30 lines
1.2 KiB
TypeScript
30 lines
1.2 KiB
TypeScript
/** Haversine distance between two lat/lng points, in kilometres. */
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export function distanceKm(
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lat1: number, lon1: number,
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lat2: number, lon2: number
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): number {
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const R = 6371;
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const dLat = ((lat2 - lat1) * Math.PI) / 180;
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const dLon = ((lon2 - lon1) * Math.PI) / 180;
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const a =
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Math.sin(dLat / 2) ** 2 +
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Math.cos((lat1 * Math.PI) / 180) *
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Math.cos((lat2 * Math.PI) / 180) *
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Math.sin(dLon / 2) ** 2;
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return R * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
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}
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export function formatDistance(km: number): string {
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return km < 1 ? `${Math.round(km * 1000)} m` : `${km.toFixed(0)} km`;
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}
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/** Geocode an Indian pincode to lat/lng using Nominatim (free, no key). */
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export async function geocodePincode(pincode: string): Promise<{ lat: number; lng: number } | null> {
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try {
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const url = `https://nominatim.openstreetmap.org/search?postalcode=${encodeURIComponent(pincode)}&countrycodes=in&format=json&limit=1`;
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const res = await fetch(url, { headers: { "User-Agent": "PelagiaPortal/1.0" } });
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const data = await res.json();
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if (data[0]) return { lat: parseFloat(data[0].lat), lng: parseFloat(data[0].lon) };
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} catch { /* ignore */ }
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return null;
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}
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