Download preplanned map area

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// Copyright 2022 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 DownloadPreplannedMapAreaView: View {
    /// A Boolean value indicating whether to select a map.
    @State private var isShowingSelectMapView = false

    /// A Boolean value indicating whether to show delete alert.
    @State private var isShowingDeleteAlert = false

    /// The view model for this sample.
    @StateObject private var model = Model()

    var body: some View {
        MapView(map: model.currentMap, viewpoint: model.currentMap.initialViewpoint?.expanded())
            .overlay(alignment: .top) {
                mapNameOverlay
            }
            .toolbar {
                ToolbarItemGroup(placement: .bottomBar) {
                    Spacer()

                    Button("Select Map") {
                        isShowingSelectMapView.toggle()
                    }
                    .popover(isPresented: $isShowingSelectMapView) {
                        MapPicker(model: model)
                            .presentationDetents([.fraction(0.5)])
                            .frame(idealWidth: 320, idealHeight: 380)
                    }

                    Spacer()

                    Button {
                        isShowingDeleteAlert = true
                    } label: {
                        Image(systemName: "trash")
                    }
                    .disabled(!model.canRemoveDownloadedMaps)
                    .alert("Delete All Offline Areas", isPresented: $isShowingDeleteAlert) {
                        Button("Delete", role: .destructive) {
                            model.removeDownloadedMaps()
                        }
                    } message: {
                        Text("Are you sure you want to delete all downloaded preplanned map areas?")
                    }
                }
            }
            .task {
                // Makes the offline map models when the view is first shown.
                await model.makeOfflineMapModels()
            }
    }

    var mapNameOverlay: some View {
        Text(model.currentMap.item?.title ?? "Unknown Map")
            .font(.footnote)
            .frame(maxWidth: .infinity)
            .padding(8)
            .background(.thinMaterial, ignoresSafeAreaEdges: .horizontal)
    }
}

private extension Viewpoint {
    /// Expands the viewpoint's geometry.
    /// - Returns: A viewpoint with it's geometry expanded by 50%.
    func expanded() -> Viewpoint {
        let builder = EnvelopeBuilder(envelope: self.targetGeometry.extent)
        builder.expand(by: 0.5)
        let zoomEnvelope = builder.toGeometry()
        return Viewpoint(boundingGeometry: zoomEnvelope)
    }
}

#Preview {
    NavigationStack {
        DownloadPreplannedMapAreaView()
    }
}