Simplify geometry

// Copyright 2025 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 SimplifyGeometryView: View {
    /// A map with a light gray basemap style.
    @State private var map = Map(basemapStyle: .arcGISLightGray)
    /// A Boolean value indicating whether the geometry has been simplified.
    @State private var isSimplified = false
    /// The graphics overlay for the original polygon.
    @State private var originalOverlay = GraphicsOverlay(graphics: [makePolygonGraphic()])
    /// The graphics overlay for the simplified geometry.
    @State private var resultOverlay = GraphicsOverlay()

    var body: some View {
        MapViewReader { mapView in
            MapView(map: map, graphicsOverlays: [originalOverlay, resultOverlay])
                .task {
                    // Center the map on London.
                    await mapView.setViewpointCenter(
                        Point(
                            x: -13150,
                            y: 6710327,
                            spatialReference: .webMercator
                        ),
                        scale: 25000
                    )
                }
        }
        .toolbar {
            ToolbarItemGroup(placement: .bottomBar) {
                Button("Simplify", role: .cancel) {
                    simplifyGeometry()
                }
                .disabled(isSimplified)

                Button("Reset") {
                    // Clear the simplified overlay and reset state.
                    resultOverlay.removeAllGraphics()
                    isSimplified = false
                }
                .disabled(!isSimplified)
            }
        }
    }

    /// Checks to see whether the polygon geometry has been simplified, if not, simplifies the geometry and then displays it in filled red.
    private func simplifyGeometry() {
        guard let original = originalOverlay.graphics.first?.geometry,
              !GeometryEngine.isSimple(original) else { return }
        if let simplified = GeometryEngine.simplify(original) {
            // Define a red-filled symbol for the simplified result.
            let redSymbol = SimpleFillSymbol(style: .solid, color: .red, outline: .lineSymbol)
            // Create a graphic from the simplified geometry and add it to the result overlay.
            let resultGraphic = Graphic(geometry: simplified, symbol: redSymbol)
            resultOverlay.addGraphic(resultGraphic)
            // Set simplified state to true.
            isSimplified = true
        }
    }

    /// Creates a polygon geometry that can be simplified.
    private static func makePolygonGraphic() -> Graphic {
        let part1 = MutablePart(
            points: [
                Point(x: -13020, y: 6710130),
                Point(x: -14160, y: 6710130),
                Point(x: -14160, y: 6709300),
                Point(x: -13020, y: 6709300),
                Point(x: -13020, y: 6710130)
            ],
            spatialReference: .webMercator
        )
        let part2 = MutablePart(
            points: [
                Point(x: -12160, y: 6710730),
                Point(x: -13160, y: 6710730),
                Point(x: -13160, y: 6709100),
                Point(x: -12160, y: 6709100),
                Point(x: -12160, y: 6710730)
            ],
            spatialReference: .webMercator
        )
        let part3 = MutablePart(
            points: [
                Point(x: -12560, y: 6710030),
                Point(x: -13520, y: 6710030),
                Point(x: -13520, y: 6709000),
                Point(x: -12560, y: 6709000),
                Point(x: -12560, y: 6710030)
            ],
            spatialReference: .webMercator
        )
        // Build the full polygon from all parts.
        let polygonBuilder = PolygonBuilder(spatialReference: .webMercator)
        polygonBuilder.parts.append(part1)
        polygonBuilder.parts.append(part2)
        polygonBuilder.parts.append(part3)
        // Convert to a geometry and wrap it in a graphic with transparent fill.
        let polygon = polygonBuilder.toGeometry()
        let fillSymbol = SimpleFillSymbol(style: .solid, color: .clear, outline: .lineSymbol)
        return Graphic(geometry: polygon, symbol: fillSymbol)
    }
}

private extension Symbol {
    static var lineSymbol: LineSymbol {
        SimpleLineSymbol(style: .solid, color: .black, width: 1)
    }
}

#Preview {
    SimplifyGeometryView()
}