1import SwiftUI
2import Photos
3
4struct ThumbnailImageInner: View {
5    @ObservedObject var assetImage: PHAssetImage
6    var size: CGFloat
7    
8    var body: some View {
9        Image(nsImage: assetImage.image)
10            .resizable()
11            .scaledToFill()
12            .clipped()
13            .frame(width: size, height: size, alignment: .center)
14    }
15}
16
17/// Render a single thumbnail image in the thumbnail picker.
18///
19/// Thumbnails are square, and they expand to fill the square.  This may
20/// mean some information gets cropped out -- that's okay, these are only
21/// small previews, not complete images.
22struct ThumbnailImage: View {
23    
24    // Implementation note: the reason we pass in a bunch of individual
25    // properties rather than the whole asset is because we need an
26    // @EnvironmentObject (the PhotosLibrary) to create the PHAssetImage,
27    // so we can stick the latter in an @ObservedObject.
28    //
29    // But EnvironmentObject values aren't passed down until you call the
30    // `body` method, which is too late!  So instead we have the parent
31    // view call into PhotosLibrary and pass in the relevant values here.
32    //
33    // The `getAssetImage` is a callback so we can load those assets somewhat
34    // lazily; the ThumbnailImageInner is separate so it can subscribe to
35    // updates to the PHAssetImage.
36    @State var assetImage: PHAssetImage? = nil
37    
38    var index: Int
39    var state: ReviewState?
40    var isFocused: Bool
41    var isFavorite: Bool
42    private var getAssetImage: () -> PHAssetImage
43    
44    init(index: Int, state: ReviewState?, isFavorite: Bool, isFocused: Bool, getAssetImage: @escaping () -> PHAssetImage) {
45        self.index = index
46        
47        self.isFavorite = isFavorite
48        self.state = state
49        
50        self.isFocused = isFocused
51        self.getAssetImage = getAssetImage
52    }
53    
54    private func size() -> CGFloat {
55        isFocused ? 70 : 50
56    }
57    
58    private func cornerRadius() -> CGFloat {
59        isFocused ? 7 : 5
60    }
61    
62    var body: some View {
63        if let thisAssetImage = assetImage {
64            ThumbnailImageInner(assetImage: thisAssetImage, size: size())
65                .cornerRadius(cornerRadius())
66                .reviewStateColor(isRejected: state == .Rejected)
67                .reviewStateBorder(for: state, with: cornerRadius())
68                .reviewStateIcon(for: state, isFocused)
69                .favoriteHeartIcon(isFavorite, isFocused)
70                
71        } else {
72            ProgressView()
73                .onAppear {
74                    self.assetImage = getAssetImage()
75                }
76        }
77        
78    }
79}