/**
* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*    http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

'use strict';

// MODULES //

var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
var replace = require( './../../replace' );
var format = require( './../../format' );


// VARIABLES //

// The following regular expression should suffice to polyfill (most?) all environments.
var RE = /^[\u0020\f\n\r\t\v\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]+/;


// MAIN //

/**
* Trims whitespace characters from the beginning of a string.
*
* @param {string} str - input string
* @throws {TypeError} must provide a string primitive
* @returns {string} trimmed string
*
* @example
* var out = ltrim( '   Whitespace   ' );
* // returns 'Whitespace   '
*
* @example
* var out = ltrim( '\t\t\tTabs\t\t\t' );
* // returns 'Tabs\t\t\t'
*
* @example
* var out = ltrim( '\n\n\nNew Lines\n\n\n' );
* // returns 'New Lines\n\n\n'
*/
function ltrim( str ) {
	if ( !isString( str ) ) {
		throw new TypeError( format( 'invalid argument. Must provide a string. Value: `%s`.', str ) );
	}
	return replace( str, RE, '' );
}


// EXPORTS //

module.exports = ltrim;