Generate offline map

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//
// Copyright 2018 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
//
//   http://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 UIKit
import ArcGIS

class GenerateOfflineMapViewController: UIViewController {
    @IBOutlet var mapView: AGSMapView!
    @IBOutlet var extentView: UIView!
    @IBOutlet var barButtonItem: UIBarButtonItem!
    @IBOutlet var progressView: UIProgressView!
    @IBOutlet var progressLabel: UILabel!
    @IBOutlet var progressParentView: UIView!
    @IBOutlet var cancelButton: UIButton!

    private var portalItem: AGSPortalItem?
    private var parameters: AGSGenerateOfflineMapParameters?
    private var offlineMapTask: AGSOfflineMapTask?
    private var generateOfflineMapJob: AGSGenerateOfflineMapJob?

    private var jobProgressObservation: NSKeyValueObservation?

    override func viewDidLoad() {
        super.viewDidLoad()

        // add the source code button item to the right of navigation bar
        (navigationItem.rightBarButtonItem as! SourceCodeBarButtonItem).filenames = ["GenerateOfflineMapViewController"]

        addMap()
    }

    private func addMap() {
        // portal for the web map
        let portal = AGSPortal.arcGISOnline(withLoginRequired: false)

        // portal item for web map
        let portalItem = AGSPortalItem(portal: portal, itemID: "acc027394bc84c2fb04d1ed317aac674")
        self.portalItem = portalItem

        // map from portal item
        let map = AGSMap(item: portalItem)

        // assign map to the map view
        mapView.map = map

        // disable the bar button item until the map loads
        mapView.map?.load { [weak self] (error) in
            guard let self = self else {
                return
            }

            if let error = error {
                if (error as NSError).code != NSUserCancelledError {
                    // show error
                    self.presentAlert(error: error)
                }
                return
            }

            self.barButtonItem.isEnabled = true
        }

        // instantiate offline map task
        offlineMapTask = AGSOfflineMapTask(portalItem: portalItem)

        // setup extent view
        extentView.layer.borderColor = UIColor.red.cgColor
        extentView.layer.borderWidth = 3
    }

    private func takeMapOffline() {
        guard let offlineMapTask = offlineMapTask,
            let parameters = parameters else {
            return
        }

        let downloadDirectory = getNewOfflineMapDirectoryURL()

        let generateOfflineMapJob = offlineMapTask.generateOfflineMapJob(with: parameters, downloadDirectory: downloadDirectory)
        self.generateOfflineMapJob = generateOfflineMapJob

        // observe the job's progress
        jobProgressObservation = generateOfflineMapJob.progress.observe(\.fractionCompleted, options: .new) { [weak self] (progress, _) in
            DispatchQueue.main.async {
                // update progress label
                self?.progressLabel.text = progress.localizedDescription
                // update progress view
                self?.progressView.progress = Float(progress.fractionCompleted)
            }
        }

        // unhide the progress parent view
        progressParentView.isHidden = false

        // start the job
        generateOfflineMapJob.start(statusHandler: nil) { [weak self] (result, error) in
            guard let self = self else {
                return
            }

            // remove KVO observer
            self.jobProgressObservation = nil

            if let error = error {
                // do not display error if user simply cancelled the request
                if (error as NSError).code != NSUserCancelledError {
                    self.presentAlert(error: error)
                }
            } else if let result = result {
                self.offlineMapGenerationDidSucceed(with: result)
            }
        }
    }

    /// Called when the generate offline map job finishes successfully.
    ///
    /// - Parameter result: The result of the generate offline map job.
    func offlineMapGenerationDidSucceed(with result: AGSGenerateOfflineMapResult) {
        // Show any layer or table errors to the user.
        if let layerErrors = result.layerErrors as? [AGSLayer: Error],
            let tableErrors = result.tableErrors as? [AGSFeatureTable: Error],
            !(layerErrors.isEmpty && tableErrors.isEmpty) {
            let errorMessages = layerErrors.map { "\($0.key.name): \($0.value.localizedDescription)" } +
                tableErrors.map { "\($0.key.displayName): \($0.value.localizedDescription)" }

            presentAlert(title: "Offline Map Generated with Errors",
                         message: "The following error(s) occurred while generating the offline map:\n\n\(errorMessages.joined(separator: "\n"))")
        }

        // disable cancel button
        cancelButton.isEnabled = false

        // assign offline map to map view
        mapView.map = result.offlineMap
    }

    // MARK: - Actions

    @IBAction func generateOfflineMapAction() {
        // disable bar button item
        barButtonItem.isEnabled = false

        // hide the extent view
        extentView.isHidden = true

        // show progress hud
        UIApplication.shared.showProgressHUD(message: "Getting default parameters")

        // get the area outlined by the extent view
        let areaOfInterest = extentViewFrameToEnvelope()

        // default parameters for offline map task
        offlineMapTask?.defaultGenerateOfflineMapParameters(withAreaOfInterest: areaOfInterest) { [weak self] (parameters: AGSGenerateOfflineMapParameters?, error: Error?) in
            // dismiss progress hud
            UIApplication.shared.hideProgressHUD()
            guard let self = self else { return }
            if let parameters = parameters {
                // The parameters for creating a job of offline maps generation.
                self.parameters = parameters

                // Take map offline.
                self.takeMapOffline()
            } else if let error = error {
                self.presentAlert(error: error)
            }
        }
    }

    @IBAction func cancelAction() {
        // cancel generate offline map job
        generateOfflineMapJob?.progress.cancel()

        progressParentView.isHidden = true
        progressView.progress = 0
        progressLabel.text = ""

        // enable take map offline bar button item
        barButtonItem.isEnabled = true

        // unhide the extent view
        extentView.isHidden = false
    }

    // MARK: - Helper methods

    private func showLoginQueryAlert() {
        let alertController = UIAlertController(title: nil, message: "This sample requires you to login in order to take the map's basemap offline. Would you like to continue?", preferredStyle: .alert)
        let loginAction = UIAlertAction(title: "Login", style: .default) { [weak self] (_) in
            self?.addMap()
        }

        let cancelAction = UIAlertAction(title: "Cancel", style: .cancel)

        alertController.addAction(cancelAction)
        alertController.addAction(loginAction)
        alertController.preferredAction = loginAction
        present(alertController, animated: true)
    }

    private func extentViewFrameToEnvelope() -> AGSEnvelope {
        let frame = mapView.convert(extentView.frame, from: view)

        // the lower-left corner
        let minPoint = mapView.screen(toLocation: frame.origin)

        // the upper-right corner
        let maxPoint = mapView.screen(toLocation: CGPoint(x: frame.maxX, y: frame.maxY))

        // return the envenlope covering the entire extent frame
        return AGSEnvelope(min: minPoint, max: maxPoint)
    }

    private func getNewOfflineMapDirectoryURL() -> URL {
        // get a suitable directory to place files
        let documentDirectoryURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!

        // create a unique name based on current timestamp
        let formattedDate = ISO8601DateFormatter().string(from: Date())

        return documentDirectoryURL.appendingPathComponent("\(formattedDate)")
    }
}