text: /*
   * Copyright 2016 Google Inc. All rights reserved.
   *
   *
   * 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.
   */
  
  #if !defined(__has_feature) || !__has_feature(objc_arc)
  #error "This file requires ARC support."
  #endif
  
  #import "GoogleMapsDemos/Samples/PolylinesViewController.h"
  
  #import <GoogleMaps/GoogleMaps.h>
  
  @interface GMSPolyline (length)
  
  @property(nonatomic, readonly) double length;
  
  @end
  
  @implementation GMSPolyline (length)
  
  - (double)length {
    GMSLengthKind kind = [self geodesic] ? kGMSLengthGeodesic : kGMSLengthRhumb;
    return [[self path] lengthOfKind:kind];
  }
  
  @end
  
  static CLLocationCoordinate2D kSydneyAustralia = {-33.866901, 151.195988};
  static CLLocationCoordinate2D kHawaiiUSA = {21.291982, -157.821856};
  static CLLocationCoordinate2D kFiji = {-18, 179};
  static CLLocationCoordinate2D kMountainViewUSA = {37.423802, -122.091859};
  static CLLocationCoordinate2D kLimaPeru = {-12, -77};
  static bool kAnimate = true;
  
  @implementation PolylinesViewController {
    NSArray *_styles;
    NSArray *_lengths;
    NSArray *_polys;
    double _pos, _step;
    GMSMapView *_mapView;
  }
  
  - (void)tick {
    for (GMSPolyline *poly in _polys) {
      poly.spans =
          GMSStyleSpansOffset(poly.path, _styles, _lengths, kGMSLengthGeodesic, _pos);
    }
    _pos -= _step;
    if (kAnimate) {
      __weak id weakSelf = self;
      dispatch_after(dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC / 10),
                     dispatch_get_main_queue(),
                     ^{ [weakSelf tick]; });
    }
  }
  
  - (void)initLines {
    if (!_polys) {
      NSMutableArray *polys = [NSMutableArray array];
      GMSMutablePath *path = [GMSMutablePath path];
      [path addCoordinate:kSydneyAustralia];
      [path addCoordinate:kFiji];
      [path addCoordinate:kHawaiiUSA];
      [path addCoordinate:kMountainViewUSA];
      [path addCoordinate:kLimaPeru];
      [path addCoordinate:kSydneyAustralia];
      path = [path pathOffsetByLatitude:-30 longitude:0];
      _lengths = @[@([path lengthOfKind:kGMSLengthGeodesic] / 21)];
      for (int i = 0; i < 30; ++i) {
        GMSPolyline *poly = [[GMSPolyline alloc] init];
        poly.path = [path pathOffsetByLatitude:(i * 1.5) longitude:0];
        poly.strokeWidth = 8;
        poly.geodesic = YES;
        poly.map = _mapView;
        [polys addObject:poly];
      }
      _polys = polys;
    }
  }
  
  - (void)viewDidLoad {
    [super viewDidLoad];
    GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:-30
                                                            longitude:-175
                                                                 zoom:3];
    GMSMapView *mapView = [GMSMapView mapWithFrame:CGRectZero camera:camera];
    mapView.accessibilityElementsHidden = YES;
    self.view = mapView;
    _mapView = mapView;
  
    CGFloat alpha = 1;
    UIColor *green = [UIColor colorWithRed:0 green:1 blue: 0 alpha:alpha];
    UIColor *greenTransp = [UIColor colorWithRed:0 green:1 blue: 0 alpha:0];
    UIColor *red = [UIColor colorWithRed:1 green:0 blue: 0 alpha:alpha];
    UIColor *redTransp = [UIColor colorWithRed:1 green:0 blue: 0 alpha:0];
    GMSStrokeStyle *grad1 = [GMSStrokeStyle gradientFromColor:green toColor:greenTransp];
    GMSStrokeStyle *grad2 = [GMSStrokeStyle gradientFromColor:redTransp toColor:red];
    _styles = @[
                grad1,
                grad2,
                [GMSStrokeStyle solidColor:[UIColor colorWithWhite:0 alpha:0]],
                ];
    _step = 50000;
    [self initLines];
    [self tick];
  }
  
  @end
  