Filter by definition expression or display filter

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// Copyright 2024 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 FilterByDefinitionExpressionOrDisplayFilterView: View {
    /// The view model for the sample.
    @StateObject private var model = Model()

    /// The draw status of the map view.
    @State private var drawStatus: DrawStatus?

    /// The result of counting the features in the current extent of the map view.
    @State private var featureCountResult: Result<Int, Error>?

    /// The filtering mode selected in the picker.
    @State private var selectedFilterMode: FilterMode = .none

    var body: some View {
        GeometryReader { geometryProxy in
            MapViewReader { mapViewProxy in
                MapView(map: model.map)
                    .onDrawStatusChanged { drawStatus = $0 }
                    .task(id: drawStatus) {
                        // Updates the feature count when the map view finishes drawing.
                        guard drawStatus == .completed else { return }

                        // Creates an envelope from the frame of the map view.
                        let viewRect = geometryProxy.frame(in: .local)

                        guard let viewExtent = mapViewProxy.envelope(fromViewRect: viewRect) else {
                            return
                        }

                        do {
                            // Gets the feature count contained within the envelope.
                            let count = try await model.numberOfFeatures(withinExtent: viewExtent)
                            featureCountResult = .success(count)
                        } catch {
                            featureCountResult = .failure(error)
                        }
                    }
                    .overlay(alignment: .top) {
                        let statusText = switch featureCountResult {
                        case .success(let featureCount): "\(featureCount) feature(s)"
                        case .failure(let failure): "\(failure)"
                        case nil: "Loading feature layer…"
                        }

                        Text(statusText)
                            .multilineTextAlignment(.center)
                            .frame(maxWidth: .infinity, alignment: .center)
                            .padding(8)
                            .background(.regularMaterial, ignoresSafeAreaEdges: .horizontal)
                    }
            }
        }
        .toolbar {
            ToolbarItem(placement: .bottomBar) {
                Picker("Filter Mode", selection: $selectedFilterMode) {
                    ForEach(FilterMode.allCases, id: \.self) { filterMode in
                        Text(filterMode.label)
                    }
                }
                .pickerStyle(.segmented)
                .onChange(of: selectedFilterMode) { newFilterMode in
                    // Filters the feature layer based on the new filter mode.
                    model.filterFeatureLayer(mode: newFilterMode)
                }
            }
        }
    }
}

private extension FilterByDefinitionExpressionOrDisplayFilterView {
    /// The view model for the sample.
    @MainActor
    final class Model: ObservableObject {
        /// A map with a topographic basemap.
        let map: Map = {
            let map = Map(basemapStyle: .arcGISTopographic)

            // Initially centers the map on San Fransisco, CA, USA.
            map.initialViewpoint = Viewpoint(latitude: 37.7762, longitude: -122.4522, scale: 7e4)
            return map
        }()

        /// A feature layer of San Fransisco 311 incidents.
        private let featureLayer = FeatureLayer(
            // Creates the feature layer from a feature service URL.
            featureTable: ServiceFeatureTable(url: .sanFransiscoIncidentsFeatureLayer)
        )

        /// A definition expression to filter for the "Tree Maintenance or Damage" type.
        private let treesDefinitionExpression = "req_type = 'Tree Maintenance or Damage'"

        /// A display filter definition to filter for the "Tree Maintenance or Damage" type.
        private let treesDisplayFilterDefinition: ManualDisplayFilterDefinition = {
            // Creates a display filter with a name and an SQL expression.
            let treesDisplayFilter = DisplayFilter(
                name: "Trees",
                whereClause: "req_type LIKE 'Tree Maintenance or Damage'"
            )

            // Creates a display filter definition from the display filter.
            return ManualDisplayFilterDefinition(
                activeFilter: treesDisplayFilter,
                availableFilters: [treesDisplayFilter]
            )
        }()

        init() {
            map.addOperationalLayer(featureLayer)
        }

        /// Filters the feature layer based on a given filter mode.
        /// - Parameter mode: The mode indicating how to filter the layer.
        func filterFeatureLayer(mode: FilterMode) {
            let (definitionExpression, displayFilterDefinition): (String, DisplayFilterDefinition?) = switch mode {
            case .definitionExpression:
                (treesDefinitionExpression, nil)
            case .displayFilterDefinition:
                ("", treesDisplayFilterDefinition)
            case .none:
                ("", nil)
            }

            // Sets the feature layer's definition expression.
            featureLayer.definitionExpression = definitionExpression
            // Sets the feature layer's display filter definition.
            featureLayer.displayFilterDefinition = displayFilterDefinition
        }

        /// The number of features on the feature layer within a given extent.
        /// - Parameter extent: The extent to query.
        /// - Returns: The number of features.
        func numberOfFeatures(withinExtent: Envelope) async throws -> Int {
            // Creates parameters to filter the results with the extent.
            let queryParameters = QueryParameters()
            queryParameters.geometry = withinExtent

            return try await featureLayer.featureTable!.queryFeatureCount(using: queryParameters)
        }
    }

    /// The mode of filtering a feature layer.
    enum FilterMode: CaseIterable {
        case definitionExpression, displayFilterDefinition, none

        /// A human-readable label for the filter mode.
        var label: String {
            switch self {
            case .definitionExpression: "Expression"
            case .displayFilterDefinition: "Display Filter"
            case .none: "None"
            }
        }
    }
}

private extension URL {
    /// The URL to the "Incidents" feature layer on the SF 311 Incidents feature server.
    static var sanFransiscoIncidentsFeatureLayer: URL {
        URL(string: "https://services2.arcgis.com/ZQgQTuoyBrtmoGdP/arcgis/rest/services/SF_311_Incidents/FeatureServer/0")!
    }
}

#Preview {
    NavigationStack {
        FilterByDefinitionExpressionOrDisplayFilterView()
    }
}