/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Provides an inset layout as well as convenience methods to create

                an inset layout.

*/

import UIKit

/// An layout that insets its child content.

struct InsetLayout<Child: Layout>: Layout {

    typealias Content = Child.Content

    var child: Child

    var insets: UIEdgeInsets

    /*

        This initializer is private because the canonical way to inset a layout

        is by using the `withInsets(...)` method family defined below.

    */

    fileprivate init(child: Child, insets: UIEdgeInsets) {

        self.child = child

        self.insets = insets

    }

    mutating func layout(in rect: CGRect) {

        let rect = UIEdgeInsetsInsetRect(rect, insets)

        child.layout(in: rect)

    }

    var contents: [Content] {

        return child.contents

    }

}

/**

    In this extension we define methods that allow us to easily chain layouts

    together. For example, you can now take any `Layout` type and call 

    `withInsets(top: 5)` to get the same layout but insetted by 5 points. This is

    a convenient alternative to using initializer syntax if you're composing multiple

    layouts together.

*/

extension Layout {

    /// Makes an inset layout.

    func withInsets(top: CGFloat = 0, left: CGFloat = 0, bottom: CGFloat = 0, right: CGFloat = 0) -> InsetLayout<Self> {

        let insets = UIEdgeInsets(top: top, left: left, bottom: bottom, right: right)

        return withInsets(insets)

    }

    /// Makes an inset layout.

    func withInsets(all insets: CGFloat) -> InsetLayout<Self> {

        return withInsets(top: insets, left: insets, bottom: insets, right: insets)

    }

    /// Makes an inset layout.

    func withInsets(_ insets: UIEdgeInsets) -> InsetLayout<Self> {

        return InsetLayout(child: self, insets: insets)

    }

}