digipinjs
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A comprehensive TypeScript library for encoding and decoding Indian geographic coordinates into DIGIPIN format (Indian Postal Digital PIN system). Features CLI tools, caching, batch processing, and Express middleware for seamless integration.
74 lines (73 loc) • 2.7 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.getDigiPin = getDigiPin;
exports.getLatLngFromDigiPin = getLatLngFromDigiPin;
const DIGIPIN_GRID = [
['F', 'C', '9', '8'],
['J', '3', '2', '7'],
['K', '4', '5', '6'],
['L', 'M', 'P', 'T']
];
const BOUNDS = { minLat: 2.5, maxLat: 38.5, minLon: 63.5, maxLon: 99.5 };
/**
* Encode latitude & longitude into DIGIPIN
*/
function getDigiPin(lat, lon) {
if (lat < BOUNDS.minLat || lat > BOUNDS.maxLat)
throw new Error('Latitude out of range');
if (lon < BOUNDS.minLon || lon > BOUNDS.maxLon)
throw new Error('Longitude out of range');
let [minLat, maxLat, minLon, maxLon] = [BOUNDS.minLat, BOUNDS.maxLat, BOUNDS.minLon, BOUNDS.maxLon];
let code = '';
for (let level = 1; level <= 10; level++) {
const latStep = (maxLat - minLat) / 4;
const lonStep = (maxLon - minLon) / 4;
let row = 3 - Math.floor((lat - minLat) / latStep);
let col = Math.floor((lon - minLon) / lonStep);
row = Math.min(3, Math.max(0, row));
col = Math.min(3, Math.max(0, col));
code += DIGIPIN_GRID[row][col];
if (level === 3 || level === 6)
code += '-';
maxLat = minLat + latStep * (4 - row);
minLat = minLat + latStep * (3 - row);
minLon = minLon + lonStep * col;
maxLon = minLon + lonStep;
}
return code;
}
/**
* Decode DIGIPIN back to lat/lon center
*/
function getLatLngFromDigiPin(pin) {
const clean = pin.replace(/-/g, '');
if (clean.length !== 10)
throw new Error('Invalid DIGIPIN');
let [minLat, maxLat, minLon, maxLon] = [BOUNDS.minLat, BOUNDS.maxLat, BOUNDS.minLon, BOUNDS.maxLon];
for (const char of clean) {
let found = false;
let ri = 0, ci = 0;
for (let r = 0; r < 4; r++) {
for (let c = 0; c < 4; c++) {
if (DIGIPIN_GRID[r][c] === char) {
ri = r;
ci = c;
found = true;
break;
}
}
if (found)
break;
}
if (!found)
throw new Error('Invalid character');
const latStep = (maxLat - minLat) / 4;
const lonStep = (maxLon - minLon) / 4;
const newMaxLat = minLat + latStep * (4 - ri);
const newMinLat = minLat + latStep * (3 - ri);
const newMinLon = minLon + lonStep * ci;
const newMaxLon = newMinLon + lonStep;
[minLat, maxLat, minLon, maxLon] = [newMinLat, newMaxLat, newMinLon, newMaxLon];
}
return { latitude: (minLat + maxLat) / 2, longitude: (minLon + maxLon) / 2 };
}