number;
}

export interface AlignmentPvi extends AlignmentNode {
  source: "auto" | "user";
  kind: string;
  grade_in_pct: number | null;
  grade_out_pct: number | null;
  curve_l_m: number | null;
  curve_r_m: number | null;
}

export interface AlignmentSegment {
  index: number;
  from_m: number;
  to_m: number;
  length_m: number;
  height_m: number;
  grade_percent: number;
}

export interface AlignmentCurve {
  pvi_index: number;
  chainage_m: number;
  bvc_m: number;
  evc_m: number;
  bvc_elevation_m: number;
  evc_elevation_m: number;
  l_m: number;
  r_m: number;
  k: number;
  delta_pct: number;
  middle_ordinate_m: number;
  omitted: boolean;
  skip_allowed: boolean;
  omit_reason: string | null;
}

export interface AlignmentStationRow {
  station_id: string | null;
  chainage_m: number;
  distance_m: number;
  ground_elevation_m: number;
  plan_elevation_m: number;
  cut_m: number;
  fill_m: number;
}

export interface AlignmentSample {
  chainage_m: number;
  elevation_m: number;
  ground_elevation_m: number;
  difference_m: number;
}

export interface AlignmentBalance {
  cut_area_m2: number;
  fill_area_m2: number;
  net_area_m2: number;
  imbalance_percent: number;
  tolerance_percent: number;
  within_tolerance: boolean;
}

export interface AlignmentViolation {
  segment_index: number;
  type: string;
  value: number;
  limit: number;
}

export interface AlignmentEdits {
  station_offsets: Record<string, number>;
  /** 변화점별 종단곡선 반경(m). 지정하지 않으면 정책 기본 반경을 쓴다. */
  curve_radii: Record<string, number>;
}

export interface ProfileAlignment {
  schema_version: number;
  policy: AlignmentPolicy;
  base_pvi: AlignmentNode[];
  edits: AlignmentEdits;
  pvi: AlignmentPvi[];
  segments: AlignmentSegment[];
  curves: AlignmentCurve[];
  stations: AlignmentStationRow[];
  samples: AlignmentSample[];
  balance: AlignmentBalance;
  violations: AlignmentViolation[];
  warnings: string[];
}

/** 자동 선형과 지반 종단 — 편집을 얹기 위한 고정 입력. */
export interface AlignmentBase {
  policy: AlignmentPolicy;
  basePvi: AlignmentNode[];
  chainage: number[];
  ground: number[];
  stations: Array<{ station_id: string | null; chainage_m: number }>;
}

/** chainage를 편집 델타 dict의 키로 바꾼다 (백엔드 `chainage_key`와 동일 규칙). */
export function chainageKey(value: number): string {
  return value.toFixed(3);
}

export function emptyEdits(): AlignmentEdits {
  return { station_offsets: {}, curve_radii: {} };
}

/** 오름차순 x 배열 위에서의 선형 보간 (범위 밖은 양 끝값으로 클램프). */
function interpolate(xs: number[], ys: number[], value: number): number {
  if (!xs.length) return 0;
  if (value <= xs[0]) return ys[0];
  if (value >= xs[xs.length - 1]) return ys[ys.length - 1];
  let low = 0;
  let high = xs.length - 1;
  while (high - low > 1) {
    const mid = (low + high) >> 1;
    if (xs[mid] <= value) low = mid;
    else high = mid;
  }
  const span = xs[high] - xs[low];
  if (span <= 0) return ys[high];
  return ys[low] + ((ys[high] - ys[low]) * (value - xs[low])) / span;
}

export function toAlignmentBase(alignment: ProfileAlignment): AlignmentBase {
  return {
    policy: alignment.policy,
    basePvi: alignment.base_pvi.map((node) => ({ ...node })),
    chainage: alignment.samples.map((sample) => sample.chainage_m),
    ground: alignment.samples.map((sample) => sample.ground_elevation_m),
    stations: alignment.stations.map((station) => ({
      station_id: station.station_id,
      chainage_m: station.chainage_m,
    })),
  };
}

