geowords/lib/index.js

Tool for encoding geographic coordinates as sequence of words from bip39 or other dictionary

import words from "./words/index.js";
import * as geonumber from "geonumber";
import { bip39, dictionaries } from "./words/index.js";
export { bip39, dictionaries };
export function countDictionaryBits(dict) {
    return BigInt(BigInt(dict.length).toString(2).length - 1);
}
export function prepareDictionaryFromText(text) {
    const dict = text.split(/[^\w]/).filter(x => x.length > 0).map(w => w.toLowerCase());
    for (let i = 0; i < dict.length; i++) {
        for (let j = i + 1; j < dict.length; j++) {
            if (dict[i] === dict[j]) {
                dict.splice(j, 1);
                j--;
            }
        }
    }
    return dict;
}
export function encodeNumber(number, wordsCount = 3, dict = words) {
    const wordBits = countDictionaryBits(dict);
    const words = new Array(wordsCount);
    let rest = number;
    for (let wordIndex = wordsCount - 1; wordIndex >= 0; wordIndex--) {
        const wordNumber = rest & ((1n << wordBits) - 1n);
        words[wordIndex] = dict[Number(wordNumber)];
        rest = rest >> wordBits;
    }
    return words;
}
export function decodeNumber(inputWords, dict = words) {
    const wordBits = countDictionaryBits(dict);
    let acc = 0n;
    for (let wordIndex = 0; wordIndex < inputWords.length; wordIndex++) {
        const word = inputWords[wordIndex].toLowerCase();
        const wordNumber = dict.findIndex(w => w === word);
        acc = (acc << wordBits) | BigInt(wordNumber);
    }
    return acc;
}
export function encodeLocation({ lat, lon }, wordsCount = 3, dict = words) {
    const wordBits = countDictionaryBits(dict);
    const bits = BigInt(wordsCount) * wordBits;
    const number = geonumber.encodeLocation({ lat, lon }, bits);
    return encodeNumber(number, wordsCount, dict);
}
export function decodeLocation(inputWords, dict = words) {
    const wordBits = countDictionaryBits(dict);
    const bits = BigInt(inputWords.length) * wordBits;
    const number = decodeNumber(inputWords, dict);
    return geonumber.decodeLocation(number, bits);
}
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