import { WALKING_ICON } from "/js/icons.js";
import { firstSymbolLayerId } from "/js/radar.js";
import { escapeHtml } from "/js/gpx.js";
import { lineLength, formatDistance } from "/js/measure.js";

// Overpass has permissive CORS (verified: Access-Control-Allow-Origin: *),
// so this queries it directly from the browser — no server-side proxy
// needed, same "public API, no key" story as the Nominatim search already
// hits from here. One query per click (not per pan/move like the
// Wikipedia layer's live refetch), so this stays well within Overpass's
// shared rate limits.
//
// Three independent public mirrors (also CORS-open, verified), raced with
// Promise.any rather than called one at a time — the shared free instances
// vary a lot in load from one moment to the next, and a multi-second wait
// on a single one was the main complaint. Whichever answers first wins;
// the others are simply left to finish and get GC'd, not worth the extra
// AbortController plumbing for a single one-off per-click request.
const OVERPASS_APIS = [
  "https://overpass-api.de/api/interpreter",
  "https://overpass.kumi.systems/api/interpreter",
  "https://overpass.private.coffee/api/interpreter",
];
const CLICK_RADIUS_M = 40;
// OSM colour tag values are free text (untrusted) — only used as a CSS
// background if they look like an actual color (hex or a plain word),
// never interpolated unchecked into a style attribute.
const SAFE_COLOR = /^(#[0-9a-fA-F]{3,8}|[a-zA-Z]+)$/;

// Pre-rendered raster tiles, not vector — waymarkedtrails.org already
// colors each route by its OSM `colour` tag (the KST/KČT-style paint-blaze
// colors used in Slovakia/Czechia), falling back to plain red where a route
// has none, so there's no styling to do here ourselves. Used whenever no
// offline extract is available at all — same "quietly renders nothing
// without a network" story as the Wikipedia/Radar/Contour lines overlays.
const ONLINE_SOURCE_ID = "hiking-trails-online";
const ONLINE_LAYER_ID = "hiking-trails-online-line";
const TILE_URL = "https://tile.waymarkedtrails.org/hiking/{z}/{x}/{y}.png";
const ATTRIBUTION =
  'Trails &copy; <a href="https://waymarkedtrails.org" target="_blank">Waymarked Trails</a> (CC-BY-SA), map data &copy; OpenStreetMap contributors';
const OPACITY = 0.85;

// Offline: one real vector line layer per country the viewer actually
// picks, GeoJSON generated at build time by Maptool::HikingTrails straight
// from the same Geofabrik .osm.pbf offline.pmtiles itself is built from
// (see lib/maptool/hiking_trails.rb, PmtilesBuilder.extract_hiking_trails)
// — no network needed, and no waiting on Overpass for click details either
// (queried locally via queryRenderedFeatures instead, see _handleClick
// below). One file per country rather than one combined file: a viewer
// covering a dozen countries' worth of offline map data rarely wants all
// of their hiking trails loaded at once, so this is opt-in per country
// instead.
function offlineSourceId(code) {
  return `hiking-trails-offline-${code}`;
}
function offlineLayerId(code) {
  return `hiking-trails-offline-${code}-line`;
}
function offlineUrl(code) {
  return `/tiles/hiking_trails/${code}.geojson`;
}

// waymarkedtrails.org's own fallback for an untagged route.
const DEFAULT_TRAIL_COLOR = "#c1272d";
// Real-world `colour` values seen in production data (see the 2026-09-13
// extraction against SK.osm.pbf) — anything outside this set (typos like
// "yelllow", multi-value combos like "blue, yellow", stray hex codes) falls
// back to DEFAULT_TRAIL_COLOR rather than being trusted as a CSS value
// straight from OSM tag text.
const KNOWN_TRAIL_COLORS = new Set(["red", "yellow", "blue", "green", "orange", "purple", "brown", "black", "white", "grey", "gray", "darkblue"]);

function normalizedTrailColor(raw) {
  if (!raw) return DEFAULT_TRAIL_COLOR;
  const trimmed = raw.trim();
  if (KNOWN_TRAIL_COLORS.has(trimmed.toLowerCase())) return trimmed.toLowerCase();
  return /^#[0-9a-fA-F]{3,8}$/.test(trimmed) ? trimmed : DEFAULT_TRAIL_COLOR;
}

// A highlight outline for whichever route(s) the last click matched — drawn
// as its own separate source/layer (real geometry, from either the offline
// vector feature or the online Overpass response) rather than a paint-
// property change on the base layer, since the online raster tiles have no
// paintable features to highlight at all. Same "yellow outline on a picked
// route" treatment the earlier SVG prototype visualization used.
const HIGHLIGHT_SOURCE_ID = "hiking-trails-highlight";
const HIGHLIGHT_LAYER_ID = "hiking-trails-highlight-line";

