text: 'use strict';
  
  // MODULES //
  
  var isObject = require( 'validate.io-object' );
  var isString = require( 'validate.io-string-primitive' );
  
  
  // VALIDATE //
  
  /**
  * FUNCTION: validate( opts, options )
  *	Validates function options.
  *
  * @param {Object} opts - destination object
  * @param {Object} options - options to validate
  * @param {String} [options.token] - Github access token
  * @param {String} [options.username] - Github username
  * @param {String} [options.useragent] - user agent string
  * @param {String} [options.state] - state of memberships to return
  * @returns {Error|Null} error or null
  */
  function validate( opts, options ) {
  	if ( !isObject( options ) ) {
  		return new TypeError( 'invalid input argument. Options argument must be an object. Value: `' + options + '`.' );
  	}
  	if ( options.hasOwnProperty( 'token' ) ) {
  		opts.token = options.token;
  		if ( !isString( opts.token ) ) {
  			return new TypeError( 'invalid option. Token option must be a string primitive. Option: `' + opts.token + '`.' );
  		}
  	}
  	if ( options.hasOwnProperty( 'username' ) ) {
  		opts.username = options.username;
  		if ( !isString( opts.username ) ) {
  			return new TypeError( 'invalid option. Username option must be a string primitive. Option: `' + opts.username + '`.' );
  		}
  	}
  	if ( options.hasOwnProperty( 'useragent' ) ) {
  		opts.useragent = options.useragent;
  		if ( !isString( opts.useragent ) ) {
  			return new TypeError( 'invalid option. User agent option must be a string primitive. Option: `' + opts.useragent + '`.' );
  		}
  	}
  	if ( options.hasOwnProperty( 'state' ) ) {
  		opts.state = options.state;
  		if ( !isString( opts.state ) ) {
  			return new TypeError( 'invalid option. State option must be a string primitive. Option: `' + opts.state + '`.' );
  		}
  	}
  	return null;
  } // end FUNCTION validate()
  
  
  // EXPORTS //
  
  module.exports = validate;
  