SwiftUI_DevLog/DevLog/Presentation/Common/LoadingState.swift at 62b618b32b1cd6009aba3a44a9a9c462e008a00e · opficdev/SwiftUI_DevLog · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
//
//  LoadingState.swift
//  DevLog
//
//  Created by opfic on 3/16/26.
//

import Foundation

@MainActor
final class LoadingState {
    private enum DefaultTarget: Hashable {
        case value
    }

    enum Mode {
        case immediate
        case delayed
    }

    private let delay: Duration
    private var immediateCountByTarget: [AnyHashable: Int] = [:]
    private var delayedCountByTarget: [AnyHashable: Int] = [:]
    private var delayedTaskByTarget: [AnyHashable: Task<Void, Never>] = [:]
    private var visibleDelayedTargets = Set<AnyHashable>()
    private var visibleTargets = Set<AnyHashable>()

    init(delay: Duration = .seconds(0.3)) {
        self.delay = delay
    }

    func begin(
        mode: Mode,
        update: @escaping @MainActor (Bool) -> Void
    ) {
        begin(target: DefaultTarget.value, mode: mode) { _, isLoading in
            update(isLoading)
        }
    }

    func begin<T: Hashable>(
        target: T,
        mode: Mode,
        update: @escaping @MainActor (T, Bool) -> Void
    ) {
        let hashableTarget = AnyHashable(target)
        begin(target: hashableTarget, mode: mode) { isLoading in
            update(target, isLoading)
        }
    }

    func end(
        mode: Mode,
        update: @escaping @MainActor (Bool) -> Void
    ) {
        end(target: DefaultTarget.value, mode: mode) { _, isLoading in
            update(isLoading)
        }
    }

    func end<T: Hashable>(
        target: T,
        mode: Mode,
        update: @escaping @MainActor (T, Bool) -> Void
    ) {
        let hashableTarget = AnyHashable(target)
        end(target: hashableTarget, mode: mode) { isLoading in
            update(target, isLoading)
        }
    }

    private func begin(
        target: AnyHashable,
        mode: Mode,
        update: @escaping @MainActor (Bool) -> Void
    ) {
        switch mode {
        case .immediate:
            immediateCountByTarget[target, default: 0] += 1
            setVisibilityIfNeeded(for: target, isVisible: true, update: update)
        case .delayed:
            delayedCountByTarget[target, default: 0] += 1
            scheduleDelayedLoadingIfNeeded(for: target, update: update)
        }
    }

    private func end(
        target: AnyHashable,
        mode: Mode,
        update: @escaping @MainActor (Bool) -> Void
    ) {
        switch mode {
        case .immediate:
            let count = immediateCountByTarget[target, default: 0]
            immediateCountByTarget[target] = max(0, count - 1)
        case .delayed:
            let count = delayedCountByTarget[target, default: 0]
            delayedCountByTarget[target] = max(0, count - 1)
        }
        updateLoadingVisibility(for: target, update: update)
    }

    private func scheduleDelayedLoadingIfNeeded(
        for target: AnyHashable,
        update: @escaping @MainActor (Bool) -> Void
    ) {
        guard delayedTaskByTarget[target] == nil,
              !visibleDelayedTargets.contains(target),
              0 < delayedCountByTarget[target, default: 0] else { return }
        delayedTaskByTarget[target] = Task { [weak self] in
            guard let self else { return }
            try? await Task.sleep(for: delay)
            if Task.isCancelled { return }
            await MainActor.run {
                self.delayedTaskByTarget[target] = nil
                guard 0 < self.delayedCountByTarget[target, default: 0] else { return }
                self.visibleDelayedTargets.insert(target)
                if self.immediateCountByTarget[target, default: 0] == 0 {
                    self.setVisibilityIfNeeded(for: target, isVisible: true, update: update)
                }
            }
        }
    }

    private func updateLoadingVisibility(
        for target: AnyHashable,
        update: @escaping @MainActor (Bool) -> Void
    ) {
        if 0 < immediateCountByTarget[target, default: 0] {
            setVisibilityIfNeeded(for: target, isVisible: true, update: update)
            return
        }
        if visibleDelayedTargets.contains(target) {
            if delayedCountByTarget[target, default: 0] == 0 {
                visibleDelayedTargets.remove(target)
                setVisibilityIfNeeded(for: target, isVisible: false, update: update)
            } else {
                setVisibilityIfNeeded(for: target, isVisible: true, update: update)
            }
            return
        }
        if 0 < delayedCountByTarget[target, default: 0] {
            if visibleTargets.contains(target) {
                setVisibilityIfNeeded(for: target, isVisible: true, update: update)
            } else {
                setVisibilityIfNeeded(for: target, isVisible: false, update: update)
            }
            scheduleDelayedLoadingIfNeeded(for: target, update: update)
            return
        }
        delayedTaskByTarget[target]?.cancel()
        delayedTaskByTarget[target] = nil
        setVisibilityIfNeeded(for: target, isVisible: false, update: update)
    }

    private func setVisibilityIfNeeded(
        for target: AnyHashable,
        isVisible: Bool,
        update: @escaping @MainActor (Bool) -> Void
    ) {
        let wasVisible = visibleTargets.contains(target)

        if isVisible {
            visibleTargets.insert(target)
        } else {
            visibleTargets.remove(target)
        }

        if wasVisible != isVisible {
            update(isVisible)
        }
    }
}