A native KML parser

KMLParser.swift

//
//  KMLParser.swift
//  KMLViewer
//
//  Translated by OOPer in cooperation with shlab.jp, on 2015/10/17.
//
//
/*
 Copyright (C) 2015 Apple Inc. All Rights Reserved.
 See LICENSE.txt for this sample’s licensing information

 Abstract:
 Implements a limited KML parser.
      The following KML types are supported:
              Style,
              LineString,
              Point,
              Polygon,
              Placemark.
           All other types are ignored
*/

import UIKit
import MapKit

/*
 Copyright (C) 2015 Apple Inc. All Rights Reserved.
 See LICENSE.txt for this sample’s licensing information

 Abstract:
 KMLElement and subclasses declared here implement a class hierarchy for storing a KML document structure.  The actual KML file is parsed with a SAX parser and only the relevant document structure is retained in the object graph produced by the parser.  Data parsed is also transformed into appropriate UIKit and MapKit classes as necessary.

      Abstract KMLElement type.  Handles storing an element identifier (id="...") as well as a buffer for accumulating character data parsed from the xml. In general, subclasses should have beginElement and endElement classes for keeping track of parsing state.  The parser will call beginElement when an interesting element is encountered, then all character data found in the element will be stored into accum, and then when endElement is called accum will be parsed according to the conventions for that particular element type in order to save the data from the element.  Finally, clearString will be called to reset the character data accumulator.
 */

// Convert a KML coordinate list string to a C array of CLLocationCoordinate2Ds.
// KML coordinate lists are longitude,latitude[,altitude] tuples specified by whitespace.
extension CLLocationCoordinate2D {
    static func strToCoords(_ str: String) -> [CLLocationCoordinate2D] {
        var coords: [CLLocationCoordinate2D] = []
        coords.reserveCapacity(10)
        
        let tuples = str.components(separatedBy: CharacterSet.whitespacesAndNewlines)
        for tuple in tuples {
            
            var lat: Double = 0.0, lon: Double = 0.0
            let scanner = Scanner(string: tuple)
            scanner.charactersToBeSkipped = CharacterSet(charactersIn: ",")
            var success = scanner.scanDouble(&lon)
            if success {
                success = scanner.scanDouble(&lat)
            }
            if success  {
                let c = CLLocationCoordinate2DMake(lat, lon)
                if CLLocationCoordinate2DIsValid(c) {
                    coords.append(c)
                }
            }
        }
        
        return coords
    }
}


class KMLParser: NSObject, XMLParserDelegate {
    private var _styles: [String: KMLStyle] = [:]
    private var _placemarks: [KMLPlacemark] = []
    
    private var _placemark: KMLPlacemark?
    private var _style: KMLStyle?
    
    private var _xmlParser: XMLParser!
    
    // After parsing has completed, this method loops over all placemarks that have
    // been parsed and looks up their corresponding KMLStyle objects according to
    // the placemark's styleUrl property and the global KMLStyle object's identifier.
    func assignStyles() {
        for placemark in _placemarks {
            if placemark.style == nil, let styleUrl = placemark.styleUrl {
                if styleUrl.hasPrefix("#") {
                    let styleID = String(styleUrl.dropFirst(1))
                    let style = _styles[styleID]
                    placemark.style = style
                }
            }
        }
    }
    
    init(url: URL) {
        _xmlParser = XMLParser(contentsOf: url)
        super.init()
        
        _xmlParser.delegate = self
    }
    
    
    func parseKML() {
        _xmlParser.parse()
        self.assignStyles()
    }
    
    // Return the list of KMLPlacemarks from the object graph that contain overlays
    // (as opposed to simply point annotations).
    var overlays: [MKOverlay] {
        return _placemarks.compactMap{$0.overlay}
    }
    
    // Return the list of KMLPlacemarks from the object graph that are simply
    // MKPointAnnotations and are not MKOverlays.
    var points: [MKAnnotation] {
        return _placemarks.compactMap{$0.point}
    }
    
    func viewForAnnotation(_ point: MKAnnotation) -> MKAnnotationView? {
        // Find the KMLPlacemark object that owns this point and get
        // the view from it.
        for placemark in _placemarks {
            if placemark.point === point {
                return placemark.annotationView
            }
        }
        return nil
    }
    
    func rendererForOverlay(_ overlay: MKOverlay) -> MKOverlayRenderer? {
        // Find the KMLPlacemark object that owns this overlay and get
        // the view from it.
        for placemark in _placemarks {
            if placemark.overlay === overlay {
                return placemark.overlayPathRenderer
            }
        }
        return nil
    }
    