/** 자동 변화점에 사용자 편집 측점을 합쳐 최종 변화점 집합을 만든다. */
function resolvePvi(
  base: AlignmentBase,
  offsets: Record<string, number>,
): Array<AlignmentNode & { source: "auto" | "user" }> {
  const baseS = base.basePvi.map((node) => node.chainage_m);
  const baseZ = base.basePvi.map((node) => node.elevation_m);
  const nodes = new Map<number, AlignmentNode & { source: "auto" | "user" }>();
  base.basePvi.forEach((node) => {
    nodes.set(Number(node.chainage_m.toFixed(3)), { ...node, source: "auto" });
  });
  Object.entries(offsets).forEach(([key, offset]) => {
    const chainage = Number(Number(key).toFixed(3));
    if (!Number.isFinite(chainage) || !Number.isFinite(offset)) return;
    if (chainage < baseS[0] - 1e-6 || chainage > baseS[baseS.length - 1] + 1e-6) return;
    nodes.set(chainage, {
      chainage_m: chainage,
      elevation_m: interpolate(baseS, baseZ, chainage) + offset,
      source: "user",
    });
  });
  return [...nodes.values()].sort((a, b) => a.chainage_m - b.chainage_m);
}

interface WorkingCurve extends AlignmentCurve {
  grade_in: number;
  grade_out: number;
}

/** 각 변화점에 대칭 종단곡선을 삽입한다 (좌우 직선이 남도록 반쪽 길이를 제한). */
function buildCurves(
  pvi: AlignmentNode[],
  policy: AlignmentPolicy,
  curveRadii: Record<string, number>,
  warnings: string[],
): WorkingCurve[] {
  const curves: WorkingCurve[] = [];
  const skipDelta = policy.curve_skip_delta_pct / 100;
  for (let index = 1; index < pvi.length - 1; index += 1) {
    const spanLeft = pvi[index].chainage_m - pvi[index - 1].chainage_m;
    const spanRight = pvi[index + 1].chainage_m - pvi[index].chainage_m;
    if (spanLeft <= 0 || spanRight <= 0) continue;
    const gradeIn = (pvi[index].elevation_m - pvi[index - 1].elevation_m) / spanLeft;
    const gradeOut = (pvi[index + 1].elevation_m - pvi[index].elevation_m) / spanRight;
    const delta = gradeOut - gradeIn;
    if (Math.abs(delta) < 1e-9) continue;
    const chainage = pvi[index].chainage_m;
    const key = chainageKey(chainage);
    const skipAllowed = !policy.paved && Math.abs(delta) <= skipDelta + 1e-12;
    const requested = curveRadii[key];
    const radius =
      Number.isFinite(requested) && requested > 0 ? requested : policy.default_curve_radius_m;
    const desired = radius * Math.abs(delta);
    const halfLimit = Math.min(spanLeft, spanRight) * policy.curve_tangent_max_ratio;
    const half = Math.min(desired / 2, halfLimit);
    if (half <= 1e-9) continue;
    if (desired / 2 - half > 1e-6) {
      warnings.push(
        `${chainage.toFixed(1)}m: 인접 직선이 짧아 종단곡선 반경을 ${((half * 2) / Math.abs(delta)).toFixed(0)}m로 줄였습니다.`,
      );
    }
    const length = half * 2;
    curves.push({
      pvi_index: index,
      chainage_m: chainage,
      bvc_m: chainage - half,
      evc_m: chainage + half,
      bvc_elevation_m: 0,
      evc_elevation_m: 0,
      l_m: length,
      r_m: length / Math.abs(delta),
      k: length / (Math.abs(delta) * 100),
      delta_pct: delta * 100,
      middle_ordinate_m: (Math.abs(delta) * length) / 8,
      omitted: skipAllowed && policy.curve_skip_legal_exception,
      skip_allowed: skipAllowed,
      omit_reason: skipAllowed
        ? `비포장 대수차 ${policy.curve_skip_delta_pct.toFixed(0)}% 이하 (법정 생략 가능)`
        : null,
      grade_in: gradeIn,
      grade_out: gradeOut,
    });
  }
  return curves;
}

