Add feature layers

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

    /// The current viewpoint of the map view.
    @State private var viewpoint: Viewpoint?

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

    var body: some View {
        MapView(map: model.map, viewpoint: viewpoint)
            .onViewpointChanged(kind: .centerAndScale) { viewpoint = $0 }
            .toolbar {
                ToolbarItem(placement: .bottomBar) {
                    Picker("Feature Layer", selection: $model.selectedFeatureLayerSource) {
                        ForEach(FeatureLayerSource.allCases, id: \.self) { source in
                            Text(source.label)
                        }
                    }
                    .task(id: model.selectedFeatureLayerSource) {
                        do {
                            // Loads the selected feature layer.
                            try await model.updateFeatureLayer()
                            viewpoint = model.featureLayerViewpoint
                        } catch {
                            // Updates the error and shows an alert if any failures occur.
                            self.error = error
                        }
                    }
                }
            }
            .errorAlert(presentingError: $error)
            .onAppear {
                // Updates the URL session challenge handler to use the
                // specified credentials and tokens for any challenges.
                ArcGISEnvironment.authenticationManager.arcGISAuthenticationChallengeHandler = ChallengeHandler()
            }
            .onDisappear {
                // Resets the URL session challenge handler to use default handling.
                ArcGISEnvironment.authenticationManager.arcGISAuthenticationChallengeHandler = nil
            }
    }
}

/// The authentication model used to handle challenges and credentials.
private struct ChallengeHandler: ArcGISAuthenticationChallengeHandler {
    func handleArcGISAuthenticationChallenge(
        _ challenge: ArcGISAuthenticationChallenge
    ) async throws -> ArcGISAuthenticationChallenge.Disposition {
        // NOTE: Never hardcode login information in a production application.
        // This is done solely for the sake of the sample.
        return .continueWithCredential(
            try await TokenCredential.credential(for: challenge, username: "viewer01", password: "I68VGU^nMurF")
        )
    }
}

private extension AddFeatureLayersView {
    /// The model used to store the geo model and other expensive objects
    /// used in this view.
    @MainActor
    class Model: ObservableObject {
        /// A map with a topographic basemap style.
        let map = Map(basemapStyle: .arcGISTopographic)

        /// The geodatabase used to create the feature layer.
        private var geodatabase: Geodatabase!

        /// The GeoPackage used to create the feature layer.
        private var geoPackage: GeoPackage!

        /// The viewpoint for a specific feature layer.
        var featureLayerViewpoint: Viewpoint?

        /// The feature layer source that is displayed.
        @Published var selectedFeatureLayerSource: FeatureLayerSource = .serviceFeatureTable

        /// Loads a feature layer with a service feature table.
        private func loadServiceFeatureTable() async throws {
            // Creates a service feature table from a feature service.
            let featureTable = ServiceFeatureTable(url: .damageAssessment)
            try await featureTable.load()
            let featureLayer = FeatureLayer(featureTable: featureTable)
            setFeatureLayer(featureLayer, viewpoint: .napervilleIL)
        }

        /// Loads a feature layer with a portal item.
        private func loadPortalItemFeatureTable() async throws {
            let portalItem = PortalItem(
                portal: .arcGISOnline(connection: .anonymous),
                id: .treesOfPortland
            )
            try await portalItem.load()
            let featureLayer = FeatureLayer(item: portalItem)
            setFeatureLayer(featureLayer, viewpoint: .portlandOR)
        }

        /// Loads a feature layer with a local geodatabase.
        private func loadGeodatabaseFeatureTable() async throws {
            // Loads the geodatabase if it does not exist.
            if geodatabase == nil {
                geodatabase = Geodatabase(fileURL: .laTrails)
                try await geodatabase.load()
            }
            // Creates a feature layer from the geodatabase's feature table and
            // sets the current feature layer to it.
            let featureTable = geodatabase.featureTable(named: "Trailheads")!
            let featureLayer = FeatureLayer(featureTable: featureTable)
            setFeatureLayer(featureLayer, viewpoint: .losAngelesCA)
        }

