passepartout-apple/Passepartout/App/Reusable/CopySavingButton.swift

//
//  CopySavingButton.swift
//  Passepartout
//
//  Created by Davide De Rosa on 4/6/22.
//  Copyright (c) 2022 Davide De Rosa. All rights reserved.
//
//  https://github.com/passepartoutvpn
//
//  This file is part of Passepartout.
//
//  Passepartout is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  Passepartout is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with Passepartout.  If not, see <http://www.gnu.org/licenses/>.
//

import SwiftUI

struct CopySavingButton<T: Equatable, Label: View>: View {
    @Binding var original: T

    @Binding var copy: T
    
    var mapping: (T) -> T
    
    let label: () -> Label

    var saveAnyway = false

    var onSave: (() -> Void)?
    
    @State private var isLoaded = false
    
    var body: some View {
        Button(action: saveToOriginal, label: label)
            .disabled(!canSave)
            .onAppear {
                loadFromOriginal(once: true)
            }.onChange(of: original) { _ in
                withAnimation {
                    loadFromOriginal(once: false)
                }
            }
    }

    private var canSave: Bool {
        isLoaded && (saveAnyway || copy != original)
    }

    private func loadFromOriginal(once: Bool) {
        guard !once || !isLoaded else {
            return
        }
        copy = original
        isLoaded = true
    }

    private func saveToOriginal() {
        if copy != original {
            original = copy
        }
        onSave?()
    }
}