    //MARK: NSXMLParserDelegate
    
    func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {
        let ident = attributeDict["id"]
        
        let style = _placemark?.style ?? _style
        
        // Style and sub-elements
        switch elementName {
        case ELTYPE("Style"):
            if let placemark = _placemark {
                placemark.beginStyleWithIdentifier(ident)
            } else if let identifier = ident {
                _style = KMLStyle(identifier: identifier)
            }
        case ELTYPE("PolyStyle"):
            style?.beginPolyStyle()
        case ELTYPE("LineStyle"):
            style?.beginLineStyle()
        case ELTYPE("color"):
            style?.beginColor()
        case ELTYPE("width"):
            style?.beginWidth()
        case ELTYPE("fill"):
            style?.beginFill()
        case ELTYPE("outline"):
            style?.beginOutline()
            // Placemark and sub-elements
        case ELTYPE("Placemark"):
            _placemark = KMLPlacemark(identifier: ident)
        case ELTYPE("Name"):
            _placemark?.beginName()
        case ELTYPE("Description"):
            _placemark?.beginDescription()
        case ELTYPE("styleUrl"):
            _placemark?.beginStyleUrl()
        case ELTYPE("Polygon"), ELTYPE("Point"), ELTYPE("LineString"):
            _placemark?.beginGeometryOfType(elementName, withIdentifier: ident)
            // Geometry sub-elements
        case ELTYPE("coordinates"):
            _placemark?.geometry?.beginCoordinates()
            // Polygon sub-elements
        case ELTYPE("outerBoundaryIs"):
            _placemark?.polygon?.beginOuterBoundary()
        case ELTYPE("innerBoundaryIs"):
            _placemark?.polygon?.beginInnerBoundary()
        case ELTYPE("LinearRing"):
            _placemark?.polygon?.beginLinearRing()
        default:
            break
        }
    }
    
    func parser(_ parser: XMLParser, didEndElement elementName: String, namespaceURI: String?, qualifiedName qName: String?) {
        let style = _placemark?.style ?? _style
        
        // Style and sub-elements
        switch elementName {
        case ELTYPE("Style"):
            if let placemark = _placemark {
                placemark.endStyle()
            } else if _style != nil {
                _styles[_style!.identifier!] = _style
                _style = nil
            }
        case ELTYPE("PolyStyle"):
            style?.endPolyStyle()
        case ELTYPE("LineStyle"):
            style?.endLineStyle()
        case ELTYPE("color"):
            style?.endColor()
        case ELTYPE("width"):
            style?.endWidth()
        case ELTYPE("fill"):
            style?.endFill()
        case ELTYPE("outline"):
            style?.endOutline()
            // Placemark and sub-elements
        case ELTYPE("Placemark"):
            if let placemark = _placemark {
                _placemarks.append(placemark)
                _placemark = nil
            }
        case ELTYPE("Name"):
            _placemark?.endName()
        case ELTYPE("Description"):
            _placemark?.endDescription()
        case ELTYPE("styleUrl"):
            _placemark?.endStyleUrl()
        case ELTYPE("Polygon"), ELTYPE("Point"), ELTYPE("LineString"):
            _placemark?.endGeometry()
            // Geometry sub-elements
        case ELTYPE("coordinates"):
            _placemark?.geometry?.endCoordinates()
            // Polygon sub-elements
        case ELTYPE("outerBoundaryIs"):
            _placemark?.polygon?.endOuterBoundary()
        case ELTYPE("innerBoundaryIs"):
            _placemark?.polygon?.endInnerBoundary()
        case ELTYPE("LinearRing"):
            _placemark?.polygon?.endLinearRing()
        default:
            break
        }
        
    }
    
    func parser(_ parser: XMLParser, foundCharacters string: String) {
        let element = _placemark ?? _style
        element?.addString(string)
    }
    
}
struct ELTYPE {
    var typeName: String
    init(_ typeName: String) {self.typeName = typeName}
}
func ~= (lhs: ELTYPE, rhs: String) -> Bool {
    return rhs.caseInsensitiveCompare(lhs.typeName) == .orderedSame
}

// Begin the implementations of KMLElement and subclasses.  These objects
// act as state machines during parsing time and then once the document is
// fully parsed they act as an object graph for describing the placemarks and
// styles that have been parsed.