/** 직선 + 종단곡선으로 구성된 계획선을 임의 chainage에서 평가한다. */
function evaluateAt(
  pviS: number[],
  pviZ: number[],
  curves: WorkingCurve[],
  chainage: number,
): number {
  for (const curve of curves) {
    if (curve.omitted) continue;
    if (chainage < curve.bvc_m || chainage > curve.evc_m) continue;
    const half = curve.l_m / 2;
    const local = chainage - curve.bvc_m;
    const startZ = pviZ[curve.pvi_index] - curve.grade_in * half;
    const delta = curve.grade_out - curve.grade_in;
    return startZ + curve.grade_in * local + (delta / (2 * curve.l_m)) * local * local;
  }
  return interpolate(pviS, pviZ, chainage);
}

/** 사다리꼴 적분 가중치(ds). */
function trapezoidWeights(chainage: number[]): number[] {
  const weights = new Array<number>(chainage.length).fill(0);
  if (chainage.length < 2) return weights;
  for (let index = 1; index < chainage.length - 1; index += 1) {
    weights[index] = (chainage[index + 1] - chainage[index - 1]) / 2;
  }
  weights[0] = (chainage[1] - chainage[0]) / 2;
  weights[chainage.length - 1] =
    (chainage[chainage.length - 1] - chainage[chainage.length - 2]) / 2;
  return weights;
}

/** 저장분·초안이 부분적으로 비어 있어도 계산이 터지지 않도록 편집 맵을 채운다. */
function normalizeEdits(edits: AlignmentEdits | undefined): AlignmentEdits {
  return {
    station_offsets: edits?.station_offsets ?? {},
    curve_radii: edits?.curve_radii ?? {},
  };
}

export function buildAlignment(base: AlignmentBase, input: AlignmentEdits): ProfileAlignment {
  const edits = normalizeEdits(input);
  const warnings: string[] = [];
  const nodes = resolvePvi(base, edits.station_offsets);
  const pviS = nodes.map((node) => node.chainage_m);
  const pviZ = nodes.map((node) => node.elevation_m);
  const curves = buildCurves(nodes, base.policy, edits.curve_radii, warnings);

  const segments: AlignmentSegment[] = [];
  for (let index = 0; index < nodes.length - 1; index += 1) {
    const length = pviS[index + 1] - pviS[index];
    const height = pviZ[index + 1] - pviZ[index];
    segments.push({
      index,
      from_m: pviS[index],
      to_m: pviS[index + 1],
      length_m: length,
      height_m: height,
      grade_percent: length > 0 ? (height / length) * 100 : 0,
    });
  }
  curves.forEach((curve) => {
    curve.bvc_elevation_m = evaluateAt(pviS, pviZ, curves, curve.bvc_m);
    curve.evc_elevation_m = evaluateAt(pviS, pviZ, curves, curve.evc_m);
  });

  // 샘플 격자에 변화점(PVI)과 종단곡선 시·종점(BVC/EVC)을 **합쳐서** 그린다.
  // 격자만 쓰면 격자 사이에 놓인 변화점(배관 구조물 자리처럼 임의 chainage에 승격된 점)의
  // 모서리를 선이 잘라먹어, 종단곡선 R이 안 보이고 편집 지점과 선이 어긋나 끊긴 것처럼
  // 보인다(2026-08-03 사용자 보고). 곡선 구간 끝점까지 넣어야 직선→곡선 이음이 정확히 붙는다.
  const sampleChainages = new Set<number>(base.chainage.map((value) => Number(value.toFixed(3))));
  const first = base.chainage[0];
  const last = base.chainage[base.chainage.length - 1];
  for (const extra of [
    ...pviS,
    ...curves.flatMap((curve) => [curve.bvc_m, curve.chainage_m, curve.evc_m]),
  ]) {
    if (extra >= first - 1e-6 && extra <= last + 1e-6) {
      sampleChainages.add(Number(extra.toFixed(3)));
    }
  }
  const samples: AlignmentSample[] = [...sampleChainages]
    .sort((a, b) => a - b)
    .map((chainage) => {
      const plan = evaluateAt(pviS, pviZ, curves, chainage);
      const ground = interpolate(base.chainage, base.ground, chainage);
      return {
        chainage_m: chainage,
        elevation_m: plan,
        ground_elevation_m: ground,
        difference_m: plan - ground,
      };
    });

