NewsBlur/clients/ios/Classes/SwiftUIUtilities.swift

//
//  SwiftUIUtilities.swift
//  NewsBlur
//
//  Created by David Sinclair on 2023-02-01.
//  Copyright © 2023 NewsBlur. All rights reserved.
//

import SwiftUI

/// Some useful SwiftUI extensions.

extension View {
    @ViewBuilder
    func `if`<Content: View>(_ condition: Bool, transform: (Self) -> Content) -> some View {
        if condition {
            transform(self)
        } else {
            self
        }
    }
}

extension View {
    @ViewBuilder
    func modify<Content: View>(@ViewBuilder _ transform: (Self) -> Content?) -> some View {
        if let view = transform(self), !(view is EmptyView) {
            view
        } else {
            self
        }
    }
}

extension View {
    func cornerRadius(_ radius: CGFloat, corners: UIRectCorner) -> some View {
        clipShape(RoundedCorner(radius: radius, corners: corners))
    }
}

struct RoundedCorner: Shape {
    var radius: CGFloat = .infinity
    var corners: UIRectCorner = .allCorners
    
    func path(in rect: CGRect) -> Path {
        let path = UIBezierPath(roundedRect: rect, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
        return Path(path.cgPath)
    }
}

extension Color {
    static var random: Color {
        return Color(red: .random(in: 0...1), green: .random(in: 0...1), blue: .random(in: 0...1)
        )
    }
    
    static func themed(_ hex: [NSNumber]) -> Color {
        return Color(ThemeManager.color(fromRGB: hex))
    }
}

// From https://www.swiftbysundell.com/articles/observing-swiftui-scrollview-content-offset/

struct PositionObservingView<Content: View>: View {
    var coordinateSpace: CoordinateSpace
    @Binding var position: CGPoint
    @ViewBuilder var content: () -> Content
    
    var body: some View {
        content()
            .background(GeometryReader { geometry in
                Color.clear.preference(
                    key: PreferenceKey.self,
                    value: geometry.frame(in: coordinateSpace).origin
                )
            })
            .onPreferenceChange(PreferenceKey.self) { position in
                self.position = position
            }
    }
}

private extension PositionObservingView {
    struct PreferenceKey: SwiftUI.PreferenceKey {
        static var defaultValue: CGPoint { .zero }
        
        static func reduce(value: inout CGPoint, nextValue: () -> CGPoint) {
            // No-op
        }
    }
}

struct OffsetObservingScrollView<Content: View>: View {
    var axes: Axis.Set = [.vertical]
    var showsIndicators = true
    @Binding var offset: CGPoint
    @ViewBuilder var content: () -> Content
    
    // The name of our coordinate space doesn't have to be
    // stable between view updates (it just needs to be
    // consistent within this view), so we'll simply use a
    // plain UUID for it:
    private let coordinateSpaceName = UUID()
    
    var body: some View {
        ScrollView(axes, showsIndicators: showsIndicators) {
            PositionObservingView(
                coordinateSpace: .named(coordinateSpaceName),
                position: Binding(
                    get: { offset },
                    set: { newOffset in
                        offset = CGPoint(
                            x: -newOffset.x,
                            y: -newOffset.y
                        )
                    }
                ),
                content: content
            )
        }
        .coordinateSpace(name: coordinateSpaceName)
    }
}