class KMLElement: NSObject {
    let identifier: String?
    fileprivate var accum: String = ""
    
    init(identifier ident: String?) {
        self.identifier = ident
        super.init()
    }
    
    
    // Returns YES if we're currently parsing an element that has character
    // data contents that we are interested in saving.
    var canAddString: Bool {
        return false
    }
    
    // Add character data parsed from the xml
    func addString(_ str: String) {
        if self.canAddString {
            accum += str
        }
    }
    
    // Once the character data for an element has been parsed, use clearString to
    // reset the character buffer to get ready to parse another element.
    func clearString() {
        accum = ""
    }
}

// Represents a KML <Style> element.  <Style> elements may either be specified
// at the top level of the KML document with identifiers or they may be
// specified anonymously within a Geometry element.
class KMLStyle: KMLElement {
    private var strokeColor: UIColor?
    private var strokeWidth: CGFloat = 0.0
    private var fillColor: UIColor?
    
    private var fill: Bool = false
    private var stroke: Bool = false
    
    private struct Flags: OptionSet {
        var rawValue: Int32
        init(rawValue: Int32) {self.rawValue = rawValue}
        static let inLineStyle = Flags(rawValue: 1<<0)
        static let inPolyStyle = Flags(rawValue: 1<<1)
        
        static let inColor = Flags(rawValue: 1<<2)
        static let inWidth = Flags(rawValue: 1<<3)
        static let inFill = Flags(rawValue: 1<<4)
        static let inOutline = Flags(rawValue: 1<<5)
    }
    private var flags: Flags = Flags(rawValue: 0)
    
    override var canAddString: Bool {
        return flags.intersection([.inColor, .inWidth, .inFill, .inOutline]) != []
    }
    
    func beginLineStyle() {
        flags.insert(.inLineStyle)
    }
    
    func endLineStyle() {
        flags.remove(.inLineStyle)
    }
    
    func beginPolyStyle() {
        flags.insert(.inPolyStyle)
    }
    
    func endPolyStyle() {
        flags.remove(.inPolyStyle)
    }
    
    func beginColor() {
        flags.insert(.inColor)
    }
    
    func endColor() {
        flags.remove(.inColor)
        
        if flags.contains(.inLineStyle) {
            strokeColor = UIColor(KMLString: accum)
        } else if flags.contains(.inPolyStyle) {
            fillColor = UIColor(KMLString: accum)
        }
        
        self.clearString()
    }
    
    func beginWidth() {
        flags.insert(.inWidth)
    }
    
    func endWidth() {
        flags.remove(.inWidth)
        strokeWidth = CGFloat(Double(accum) ?? 0.0)
        self.clearString()
    }
    
    func beginFill() {
        flags.insert(.inFill)
    }
    
    func endFill() {
        flags.remove(.inFill)
        fill = (accum as NSString).boolValue
        self.clearString()
    }
    
    func beginOutline() {
        flags.insert(.inOutline)
    }
    
    func endOutline() {
        stroke = (accum as NSString).boolValue
        self.clearString()
    }
    
    func applyToOverlayPathRenderer(_ renderer: MKOverlayPathRenderer) {
        renderer.strokeColor = strokeColor
        renderer.fillColor = fillColor
        renderer.lineWidth = strokeWidth
    }
    
}

class KMLGeometry: KMLElement {
    fileprivate struct Flags: OptionSet {
        var rawValue: Int32
        init(rawValue: Int32) {self.rawValue = rawValue}
        
        static let inCoords = Flags(rawValue: 1<<0)
    }
    fileprivate var flags: Flags = Flags(rawValue: 0)
    
    override var canAddString: Bool {
        return flags.contains(.inCoords)
    }
    
    func beginCoordinates() {
        flags.insert(.inCoords)
    }
    
    func endCoordinates() {
        flags.remove(.inCoords)
    }
    
    // Create (if necessary) and return the corresponding Map Kit MKShape object
    // corresponding to this KML Geometry node.
    var mapkitShape: MKShape? {
        return nil
    }
    
    // Create (if necessary) and return the corresponding MKOverlayPathRenderer for
    // the MKShape object.
    func createOverlayPathRenderer(_ shape: MKShape) -> MKOverlayPathRenderer? {
        return nil
    }
    
}

// A KMLPoint element corresponds to an MKAnnotation and MKPinAnnotationView
class KMLPoint: KMLGeometry {
    var point: CLLocationCoordinate2D = CLLocationCoordinate2D()
    
    override func endCoordinates() {
        flags.remove(.inCoords)
        
        let points = CLLocationCoordinate2D.strToCoords(accum)
        if points.count == 1 {
            point = points[0]
        }
        
        self.clearString()
    }
    
    override var mapkitShape: MKShape? {
        // KMLPoint corresponds to MKPointAnnotation
        let annotation = MKPointAnnotation()
        annotation.coordinate = point
        return annotation
    }
    
    // KMLPoint does not override MKOverlayPathRenderer: because there is no such
    // thing as an overlay view for a point.  They use MKAnnotationViews which
    // are vended by the KMLPlacemark class.
    
