/**
* @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';

/**
* Tests that a value is a valid constructor.
*
* @private
* @param {*} value - value to test
* @returns {(Error|null)} error object or null
*
* @example
* var ctor = function ctor() {};
*
* var err = validate( ctor );
* // returns null
*
* err = validate( null );
* // returns <TypeError>
*/
function validate( value ) {
	var type = typeof value;
	if (
		value === null ||
		(type !== 'object' && type !== 'function')
	) {
		return new TypeError( 'invalid argument. A provided constructor must be either an object (except null) or a function. Value: `'+value+'`.' );
	}
	return null;
}


// EXPORTS //

module.exports = validate;