import type { CrossSection, SectionSample } from "./B06_Section_Api_Fetch";
import { CROSS_HEIGHT, CROSS_PAD, validElevation } from "./B06_Section_UI_Section_Common";
import { culvertRequiredHalfWidth } from "./B06_Section_UI_Cross_Culvert_Wire";
import { toeFitHalfWidth } from "./B06_Section_UI_Cross_Fit";

const AREA_OVERLAY_HEADROOM_PX = 58;

export interface CrossPlotMetrics {
  sourceSamples: SectionSample[];
  minOffset: number;
  maxOffset: number;
  elevationMid: number;
  displaySpan: number;
  displayMax: number;
  pixelsPerMeter: number;
  heightPx: number;
}

/**
 * 강제 높이를 얹기 **전**까지의 값 — 카드 두 벌(행 높이 재기 / 실제 그리기)이 나눠 쓴다.
 * 예전에는 같은 측점의 기하를 두 번 계산했고, 그 값이 B06 진입에서 `draw` 자기 시간
 * 213ms 의 대부분이었다(2026-09-06 CPU 프로파일, 측점 67곳 기준 3.2ms/장).
 */
export interface CrossPlotBase {
  sourceSamples: SectionSample[];
  minOffset: number;
  maxOffset: number;
  elevationMid: number;
  pixelsPerMeter: number;
  /** 강제 높이가 없을 때 쓰는 높이(바닥 `CROSS_HEIGHT` 적용 전). */
  naturalHeight: number;
}

export function crossPlotBase(
  section: CrossSection,
  verticalExaggeration: number,
  widthPx: number,
  crossHalfWidth?: number,
  designElevation?: number,
): CrossPlotBase | null {
  const sourceSamples = section.samples.filter(
    (sample) =>
      crossHalfWidth === undefined || Math.abs(sample.offset_m ?? 0) <= crossHalfWidth + 1e-6,
  );
  const valid = sourceSamples.filter(validElevation);
  if (!valid.length) return null;
  const offsets = sourceSamples.map((sample) => sample.offset_m ?? 0);
  const minOffset = Math.min(...offsets, -1);
  const maxOffset = Math.max(...offsets, 1);
  const elevations = valid.map((sample) => sample.elevation_m);
  if (designElevation !== undefined && Number.isFinite(designElevation))
    elevations.push(designElevation);
  const rawMin = Math.min(...elevations);
  const rawMax = Math.max(...elevations);
  const elevationMid = (rawMin + rawMax) / 2;
  const padding = rawMax > rawMin ? (rawMax - rawMin) * 0.08 : 0.5;
  const pixelsPerMeter =
    (widthPx - CROSS_PAD.left - CROSS_PAD.right) / Math.max(maxOffset - minOffset, 1e-6);
  const rawSpan = Math.max(
    (rawMax - rawMin + padding * 2) * Math.max(verticalExaggeration, 0.1),
    1e-6,
  );
  const naturalHeight =
    rawSpan * pixelsPerMeter + CROSS_PAD.top + CROSS_PAD.bottom + AREA_OVERLAY_HEADROOM_PX;
  return { sourceSamples, minOffset, maxOffset, elevationMid, pixelsPerMeter, naturalHeight };
}

/** 재 둔 기하에 행 높이만 얹는다 — 다시 계산하지 않는다. */
export function crossPlotFromBase(base: CrossPlotBase, forcedHeightPx?: number): CrossPlotMetrics {
  const heightPx = forcedHeightPx ?? Math.max(base.naturalHeight, CROSS_HEIGHT);
  const displaySpan =
    Math.max(heightPx - CROSS_PAD.top - CROSS_PAD.bottom, 1e-6) / base.pixelsPerMeter;
  const displayMax =
    base.elevationMid + displaySpan / 2 + AREA_OVERLAY_HEADROOM_PX / base.pixelsPerMeter / 2;
  return {
    sourceSamples: base.sourceSamples,
    minOffset: base.minOffset,
    maxOffset: base.maxOffset,
    elevationMid: base.elevationMid,
    displaySpan,
    displayMax,
    pixelsPerMeter: base.pixelsPerMeter,
    heightPx,
  };
}

export function crossPlotMetrics(
  section: CrossSection,
  verticalExaggeration: number,
  widthPx: number,
  crossHalfWidth?: number,
  designElevation?: number,
  forcedHeightPx?: number,
): CrossPlotMetrics | null {
  const base = crossPlotBase(
    section,
    verticalExaggeration,
    widthPx,
    crossHalfWidth,
    designElevation,
  );
  return base ? crossPlotFromBase(base, forcedHeightPx) : null;
}

/**
 * 카드가 실제로 그릴 표시 반폭 — 개별값 > 전역값(2026-08-06).
 *
 * 절·성토선이 원지반과 만나는 지점(교차점)이 반폭 밖이면 **이 카드만** 자동 줌아웃한다
 * (2026-08-22, 판정 기준 개편 2026-08-23: 배수관용 5m 사면 규칙 대신 실제 교차점).
 * 보유 샘플 밖까지는 넓히지 않는다 — 지반이 없어 빈 화면이 될 뿐이고, 그 경우
 * [보기 반폭 적용]이 필요한 폭으로 백엔드 재생성을 건다.
 */
export function effectiveCardHalfWidth(
  section: CrossSection,
  baseHalfWidth: number | undefined,
): number | undefined {
  const sampledExtent = Math.max(
    0,
    ...section.samples.map((sample) => Math.abs(sample.offset_m ?? 0)),
  );
  const requiredHalfWidth = Math.min(
    Math.max(culvertRequiredHalfWidth(section) ?? 0, toeFitHalfWidth(section) ?? 0),
    sampledExtent,
  );
  return baseHalfWidth !== undefined && requiredHalfWidth > 0
    ? Math.max(baseHalfWidth, requiredHalfWidth)
    : baseHalfWidth;
}