[ios, osx] Secure coding, copying for offline regions

Implemented NSSecureCoding and NSCopying protocols for MGLTilePyramidOfflineRegion so that it can be used more fluidly by client code.

platform/darwin/include/MGLTilePyramidOfflineRegion.h

@@ -9,7 +9,7 @@ NS_ASSUME_NONNULL_BEGIN
  An offline region defined by a style URL, geographic coordinate bounds, and
  range of zoom levels.
  */
-@interface MGLTilePyramidOfflineRegion : NSObject <MGLOfflineRegion>
+@interface MGLTilePyramidOfflineRegion : NSObject <MGLOfflineRegion, NSSecureCoding, NSCopying>
 
 /**
  URL of the style whose resources are required for offline viewing.

platform/darwin/src/MGLTilePyramidOfflineRegion.mm

@@ -18,6 +18,10 @@
 
 @synthesize styleURL = _styleURL;
 
++ (BOOL)supportsSecureCoding {
+    return YES;
+}
+
 - (instancetype)init {
     [NSException raise:@"Method unavailable"
                 format:
@@ -67,4 +71,54 @@
                                                     scaleFactor);
 }
 
+- (nullable instancetype)initWithCoder:(NSCoder *)coder {
+    NSURL *styleURL = [coder decodeObjectForKey:@"styleURL"];
+    CLLocationCoordinate2D sw = CLLocationCoordinate2DMake([coder decodeDoubleForKey:@"southWestLatitude"],
+                                                           [coder decodeDoubleForKey:@"southWestLongitude"]);
+    CLLocationCoordinate2D ne = CLLocationCoordinate2DMake([coder decodeDoubleForKey:@"northEastLatitude"],
+                                                           [coder decodeDoubleForKey:@"northEastLongitude"]);
+    MGLCoordinateBounds bounds = MGLCoordinateBoundsMake(sw, ne);
+    double minimumZoomLevel = [coder decodeDoubleForKey:@"minimumZoomLevel"];
+    double maximumZoomLevel = [coder decodeDoubleForKey:@"maximumZoomLevel"];
+    
+    return [self initWithStyleURL:styleURL bounds:bounds fromZoomLevel:minimumZoomLevel toZoomLevel:maximumZoomLevel];
+}
+
+- (void)encodeWithCoder:(NSCoder *)coder
+{
+    [coder encodeObject:_styleURL forKey:@"styleURL"];
+    [coder encodeDouble:_bounds.sw.latitude forKey:@"southWestLatitude"];
+    [coder encodeDouble:_bounds.sw.longitude forKey:@"southWestLongitude"];
+    [coder encodeDouble:_bounds.ne.latitude forKey:@"northEastLatitude"];
+    [coder encodeDouble:_bounds.ne.longitude forKey:@"northEastLongitude"];
+    [coder encodeDouble:_maximumZoomLevel forKey:@"maximumZoomLevel"];
+    [coder encodeDouble:_minimumZoomLevel forKey:@"minimumZoomLevel"];
+}
+
+- (id)copyWithZone:(nullable NSZone *)zone {
+    return [[[self class] allocWithZone:zone] initWithStyleURL:_styleURL bounds:_bounds fromZoomLevel:_minimumZoomLevel toZoomLevel:_maximumZoomLevel];
+}
+
+- (BOOL)isEqual:(id)other {
+    if (other == self) {
+        return YES;
+    }
+    if (![other isKindOfClass:[self class]]) {
+        return NO;
+    }
+    
+    MGLTilePyramidOfflineRegion *otherRegion = other;
+    return (_minimumZoomLevel == otherRegion->_minimumZoomLevel
+            && _maximumZoomLevel == otherRegion->_maximumZoomLevel
+            && MGLCoordinateBoundsEqualToCoordinateBounds(_bounds, otherRegion->_bounds)
+            && [_styleURL isEqual:otherRegion->_styleURL]);
+}
+
+- (NSUInteger)hash {
+    return (_styleURL.hash
+            + @(_bounds.sw.latitude).hash + @(_bounds.sw.longitude).hash
+            + @(_bounds.ne.latitude).hash + @(_bounds.ne.longitude).hash
+            + @(_minimumZoomLevel).hash + @(_maximumZoomLevel).hash);
+}
+
 @end