Medium.com RSS XML parser written in Swift

MediumRSSXMLParser.swift

//  Created by norsez on 30/4/18.
import Foundation

struct RssItem {
    var title = "unknown"
    var categories: [String] = []
    var pubDate = "unknown"
    var link = "http://"
    var content = "<h1>Hello World</h1>"
    var creator = "n.a."
}

struct RssFeed {
    var title = "unknown"
    var description = "n.a."
    var link = "http://"
    var icon = "http://"
    
    var items: [RssItem] = []
}

class DevMediumRSSXMLParser: NSObject, XMLParserDelegate {
    var stringBuf = ""
    var cdataBuf = ""
    var feed = RssFeed()
    var currentPathStack = [String]()
    var currentItem: RssItem?
    
    //MARK: Tags
    struct Tag {
        static let RSS = "rss"
        static let Channel = "channel"
        static let Title = "title"
        static let Description = "description"
        static let Link = "link"
        static let Image = "image"
        static let Url = "url"
        static let ContentEncoded = "content:encoded"
        static let AtomUpdated = "atom:updated"
        static let Category = "category"
        static let DcCreator = "dc:creator"
        static let Item = "item"
        
        static let path_feed_title = [Tag.RSS, Tag.Channel, Tag.Title]
        static let path_feed_desc = [Tag.RSS, Tag.Channel, Tag.Description]
        static let path_feed_link = [Tag.RSS, Tag.Channel, Tag.Link]
        static let path_feed_icon = [Tag.RSS, Tag.Channel, Image, Tag.Url]
        
        static let path_feed_item = [Tag.RSS, Tag.Channel, Tag.Item]
        static let path_feed_item_title = [Tag.RSS, Tag.Channel, Tag.Item, Tag.Title]
        static let path_feed_item_link = [Tag.RSS, Tag.Channel, Tag.Item, Tag.Link]
        static let path_feed_item_category = [Tag.RSS, Tag.Channel, Tag.Item, Tag.Category]
        static let path_feed_item_creator = [Tag.RSS, Tag.Channel, Tag.Item, Tag.DcCreator]
        static let path_feed_item_createdDate = [Tag.RSS, Tag.Channel, Tag.Item, Tag.AtomUpdated]
        static let path_feed_item_content = [Tag.RSS, Tag.Channel, Tag.Item, Tag.ContentEncoded]
        
        //Convenience method for checking the equality of two path stacks
        static func pathEquals(path1: [String], path2: [String]) -> Bool {
            
            if path1.count != path2.count {
                return false
            }
            
            for index in stride(from: path1.count-1, to: 0, by: -1) {
                if path1[index] != path2[index] {
                    return false
                }
            }
            
            return true
        }
    }
    
    //MARK: parser method
    func processParsing() {
        if Tag.pathEquals(path1: Tag.path_feed_title, path2: self.currentPathStack) {
            self.feed.title = self.cdataBuf
        }else if Tag.pathEquals(path1: Tag.path_feed_desc, path2: self.currentPathStack) {
            self.feed.description = self.cdataBuf
        }else if Tag.pathEquals(path1: Tag.path_feed_link, path2: self.currentPathStack) {
            self.feed.link = self.stringBuf
        }else if Tag.pathEquals(path1: Tag.path_feed_icon, path2: self.currentPathStack) {
            self.feed.icon = self.stringBuf
        }else if Tag.pathEquals(path1: Tag.path_feed_title, path2: self.currentPathStack) {
            self.feed.title = self.cdataBuf
        }else if Tag.pathEquals(path1: Tag.path_feed_item_title, path2: self.currentPathStack) {
            self.currentItem?.title = self.cdataBuf
        }else if Tag.pathEquals(path1: Tag.path_feed_item_link, path2: self.currentPathStack) {
            self.currentItem?.link = self.stringBuf
        }else if Tag.pathEquals(path1: Tag.path_feed_item_category, path2: self.currentPathStack) {
            self.currentItem?.categories.append(self.cdataBuf)
        }else if Tag.pathEquals(path1: Tag.path_feed_item_createdDate, path2: self.currentPathStack) {
            self.currentItem?.pubDate = self.stringBuf
        }else if Tag.pathEquals(path1: Tag.path_feed_item_creator, path2: self.currentPathStack) {
            self.currentItem?.creator = self.cdataBuf
        }else if Tag.pathEquals(path1: Tag.path_feed_item_content, path2: self.currentPathStack) {
            self.currentItem?.content = self.cdataBuf
        }
    }
    
    func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String] = [:]) {
        self.currentPathStack.append(elementName)
        
        if elementName == Tag.Item {
            self.currentItem = RssItem()
        }
    }
    
    func parser(_ parser: XMLParser, didEndElement elementName: String, namespaceURI: String?, qualifiedName qName: String?) {
        
        processParsing()
        
        //buffer clean up
        if let lastElem = self.currentPathStack.popLast() {
            if lastElem != elementName {
                Logger.log(withText: "warning: unmatched element stack popped \(lastElem) Vs. actual: \(elementName)")
            }
        }
        self.stringBuf = ""
        self.cdataBuf = ""
        if elementName == Tag.Item {
            if let item = self.currentItem {
                self.feed.items.append(item)
                self.currentItem = nil
            }
        }
    }
    
    func parser(_ parser: XMLParser, foundCDATA CDATABlock: Data) {
        if let cdblock = NSString(data: CDATABlock, encoding: String.Encoding.utf8.rawValue) as String?{
            self.cdataBuf.append(contentsOf: cdblock)
        }
    }
    
    func parser(_ parser: XMLParser, foundCharacters string: String) {
        self.stringBuf.append(contentsOf: string)
    }
    
    func parser(_ parser: XMLParser, parseErrorOccurred parseError: Error) {
        Logger.log(withErrorText: parseError.localizedDescription)
    }
    
}