        /// Loads a feature layer with a local GeoPackage.
        private func loadGeoPackageFeatureTable() async throws {
            // Loads the GeoPackage if it does not exist.
            if geoPackage == nil {
                geoPackage = GeoPackage(fileURL: .auroraCO)
                try await geoPackage.load()
            }
            // Creates a feature layer from the GeoPackage's feature tables and
            // sets the current feature layer to the first one.
            let featureTable = geoPackage.featureTables.first!
            let featureLayer = FeatureLayer(featureTable: featureTable)
            setFeatureLayer(featureLayer, viewpoint: .auroraCO)
        }

        /// Loads a feature layer with a local shapefile.
        private func loadShapefileFeatureTable() async throws {
            let shapefileFeatureTable = ShapefileFeatureTable(fileURL: .reserveBoundaries)
            try await shapefileFeatureTable.load()
            let featureLayer = FeatureLayer(featureTable: shapefileFeatureTable)
            setFeatureLayer(featureLayer, viewpoint: .scotland)
        }

        /// Sets the map's operational layers to the given feature layer and updates the current viewpoint.
        private func setFeatureLayer(_ featureLayer: FeatureLayer, viewpoint: Viewpoint) {
            // Updates the map's operational layers.
            map.removeAllOperationalLayers()
            map.addOperationalLayer(featureLayer)
            // Updates the current viewpoint.
            featureLayerViewpoint = viewpoint
        }

        /// Updates the feature layer to reflect the source chosen by the user.
        func updateFeatureLayer() async throws {
            switch selectedFeatureLayerSource {
            case .serviceFeatureTable:
                try await loadServiceFeatureTable()
            case .portalItem:
                try await loadPortalItemFeatureTable()
            case .geodatabase:
                try await loadGeodatabaseFeatureTable()
            case .geoPackage:
                try await loadGeoPackageFeatureTable()
            case .shapefile:
                try await loadShapefileFeatureTable()
            }
        }
    }
}

private extension AddFeatureLayersView {
    /// The various feature layer sources for the sample.
    enum FeatureLayerSource: CaseIterable, Equatable {
        case shapefile, geoPackage, geodatabase, portalItem, serviceFeatureTable

        /// A human-readable label for each feature layer source.
        var label: String {
            switch self {
            case .serviceFeatureTable: return "Service Feature Table"
            case .portalItem: return "Portal Item"
            case .geodatabase: return "Mobile Geodatabase"
            case .geoPackage: return "GeoPackage"
            case .shapefile: return "Shapefile"
            }
        }
    }
}

private extension Viewpoint {
    /// The viewpoint for Naperville, IL.
    static var napervilleIL: Viewpoint {
        Viewpoint(latitude: 41.7735, longitude: -88.1431, scale: 4e3)
    }

    /// The viewpoint for Portland, OR.
    static var portlandOR: Viewpoint {
        Viewpoint(latitude: 45.5266, longitude: -122.6219, scale: 6e3)
    }

    /// The viewpoint for Los Angeles, CA.
    static var losAngelesCA: Viewpoint {
        Viewpoint(latitude: 34.0772, longitude: -118.7989, scale: 6e5)
    }

    /// The viewpoint for Aurora, CO.
    static var auroraCO: Viewpoint {
        Viewpoint(latitude: 39.7294, longitude: -104.8319, scale: 5e5)
    }

    /// The viewpoint for Scotland.
    static var scotland: Viewpoint {
        Viewpoint(latitude: 56.6413, longitude: -3.8890, scale: 6e6)
    }
}

private extension PortalItem.ID {
    /// The ID used in the "Trees of Portland" portal item.
    static var treesOfPortland: Self { Self("1759fd3e8a324358a0c58d9a687a8578")! }
}

private extension URL {
    /// Naperville damage assessment service.
    static var damageAssessment: URL { .init(string: "https://sampleserver7.arcgisonline.com/server/rest/services/DamageAssessment/FeatureServer/0")! }

    /// Los Angeles Trailheads geodatabase.
    static var laTrails: URL { Bundle.main.url(forResource: "LA_Trails", withExtension: "geodatabase")! }

    /// Aurora, Colorado GeoPackage.
    static var auroraCO: URL { Bundle.main.url(forResource: "AuroraCO", withExtension: "gpkg")! }

    /// Scottish Wildlife Trust Reserves Shapefile.
    static var reserveBoundaries: URL { Bundle.main.url(forResource: "ScottishWildlifeTrust_ReserveBoundaries_20201102", withExtension: "shp", subdirectory: "ScottishWildlifeTrust_reserves")! }
}