/* =============================================================================
 * B05_Profile_Footprint_Strokes.ts
 * 평면 발자국(가게 키 `footprint` · 계약 `PlanFootprint`) → 그릴 선 갈래(PLAN 346-2).
 *
 * 도로 끝 좌 · 우 = `road` · 비탈 끝 = 점마다 깎기 여부(`slopeLeftCut` · `slopeRightCut` —
 * footprint 단계가 붙임)로 `cut` · `fill` 조각 · 깎기 여부가 없으면 `slope` 한 줄.
 * 조각이 바뀌는 점은 앞뒤 조각이 함께 가짐(선이 끊겨 보이지 않게 · `splitRuns` 와 같은 규칙).
 * ========================================================================== */

import type { PlanFootprint, Vertex } from "../../A00_Common/design/logic/design_pipeline_types";

export type FootprintStrokeKind = "road" | "cut" | "fill" | "slope";

export interface FootprintStroke {
  kind: FootprintStrokeKind;
  points: Vertex[];
}

/** footprint 단계 출력 — 계약 칸 + 비탈 끝 점마다 깎기 여부(없을 수 있음). */
export type FootprintValue = PlanFootprint & {
  slopeLeftCut?: ReadonlyArray<boolean>;
  slopeRightCut?: ReadonlyArray<boolean>;
};

function slopeRuns(points: Vertex[], cut: ReadonlyArray<boolean> | undefined): FootprintStroke[] {
  if (points.length < 2) return [];
  if (!cut || cut.length !== points.length) return [{ kind: "slope", points }];
  const runs: FootprintStroke[] = [];
  let current: FootprintStroke | null = null;
  points.forEach((point, index) => {
    const kind = cut[index] ? "cut" : "fill";
    if (current?.kind !== kind) {
      current?.points.push(point);
      current = { kind, points: [point] };
      runs.push(current);
    } else {
      current.points.push(point);
    }
  });
  return runs.filter((run) => run.points.length >= 2);
}

/** 그릴 선 — 도로 끝 둘 · 비탈 끝 조각들(2점 미만은 뺌). */
export function footprintStrokes(footprint: FootprintValue | null): FootprintStroke[] {
  if (!footprint) return [];
  const road = [footprint.roadLeft, footprint.roadRight]
    .filter((points) => points?.length >= 2)
    .map((points): FootprintStroke => ({ kind: "road", points }));
  return [
    ...road,
    ...slopeRuns(footprint.slopeLeft ?? [], footprint.slopeLeftCut),
    ...slopeRuns(footprint.slopeRight ?? [], footprint.slopeRightCut),
  ];
}