Angular2/Ionic2 Helper

helpers.ts

import {$log} from "./$log";
import {jsObjectPrettyPrint} from "./js-object-pretty-print";


/**
 * try to avoid circular references
 * @param obj
 * @returns {string}
 */
export function jStringify(obj) {
	return jsObjectPrettyPrint(obj);
}


/**
 * programmatically open external browser
 * @param url
 */
export function openExternal(url) {
	$log.debug('openExternal',url);
	window.open( url, '_system', 'location=yes');
	return;
}


/**
 * Simple transparent image
 */
export const TRANSPARENT_GIF = 'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7';
export const BLACK_GIF = 'data:image/gif;base64,R0lGODlhAQABAIAAAAUEBAAAACwAAAAAAQABAAACAkQBADs=';


export function to_radians(degrees:number): number {
	return degrees * Math.PI / 180;
}


/**
 *
 * @param lat1
 * @param lon1
 * @param lat2
 * @param lon2
 * @returns {number} metri
 */
export function approximate_distance(lat1:number,lon1:number,lat2:number,lon2:number): number {
	 let x = to_radians(lon2 - lon1) * Math.cos( to_radians(lat2+lat1)/2 );
	 let y = to_radians(lat2 - lat1);
	 return 6371 * 1000 * Math.sqrt( (x*x) + (y*y) );
}


// TODO to be tested
function geo_distance(lat1:number,lon1:number,lat2:number,lon2:number): number {
	let R = 6378137;
	let dLat = to_radians(lat2 - lat1);
	let dLong = to_radians(lon2 - lon1);
	let rlat1 = to_radians(lat1);
	let rlat2 = to_radians(lat2);
	let a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
		Math.cos(rlat1) * Math.cos(rlat2) *
		Math.sin(dLong/2) * Math.sin(dLong/2);
	let c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
	return R * c;
}


export function AgxGetImage(url): Promise<HTMLImageElement>{
	return new Promise(function(resolve, reject){
		let img = new Image();
		img.onload = function(){
			resolve(img);
		};
		img.onerror = function(err){
			$log.error('AgxGetImage', err);
			reject(err)
		};
		img.src = url;
	});
}


export function AgxGetImageDataUrl(url): Promise<string>{
	return new Promise(function(resolve, reject){
		let img = new Image();
		img.onload = function(){
			$log.debug('img load ok', url);
			let canvas = document.createElement('canvas');
			canvas.width = img.width;
			canvas.height = img.height;
			let ctx = canvas.getContext("2d");
			ctx.drawImage(img, 0, 0);
			try{
				let data = canvas.toDataURL();
				return resolve(data);
			}catch(e){
				$log.error('AgxGetImageDataUrl Exception',e);
				return reject(e);
			}
		};
		img.onerror = function(err){
			return reject(err)
		};
		// start
		img.setAttribute('crossOrigin', 'anonymous');
		img.src = url;
	});
}


export function DateFromItalian(d:string): Date {
	if (!d || d=='') return null;
	let parts = d.split("/");
	return new Date(
		parseInt(parts[2], 10),
		parseInt(parts[1], 10)-1,
		parseInt(parts[0], 10)
	);
}


export function DateToIsoString(d:Date):string {
	if (!d) return null;
	let mn: number = d.getMonth()+1;
	let ms: string = mn<10 ? ('0'+mn) : mn.toString();
	let dn: number = d.getDate();
	let ds: string = dn<10 ? ('0'+dn) : dn.toString();
	return d.getFullYear()+'-'+ms+'-'+ds;
}