Set map image layer sublayer visibility

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// Copyright 2025 Esri
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import ArcGIS
import SwiftUI

struct SetMapImageLayerSublayerVisibilityView: View {
    /// The error shown in the error alert.
    @State private var error: Error?

    /// A map with no specified style and initial viewpoint.
    @State private var map: Map = {
        let map = Map()
        map.initialViewpoint = Viewpoint(
            center: Point(
                x: -11e6,
                y: 6e6,
                spatialReference: .webMercator
            ),
            scale: 9e7
        )

        return map
    }()

    /// The map image layer.
    @State private var mapImageLayer = ArcGISMapImageLayer(url: .arcGISMapImageLayerSample)

    /// The sublayer options to control the visibility.
    @State private var sublayerOptions: [SublayerOption] = []

    var body: some View {
        MapView(map: map)
            .task {
                do {
                    // Loads the map image layer.
                    try await mapImageLayer.load()
                    // Adds the map image layer to the map.
                    map.addOperationalLayer(mapImageLayer)
                    sublayerOptions = mapImageLayer.mapImageSublayers.map { mapImageSublayer in
                        SublayerOption(
                            name: mapImageSublayer.name,
                            id: mapImageSublayer.id,
                            isVisible: mapImageSublayer.isVisible,
                            sublayer: mapImageSublayer
                        )
                    }
                } catch {
                    self.error = error
                }
            }
            .toolbar {
                ToolbarItem(placement: .bottomBar) {
                    Menu {
                        ForEach($sublayerOptions, id: \.id) { $sublayerOption in
                            Toggle(isOn: $sublayerOption.isVisible) {
                                Text(sublayerOption.name)
                            }
                            .onChange(of: sublayerOption.isVisible) {
                                sublayerOption.sublayer.isVisible = sublayerOption.isVisible
                            }
                        }
                    } label: {
                        Text("Sublayers")
                    }
                }
            }
            .errorAlert(presentingError: $error)
    }
}

private struct SublayerOption: Equatable, Identifiable {
    let name: String
    let id: Int
    var isVisible = true
    let sublayer: ArcGISMapImageSublayer
}

extension SublayerOption: Hashable {
    func hash(into hasher: inout Hasher) {
        hasher.combine(id)
    }
}

extension URL {
    static var arcGISMapImageLayerSample: URL {
        URL(
            string: "https://sampleserver6.arcgisonline.com/arcgis/rest/services/SampleWorldCities/MapServer"
        )!
    }
}

#Preview {
    SetMapImageLayerSublayerVisibilityView()
}