BartRunnerAndroid/app/src/main/java/com/dougkeen/bart/networktasks/AlertListConverter.java

package com.dougkeen.bart.networktasks;

import java.io.IOException;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.apache.commons.io.IOUtils;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

import android.util.Log;
import android.util.Xml;

import com.dougkeen.bart.model.Alert;

public class AlertListConverter extends
		AbstractHttpMessageConverter<Alert.AlertList> {

	@Override
	protected Alert.AlertList readInternal(
			Class<? extends Alert.AlertList> clazz,
			HttpInputMessage inputMessage) throws IOException,
			HttpMessageNotReadableException {
		StringWriter writer = new StringWriter();
		IOUtils.copy(inputMessage.getBody(), writer, "UTF-8");

		String xml = writer.toString();
		if (xml.length() == 0) {
			throw new IOException("Server returned blank xml document");
		}

		AlertListHandler handler = new AlertListHandler();
		try {
			Xml.parse(xml, handler);
		} catch (SAXException e) {
			Log.e("AlertListConverter", "XML parsing error", e);
			return null;
		}

		return handler.getAlertList();
	}

	@Override
	protected boolean supports(Class<?> clazz) {
		return Alert.AlertList.class.equals(clazz);
	}

	@Override
	public List<MediaType> getSupportedMediaTypes() {
		final List<MediaType> supportedMediaTypes = new ArrayList<MediaType>();
		supportedMediaTypes.add(MediaType.TEXT_HTML);
		supportedMediaTypes.add(MediaType.TEXT_XML);
		supportedMediaTypes.addAll(super.getSupportedMediaTypes());
		return supportedMediaTypes;
	}

	@Override
	protected void writeInternal(Alert.AlertList arg0, HttpOutputMessage arg1)
			throws IOException, HttpMessageNotWritableException {
		throw new UnsupportedOperationException();
	}

	private static class AlertListHandler extends DefaultHandler {
		private final static List<String> TAGS = Arrays.asList("bsa", "type",
				"description", "posted", "expires");

		private String currentValue;
		private boolean isParsingTag;
		private Alert currentAlert;
		private Alert.AlertList returnList = new Alert.AlertList();

		public Alert.AlertList getAlertList() {
			return returnList;
		}

		@Override
		public void characters(char[] ch, int start, int length)
				throws SAXException {
			if (isParsingTag) {
				currentValue = new String(ch, start, length);
			}
		}

		@Override
		public void startElement(String uri, String localName, String qName,
				Attributes attributes) throws SAXException {
			if (TAGS.contains(localName)) {
				isParsingTag = true;
			}
			final int numberOfAttributes = attributes.getLength();
			if (localName.equals("bsa")) {
				for (int i = 0; i < numberOfAttributes; i++) {
					if (attributes.getLocalName(i).equalsIgnoreCase("id")) {
						currentAlert = new Alert(attributes.getValue(i));
						break;
					}
				}
			}
		}

		@Override
		public void endElement(String uri, String localName, String qName)
				throws SAXException {
			if (currentAlert != null) {
				if (localName.equals("type")) {
					currentAlert.setType(currentValue);
				} else if (localName.equals("description")) {
					currentAlert.setDescription(currentValue);
				} else if (localName.equals("posted")) {
					currentAlert.setPostedTime(currentValue);
				} else if (localName.equals("expires")) {
					currentAlert.setExpiresTime(currentValue);
				} else if (localName.equals("bsa")) {
					returnList.addAlert(currentAlert);
					currentAlert = null;
				}
			}
			isParsingTag = false;
			currentValue = null;
		}

		@Override
		public void endDocument() throws SAXException {
			super.endDocument();
			if (!returnList.hasAlerts()) {
				returnList.setNoDelaysReported(true);
			}
		}

	}
}