  // 면적 가중치도 **합쳐진 샘플 격자**로 계산해야 한다 — base.chainage로 두면 추가된
  // 변화점 샘플과 인덱스가 어긋나 절·성토 면적이 통째로 틀어진다.
  const weights = trapezoidWeights(samples.map((sample) => sample.chainage_m));
  let cutArea = 0;
  let fillArea = 0;
  samples.forEach((sample, index) => {
    if (sample.difference_m < 0) cutArea += weights[index] * -sample.difference_m;
    else fillArea += weights[index] * sample.difference_m;
  });
  const reference = Math.max(cutArea, fillArea);
  const imbalance = reference > 1e-9 ? (Math.abs(cutArea - fillArea) / reference) * 100 : 0;

  const stations: AlignmentStationRow[] = base.stations.map((station, index) => {
    const plan = evaluateAt(pviS, pviZ, curves, station.chainage_m);
    const ground = interpolate(base.chainage, base.ground, station.chainage_m);
    return {
      station_id: station.station_id,
      chainage_m: station.chainage_m,
      distance_m: index ? station.chainage_m - base.stations[index - 1].chainage_m : 0,
      ground_elevation_m: ground,
      plan_elevation_m: plan,
      cut_m: Math.max(ground - plan, 0),
      fill_m: Math.max(plan - ground, 0),
    };
  });

  const curveByPvi = new Map(curves.map((curve) => [curve.pvi_index, curve]));
  const pviRows: AlignmentPvi[] = nodes.map((node, index) => {
    const curve = curveByPvi.get(index);
    return {
      chainage_m: node.chainage_m,
      elevation_m: node.elevation_m,
      source: node.source,
      kind: index === 0 ? "bp" : index === nodes.length - 1 ? "ep" : "pvi",
      grade_in_pct: index ? segments[index - 1].grade_percent : null,
      grade_out_pct: index < segments.length ? segments[index].grade_percent : null,
      curve_l_m: curve ? curve.l_m : null,
      curve_r_m: curve ? curve.r_m : null,
    };
  });

  const violations: AlignmentViolation[] = segments
    .filter((segment) => Math.abs(segment.grade_percent) > base.policy.max_grade_pct + 1e-6)
    .map((segment) => ({
      segment_index: segment.index,
      type: "grade_over",
      value: segment.grade_percent,
      limit: base.policy.max_grade_pct,
    }));
  const withinTolerance = imbalance <= base.policy.balance_tolerance_percent + 1e-9;

  return {
    schema_version: 1,
    policy: base.policy,
    base_pvi: base.basePvi,
    edits,
    pvi: pviRows,
    segments,
    curves: curves.map(({ grade_in: _in, grade_out: _out, ...rest }) => rest),
    stations,
    samples,
    balance: {
      cut_area_m2: cutArea,
      fill_area_m2: fillArea,
      net_area_m2: fillArea - cutArea,
      imbalance_percent: imbalance,
      tolerance_percent: base.policy.balance_tolerance_percent,
      within_tolerance: withinTolerance,
    },
    violations,
    warnings,
  };
}

/**
 * 계획선 위 지점의 계획고.
 * 측점 위라면 곡선까지 반영해 정확히 계산된 측점 행 값을 쓰고, 그 밖에서는
 * 샘플 보간으로 폴백한다(편집 판정은 항상 측점 위에서 일어난다).
 */
export function planElevationAt(alignment: ProfileAlignment, chainageM: number): number {
  const station = alignment.stations.find((row) => Math.abs(row.chainage_m - chainageM) < 1e-6);
  if (station) return station.plan_elevation_m;
  return interpolate(
    alignment.samples.map((sample) => sample.chainage_m),
    alignment.samples.map((sample) => sample.elevation_m),
    chainageM,
  );
}

const FEEDBACK_PASSES = 4;
const FEEDBACK_TOLERANCE_M = 1e-4;

