/* =============================================================================
 * D03_PlanAnalysis_UI_Measure.ts
 * D03 거리재기 겹(PLAN 562-3) — 두 점을 누르면 그 사이 길이(m) · 원지반 기울기(%) · 높이 차(m).
 *   셋째 누름 = 새로 잼 · Esc = 지움. 지반고 = 받은 지형 `heightAt` · 셈 = 562-1 짝(`logic/D03_PlanAnalysis_Draw`).
 * ========================================================================== */

import { groundSlopePct, segmentLength } from "./logic/D03_PlanAnalysis_Draw";
import type { Vertex } from "./logic/D03_PlanAnalysis_Plan";
import { planColors, type PlanMapLayer, type ScreenMap } from "./D03_PlanAnalysis_UI_Map";

export interface PlanMeasure {
  layer: PlanMapLayer;
  /** 지움(Esc · 끔). */
  clear: () => void;
  /** 검증 창구 — 잰 값(두 점이 다 있으면). */
  result: () => { lengthM: number; slopePct: number | null; riseM: number | null } | null;
}

const fmt = (value: number, digits = 1): string => value.toFixed(digits);
const signed = (value: number, digits = 1): string =>
  `${value >= 0 ? "+" : ""}${fmt(value, digits)}`;

export function createPlanMeasure(heightAt: () => (x: number, y: number) => number): PlanMeasure {
  let from: Vertex | null = null;
  let to: Vertex | null = null;
  let fixed = false;

  const measure = (a: Vertex, b: Vertex) => {
    const z = heightAt();
    const rise = z(b[0], b[1]) - z(a[0], a[1]);
    return {
      lengthM: segmentLength(a, b),
      slopePct: groundSlopePct(a, b, z),
      riseM: Number.isFinite(rise) ? rise : null,
    };
  };

  const layer: PlanMapLayer = {
    draw(context, map: ScreenMap) {
      if (!from) return;
      const colors = planColors();
      const [ax, ay] = map.toScreen(from);
      context.lineWidth = 2;
      context.strokeStyle = colors.active;
      context.fillStyle = colors.active;
      context.setLineDash([6, 4]);
      if (to) {
        const [bx, by] = map.toScreen(to);
        context.beginPath();
        context.moveTo(ax, ay);
        context.lineTo(bx, by);
        context.stroke();
        context.setLineDash([]);
        for (const [x, y] of [
          [ax, ay],
          [bx, by],
        ]) {
          context.beginPath();
          context.arc(x, y, 4, 0, Math.PI * 2);
          context.fill();
        }
        const { lengthM, slopePct, riseM } = measure(from, to);
        const text =
          `${fmt(lengthM)} m · ` +
          (slopePct === null ? "지형 밖" : `${signed(slopePct)} % · Δh ${signed(riseM ?? 0)} m`);
        const [mx, my] = [(ax + bx) / 2, (ay + by) / 2 - 14];
        map.upright(context, mx, my, () => {
          context.font = "12px system-ui, sans-serif";
          context.textAlign = "center";
          context.textBaseline = "middle";
          context.lineWidth = 3;
          context.strokeStyle = colors.halo;
          context.strokeText(text, mx, my);
          context.fillStyle = "#ffffff";
          context.fillText(text, mx, my);
        });
      } else {
        context.beginPath();
        context.arc(ax, ay, 4, 0, Math.PI * 2);
        context.fill();
      }
    },
    press(px, py, map, button) {
      if (button !== 0) return false;
      const point = map.toMetric(px, py);
      if (!from || fixed) {
        [from, to, fixed] = [point, null, false];
      } else {
        [to, fixed] = [point, true];
      }
      return true;
    },
    hover(px, py, map) {
      if (from && !fixed) to = map.toMetric(px, py);
    },
  };

  return {
    layer,
    clear: () => {
      [from, to, fixed] = [null, null, false];
    },
    result: () => (from && to && fixed ? measure(from, to) : null),
  };
}