const DEFAULT_OVERPASS_URL = 'https://overpass-api.de/api/interpreter';
const METERS_PER_MILE = 1609.344;
const MIN_RADIUS_MILES = 1;
const MAX_RADIUS_MILES = 50;
const DEFAULT_RADIUS_MILES = 25;

const ALLOWED_HOSTS = new Set(['overpass-api.de', 'overpass.kumi.systems']);

function assertAllowedHost(url) {
  const host = new URL(url).hostname.toLowerCase();
  if (!ALLOWED_HOSTS.has(host)) {
    throw new Error(`[overpass] Host not allowlisted: ${host}`);
  }
}

/**
 * @param {number} miles
 * @returns {number}
 */
export function clampRadiusMiles(miles) {
  const value = Number(miles);
  if (!Number.isFinite(value)) {
    return DEFAULT_RADIUS_MILES;
  }
  return Math.min(MAX_RADIUS_MILES, Math.max(MIN_RADIUS_MILES, value));
}

/**
 * @param {number} miles
 * @returns {number}
 */
export function milesToMeters(miles) {
  return Math.round(clampRadiusMiles(miles) * METERS_PER_MILE);
}

/**
 * Build Overpass QL from validated numeric inputs only — never user strings.
 * @param {{ lat: number, lng: number, radiusMeters: number }} params
 * @returns {string}
 */
export function buildOverpassQuery({ lat, lng, radiusMeters }) {
  const safeLat = Number(lat);
  const safeLng = Number(lng);
  const safeRadius = Math.round(Number(radiusMeters));

  if (!Number.isFinite(safeLat) || !Number.isFinite(safeLng) || !Number.isFinite(safeRadius)) {
    throw new Error('[overpass] Invalid numeric query parameters');
  }
  if (safeRadius < 1 || safeRadius > Math.round(MAX_RADIUS_MILES * METERS_PER_MILE)) {
    throw new Error('[overpass] Radius out of bounds');
  }

  return `[out:json][timeout:25];
(
  node["shop"="games"](around:${safeRadius},${safeLat},${safeLng});
  node["shop"="hobby"](around:${safeRadius},${safeLat},${safeLng});
  way["shop"="games"](around:${safeRadius},${safeLat},${safeLng});
  way["shop"="hobby"](around:${safeRadius},${safeLat},${safeLng});
);
out center tags;`;
}

function formatAddress(tags) {
  const parts = [
    tags['addr:housenumber'],
    tags['addr:street'],
    tags['addr:city'],
    tags['addr:state'],
    tags['addr:postcode'],
  ].filter(Boolean);
  if (parts.length > 0) {
    return parts.join(', ');
  }
  return tags['addr:full'] ?? '';
}

function elementCoords(element) {
  if (element.type === 'node' && element.lat != null && element.lon != null) {
    return { lat: Number(element.lat), lng: Number(element.lon) };
  }
  if (element.center?.lat != null && element.center?.lon != null) {
    return { lat: Number(element.center.lat), lng: Number(element.center.lon) };
  }
  return null;
}

function osmUrl(element) {
  const type = element.type === 'node' ? 'node' : 'way';
  return `https://www.openstreetmap.org/${type}/${element.id}`;
}

/**
 * @param {unknown} data
 * @param {{ originLat: number, originLng: number }} origin
 * @returns {Array<{
 *   id: string,
 *   name: string,
 *   address: string,
 *   lat: number,
 *   lng: number,
 *   distanceMiles: number,
 *   phone: string | null,
 *   website: string | null,
 *   osmUrl: string,
 * }>}
 */
export function parseOverpassResponse(data, { originLat, originLng }) {
  const elements = data?.elements;
  if (!Array.isArray(elements)) {
    return [];
  }

  const stores = [];

  for (const element of elements) {
    const tags = element.tags ?? {};
    const name = tags.name;
    if (!name) continue;

    const coords = elementCoords(element);
    if (!coords || !Number.isFinite(coords.lat) || !Number.isFinite(coords.lng)) {
      continue;
    }

    stores.push({
      id: `${element.type}/${element.id}`,
      name,
      address: formatAddress(tags),
      lat: coords.lat,
      lng: coords.lng,
      distanceMiles: haversineMiles(originLat, originLng, coords.lat, coords.lng),
      phone: tags.phone ?? tags['contact:phone'] ?? null,
      website: tags.website ?? tags['contact:website'] ?? null,
      osmUrl: osmUrl(element),
    });
  }

  stores.sort((a, b) => a.distanceMiles - b.distanceMiles);
  return stores;
}

/**
 * @param {number} lat
 * @param {number} lng
 * @param {number} radiusMeters
 * @param {{ fetchImpl?: typeof fetch }} [options]
 * @returns {Promise<ReturnType<typeof parseOverpassResponse>>}
 */
export async function fetchGameStores(lat, lng, radiusMeters, { fetchImpl = fetch } = {}) {
  const endpoint = process.env.OVERPASS_URL ?? DEFAULT_OVERPASS_URL;
  assertAllowedHost(endpoint);

  const query = buildOverpassQuery({ lat, lng, radiusMeters });
  const response = await fetchImpl(endpoint, {
    method: 'POST',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    body: `data=${encodeURIComponent(query)}`,
  });

  if (!response.ok) {
    throw new Error(`[overpass] HTTP ${response.status}`);
  }

  const data = await response.json();
  return parseOverpassResponse(data, { originLat: lat, originLng: lng });
}

function haversineMiles(lat1, lng1, lat2, lng2) {
  const toRad = (deg) => (deg * Math.PI) / 180;
  const dLat = toRad(lat2 - lat1);
  const dLng = toRad(lng2 - lng1);
  const a =
    Math.sin(dLat / 2) ** 2 +
    Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) * Math.sin(dLng / 2) ** 2;
  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  const earthRadiusMiles = 3958.8;
  return Math.round(c * earthRadiusMiles * 10) / 10;
}