/**
 * 측점 계획고를 delta만큼 올리거나 내린 편집 델타를 만든다.
 *
 * 변화점이 새로 생기면 종단곡선의 중앙종거만큼 계획고가 함께 내려가(또는 올라가)
 * 버튼 1클릭이 정확히 0.1m가 되지 않는다. **화면에 보이는 계획고**가 정확히 delta만큼
 * 움직이도록 중앙종거 변화분을 몇 번 되먹여 보정한다.
 */
export function adjustStation(
  base: AlignmentBase,
  edits: AlignmentEdits,
  chainageM: number,
  delta: number,
): AlignmentEdits {
  const key = chainageKey(chainageM);
  const current = buildAlignment(base, edits);
  const target = planElevationAt(current, chainageM) + delta;
  const baseElevation = interpolate(
    base.basePvi.map((node) => node.chainage_m),
    base.basePvi.map((node) => node.elevation_m),
    chainageM,
  );
  let offset =
    (edits.station_offsets[key] ?? planElevationAt(current, chainageM) - baseElevation) + delta;
  const withOffset = (value: number): AlignmentEdits => ({
    ...edits,
    station_offsets: { ...edits.station_offsets, [key]: Number(value.toFixed(6)) },
  });
  let next = withOffset(offset);
  for (let pass = 0; pass < FEEDBACK_PASSES; pass += 1) {
    const error = target - planElevationAt(buildAlignment(base, next), chainageM);
    if (Math.abs(error) < FEEDBACK_TOLERANCE_M) break;
    offset += error;
    next = withOffset(offset);
  }
  return next;
}

/**
 * 직선 구간 전체를 평행이동한다 (기울기 유지, 양 끝 변화점 동시 이동).
 *
 * 측점 버튼은 그 점을 꺾는 조작이라 "구배는 그대로 두고 높이만" 옮길 수 없다.
 * 구간 양 끝에 같은 델타를 주면 그 직선의 기울기는 보존되고 인접 직선의 각도만 바뀐다.
 */
export function shiftSegment(
  base: AlignmentBase,
  edits: AlignmentEdits,
  segment: AlignmentSegment,
  delta: number,
): AlignmentEdits {
  const baseS = base.basePvi.map((node) => node.chainage_m);
  const baseZ = base.basePvi.map((node) => node.elevation_m);
  const current = buildAlignment(base, edits);
  const offsets = { ...edits.station_offsets };
  [segment.from_m, segment.to_m].forEach((chainage) => {
    const key = chainageKey(chainage);
    const existing =
      offsets[key] ?? planElevationAt(current, chainage) - interpolate(baseS, baseZ, chainage);
    offsets[key] = Number((existing + delta).toFixed(6));
  });
  return { ...edits, station_offsets: offsets };
}

/**
 * 곡선 행의 R 입력을 저장한다. R이 1차 값이므로 그대로 담고, 곡선길이는
 * L = R × |대수차| 로 매 렌더마다 다시 계산된다(계획고를 편집해도 R은 유지된다).
 * 빈 값이면 키를 지워 정책 기본 반경으로 돌아간다.
 */
export function setCurveRadius(
  edits: AlignmentEdits,
  curve: AlignmentCurve,
  radiusM: number,
): AlignmentEdits {
  const key = chainageKey(curve.chainage_m);
  const curveRadii = { ...edits.curve_radii };
  if (!Number.isFinite(radiusM) || radiusM <= 0) delete curveRadii[key];
  else curveRadii[key] = Number(radiusM.toFixed(6));
  return { ...edits, curve_radii: curveRadii };
}

export function hasEdits(edits: AlignmentEdits): boolean {
  const safe = normalizeEdits(edits);
  return Object.keys(safe.station_offsets).length > 0 || Object.keys(safe.curve_radii).length > 0;
}