/* =============================================================================
 * 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`).
 *   600-2 — 첫 누름이 노선 위면 「노선 따라」: 둘째 점 = 이어진 노선 위 가장 가까운 자리 · 길이 = 노선 따라
 *   (`logic/D03_PlanAnalysis_Measure`) · 첫 누름이 선 밖이면 곧은 거리 그대로.
 * ========================================================================== */

import { groundSlopePct, segmentLength } from "./logic/D03_PlanAnalysis_Draw";
import {
  nearestOnRoute,
  routeSpan,
  type RoutePos,
  type RouteSpan,
} from "./logic/D03_PlanAnalysis_Measure";
import type { PlanNetwork, Vertex } from "./logic/D03_PlanAnalysis_Plan";
import { planColors, type PlanMapLayer, type ScreenMap } from "./D03_PlanAnalysis_UI_Map";
import { lineAt, strokeCased } from "./D03_PlanAnalysis_UI_DrawPaint";

export interface PlanMeasure {
  layer: PlanMapLayer;
  /** 지움(Esc · 끔). */
  clear: () => void;
  /** 검증 창구 — 잰 값(두 점이 다 있으면) · `alongRoute` = 노선 따라 쟀나. */
  result: () => {
    lengthM: number;
    slopePct: number | null;
    riseM: number | null;
    alongRoute: boolean;
  } | 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,
  network: () => PlanNetwork,
): PlanMeasure {
  let from: Vertex | null = null;
  let to: Vertex | null = null;
  let fixed = false;
  /** 첫 누름이 노선 위였던 자리 · 둘째 점이 노선 위에 놓인 길. */
  let fromPos: RoutePos | null = null;
  let span: RouteSpan | null = null;

  const measure = (a: Vertex, b: Vertex) => {
    const z = heightAt();
    const rise = z(b[0], b[1]) - z(a[0], a[1]);
    const lengthM = span ? span.lengthM : segmentLength(a, b);
    return {
      lengthM,
      slopePct: span
        ? Number.isFinite(rise) && lengthM > 0
          ? (rise / lengthM) * 100
          : null
        : groundSlopePct(a, b, z),
      riseM: Number.isFinite(rise) ? rise : null,
      alongRoute: !!span,
    };
  };

  /** 둘째 점 놓기 — 노선 위 첫 점이면 이어진 노선 위 가까운 자리 · 아니면 누른 자리. */
  const place = (point: Vertex): void => {
    const near = fromPos ? nearestOnRoute(network(), point, fromPos) : null;
    span = near && fromPos ? routeSpan(network(), fromPos, near) : null;
    to = near && span ? near.point : point;
  };

  const layer: PlanMapLayer = {
    draw(context, map: ScreenMap) {
      if (!from) return;
      const colors = planColors();
      const [ax, ay] = map.toScreen(from);
      const dot = (x: number, y: number): void => {
        context.beginPath();
        context.arc(x, y, 4.5, 0, Math.PI * 2);
        context.fillStyle = colors.measure;
        context.fill();
        context.lineWidth = 1.5;
        context.strokeStyle = colors.casing;
        context.stroke();
      };
      context.lineCap = "round";
      context.lineJoin = "round";
      if (to) {
        const [bx, by] = map.toScreen(to);
        context.beginPath();
        if (span) {
          span.path.forEach((point, i) => {
            const [sx, sy] = map.toScreen(point);
            if (i) context.lineTo(sx, sy);
            else context.moveTo(sx, sy);
          });
          strokeCased(context, colors.measure, 4);
        } else {
          context.moveTo(ax, ay);
          context.lineTo(bx, by);
          strokeCased(context, colors.measure, 2.5, [6, 4]);
        }
        dot(ax, ay);
        dot(bx, by);
        const { lengthM, slopePct, riseM } = measure(from, to);
        const rise = riseM === null ? "지형 밖" : `Δh ${signed(riseM)} m`;
        const text = span
          ? `노선 따라 ${fmt(lengthM)} m · ` +
            (span.stations ? `측점 ${fmt(span.stations[0])} ~ ${fmt(span.stations[1])} m · ` : "") +
            rise
          : `${fmt(lengthM)} m · ` +
            (slopePct === null ? "지형 밖" : `${signed(slopePct)} % · ${rise}`);
        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 {
        dot(ax, ay);
      }
    },
    press(px, py, map, button) {
      if (button !== 0) return false;
      const point = map.toMetric(px, py);
      if (!from || fixed) {
        // 첫 누름 — 노선 위(선 8 px · 꺾임점 12 px)면 노선 따라 · 아니면 곧은 거리
        const net = network();
        const hit = lineAt(net, px, py, map);
        fromPos = hit ? { line: net.lines[hit.line].id, atM: hit.atM } : null;
        [from, to, fixed, span] = [hit ? hit.point : point, null, false, null];
      } else {
        place(point);
        fixed = true;
      }
      return true;
    },
    hover(px, py, map) {
      if (from && !fixed) place(map.toMetric(px, py));
    },
  };

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