MKMapView+Additions.swift

//
//  MKMapView+Additions.swift
//
//  The MIT License (MIT)
//
//  Copyright (c) 2015-present patrick piemonte (http://patrickpiemonte.com/)
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//  SOFTWARE.
//

import Foundation
import MapKit

extension MKMapView {

    public var isEmptyExceptUserLocation: Bool {
        let annotations = self.annotations.filter { !($0 is MKUserLocation) }
        return annotations.isEmpty
    }

    /// https://gist.github.com/andrewgleave/915374
    public func setVisibleMapRectToFitAllAnnotations(edgePadding: UIEdgeInsets = UIEdgeInsets(top: 35, left: 35, bottom: 35, right: 35),
                                                     animated: Bool = true) {
        var zoomRect = MKMapRect.null
        let annotations = self.annotations.filter { !($0 is MKUserLocation) }
        for annotation in annotations {
            let annotationPoint = MKMapPoint(annotation.coordinate)
            let pointRect = MKMapRect(x: annotationPoint.x, y: annotationPoint.y, width: 0, height: 0)
            if zoomRect.isNull {
                zoomRect = pointRect
            } else {
                zoomRect = zoomRect.union(pointRect)
            }
        }
        self.setVisibleMapRect(zoomRect, edgePadding: edgePadding, animated: true)
    }

    public var visibleAreaInMeters: Double {
        let topLeft = visibleMapRect.origin
        let topRight = MKMapPoint(x: visibleMapRect.origin.x + visibleMapRect.size.width, y: visibleMapRect.origin.y)
        let bottomRight = MKMapPoint(x: visibleMapRect.origin.x + visibleMapRect.size.width, y: visibleMapRect.origin.y + visibleMapRect.size.height)
        let hDist = topLeft.distance(to: topRight)
        let vDist = topRight.distance(to: bottomRight)
        return hDist * vDist
    }

    public var zoomLevel: Double {
        get {
            log2(360.0 * Double(self.frame.size.width) / (256.0 * self.region.span.longitudeDelta))
        }
        set (newZoomLevel) {
            setCenterCoordinate(coordinate: self.centerCoordinate, zoomLevel: newZoomLevel, animated: false)
        }
    }

    public func setCenterCoordinate(coordinate: CLLocationCoordinate2D, zoomLevel: Double, animated: Bool) {
        let span = MKCoordinateSpan(latitudeDelta: 0,
                                    longitudeDelta: 360 / pow(2, zoomLevel) * Double(self.frame.size.width) / 256)
        setRegion(MKCoordinateRegion(center: coordinate, span: span), animated: animated)
    }

}