'use client';

import { useEffect, useRef, useState, type ChangeEvent } from 'react';
import * as maplibregl from 'maplibre-gl';
import 'maplibre-gl/dist/maplibre-gl.css';
import pkg from '../package.json';
import { DEFAULT_STYLE_ID, STYLES, STYLE_STORAGE_KEY, isStyleId, localAssetsAvailable, styleUrlFor } from '../lib/mapStyles';

const EUROPE_CENTER: [number, number] = [10, 52];
const INITIAL_ZOOM = 4;
// Flat 2D view only. Max zoom ≈ ~100 km across a typical desktop viewport width at
// European latitudes (~47 m/px at z11, 52°N); street-level zoom has no gameplay value.
export const MIN_ZOOM = 3;
export const MAX_ZOOM = 11;

const AIRPORTS_SOURCE_ID = 'airports';
const AIRPORTS_LAYER_ID = 'airports-circles';

function escapeHtml(s: string): string {
  return s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
}

export default function Map() {
  const containerRef = useRef<HTMLDivElement>(null);
  const mapRef = useRef<maplibregl.Map | null>(null);
  // /api/airports is fetched at most once per page life: every styledata event
  // (initial load AND after each setStyle) reuses this promise.
  const airportsPromiseRef = useRef<Promise<{ features: unknown[] }> | null>(null);
  const [airportCount, setAirportCount] = useState<number | null>(null);
  const [styleId, setStyleId] = useState<string>(DEFAULT_STYLE_ID);

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

    // Bundlers (Turbopack) break MapLibre's derived worker URL, so point it at a
    // route that serves the worker script (and its relative imports) from node_modules.
    maplibregl.setWorkerUrl('/api/mlworker/maplibre-gl-worker.mjs');

    let cancelled = false;

    // Defer map creation until the asset-pack probe resolves — one cheap local
    // request decides between self-hosted styles (volume-mounted public/) and the
    // remote openfreemap.org fallback. The persisted style choice is read here,
    // post-mount: SSR hydration stays safe (server + first paint use the default),
    // and applying it at creation time avoids a fiord→saved-style flash.
    void localAssetsAvailable().then((available) => {
      if (cancelled || !containerRef.current) return;

      const saved = window.localStorage.getItem(STYLE_STORAGE_KEY);
      const initialId = saved && isStyleId(saved) ? saved : DEFAULT_STYLE_ID;
      setStyleId(initialId);

      const map = new maplibregl.Map({
        container: containerRef.current,
        style: styleUrlFor(initialId, available), // local pack or remote OFM fallback
        center: EUROPE_CENTER,
        zoom: INITIAL_ZOOM,
        minZoom: MIN_ZOOM,
        maxZoom: MAX_ZOOM,
      });
      mapRef.current = map;
      // Dev/e2e hook so tests can project coordinates to screen space.
      (window as unknown as Record<string, unknown>).__flightMap = map;

      const onAirportClick = (e: maplibregl.MapLayerMouseEvent) => {
        const f = e.features?.[0];
        if (!f) return;
        const p = f.properties as { name: string; icao: string };
        new maplibregl.Popup({ offset: 10 })
          .setLngLat(f.geometry.coordinates as [number, number])
          .setHTML(
            `<div data-testid="airport-popup"><strong>${escapeHtml(p.name)}</strong><br/>${escapeHtml(p.icao)}</div>`,
          )
          .addTo(map);
      };

      const loadAirports = () => {
        if (!airportsPromiseRef.current) {
          airportsPromiseRef.current = fetch('/api/airports')
            .then((res) => {
              if (!res.ok) throw new Error(`GET /api/airports → HTTP ${res.status}`);
              return res.json() as Promise<{ features: unknown[] }>;
            })
            .then((data) => {
              setAirportCount(data.features.length); // exactly once per page life
              return data;
            });
        }
        return airportsPromiseRef.current;
      };

      // Idempotent, so it can run on EVERY styledata event: map.setStyle() removes all
      // sources/layers not in the new style, which wipes our GeoJSON layer after each
      // switch — this re-establishes it (and the initial load goes through here too).
      const ensureAirportsLayer = async () => {
        let data: { features: unknown[] };
        try {
          data = await loadAirports();
        } catch (err) {
          console.error('failed to load airports', err);
          return;
        }
        if (!map.getSource(AIRPORTS_SOURCE_ID)) {
          map.addSource(AIRPORTS_SOURCE_ID, { type: 'geojson', data });
        }
        if (!map.getLayer(AIRPORTS_LAYER_ID)) {
          map.addLayer({
            id: AIRPORTS_LAYER_ID,
            type: 'circle',
            source: AIRPORTS_SOURCE_ID,
            paint: {
              'circle-radius': 3,
              'circle-color': '#e11d48',
              'circle-stroke-width': 1,
              'circle-stroke-color': '#ffffff',
            },
          });
        }
        // Layer-scoped listeners survive setStyle (they filter by layer id at event
        // time), so off+on with the same reference re-wires without duplicating.
        map.off('click', AIRPORTS_LAYER_ID, onAirportClick);
        map.on('click', AIRPORTS_LAYER_ID, onAirportClick);
      };

      if (map.isStyleLoaded()) void ensureAirportsLayer();
      else map.on('styledata', () => void ensureAirportsLayer());
    });

    return () => {
      cancelled = true;
      delete (window as unknown as Record<string, unknown>).__flightMap;
      const map = mapRef.current; // may be null if the probe hasn't resolved yet
      mapRef.current = null;
      if (map) map.remove();
    };
  }, []);

  const onStyleChange = (e: React.ChangeEvent<HTMLSelectElement>) => {
    const id = e.target.value;
    if (!isStyleId(id)) return;
    setStyleId(id);
    window.localStorage.setItem(STYLE_STORAGE_KEY, id);
    // The probe promise is cached module-wide and has resolved by the time a user
    // interacts — this just picks local vs remote for the new style.
    void localAssetsAvailable().then((available) => mapRef.current?.setStyle(styleUrlFor(id, available)));
  };

  return (
    <div className="map-wrap">
      <header data-testid="app-header" className="app-header">
        <h1>Flight Ops</h1>
        <small>v{pkg.version}</small>
        <select
          data-testid="style-switch"
          className="style-switch"
          aria-label="Map style"
          value={styleId}
          onChange={onStyleChange}
        >
          {STYLES.map((s) => (
            <option key={s.id} value={s.id}>
              {s.label}
            </option>
          ))}
        </select>
        <span data-testid="airport-count">
          {airportCount === null ? 'loading airports…' : `${airportCount} EU airports`}
        </span>
      </header>
      <div ref={containerRef} data-testid="map" className="map-container" />
    </div>
  );
}