wp_enqueue_code_editor

 *
 * @return bool True if the user can access the visual editor, false otherwise.
 */
function user_can_richedit() {
	global $wp_rich_edit, $is_gecko, $is_opera, $is_safari, $is_chrome, $is_IE, $is_edge;

	if ( ! isset( $wp_rich_edit ) ) {
		$wp_rich_edit = false;

		if ( 'true' === get_user_option( 'rich_editing' ) || ! is_user_logged_in() ) { // Default to 'true' for logged out users.
			if ( $is_safari ) {
				$wp_rich_edit = ! wp_is_mobile() || ( preg_match( '!AppleWebKit/(\d+)!', $_SERVER['HTTP_USER_AGENT'], $match ) && intval( $match[1] ) >= 534 );
			} elseif ( $is_IE ) {
				$wp_rich_edit = ( strpos( $_SERVER['HTTP_USER_AGENT'], 'Trident/7.0;' ) !== false );
			} elseif ( $is_gecko || $is_chrome || $is_edge || ( $is_opera && ! wp_is_mobile() ) ) {
				$wp_rich_edit = true;
			}
		}
	}

	/**
	 * Filters whether the user can access the visual editor.
	 *
	 * @since 2.1.0
	 *
	 * @param bool $wp_rich_edit Whether the user can access the visual editor.
	 */
	return apply_filters( 'user_can_richedit', $wp_rich_edit );
}

/**
 * Find out which editor should be displayed by default.
 *
 * Works out which of the two editors to display as the current editor for a
 * user. The 'html' setting is for the "Text" editor tab.
 *
 * @since 2.5.0
 *
 * @return string Either 'tinymce', or 'html', or 'test'
 */
function wp_default_editor() {
	$r = user_can_richedit() ? 'tinymce' : 'html'; // Defaults.
	if ( wp_get_current_user() ) { // Look for cookie.
		$ed = get_user_setting( 'editor', 'tinymce' );
		$r  = ( in_array( $ed, array( 'tinymce', 'html', 'test' ), true ) ) ? $ed : $r;
	}

	/**
	 * Filters which editor should be displayed by default.
	 *
	 * @since 2.5.0
	 *
	 * @param string $r Which editor should be displayed by default. Either 'tinymce', 'html', or 'test'.
	 */
	return apply_filters( 'wp_default_editor', $r );
}

/**
 * Renders an editor.
 *
 * Using this function is the proper way to output all needed components for both TinyMCE and Quicktags.
 * _WP_Editors should not be used directly. See https://core.trac.wordpress.org/ticket/17144.
 *
 * NOTE: Once initialized the TinyMCE editor cannot be safely moved in the DOM. For that reason
 * running wp_editor() inside of a meta box is not a good idea unless only Quicktags is used.
 * On the post edit screen several actions can be used to include additional editors
 * containing TinyMCE: 'edit_page_form', 'edit_form_advanced' and 'dbx_post_sidebar'.
 * See https://core.trac.wordpress.org/ticket/19173 for more information.
 *