Find nearest vertex

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// Copyright 2023 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 FindNearestVertexView: View {
    /// The view model for the sample.
    @StateObject private var model = Model()

    /// A location callout placement.
    @State var calloutPlacement: CalloutPlacement?

    /// The tap location.
    @State var tapLocation: Point!

    var body: some View {
        MapView(map: model.map, graphicsOverlays: [model.graphicsOverlay])
            .onSingleTapGesture { _, mapPoint in
                // Normalize map point.
                guard let normalizedMapPoint = GeometryEngine.normalizeCentralMeridian(of: mapPoint) as? Point else { return }
                tapLocation = normalizedMapPoint
                if calloutPlacement == nil {
                    // Draw the point graphics.
                    model.updateNearestPoints(point: tapLocation)
                    // Show the callout at the tapped location.
                    calloutPlacement = CalloutPlacement.location(tapLocation)
                } else {
                    // Remove points and hide callout.
                    model.tapLocationGraphic.geometry = nil
                    model.nearestCoordinateGraphic.geometry = nil
                    model.nearestVertexGraphic.geometry = nil
                    calloutPlacement = nil
                }
            }
            .callout(placement: $calloutPlacement.animation(.default.speed(2))) { _ in
                VStack(alignment: .leading) {
                    Text("Proximity Result")
                        .font(.headline)
                    Text("Vertex dist: \(model.nearestVertexDistance); Point dist: \(model.nearestCoordinateDistance)")
                        .font(.callout)
                }
                .padding(5)
            }
    }
}

private extension FindNearestVertexView {
    /// The view model for the sample.
    class Model: ObservableObject {
        /// A map with a generalized US states feature layer and centered on
        /// the example polygon in California.
        let map: Map = {
            let map = Map(spatialReference: .statePlaneCaliforniaZone5)

            // Center map on the example polygon.
            map.initialViewpoint = Viewpoint(
                center: .sanBernardinoCounty.extent.center,
                scale: 8e6
            )

            // Add US states feature layer to the map.
            let usStatesGeneralizedLayer = FeatureLayer(
                item: PortalItem(
                    portal: .arcGISOnline(connection: .anonymous),
                    id: .usStatesGeneralized
                )
            )
            map.addOperationalLayer(usStatesGeneralizedLayer)

            return map
        }()

        /// The graphics overlay for the point and polygon graphics.
        let graphicsOverlay = GraphicsOverlay()

        /// An orange cross graphic for the tap location point.
        let tapLocationGraphic: Graphic = {
            let symbol = SimpleMarkerSymbol(style: .x, color: .orange, size: 15)
            return Graphic(symbol: symbol)
        }()

        /// A blue circle graphic for the nearest vertex point.
        let nearestVertexGraphic: Graphic = {
            let symbol = SimpleMarkerSymbol(style: .circle, color: .blue, size: 15)
            return Graphic(symbol: symbol)
        }()

        /// A red diamond graphic for the nearest coordinate point.
        let nearestCoordinateGraphic: Graphic = {
            let symbol = SimpleMarkerSymbol(style: .diamond, color: .red, size: 10)
            return Graphic(symbol: symbol)
        }()

        /// The nearest coordinate distance on the polygon to the tap location.
        var nearestCoordinateDistance: String = ""

        /// The nearest vertex distance on the polygon to the tap location.
        var nearestVertexDistance: String = ""

        init() {
            // Create graphic for the example polygon.
            let polygonFillSymbol = SimpleFillSymbol(
                style: .forwardDiagonal,
                color: .green,
                outline: SimpleLineSymbol(style: .solid, color: .green, width: 2)
            )
            let polygonGraphic = Graphic(
                geometry: .sanBernardinoCounty,
                symbol: polygonFillSymbol
            )

            // Add graphics to the graphicOverlay.
            graphicsOverlay.addGraphics([
                polygonGraphic,
                tapLocationGraphic,
                nearestCoordinateGraphic,
                nearestVertexGraphic
            ])
        }

        /// Draws the nearest coordinate and vertex to the point on the example polygon.
        /// - Parameter point: A `Point` to measure against.
        func updateNearestPoints(point: Point) {
            // Get nearest vertex and coordinate to the point.
            let nearestVertexResult = GeometryEngine.nearestVertex(in: .sanBernardinoCounty, to: point)!
            let nearestCoordinateResult = GeometryEngine.nearestCoordinate(in: .sanBernardinoCounty, to: point)!

            // Set the geometries for the tapped, nearest coordinate, and
            // nearest vertex point graphics.
            tapLocationGraphic.geometry = point
            nearestVertexGraphic.geometry = nearestVertexResult.coordinate
            nearestCoordinateGraphic.geometry = nearestCoordinateResult.coordinate

            // The format style with a decimal point.
            let formatStyle = Measurement<UnitLength>.FormatStyle(
                width: .abbreviated,
                numberFormatStyle: .number.precision(.fractionLength(1))
            )

            // Set the distance to the nearest vertex in the polygon.
            let vertexDistance = Measurement(
                value: nearestVertexResult.distance,
                unit: UnitLength.feet
            )
            nearestVertexDistance = vertexDistance.formatted(formatStyle)

            // Set the distance to the nearest coordinate in the polygon.
            let coordinateDistance = Measurement(
                value: nearestCoordinateResult.distance,
                unit: UnitLength.feet
            )
            nearestCoordinateDistance = coordinateDistance.formatted(formatStyle)
        }
    }
}

private extension Geometry {
    /// A polygon near San Bernardino County, California.
    static let sanBernardinoCounty: ArcGIS.Polygon = {
        let polygonBuilder = PolygonBuilder(spatialReference: .statePlaneCaliforniaZone5)
        polygonBuilder.add(Point(x: 6627416.41469281, y: 1804532.53233782))
        polygonBuilder.add(Point(x: 6669147.89779046, y: 2479145.16609522))
        polygonBuilder.add(Point(x: 7265673.02678292, y: 2484254.50442408))
        polygonBuilder.add(Point(x: 7676192.55880379, y: 2001458.66365744))
        polygonBuilder.add(Point(x: 7175695.94143837, y: 1840722.34474458))
        return polygonBuilder.toGeometry()
    }()
}

private extension SpatialReference {
    /// The spatial reference for the sample.
    static var statePlaneCaliforniaZone5: Self { SpatialReference(wkid: WKID(2229)!)! }
}

private extension PortalItem.ID {
    /// The ID used in the "US States Generalized" portal item.
    static var usStatesGeneralized: Self { Self("8c2d6d7df8fa4142b0a1211c8dd66903")! }
}

#Preview {
    FindNearestVertexView()
}