/*

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

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Contains the `ImageViewerController` view controller class, which displays an `ImageFile.`

*/

import Cocoa

/**

    `ImageViewerController` displays an `ImageFile` in a scrollable `NSImageView`. It shows

    shows the title of the set image file in a `NSTextField` label.

*/

class ImageViewerController: NSViewController {

    // MARK: Properties

    override var nibName : String {

        return "ImageViewerController"

    }

    @IBOutlet var imageView: NSImageView!

    @IBOutlet var scrollView: NSScrollView!

    @IBOutlet var titleField: NSTextField!

    @IBOutlet var bottomOverlayView: NSVisualEffectView!

    var imageFile: ImageFile? {

        didSet {

            guard isViewLoaded else { return }

            updateImageViewWithImageFile(imageFile)

        }

    }

    // MARK: Life Cycle

    override func viewDidLoad() {

        super.viewDidLoad()

        /*

            Turn on translatesAutoresizingMaskIntoConstraints, Interface Builder

            turns this off for all views in a nib. The `NSScrollView` and `NSClipView` 

            expect to be able to control their documentView via modifying its `frame`.

        */

        imageView.translatesAutoresizingMaskIntoConstraints = true

        /*

            Turn off the automatic content insets on the image's scroll view. The

            bottom overlay view will be included in the content insets, which will

            be manually added in.

        */

        scrollView.automaticallyAdjustsContentInsets = false

        updateImageViewWithImageFile(imageFile)

    }

    override func viewDidAppear() {

        super.viewDidAppear()

        // Update the content insets now that the image viewer is in a window.

        updateScrollViewContentInsets()

    }

    /**

        Updates the `scrollView`'s `contentInsets` based on the containing window's

        `contentLayoutRect` and the size of the bottom bar that covers the bottom 

        of the scroll view.

    */

    fileprivate func updateScrollViewContentInsets() {

        // Verify the view is loaded and in a window.

        guard isViewLoaded else { return }

        guard let window = view.window else { return }

        let contentLayoutRect = window.contentLayoutRect

        /*

            Convert the `contentLayoutRect` to the coordinate space of and clipped 

            to the bounds of the image view's scroll view.

        */

        let scrollViewContentLayoutRect = scrollView.convert(contentLayoutRect, from: nil).intersection(scrollView.bounds)

        let minYContentLayoutRectInset = scrollViewContentLayoutRect.minY - scrollView.bounds.minY

        let maxYContentLayoutRectInset = scrollView.bounds.maxY - scrollViewContentLayoutRect.maxY

        /*

            Get the rect of the bottom bar in the coordinate space of and clipped 

            to the bounds of the image view's scroll view.

        */

        let scrollViewBottomBarRect = scrollView.convert(bottomOverlayView.bounds, from: bottomOverlayView).intersection(scrollView.bounds)

        /*

            Calculate the contentInsets based on the `contentLayoutRect` and the

            bottom bar. The top inset is purely based on the `contentLayoutRect`'s

            inset. The bottom inset is the maximum of the inset from the 

            `contentLayoutRect` and the bottom bar.

        */

        let topEdgeInset = scrollView.isFlipped ? minYContentLayoutRectInset : maxYContentLayoutRectInset

        let bottomEdgeInset = max((scrollView.isFlipped ? maxYContentLayoutRectInset : minYContentLayoutRectInset), scrollViewBottomBarRect.height)

        scrollView.contentInsets = EdgeInsets(top: topEdgeInset, left: 0, bottom: bottomEdgeInset, right: 0)

    }

    func updateImageViewWithImageFile(_ imageFile: ImageFile?) {

        if let imageFile = imageFile {

            /*

                Fetch the `ImageFile`'s image representation and update set it on

                the image view.

            */

            imageFile.fetchImageWithCompletionHandler { image in

                /*

                    Verify that the loaded image representation is from the currently

                    set `ImageFile`.

                */                

                guard self.imageFile == imageFile else { return }

                self.imageView.image = image

                /*

                    Size the ImageView to match the new image size, and zoom

                    to fit the entire new image.

                */

                self.imageView.frame = NSRect(origin: NSPoint.zero, size: image.size)

                self.scrollView.magnify(toFit: self.imageView.frame)

            }

        }

        else {

            imageView.image = nil

        }

        /*

            Update the title field using the image name, using an empty string if

            there is none.

        */

        titleField.stringValue = imageFile?.fileNameExcludingExtension ?? ""

    }

}