}

// A KMLPolygon element corresponds to an MKPolygon and MKPolygonView
class KMLPolygon: KMLGeometry {
    private var outerRing: String = ""
    private var innerRings: [String] = []
    
    private struct PolyFlags: OptionSet {
        var rawValue: Int32
        init(rawValue: Int32) {self.rawValue = rawValue}
        
        static let inOuterBoundary = PolyFlags(rawValue: 1<<0)
        static let inInnerBoundary = PolyFlags(rawValue: 1<<1)
        static let inLinearRing = PolyFlags(rawValue: 1<<2)
    }
    private var polyFlags: PolyFlags = PolyFlags(rawValue: 0)
    
    
    override var canAddString: Bool {
        return polyFlags.contains(.inLinearRing) && flags.contains(.inCoords)
    }
    
    func beginOuterBoundary() {
        polyFlags.insert(.inOuterBoundary)
    }
    
    func endOuterBoundary() {
        polyFlags.remove(.inOuterBoundary)
        outerRing = accum
        self.clearString()
    }
    
    func beginInnerBoundary() {
        polyFlags.insert(.inInnerBoundary)
    }
    
    func endInnerBoundary() {
        polyFlags.remove(.inInnerBoundary)
        let ring = accum
        innerRings.append(ring)
        self.clearString()
    }
    
    func beginLinearRing() {
        polyFlags.insert(.inLinearRing)
    }
    
    func endLinearRing() {
        polyFlags.remove(.inLinearRing)
    }
    
    override var mapkitShape: MKShape? {
        // KMLPolygon corresponds to MKPolygon
        
        // The inner and outer rings of the polygon are stored as kml coordinate
        // list strings until we're asked for mapkitShape.  Only once we're here
        // do we lazily transform them into CLLocationCoordinate2D arrays.
        
        // First build up a list of MKPolygon cutouts for the interior rings.
        let innerPolys: [MKPolygon] = innerRings.map {coordStr in
            var coords = CLLocationCoordinate2D.strToCoords(coordStr)
            return MKPolygon(coordinates: &coords, count: coords.count)
        }
        // Now parse the outer ring.
        
        var coords = CLLocationCoordinate2D.strToCoords(outerRing)
        
        // Build a polygon using both the outer coordinates and the list (if applicable)
        // of interior polygons parsed.
        let poly = MKPolygon(coordinates: &coords, count: coords.count, interiorPolygons: innerPolys)
        return poly
    }
    
    override func createOverlayPathRenderer(_ shape: MKShape) -> MKOverlayPathRenderer? {
        let polyPath = MKPolygonRenderer(polygon: shape as! MKPolygon)
        return polyPath
    }
    
}

class KMLLineString: KMLGeometry {
    var points: [CLLocationCoordinate2D] = []
    
    override func endCoordinates() {
        flags.remove(.inCoords)
        
        points = CLLocationCoordinate2D.strToCoords(accum)
        
        self.clearString()
    }
    
    override var mapkitShape: MKShape? {
        // KMLLineString corresponds to MKPolyline
        return MKPolyline(coordinates: &points, count: points.count)
    }
    
    override func createOverlayPathRenderer(_ shape: MKShape) -> MKOverlayPathRenderer? {
        let polyLine = MKPolylineRenderer(polyline: shape as! MKPolyline)
        return polyLine
    }
    
}

class KMLPlacemark: KMLElement {
    var style: KMLStyle?
    private(set) var geometry: KMLGeometry?
    
