import Foundation

class PropfindParser: NSObject, XMLParserDelegate {
    private let data: Data
    private var result: [DenoteNote] = []

    private var currentHref = ""
    private var currentModifiedDate: Date?
    private var isCollection = false
    private var currentText = ""

    private let dateFormatter: DateFormatter = {
        let f = DateFormatter()
        f.locale = Locale(identifier: "en_US_POSIX")
        f.dateFormat = "EEE, dd MMM yyyy HH:mm:ss zzz"
        return f
    }()

    init(data: Data) { self.data = data }

    func parse() -> [DenoteNote] {
        let parser = XMLParser(data: data)
        parser.delegate = self
        parser.shouldProcessNamespaces = true
        parser.parse()
        return result
    }

    func parser(_ parser: XMLParser, didStartElement elementName: String,
                namespaceURI: String?, qualifiedName: String?,
                attributes: [String: String] = [:]) {
        currentText = ""
        switch elementName {
        case "response":
            currentHref = ""
            currentModifiedDate = nil
            isCollection = false
        case "collection":
            isCollection = true
        default:
            break
        }
    }

    func parser(_ parser: XMLParser, foundCharacters string: String) {
        currentText += string
    }

    func parser(_ parser: XMLParser, didEndElement elementName: String,
                namespaceURI: String?, qualifiedName: String?) {
        let text = currentText.trimmingCharacters(in: .whitespacesAndNewlines)
        switch elementName {
        case "href":
            currentHref = text
        case "getlastmodified":
            currentModifiedDate = dateFormatter.date(from: text)
        case "response":
            guard !isCollection else { return }
            if let note = DenoteNote.parse(href: currentHref, modifiedDate: currentModifiedDate) {
                result.append(note)
            }
        default:
            break
        }
    }
}