GoogleMaps.swift

import UIKit
import GoogleMaps
import GooglePlaces
import CoreLocation

class ViewController: UIViewController {
    var locationManager: CLLocationManager!
    var resultsViewController: GMSAutocompleteResultsViewController?
    var searchController: UISearchController?
    var resultView: UITextView?
    var currentLocation: CLLocation?
    var placesClient: GMSPlacesClient!
    
    @IBOutlet var mapView: GMSMapView!
    
    override func viewDidLoad() {
                
        //searchbox
        resultsViewController = GMSAutocompleteResultsViewController()
        resultsViewController?.delegate = self
        searchController = UISearchController(searchResultsController: resultsViewController)
        searchController?.searchResultsUpdater = resultsViewController
        searchController?.searchBar.sizeToFit()
        navigationItem.titleView = searchController?.searchBar
        
        // When UISearchController presents the results view, present it in
        // this view controller, not one further up the chain.
        definesPresentationContext = true
        
        // Prevent the navigation bar from being hidden when searching.
        searchController?.hidesNavigationBarDuringPresentation = false
        
        placesClient = GMSPlacesClient.shared()
    }
}

/**
This extension inherit GMSAutoCompleteResult to handle
text from search bar, when user click one of result placemark
it will fetching directions api google maps
**/
extension ViewController: GMSAutocompleteResultsViewControllerDelegate {
    func resultsController(_ resultsController: GMSAutocompleteResultsViewController,
                           didAutocompleteWith place: GMSPlace) {
        searchController?.isActive = false
        
        fetchRoute(from: locationManager.location!.coordinate, to: place.coordinate)
    }
    
    func fetchRoute(from source: CLLocationCoordinate2D, to destination: CLLocationCoordinate2D) {
        //fetching google maps api with parameters coordinate origin and coordinate destination
        let url = URL(string: "https://maps.googleapis.com/maps/api/directions/json?origin=\(source.latitude),\(source.longitude)&destination=\(destination.latitude),\(destination.longitude)&sensor=false&mode=driving&key=\(googleApiKey)")!
        
        //process the result from fetching api
        URLSession.shared.dataTask(with: url, completionHandler: {
            (data, response, error) in
            if(error != nil){
                print("error")
            }else{
                
                DispatchQueue.main.async {
                    self.mapView.clear()
                    
                }
                
                do{
                    //get the json from the result
                    let json = try JSONSerialization.jsonObject(with: data!, options:.allowFragments) as! [String : AnyObject]

                    let routes = json["routes"] as! NSArray
                    
                    OperationQueue.main.addOperation({
                        for route in routes {
                            if let legs = (route as AnyObject) as? [String : AnyObject]{
                                let legs = legs["legs"] as! [[String : AnyObject]]
                                for leg in legs {
                                    let durations:NSDictionary = (leg as NSDictionary).value(forKey: "duration") as! NSDictionary
                                    let textDuration = durations.object(forKey: "text")
                                    
                                    let distance:NSDictionary = (leg as NSDictionary).value(forKey: "distance") as! NSDictionary
                                    let textDistance = distance.object(forKey: "text")
                                    self.showEstimate(distance: textDistance as! String, duration: textDuration as! String)
                                    
                                    let end_location: NSDictionary = (leg as NSDictionary).value(forKey: "end_location") as! NSDictionary
                                    let textLat = end_location.object(forKey: "lat")
                                    let textLong = end_location.object(forKey: "lng")
                                    self.showPinPoint(latitude: textLat as! Double, longitude: textLong as! Double)
                                }
                            }
                            
                            let routeOverviewPolyline:NSDictionary = (route as! NSDictionary).value(forKey: "overview_polyline") as! NSDictionary
                            let points = routeOverviewPolyline.object(forKey: "points")
                            self.drawPath(from: points as! String)
                        }
                    })
                } catch let error as NSError{
                    print("error:\(error)")
                }
            }
        }).resume()
    }
    
/**
This function used to generate the polyline
using parameters of points from overview_polyline
also move camera for user visibility
**/
    func drawPath(from polyStr: String){
        let path = GMSPath.init(fromEncodedPath: polyStr)
        let polyline = GMSPolyline.init(path: path)
        . . .
    }

/**
This function used to give user information 
about the distance and duration
**/
    func showEstimate(distance: String, duration: String){
        . . .
    }

/**
This function used to dropped pin
in location that have been choosen by user
**/
    func showPinPoint(latitude lat: Double, longitude long: Double){
        . . .
    }
    
    func resultsController(_ resultsController: GMSAutocompleteResultsViewController,
                           didFailAutocompleteWithError error: Error){
        // TODO: handle the error.
        print("Error: ", error.localizedDescription)
    }
    
    // Turn the network activity indicator on and off again.
    func didRequestAutocompletePredictions(_ viewController: GMSAutocompleteViewController) {
        UIApplication.shared.isNetworkActivityIndicatorVisible = true
    }
    
    func didUpdateAutocompletePredictions(_ viewController: GMSAutocompleteViewController) {
        UIApplication.shared.isNetworkActivityIndicatorVisible = false
    }
}

extension ViewController: CLLocationManagerDelegate {
    
    // Handle incoming location events.
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
      . . .
    }
    
    // Handle authorization for the location manager.
    func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
        // Check accuracy authorization
        let accuracy = manager.accuracyAuthorization
        switch accuracy {
        case .fullAccuracy:
            . . .
        case .reducedAccuracy:
            . . .
        @unknown default:
            fatalError()
        }
        
        // Handle authorization status
        switch status {
        case .restricted:
            . . .
        case .denied:
            . . .
        case .notDetermined:
            . . .
        case .authorizedAlways, .authorizedWhenInUse :
            . . .
        @unknown default:
            fatalError()
        }
    }
    
    // Handle location manager errors.
    func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
        locationManager.stopUpdatingLocation()
        print("Error: \(error)")
    }
}