/**
* @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 isBoolean = require( '@stdlib/assert/is-boolean' ).isPrimitive;
var getThis = require( './codegen.js' );
var Self = require( './self.js' );
var Win = require( './window.js' );
var Global = require( './global.js' );


// MAIN //

/**
* Returns the global object.
*
* ## Notes
*
* -   Using code generation is the **most** reliable way to resolve the global object; however, doing so is likely to violate content security policies (CSPs) in, e.g., Chrome Apps and elsewhere.
*
* @param {boolean} [codegen=false] - boolean indicating whether to use code generation to resolve the global object
* @throws {TypeError} must provide a boolean
* @throws {Error} unable to resolve global object
* @returns {Object} global object
*
* @example
* var g = getGlobal();
* // returns {...}
*/
function getGlobal( codegen ) {
	if ( arguments.length ) {
		if ( !isBoolean( codegen ) ) {
			throw new TypeError( 'invalid argument. Must provide a boolean primitive. Value: `'+codegen+'`.' );
		}
		if ( codegen ) {
			return getThis();
		}
		// Fall through...
	}
	// Case: browsers and web workers
	if ( Self ) {
		return Self;
	}
	// Case: browsers
	if ( Win ) {
		return Win;
	}
	// Case: Node.js
	if ( Global ) {
		return Global;
	}
	// Case: unknown
	throw new Error( 'unexpected error. Unable to resolve global object.' );
}


// EXPORTS //

module.exports = getGlobal;
