// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/rendering.dart';

import 'basic.dart';
import 'framework.dart';

/// Spacer creates an adjustable, empty spacer that can be used to tune the
/// spacing between widgets, like [Row] or [Column].
///
/// Different implementations include:
/// - An optional flex: parameter causes the Spacer to utilize
/// an Expanded that defaults to 1 if all parameters are left null.
///
/// - Setting a value for the flex: parameter will cause the Spacer to
/// utilize that value for it's Expanded.
///
/// - Setting a value for width: and/or height: will cause the Spacer to
/// use only a SizedBox with the width: or height: specified. In this case,
/// the Spacer will not utilize an expanded at all.
///
/// By default, with no parameters set, the [Spacer] widget will  take up any
/// available space, so setting the [Flex.mainAxisAlignment] on a flex container
/// that contains a [Spacer] to [MainAxisAlignment.spaceAround],
/// [MainAxisAlignment.spaceBetween], or [MainAxisAlignment.spaceEvenly] will not
/// have any visible effect: the [Spacer] has taken up all of the additional space,
/// so there is none left to redistribute.
///
///
///
/// ## Sample code examples
///
/// ```dart
/// new Row(
///   children: <Widget>[
///     new Text('Begin'),
///     new Spacer(), // Defaults to a flex of one.
///     new Text('Middle'),
///     // Gives twice the space between Middle and End than Begin and Middle.
///     new Spacer(flex: 2),
///     new Text('End'),
///   ],
/// )
/// ```
///
/// /// ```dart
///// new Row(
/////   children: <Widget>[
/////     new Text('Begin'),
/////     new Spacer(
/////       height: 100,
/////     ), // Utilizes a SizedBox with a height of 100.
/////     new Text('End'),
/////   ],
///// )
///// ```
///
/// See also:
///
///  * [Row] and [Column], which are the most common containers to use a Spacer
///    in.
///  * [SizedBox], to create a box with a specific size and an optional child.
class Spacer extends StatelessWidget {
  /// Creates a flexible space to insert into a [Flexible] widget.
  ///
  /// The [flex] parameter may not be null or less than one.
  const Spacer({Key key, this.flex = 1})
      : assert(flex > 0),
        super(key: key);

  const Spacer.fromSize({
	  Key key,
	  this.width,
	  this.height,
})
  /// The flex factor to use in determining how much space to take up.
  ///
  /// The amount of space the [Spacer] can occupy in the main axis is determined
  /// by dividing the free space proportionately, after placing the inflexible
  /// children, according to the flex factors of the flexible children.
  ///
  /// Defaults to one.
  final int flex;
  final double width;
  final double height;

  @override
  Widget build(BuildContext context) {
    return
		width != null || height != null ? SizedBox(
			width: width,
			height: height)
	  :	Expanded(
      flex: flex,
      child: const SizedBox(
        height: 0.0,
        width: 0.0,
      ),
    );
  }
}