// An Overlays panel item — a plain on/off checkbox (raster overlay) until
// offline extracts exist for at least one country, at which point it
// becomes an expandable per-country checklist instead (same expand shape
// as RadarControl), since a viewer with a dozen countries' worth of
// offline map data rarely wants all of their hiking trails loaded, let
// alone parsed by the browser, at once.
export class HikingTrailsControl {
  constructor(map) {
    this._map = map;
    this._active = false; // the online-mode checkbox's own state
    this._offlineCountries = []; // codes with an extract available on the server
    this._selectedCountries = new Set(); // codes currently shown, offline mode

    map.on("click", (event) => this._handleClick(event));

    this._panel = document.getElementById("trail-panel");
    this._panelBody = this._panel.querySelector(".trail-panel__body");
    this._panel.querySelector(".trail-panel__close").addEventListener("click", () => this._hidePanel());

    // setStyle() (switching Online/Offline) tears down all custom sources/
    // layers — put whatever was showing back, same as every other
    // Overlays control. The highlight is transient (tied to whichever
    // trail is showing in the panel, if any) — simpler to just drop it
    // here than try to carry it across a style swap.
    map.on("style.load", () => {
      if (this._active) this._addOnlineLayer();
      for (const code of this._selectedCountries) this._addOfflineLayer(code);
      this._clearHighlight();
    });
  }

  mount(li) {
    li.innerHTML = `
      <div class="overlays-panel__row">
        <input type="checkbox" class="overlays-panel__toggle">
        <span class="overlays-panel__icon">${WALKING_ICON}</span>
        <button type="button" class="overlays-panel__name">Hiking trails</button>
      </div>
      <div class="overlays-panel__details" hidden>
        <ul class="hiking-trail-countries"></ul>
      </div>
    `;
    this._checkbox = li.querySelector(".overlays-panel__toggle");
    this._nameButton = li.querySelector(".overlays-panel__name");
    this._details = li.querySelector(".overlays-panel__details");
    this._countryList = li.querySelector(".hiking-trail-countries");

    this._checkbox.addEventListener("change", (event) => this._toggleOnline(event.target.checked));
    this._nameButton.addEventListener("click", () => {
      if (this._offlineCountries.length === 0) return; // nothing to expand into yet
      const expanding = this._details.hidden;
      this._details.hidden = !expanding;
      this._nameButton.setAttribute("aria-expanded", String(expanding));
    });
  }

  // Called once map.js's GET /api/hiking-trails check resolves. Switches
  // this item from "online raster, plain on/off" to "offline vector,
  // pick your countries" — the two are mutually exclusive rather than
  // both offered at once, since once a real local extract exists there's
  // no reason to still fall back to a third-party tile server for any of
  // it.
  setOfflineCountries(countries) {
    this._offlineCountries = countries;
    if (countries.length === 0) return;

    if (this._active) this._toggleOnline(false);
    this._checkbox.hidden = true;

    this._countryList.innerHTML = countries
      .map(
        (code) => `
          <li class="hiking-trail-countries__item">
            <label>
              <input type="checkbox" class="hiking-trail-countries__toggle" value="${code}">
              ${code}
            </label>
          </li>
        `,
      )
      .join("");
    this._countryList.querySelectorAll(".hiking-trail-countries__toggle").forEach((input) => {
      input.addEventListener("change", (event) => this._toggleCountry(event.target.value, event.target.checked));
    });
  }

  _toggleOnline(active) {
    this._active = active;
    if (active) this._addOnlineLayer();
    else this._removeOnlineLayer();
  }

  _toggleCountry(code, active) {
    if (active) {
      this._selectedCountries.add(code);
      this._addOfflineLayer(code);
    } else {
      this._selectedCountries.delete(code);
      this._removeOfflineLayer(code);
    }
  }

  _handleClick(event) {
    if (this._selectedCountries.size > 0) this._handleOfflineClick(event);
    else if (this._active) this._handleOnlineClick(event);
  }

  // The local vector layers have real features to hit-test directly — no
  // network round-trip, so this resolves instantly. A genuine miss (empty
  // result) just closes an already-open panel rather than showing a "not
  // found" message, same as clicking empty space anywhere else on the map.
  _handleOfflineClick(event) {
    const layers = [...this._selectedCountries].map(offlineLayerId).filter((id) => this._map.getLayer(id));
    if (layers.length === 0) return;

    const features = this._map.queryRenderedFeatures(event.point, { layers });
    if (features.length === 0) {
      this._hidePanel();
      return;
    }

    const matched = features.filter((feature, i) => features.findIndex((f) => f.properties.id === feature.properties.id) === i);
    const html = matched.map((feature) => routeHtml(feature.properties)).join("<hr>");
    this._setHighlight(matched.map((feature) => ({ geometry: feature.geometry, color: feature.properties.color })));
    this._showPanel(html);
  }

