// Timeboxed probe: can ol-ext's Transform carry generic handle hit-testing,
// pointer lifecycle and visual feedback for us?
//
// It is bound to a throwaway proxy Point only. `Transform` translates the
// geometry of whatever feature it is given, so the baseline layer is never
// passed to it — and this page counts every write to that layer to prove it.

import { useEffect, useRef, useState } from 'react';
import Feature from 'ol/Feature';
import Map from 'ol/Map';
import View from 'ol/View';
import LineString from 'ol/geom/LineString';
import Point from 'ol/geom/Point';
import Polygon from 'ol/geom/Polygon';
import type SimpleGeometry from 'ol/geom/SimpleGeometry';
import VectorLayer from 'ol/layer/Vector';
import VectorSource from 'ol/source/Vector';
import CircleStyle from 'ol/style/Circle';
import Fill from 'ol/style/Fill';
import Stroke from 'ol/style/Stroke';
import Style from 'ol/style/Style';
import Transform, { type TransformEvents } from 'ol-ext/interaction/Transform';
import { fromLonLat, signedMetersAlongAxis, type Coordinate } from '../../src/edit/meters';
import { projectHandleValue } from '../../src/edit/projection';
import { CENTERLINE, laneDividerLines, PROBE_HANDLE, roadSurfaceRing } from './fixture';

/** Survives re-renders so a rebuilt Map is impossible to miss. */
let mapInstances = 0;

interface Report {
  mapInstanceId: number;
  baselineWrites: number;
  baselineChanged: boolean;
  drags: number;
  moves: number;
  /** Unclamped signed meters along the axis — shows tracking quality. */
  rawMeters: number | null;
  /** The clamped value a constraint would actually carry. */
  draftMeters: number | null;
  log: string[];
}

const EMPTY: Report = {
  mapInstanceId: 0,
  baselineWrites: 0,
  baselineChanged: false,
  drags: 0,
  moves: 0,
  rawMeters: null,
  draftMeters: null,
  log: [],
};

const project = (point: Coordinate) => fromLonLat(point);
const fingerprint = (source: VectorSource) =>
  JSON.stringify(source.getFeatures().map((feature) => (feature.getGeometry() as SimpleGeometry).getCoordinates()));

export function ProbeMap() {
  const target = useRef<HTMLDivElement>(null);
  const renders = useRef(0);
  const [report, setReport] = useState<Report>(EMPTY);
  const [nudge, setNudge] = useState(0);
  renders.current += 1;

  useEffect(() => {
    if (!target.current) return;

    // Baseline: read-only compiler output. Nothing below may write to it.
    const baseline = new VectorSource({
      features: [
        new Feature(new Polygon([roadSurfaceRing().map(project)])),
        ...laneDividerLines().map((line) => new Feature(new LineString(line.map(project)))),
        new Feature(new LineString(CENTERLINE.map(project))),
      ],
    });
    const baselineAtStart = fingerprint(baseline);
    let writes = 0;
    const onWrite = () => {
      writes += 1;
      // Read the source now, not inside the updater: React may run an updater
      // later and more than once, which would sample a different moment.
      const changed = fingerprint(baseline) !== baselineAtStart;
      setReport((current) => ({ ...current, baselineWrites: writes, baselineChanged: changed }));
    };
    for (const type of ['addfeature', 'changefeature', 'removefeature'] as const) baseline.on(type, onWrite);

    // Proxy: a single throwaway handle feature, the only thing Transform sees.
    const proxyFeature = new Feature(new Point(project(PROBE_HANDLE.position)));
    const proxyLayer = new VectorLayer({
      source: new VectorSource({ features: [proxyFeature] }),
      style: new Style({
        image: new CircleStyle({
          radius: 8,
          fill: new Fill({ color: '#00a5cf' }),
          stroke: new Stroke({ color: '#fff', width: 2 }),
        }),
      }),
    });

    const map = new Map({
      target: target.current,
      layers: [
        new VectorLayer({
          source: baseline,
          style: new Style({ fill: new Fill({ color: '#3f4b5088' }), stroke: new Stroke({ color: '#296956' }) }),
        }),
        proxyLayer,
      ],
      // Zoom 20: the ±5.4 m clamp spans ~47 px here, so tracking is observable.
      // At zoom 18 it was ~12 px and every drag saturated instantly.
      view: new View({ center: project(PROBE_HANDLE.position), zoom: 20 }),
    });
    mapInstances += 1;
    const instance = mapInstances;

    const transform = new Transform({
      layers: [proxyLayer],
      filter: (feature) => feature === proxyFeature,
      hitTolerance: 12,
      translate: true,
      translateFeature: true,
      scale: false,
      rotate: false,
      stretch: false,
    });
    map.addInteraction(transform);

    let start: Coordinate | null = null;
    let drags = 0;
    let moves = 0;
    let frame = 0;
    let pending: { raw: number; draft: number } | null = null;
    const note = (line: string) => setReport((current) => ({ ...current, log: [line, ...current.log].slice(0, 12) }));
    const coordinates = () => (proxyFeature.getGeometry() as Point).getCoordinates() as Coordinate;
    // PROBE_HANDLE is a left-side handle, so "outward" is the positive axis
    // direction and the raw projection needs no sign flip.
    const rawMeters = (from: Coordinate, to: Coordinate) =>
      PROBE_HANDLE.value.current + signedMetersAlongAxis(from, to, PROBE_HANDLE.axisAzimuth);

