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* File: utils.js
* Project: geohash
* @author Nick Soggin <iSkore@users.noreply.github.com> on 19-Feb-2019
*******************************************************************************************************/
'use strict';
const
{
ENCODE_AUTO,
MIN_LNG,
MIN_LAT,
MAX_LNG,
MAX_LAT
} = require( './variables' );
/**
* isNumber
* @description
* determine if value is a valid number
* @param {number} n - value
* @return {boolean} - true if value is a number
*/
function isNumber( n ) {
return n === n && n === +n;
}
/**
* clamp
* @description
* basic number clamp
* @param {number} n - number to clamp
* @param {number} min - minimum value
* @param {number} max - maximum value
* @return {number|*} - clamped value
*/
function clamp( n, min, max ) {
return Math.min( Math.max( min, n ), max );
}
/**
* longitudeClamp
* @description
* Determines if longitude is in the realm of possibility
* If it's not, clamp the longitude value to the MIN/MAX
* @param {number} lng - longitude
* @returns {number} - longitude
*/
function longitudeClamp( lng ) {
if ( !isNumber( lng ) ) {
throw new Error( 'number required for `lng`' );
}
return clamp( lng, MIN_LNG, MAX_LNG );
}
/**
* latitudeClamp
* @description
* Determines if latitude is in the realm of possibility
* If it's not, clamp the latitude value to the MIN/MAX
* @param {number} lat - latitude
* @returns {number} - latitude
*/
function latitudeClamp( lat ) {
if ( !isNumber( lat ) ) {
throw new Error( 'number required for `lat`' );
}
return clamp( lat, MIN_LAT, MAX_LAT );
}
/**
* clampRelative
* @description
* basic relative value clamp
* @param {number} n - number to clamp
* @param {number} min - minimum value
* @param {number} max - maximum value
* @return {number|*} - clamped value or offset
*/
function clampRelative( n, min, max ) {
return isNumber( n ) ?
n > max ? min + n % max :
n < min ? max + n % max :
n : n;
}
/**
* longitudeClampRelative
* @description
* Determines if longitude is in the realm of possibility
* If it's not, return the longitude position relative to the amount offset
* @param {number} lng - longitude
* @returns {number} - longitude
*/
function longitudeClampRelative( lng ) {
if ( !isNumber( lng ) ) {
throw new Error( 'number required for `lng`' );
}
return clampRelative( lng, MIN_LNG, MAX_LNG );
}
/**
* latitudeClampRelative
* @description
* Determines if latitude is in the realm of possibility
* If it's not, return the latitude position relative to the amount offset
* @param {number} lat - latitude
* @returns {number} - latitude
*/
function latitudeClampRelative( lat ) {
if ( !isNumber( lat ) ) {
throw new Error( 'number required for `lat`' );
}
return clampRelative( lat, MIN_LAT, MAX_LAT );
}
/**
* determinePrecision
* @description
* Estimate what precision to use based on the input longitude/latitude
*
* @param {number} lng - longitude
* @param {number} lat - latitude
* @param {number?} [precision=ENCODE_AUTO] - precision override
* @returns {number} - precision estimate
*/
function determinePrecision( lng, lat, precision = ENCODE_AUTO ) {
if ( !isNumber( precision ) ) {
throw new Error( 'number required for `precision`' );
}
if ( precision === ENCODE_AUTO ) {
if ( !isNumber( lng ) ) {
throw new Error( 'number required for `lng`' );
}
else if ( !isNumber( lat ) ) {
throw new Error( 'number required for `lat`' );
}
lng = longitudeClampRelative( lng );
lat = latitudeClampRelative( lat );
if ( ~~lat === lat && ~~lng === lng ) {
precision = 0;
}
else {
const
latLen = +( lat.toString( 10 ).length ),
lngLen = +( lng.toString( 10 ).length ),
average = ( latLen + lngLen ) / 2;
precision = average >= 12 ? 12 : average;
}
}
return ~~precision;
}
function determineDirection( [ x, y ] ) {
if ( !isNumber( x ) ) {
throw new Error( 'number required for `x`' );
}
else if ( !isNumber( y ) ) {
throw new Error( 'number required for `y`' );
}
else if ( x === 0 && y === 0 ) {
return 'c';
}
else if ( !( x ^ y ) ) {
return ( x & y ) === 1 ? 'ne' : 'sw';
}
else if ( !!( x & y ) ) {
return x === 1 ? 'se' : 'nw';
}
else if ( ( x | y ) > 0 ) {
return !!x ? 'e' : 'n';
}
else {
return !!x ? 'w' : 's';
}
}
module.exports = {
isNumber,
clampRelative,
longitudeClamp,
latitudeClamp,
longitudeClampRelative,
latitudeClampRelative,
determinePrecision,
determineDirection
};
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