import { Injectable } from '../decorators'


@Injectable('urlModificationService')
export default class UrlModificationService {

	// http://stackoverflow.com/questions/5999118/add-or-update-query-string-parameter
	updateQueryStringParameter(uri: string, key: string, value: string): string {

		// construct a regex for the desired key consisting of the possible prefix character (? or &),
		// the key itself, the = and value, up to whichever separator character may exist (& # or $) or the end
		const re = new RegExp('([?&])' + key + '=.*?(&|#|$)', 'i')

		if (uri.match(re)) {
			// if the regex is found in the uri, then replace to update the value
			return uri.replace(re, '$1' + key + '=' + value + '$2')

		} else {
			// if the regex is not found in the uri
			// first, check for the presence of a hash in the uri and adjust if needed
			let hash = ''
			if ( uri.indexOf('#') !== -1 ) {
				hash = uri.replace(/.*#/, '#')
				uri = uri.replace(/#.*/, '')
			}

			// determine which parameter prefix character to use
			const separator = uri.indexOf('?') !== -1 ? '&' : '?'
			// and append the key and value
			return uri + separator + key + '=' + value + hash
		}
	}
}