    // Per-pointermove React state updates were the previous run's 1656 renders.
    // Coalescing to one frame keeps the readout honest without making React the
    // bottleneck. Production must go further: the ghost writes to its own OL
    // source directly and never re-renders the tree per pointer move.
    const flush = () => {
      frame = 0;
      if (!pending) return;
      const { raw, draft } = pending;
      setReport((current) => ({ ...current, moves, rawMeters: raw, draftMeters: draft }));
    };

    const onStart = () => {
      start = [...coordinates()] as Coordinate;
      note('translatestart');
    };
    const onMove = () => {
      if (!start) return;
      moves += 1;
      const now = coordinates();
      pending = { raw: rawMeters(start, now), draft: projectHandleValue(PROBE_HANDLE, start, now) };
      if (!frame) frame = requestAnimationFrame(flush);
    };
    const onEnd = () => {
      drags += 1;
      const now = coordinates();
      const raw = start ? rawMeters(start, now) : null;
      const draft = start ? projectHandleValue(PROBE_HANDLE, start, now) : null;
      setReport((current) => ({ ...current, drags, moves, rawMeters: raw, draftMeters: draft }));
      note(`translateend -> raw ${raw?.toFixed(3) ?? 'n/a'} / draft ${draft?.toFixed(3) ?? 'n/a'}`);
      start = null;
    };
    // ol-ext's event names live outside OpenLayers' typed event unions; narrow
    // once here rather than casting at every listener.
    const events = transform as unknown as TransformEvents;
    const onSelect = () => note('select');
    events.on('translatestart', onStart);
    events.on('translating', onMove);
    events.on('translateend', onEnd);
    events.on('select', onSelect);

    setReport({ ...EMPTY, mapInstanceId: instance });

    return () => {
      if (frame) cancelAnimationFrame(frame);
      events.un('translatestart', onStart);
      events.un('translating', onMove);
      events.un('translateend', onEnd);
      events.un('select', onSelect);
      for (const type of ['addfeature', 'changefeature', 'removefeature'] as const) baseline.un(type, onWrite);
      map.setTarget(undefined);
    };
    // Built once per mount, exactly like the production MapCanvas.
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  const pass = (ok: boolean) => (ok ? '通过' : '未通过');
  const saturated = report.draftMeters !== null && Math.abs(report.draftMeters) >= PROBE_HANDLE.value.max - 0.001;
  return (
    <div className="probe">
      <div className="probe-map" ref={target} aria-label="ol-ext 探针地图" />
      <aside className="probe-panel">
        <h1>ol-ext Transform 探针</h1>

        <section className="probe-howto">
          <h2>你要做的事（约 30 秒）</h2>
          <ol>
            <li>
              按住地图上那个<strong>蓝色圆点</strong>，<strong>左右</strong>慢慢拖动
            </li>
            <li>盯住下面那个大字数字，看它跟不跟手</li>
            <li>再故意快速、大幅度拖十几次，试着把它拖崩</li>
          </ol>
          <p>全程那块灰绿色道路面必须一动不动。</p>
        </section>

        <section className="probe-live">
          <h2>跟手位移</h2>
          <strong className="probe-big">
            {report.rawMeters === null ? '拖一下试试' : `${report.rawMeters.toFixed(2)} 米`}
          </strong>
          <p>拖的时候它应该连续变化、不跳数；松手之后不应该自己变。</p>
        </section>

        <section className="probe-ask">
          <h2>回报给我这三个答案</h2>
          <ol>
            <li>拖动时数字连续吗？会不会卡顿、跳数、突然归零？</li>
            <li>松开鼠标后，数字会不会自己弹回去或突变？</li>
            <li>反复拖十几次，蓝点会不会抓不住？页面会不会报错？</li>
          </ol>
          <p>页面若崩溃，会显示红色报错框，把那整段发我即可。</p>
        </section>
        <section>
          <h2>自动判定，不用你操心</h2>
          <dl>
            <dt>地图没被重建</dt>
            <dd>
              {pass(mapInstances === report.mapInstanceId)}（实例 #{report.mapInstanceId}／共构造 {mapInstances} 次，
              React 渲染 {renders.current} 次）
            </dd>
            <dt>基线道路面没被改写</dt>
            <dd>
              {pass(report.baselineWrites === 0 && !report.baselineChanged)}（写入 {report.baselineWrites} 次，几何
              {report.baselineChanged ? '已改变' : '未改变'}）
            </dd>
          </dl>
        </section>

        <details>
          <summary>技术细节</summary>
          <p>
            完成 {report.drags} 次拖拽，收到 {report.moves} 个 translating 事件。
            <br />
            约束值（带生产钳位 ±{PROBE_HANDLE.value.max.toFixed(1)} 米）
            {report.draftMeters === null ? ' —' : ` ${report.draftMeters.toFixed(3)} 米`}
            {saturated ? '，已顶到边界，属正常' : ''}。
          </p>
          <button type="button" onClick={() => setNudge(nudge + 1)}>
            强制 React 重渲染（已 {nudge} 次）
          </button>
          <ul>
            {report.log.map((line, index) => (
              <li key={`${line}-${index}`}>{line}</li>
            ))}
          </ul>
        </details>
      </aside>
    </div>
  );
}