1//
2//  NewThumbnailList.swift
3//  BlinkReviewer
4//
5//  Created by Alex Chan on 10/06/2023.
6//
7
8import SwiftUI
9
10struct ThumbnailList: View {
11    @EnvironmentObject var photosLibrary: PhotosLibrary
12    @Binding var focusedAssetIndex: Int
13    
14    var body: some View {
15        ScrollViewReader { proxy in
16            PHAssetHStack(assetIdentifiers: photosLibrary.assetIdentifiers) { localIdentifier, index in
17                ThumbnailImage(
18                    index: index,
19                    state: photosLibrary.state(ofLocalIdentifier: localIdentifier),
20                    isFavorite: photosLibrary.isFavorite(localIdentifier: localIdentifier),
21                    isFocused: index == focusedAssetIndex,
22                    getAssetImage: {
23                        photosLibrary.getThumbnail(for: photosLibrary.asset(at: index))
24                    }
25                )
26                .environmentObject(photosLibrary)
27                .onTapGesture {
28                    focusedAssetIndex = index
29                }
30            }
31            // When the focusedAssetIndex changes, scroll to the new position.
32            //
33            // By default this is an animated scroll, but if the user is scrolling
34            // a long way, we skip the animation and jump straight to it -- if somebody
35            // jumps over several thousand images in one go, it looks better to snap
36            // rather than do a jaggy animation.
37            .onChange(of: focusedAssetIndex, perform: { [oldIndex = focusedAssetIndex] newIndex in
38                withAnimation(abs(newIndex - oldIndex) < 100 ? .default : nil) {
39                    proxy.scrollTo(
40                        photosLibrary.asset(at: newIndex).localIdentifier,
41                        anchor: .center
42                    )
43                }
44            })
45        }
46    }
47}