/*

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

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Contains the `ImageToolsViewController` class, which manages the UI of a stack of tools buttons.

*/

import Cocoa

/**

    `ImageToolsViewController` manages a list of tool controls. The controls can be

    detached from the tool stack once their contained view becomes too small and 

    displayed in an overflow menu.

*/

class ImageToolsViewController: NSViewController, NSStackViewDelegate {

    // MARK: Properties

    @IBOutlet var stackView: NSStackView!

    /**

        The button shown when the tool stack is too small to present all of its

        buttons. Clicking on the overflow button shows a menu with representations 

        of the detached buttons.

    */

    lazy var overflowRevealButton: NSButton = {

        let overflowRevealButton = NSButton()

        overflowRevealButton.bezelStyle = .shadowlessSquare

        overflowRevealButton.translatesAutoresizingMaskIntoConstraints = false

        overflowRevealButton.attributedTitle = NSAttributedString(string: "...", attributes: [

            NSFontAttributeName: NSFont.boldSystemFont(ofSize: 13.0)

        ])

        overflowRevealButton.alphaValue = 0.75

        overflowRevealButton.target = self

        overflowRevealButton.action = #selector(ImageToolsViewController.popUpOverflowMenu(_:))

        return overflowRevealButton

    }()

    // MARK: Life Cycle

    override func viewDidLoad() {

        super.viewDidLoad()

        stackView.detachesHiddenViews = true

    }

    // MARK: Overflow Menu

    /**

        Creates a menu for the detached views in the stack. The title, target, 

        and action of the menu items match the associated buttons. If there were 

        no detached items, returns nil.

    */

    var overflowMenu: NSMenu? {

        let detachedButtons = stackView.detachedViews.flatMap { $0 as? NSButton }

        if !detachedButtons.isEmpty {

            let menu = NSMenu(title: "Detached Items")

            /*

                Do not use auto-validation, the menu items will have the same 

                enabled state as their represented button.

            */

            menu.autoenablesItems = false

            /* 

                Add a menu item for each detached button, transferring the applicable

                button state to the menu item.

            */

            for button in detachedButtons {

                let menuItem = menu.addItem(withTitle: button.title, action: button.action, keyEquivalent: button.keyEquivalent)

                menuItem.target = button.target

                menuItem.isEnabled = button.isEnabled

                menuItem.representedObject = button

            }

            return menu

        }

        return nil

    }

    @objc fileprivate func popUpOverflowMenu(_ sender: AnyObject?) {

        // Show the overflow menu (if we one exists) underneath the overflow button.

        let popUpMenuLocation = NSPoint(x: overflowRevealButton.bounds.minX, y: overflowRevealButton.bounds.maxY)

        overflowMenu?.popUp(positioning: nil, at: popUpMenuLocation, in: overflowRevealButton)

    }

    // MARK: NSStackView Delegate

    func stackView(_ stackView: NSStackView, willDetach views: [NSView]) {

        /*

            If the stack view did not previously have any detached views, these 

            are the first, so the overflow button needs to be added and constrained.

        */

        if stackView.detachedViews.isEmpty {

            /*

                Add the overflow button (not as an arranged subview), and constraints 

                to position it on the trailing edge of the stack view.

            */

            stackView.addSubview(overflowRevealButton)

            overflowRevealButton.trailingAnchor.constraint(equalTo: stackView.trailingAnchor).isActive = true

            overflowRevealButton.topAnchor.constraint(equalTo: stackView.topAnchor).isActive = true

            overflowRevealButton.bottomAnchor.constraint(equalTo: stackView.bottomAnchor).isActive = true

        }

    }

    func stackView(_ stackView: NSStackView, didReattach views: [NSView]) {

        /*

            If the stack view no longer has any detached views, these were the last, 

            so the overflow button needs to be removed.

        */

        if stackView.detachedViews.isEmpty {

            // Removing the overflow button will also remove constraints associated with it.

            overflowRevealButton.removeFromSuperview()

        }

    }

}