    // Corresponds to the title property on MKAnnotation
    private(set) var name: String?
    // Corresponds to the subtitle property on MKAnnotation
    private(set) var placemarkDescription: String?
    
    var styleUrl: String?
    
    private var mkShape: MKShape?
    
    private var _annotationView: MKAnnotationView?
    private var _overlayPathRenderer: MKOverlayPathRenderer?
    
    struct Flags: OptionSet {
        var rawValue: Int32
        init(rawValue: Int32) {self.rawValue = rawValue}
        
        static let inName = Flags(rawValue: 1<<0)
        static let inDescription = Flags(rawValue: 1<<1)
        static let inStyle = Flags(rawValue: 1<<2)
        static let inGeometry = Flags(rawValue: 1<<3)
        static let inStyleUrl = Flags(rawValue: 1<<4)
    }
    var flags: Flags = Flags(rawValue: 0)
    
    override var canAddString: Bool {
        return flags.intersection([.inName, .inStyleUrl, .inDescription]) != []
    }
    
    override func addString(_ str: String) {
        if flags.contains(.inStyle) {
            style?.addString(str)
        } else if flags.contains(.inGeometry) {
            geometry?.addString(str)
        } else {
            super.addString(str)
        }
    }
    
    func beginName() {
        flags.insert(.inName)
    }
    
    func endName() {
        flags.remove(.inName)
        name = accum
        self.clearString()
    }
    
    func beginDescription() {
        flags.insert(.inDescription)
    }
    
    func endDescription() {
        flags.remove(.inDescription)
        placemarkDescription = accum
        self.clearString()
    }
    
    func beginStyleUrl() {
        flags.insert(.inStyleUrl)
    }
    
    func endStyleUrl() {
        flags.remove(.inStyleUrl)
        styleUrl = accum
        self.clearString()
    }
    
    func beginStyleWithIdentifier(_ ident: String?) {
        flags.insert(.inStyle)
        style = KMLStyle(identifier: ident)
    }
    
    func endStyle() {
        flags.remove(.inStyle)
    }
    
    func beginGeometryOfType(_ elementName: String, withIdentifier ident: String?) {
        flags.insert(.inGeometry)
        switch elementName {
        case ELTYPE("Point"):
            geometry = KMLPoint(identifier: ident)
        case ELTYPE("Polygon"):
            geometry = KMLPolygon(identifier: ident)
        case ELTYPE("LineString"):
            geometry = KMLLineString(identifier: ident)
        default:
            break
        }
    }
    
    func endGeometry() {
        flags.remove(.inGeometry)
    }
    
    var polygon: KMLPolygon? {
        return geometry as? KMLPolygon
    }
    
    private func _createShape() {
        if mkShape == nil {
            mkShape = geometry?.mapkitShape
            mkShape?.title = name
            // Skip setting the subtitle for now because they're frequently
            // too verbose for viewing on in a callout in most kml files.
            //        mkShape.subtitle = placemarkDescription;
        }
    }
    
    var overlay: MKOverlay? {
        self._createShape()
        
        return mkShape as? MKOverlay
        
    }
    
    var point: MKAnnotation? {
        self._createShape()
        
        // Make sure to check if this is an MKPointAnnotation.  MKOverlays also
        // conform to MKAnnotation, so it isn't sufficient to just check to
        // conformance to MKAnnotation.
        return mkShape as? MKPointAnnotation
        
    }
    
    var overlayPathRenderer: MKOverlayPathRenderer? {
        if _overlayPathRenderer == nil {
            if let overlay = self.overlay {
                _overlayPathRenderer = geometry?.createOverlayPathRenderer(overlay as! MKShape)
                style?.applyToOverlayPathRenderer(_overlayPathRenderer!)
            }
        }
        return _overlayPathRenderer
    }
    
    var annotationView: MKAnnotationView? {
        if _annotationView == nil {
            if let annotation = self.point {
                let pin = MKPinAnnotationView(annotation: annotation, reuseIdentifier: nil)
                pin.canShowCallout = true
                pin.animatesDrop = true
                _annotationView = pin
            }
        }
        return _annotationView
    }
    
}

extension UIColor {
    
    // Parse a KML string based color into a UIColor.  KML colors are agbr hex encoded.
    convenience init(KMLString kmlColorString: String) {
        let scanner = Scanner(string: kmlColorString)
        var color: UInt32 = 0
        scanner.scanHexInt32(&color)
        
        let a = (color >> 24) & 0x000000FF
        let b = (color >> 16) & 0x000000FF
        let g = (color >> 8) & 0x000000FF
        let r = color & 0x000000FF
        
        let rf = CGFloat(r) / 255.0
        let gf = CGFloat(g) / 255.0
        let bf = CGFloat(b) / 255.0
        let af = CGFloat(a) / 255.0
        
        self.init(red: rf, green: gf, blue: bf, alpha: af)
    }
    
}