  _showPanel(html) {
    this._panelBody.innerHTML = html;
    this._panel.hidden = false;
  }

  _hidePanel() {
    if (this._panel.hidden) return;
    this._panel.hidden = true;
    this._clearHighlight();
  }

  // The raster tiles have no queryable features (they're pixels), so
  // "what trail is this" is answered with a one-off Overpass query instead
  // of a MapLibre feature hit-test — an `around` search rather than an
  // exact point match, since a click rarely lands exactly on the (already
  // pixel-thick) rendered line.
  async _handleOnlineClick(event) {
    const { lng, lat } = event.lngLat;
    this._showPanel(`<p class="gpx-popup__category">Looking for trails…</p>`);
    // A newer click's request replaces this one while Overpass is still
    // answering — same "in-flight response arrives after it's already
    // stale" guard the old Popup-identity check gave, just keyed off a
    // fresh token each click instead of a fresh Popup instance.
    const request = (this._onlineRequest = {});

    let relations;
    try {
      relations = await fetchNearbyRoutes(lng, lat);
    } catch {
      if (this._onlineRequest === request) this._panelBody.innerHTML = `<p class="gpx-popup__category">Could not reach Overpass.</p>`;
      return;
    }
    if (this._onlineRequest !== request) return;

    if (relations.length === 0) {
      this._panelBody.innerHTML = `<p class="gpx-popup__category">No hiking trail found here.</p>`;
      return;
    }
    this._panelBody.innerHTML = relations.map((relation) => routeHtml(overpassRouteInfo(relation))).join("<hr>");
    this._setHighlight(relations.map((relation) => ({ geometry: routeGeometry(relation), color: normalizedTrailColor(relation.tags?.colour) })));
  }

  _addOnlineLayer() {
    if (this._map.getSource(ONLINE_SOURCE_ID)) return;

    this._map.addSource(ONLINE_SOURCE_ID, {
      type: "raster",
      tiles: [TILE_URL],
      tileSize: 256,
      maxzoom: 17,
      attribution: ATTRIBUTION,
    });
    // Below labels (same firstSymbolLayerId spot contour.js/radar.js use),
    // so place names/POI icons stay readable on top of the trail lines.
    this._map.addLayer(
      { id: ONLINE_LAYER_ID, type: "raster", source: ONLINE_SOURCE_ID, paint: { "raster-opacity": OPACITY } },
      firstSymbolLayerId(this._map),
    );
  }

  _removeOnlineLayer() {
    if (this._map.getLayer(ONLINE_LAYER_ID)) this._map.removeLayer(ONLINE_LAYER_ID);
    if (this._map.getSource(ONLINE_SOURCE_ID)) this._map.removeSource(ONLINE_SOURCE_ID);
  }

  async _addOfflineLayer(code) {
    if (this._map.getSource(offlineSourceId(code))) return;

    let geojson;
    try {
      geojson = await (await fetch(offlineUrl(code))).json();
    } catch {
      return; // degrade quietly, same story as every other optional layer here
    }
    // Toggled back off, or the base map switched, while this was fetching.
    if (!this._selectedCountries.has(code) || this._map.getSource(offlineSourceId(code))) return;

    // Normalized once here (rather than a MapLibre expression in the paint
    // property below) so an untrustworthy `colour` tag value never reaches
    // a style property directly — same reasoning gpx.js's own
    // feature.properties.color ||= TRACK_COLOR normalization gives.
    for (const feature of geojson.features) {
      feature.properties.color = normalizedTrailColor(feature.properties.colour);
    }

    this._map.addSource(offlineSourceId(code), { type: "geojson", data: geojson });
    this._map.addLayer(
      {
        id: offlineLayerId(code),
        type: "line",
        source: offlineSourceId(code),
        layout: { "line-cap": "round", "line-join": "round" },
        paint: { "line-color": ["get", "color"], "line-width": 2 },
      },
      firstSymbolLayerId(this._map),
    );
  }

  _removeOfflineLayer(code) {
    if (this._map.getLayer(offlineLayerId(code))) this._map.removeLayer(offlineLayerId(code));
    if (this._map.getSource(offlineSourceId(code))) this._map.removeSource(offlineSourceId(code));
  }

  // features: an array of { geometry, color } — geometry a GeoJSON
  // LineString or MultiLineString (mixed is fine), color the trail's own
  // (already-normalized) colour — everything the last click matched, drawn
  // as one highlight layer (a wider outline in the trail's own color,
  // rather than a fixed color that would repaint it) on top of the base
  // trail rendering.
  _setHighlight(features) {
    const data = {
      type: "FeatureCollection",
      features: features.map(({ geometry, color }) => ({ type: "Feature", properties: { color }, geometry })),
    };
    const source = this._map.getSource(HIGHLIGHT_SOURCE_ID);
    if (source) {
      source.setData(data);
      return;
    }
    this._map.addSource(HIGHLIGHT_SOURCE_ID, { type: "geojson", data });
    this._map.addLayer({
      id: HIGHLIGHT_LAYER_ID,
      type: "line",
      source: HIGHLIGHT_SOURCE_ID,
      layout: { "line-cap": "round", "line-join": "round" },
      paint: { "line-color": ["get", "color"], "line-width": 5, "line-opacity": 0.9 },
    });
  }

