encode&decode

// compression.js
const defaultPrecision = 10;

const encode = (a, b, mPrecision=defaultPrecision) => {
	const precision = mPrecision;
	const base = Math.floor(Math.sqrt(Math.pow(93, precision)));

	let lat = a, lng = b;
	let lng935 = Math.floor( ( parseFloat(lng) +180)*base/360 );
	let lat935 = Math.floor( ( parseFloat(lat) +90)*base/180 );
	let result = lat935*base+lng935;
	let code = "", sub, rank = 0; 

	for (let i=0; i<precision; i++) {
		sub = Math.floor( result/Math.pow(93, i) )%93; 
		code += String.fromCharCode(33 + sub);
	}

	return code;
}


const decode = (str, mPrecision=defaultPrecision) => {
	const precision = mPrecision;
	const base = Math.floor(Math.sqrt(Math.pow(93, precision)));

	let result = 0;
	for (let i=0; i<precision; i++) {
		result += ( str.charCodeAt(i)-33 )*Math.pow(93, i);
	}

	let lngBis = ( ( result%base )*360/base )-180;
	let latBis = ( (result-lngBis*base)*180/base )/base-90;

	return [latBis, lngBis];
}



module.exports = {
	encode,
	decode
}