TSTU-Student-App-Android/app/src/main/java/ru/defend/defdevteam/tstu/FeedParser.java

package ru.defend.defdevteam.tstu;

import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

import java.io.StringReader;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

/**
 * Created by thedefend on 29.11.16.
 */

public class FeedParser {

    ParserCallback callback;
    String inputXML;

    interface ParserCallback {
        void onSuccessParsing();
        void onFailureParsing();
        void contentDispatcher(String title, String text, String link);
    }

    void registerCallback(ParserCallback callback) {
        this.callback = callback;
    }

    FeedParser() {}


    void parseXML(String inputXML) {
        try {
            this.inputXML = inputXML;
            SAXParserFactory factory = SAXParserFactory.newInstance();
            SAXParser parser = factory.newSAXParser();
            ExtendedHandler handler = new ExtendedHandler();
            InputSource inputSource = new InputSource(new StringReader(inputXML));
            parser.parse(inputSource, handler);
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    public String deleteHtmlTag(String Line, String a, String b){
        while(true) {
            if (Line.contains(a) && Line.contains(b)) {
                Line = Line.substring(0, Line.indexOf(a)) +
                        Line.substring(Line.indexOf(b) + 1, Line.length());
            } else {
                break;
            }
        }
        return Line;
    }

    public String getImageLink(String Line){
        String a = "<img src=\"";
        String b = "\" border=\"0\"";
        Line = Line.substring(Line.indexOf(a)+ a.length());
        Line = Line.substring(0, Line.indexOf(b));
        return Line;
    }

    public String getDescriptionShort(String Line){
        String a = "<div class=\"K2FeedIntroText\">";
        String b = "</div>";
        Line = Line.substring(Line.indexOf(a)+ a.length());
        Line = Line.substring(0, Line.indexOf(b));
        return deleteHtmlTag(Line, "<", ">");
    }


    public class ExtendedHandler extends DefaultHandler {
        boolean item = false;
        final String title = "title";
        final String description = "description";
        final String link = "link";
        final String date = "date";
        String titleStr = "";
        String descriptionStr = "";
        String linkStr = "";
        String dateStr = "";
        String currentItem = "";

        void refreshStrings() {
            this.titleStr = "";
            this.descriptionStr = "";
            this.linkStr = "";
            this.dateStr = "";
        }

        @Override
        public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
            currentItem = qName.toLowerCase();
            if (qName.equalsIgnoreCase("item")) {
                item = true;
            }
        }

        @Override
        public void characters(char ch[], int start, int length) throws SAXException {
            if(item) {
                switch (currentItem) {
                    case title:
                        titleStr = titleStr.concat(new String(ch, start, length));
                        break;
                    case description:
                        descriptionStr = descriptionStr.concat(new String(ch, start, length));
                        break;
                    case link:
                        linkStr = linkStr.concat(new String(ch, start, length));
                        break;
                    case date:
                        dateStr = dateStr.concat(new String(ch, start, length));
                        break;
                }
            }
        }

        @Override
        public void endElement(String uri, String localName, String qName) throws SAXException {
            if (qName.equalsIgnoreCase("item") && item) {
                item = false;
                String imageLink = getImageLink(descriptionStr);
                descriptionStr = getDescriptionShort(descriptionStr);
                callback.contentDispatcher(titleStr, descriptionStr, imageLink);
                refreshStrings();
            }
        }

        @Override
        public void endDocument() throws SAXException {
            callback.onSuccessParsing();
        }
    }

}