  _clearHighlight() {
    if (this._map.getLayer(HIGHLIGHT_LAYER_ID)) this._map.removeLayer(HIGHLIGHT_LAYER_ID);
    if (this._map.getSource(HIGHLIGHT_SOURCE_ID)) this._map.removeSource(HIGHLIGHT_SOURCE_ID);
  }
}

// way(around:...) finds candidate ways near the click, then rel(bw...)
// walks backward from those to their parent relations — the same
// find-the-way-then-its-relation shape as clicking a route on
// waymarkedtrails.org's own site. `out geom` inlines each member way's
// full coordinate list right on the relation, so no separate stitching
// step is needed to get real geometry back.
async function queryOverpass(url, query) {
  const response = await fetch(url, { method: "POST", body: `data=${encodeURIComponent(query)}` });
  if (!response.ok) throw new Error(`overpass ${response.status}`);
  return response.json();
}

async function fetchNearbyRoutes(lng, lat) {
  const query = `[out:json][timeout:15];way(around:${CLICK_RADIUS_M},${lat},${lng})->.w;rel(bw.w)["route"="hiking"];out geom;`;
  const data = await Promise.any(OVERPASS_APIS.map((url) => queryOverpass(url, query)));
  return (data.elements || []).filter((element) => element.type === "relation");
}

// OSM doesn't tag a route's length directly — summed from each member
// way's own geometry instead, same haversine-sum measure.js's own Measure
// tool uses for a hand-drawn line. Shared endpoints between adjacent ways
// get walked twice, same as how a real hike over those ways would. Mirrors
// Maptool::HikingTrails.relation_feature's own distance calc server-side
// (lib/maptool/hiking_trails.rb) — this is the online, no-server-file path.
function routeDistance(relation) {
  return (relation.members || [])
    .filter((member) => member.type === "way" && member.geometry)
    .reduce((total, member) => total + lineLength(member.geometry.map((point) => [point.lon, point.lat])), 0);
}

// Same member-way walk as routeDistance above, collecting coordinates
// instead of summing them — the online click highlight's geometry source,
// since there's no vector feature to read it back from the way the offline
// layer's own queryRenderedFeatures result already carries one.
function routeGeometry(relation) {
  const lines = (relation.members || [])
    .filter((member) => member.type === "way" && member.geometry)
    .map((member) => member.geometry.map((point) => [point.lon, point.lat]));
  return { type: "MultiLineString", coordinates: lines };
}

// Adapts a raw Overpass relation into the same shape offline GeoJSON
// features' properties already carry (lib/maptool/hiking_trails.rb's own
// ROUTE_TAGS + distance_meters + id) — one HTML builder (routeHtml) below
// serves both instead of two near-identical ones.
function overpassRouteInfo(relation) {
  const tags = relation.tags || {};
  return {
    id: relation.id,
    name: tags.name,
    description: tags.description,
    colour: tags.colour,
    network: tags.network,
    operator: tags.operator,
    ref: tags.ref,
    distance_meters: routeDistance(relation),
  };
}

function routeHtml(info) {
  const name = info.name || info.description || "Hiking trail";
  const swatch = SAFE_COLOR.test(info.colour || "")
    ? `<span class="hiking-trail-popup__swatch" style="background:${info.colour}"></span>`
    : "";
  const meta = [formatDistance(info.distance_meters || 0)];
  if (info.ref) meta.push(`#${info.ref}`);
  if (info.network) meta.push(info.network);
  if (info.operator) meta.push(escapeHtml(info.operator));

  const parts = [
    `<div class="gpx-popup__header"><strong>${escapeHtml(name)}</strong>${swatch}</div>`,
    `<p class="gpx-popup__category">${meta.filter(Boolean).join(" · ")}</p>`,
  ];
  // description already used as the title above when there's no name — only
  // shown again here as its own line if there both is a name *and* a
  // description to add, so it's never rendered twice for the common
  // no-name case.
  if (info.name && info.description) parts.push(`<p class="gpx-popup__description">${escapeHtml(info.description)}</p>`);
  parts.push(
    `<p class="gpx-popup__link"><a href="https://www.openstreetmap.org/relation/${info.id}" target="_blank" rel="noopener noreferrer">View on OpenStreetMap →</a></p>`,
  );
  return parts.join("");
}