Browse OGC API feature service

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
// 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 BrowseOGCAPIFeatureServiceView: View {
    /// The error shown in the error alert.
    @State private var error: Error?

    /// A Boolean value indicating whether the textfield alert should be presented.
    @State private var textfieldAlertIsPresented = true

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

    /// The user input for the OGC service resource.
    @State private var userInput = URL.daraaService.absoluteString

    /// The selected feature collection's title.
    @State private var selectedTitle = ""

    var body: some View {
        MapViewReader { mapProxy in
            MapView(map: model.map)
                .toolbar {
                    ToolbarItemGroup(placement: .bottomBar) {
                        Button("Open Service") {
                            textfieldAlertIsPresented = true
                        }

                        Spacer()

                        if !model.featureCollectionTitles.isEmpty {
                            Picker("Layers", selection: $selectedTitle) {
                                ForEach(model.featureCollectionTitles, id: \.self) { title in
                                    Text(title)
                                }
                            }
                            .task(id: selectedTitle) {
                                guard !selectedTitle.isEmpty else { return }
                                let featureCollectionInfo = model.featureCollectionInfos[selectedTitle]!
                                do {
                                    try await model.displayLayer(with: featureCollectionInfo)
                                    if let extent = featureCollectionInfo.extent {
                                        await mapProxy.setViewpointGeometry(extent, padding: 100)
                                    }
                                } catch {
                                    self.error = error
                                }
                            }
                        }
                    }
                }
                .alert("Load OGC API feature service", isPresented: $textfieldAlertIsPresented) {
                    // Textfield has a default OGC API URL.
                    TextField("URL", text: $userInput)
                        .keyboardType(.URL)
                        .textContentType(.URL)
                    Button("Load") {
                        guard let url = URL(string: userInput) else { return }
                        Task {
                            do {
                                try await model.loadOGCFeatureData(url: url)
                                // Set the picker selection to the first title in the title list.
                                if let title = model.featureCollectionTitles.first,
                                   let extent = model.featureCollectionInfos[title]?.extent {
                                    selectedTitle = title
                                    await mapProxy.setViewpointGeometry(extent, padding: 100)
                                }
                            } catch {
                                self.error = error
                            }
                        }
                    }
                    .disabled(userInput.isEmpty)
                    Button("Cancel", role: .cancel) {
                        // Reset the default value of the textfield.
                        userInput = URL.daraaService.absoluteString
                    }
                } message: {
                    Text("Please provide a URL to an OGC API feature service.")
                }
                .errorAlert(presentingError: $error)
        }
    }
}

private extension BrowseOGCAPIFeatureServiceView {
    @MainActor
    class Model: ObservableObject {
        /// A map with a topographic basemap of the Daraa, Syria.
        let map: Map = {
            let map = Map(basemapStyle: .arcGISTopographic)
            map.initialViewpoint = Viewpoint(
                center: Point(latitude: 32.62, longitude: 36.10),
                scale: 200_000
            )
            return map
        }()

        /// The titles of the feature collection infos in the OGC API.
        @Published private(set) var featureCollectionTitles: [String] = []

        /// The OGC feature collection info from the OCG API.
        private(set) var featureCollectionInfos: [String: OGCFeatureCollectionInfo] = [:]

        /// The OGC API feature service.
        private var service: OGCFeatureService!

        /// The query parameters to populate features from the OGC API service.
        private let queryParameters: QueryParameters = {
            let queryParameters = QueryParameters()
            // Set a limit of 1000 on the number of returned features per request,
            // because the default on some services could be as low as 10.
            queryParameters.maxFeatures = 1_000
            return queryParameters
        }()

        /// Returns a renderer with the appropriate symbol type for a geometry type.
        /// - Parameter geometryType: The geometry type.
        /// - Returns: A `SimpleRenderer` with the correct symbol for the given geometry.
        private func makeRenderer(withType geometryType: Geometry.Type) -> SimpleRenderer? {
            let symbol: Symbol
            switch geometryType {
            case is Point.Type, is Multipoint.Type:
                symbol = SimpleMarkerSymbol(style: .circle, color: .blue, size: 5)
            case is Polyline.Type:
                symbol = SimpleLineSymbol(style: .solid, color: .blue, width: 1)
            case is ArcGIS.Polygon.Type, is Envelope.Type:
                symbol = SimpleFillSymbol(style: .solid, color: .blue)
            default:
                return nil
            }
            return SimpleRenderer(symbol: symbol)
        }

        /// Creates and loads the OGC API features service from a URL.
        /// - Parameter url: The URL of the OGC service.
        /// - Returns: Returns a loaded `OCGFeatureService`.
        private func makeService(url: URL) async throws -> OGCFeatureService {
            let service = OGCFeatureService(url: url)
            try await service.load()
            if let serviceInfo = service.serviceInfo {
                let infos = serviceInfo.featureCollectionInfos
                featureCollectionTitles = infos.map(\.title)
                // The sample assumes there is no duplicate titles in the service.
                // Collections with duplicate titles will be discarded.
                featureCollectionInfos = Dictionary(
                    infos.map { ($0.title, $0) },
                    uniquingKeysWith: { (title, _) in title }
                )
            }
            return service
        }

        /// Loads OGC service for a URL so that it can be rendered on the map.
        /// - Parameter url: The URL of the OGC service.
        func loadOGCFeatureData(url: URL) async throws {
            service = try await makeService(url: url)
            if let firstFeatureCollectionTitle = featureCollectionTitles.first,
               let info = featureCollectionInfos[firstFeatureCollectionTitle] {
                try await displayLayer(with: info)
            }
        }

        /// Populates and displays a feature layer from an OGC feature collection table.
        /// - Parameter info: The `OGCFeatureCollectionInfo` selected by user.
        func displayLayer(with info: OGCFeatureCollectionInfo) async throws {
            map.removeAllOperationalLayers()
            let table = OGCFeatureCollectionTable(featureCollectionInfo: info)
            // Set the feature request mode to manual (only manual is currently
            // supported). In this mode, you must manually populate the table -
            // panning and zooming won't request features automatically.
            table.featureRequestMode = .manualCache
            _ = try await table.populateFromService(
                using: queryParameters,
                clearCache: false
            )
            let featureLayer = FeatureLayer(featureTable: table)
            if let geometryType = table.geometryType {
                featureLayer.renderer = makeRenderer(withType: geometryType)
                map.addOperationalLayer(featureLayer)
            }
        }
    }
}

private extension URL {
    /// The Daraa, Syria OGC API feature service URL.
    static var daraaService: URL { URL(string: "https://demo.ldproxy.net/daraa")! }
}

#Preview {
    BrowseOGCAPIFeatureServiceView()
}