//class made by Teo ( www.teodorfilimon.com ). More about the app in readme.txt

package com.android.todo.sync;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLSession;

/**
 * This class is in charge of synchronizing the events (with due dates) with
 * Google Calendar
 */
public final class GoogleCalendar {
	private static String mAuthToken = null;
	private static String mUsername = "", mPassword = "";
	private static long mLastActivity = 0;
	private final static HostnameVerifier HOSTNAME_VERIFIER = new HostnameVerifier() {
		public boolean verify(String hostname, SSLSession session) {
			return "www.google.com".equals(hostname);
		}
	};

	/**
	 * The login has to be set by someone, either in a configuration window, or
	 * in the main view, on creation, etc.
	 * 
	 * @param username
	 * @param password
	 */
	public final static void setLogin(String username, String password) {
		mUsername = username;
		mPassword = password;
	}

	/**
	 * Initiates the proper communications with Google to add an event in the
	 * user's main calendar
	 * 
	 * @param title
	 *            Name of the task and future event
	 * @param year
	 * @param month
	 * @param day
	 * @return true if the event was created
	 * @throws Exception
	 */
	public final static boolean createEvent(String title, int year, int month,
			int day) throws Exception {

		authenticate(false);
		boolean redirect = false;
		month++; // our months are from 0 to 11
		String sessionUrl = "http://www.google.com/calendar/feeds/default/private/full";
		do {
			HttpURLConnection uc = (HttpURLConnection) new URL(sessionUrl)
					.openConnection();
			uc.setDoOutput(true);
			uc.setUseCaches(false);
			uc.setRequestMethod("POST");
			uc.setRequestProperty("Content-Type", "application/atom+xml");
			uc.setRequestProperty("Authorization", "GoogleLogin auth="
					+ mAuthToken);
			BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(uc
					.getOutputStream()));
			bw
					.write("<entry xmlns='http://www.w3.org/2005/Atom' xmlns:gd='http://schemas.google.com/g/2005'>\n<category scheme='http://schemas.google.com/g/2005#kind' term='http://schemas.google.com/g/2005#event'></category>\n<title type='text'>"
							+ title.replace('\'', '"')
							+ "</title>\n<content type='text'>event created through Tag-ToDo-List, on an Android phone</content>\n<gd:transparency value='http://schemas.google.com/g/2005#event.opaque'></gd:transparency>\n<gd:eventStatus value='http://schemas.google.com/g/2005#event.confirmed'></gd:eventStatus>\n<gd:when startTime='"
							+ year
							+ "-"
							+ (month / 10 < 1 ? "0" + month : month)
							+ "-"
							+ (day / 10 < 1 ? "0" + day : day)
							+ "'></gd:when>\n</entry>");
			bw.flush();
			bw.close();
			if (!(redirect) && uc.getResponseCode() == 302) { // REDIRECT
				redirect = true;
				sessionUrl = uc.getHeaderField("Location");
			} else {
				redirect = false;
				if (uc.getResponseCode() == HttpURLConnection.HTTP_CREATED) {
					return true;
				}
			}
		} while (redirect);
		return false;
	}

	/**
	 * Authentication in the Google Calendar service through HTTPS
	 * 
	 * @param force
	 *            - if true, it forces a re-authentication, even if the present
	 *            session isn't timeout
	 * @return true if authentication succeeds
	 * @throws Exception
	 */
	public final static boolean authenticate(boolean force) throws Exception {

		long millis = System.currentTimeMillis();
		if (!(force) && millis - mLastActivity < 1800000) {
			mLastActivity = millis;
			return true;
		} else {
			mLastActivity = millis;
		}

		HttpsURLConnection uc = (HttpsURLConnection) new URL(
				"https://www.google.com/accounts/ClientLogin").openConnection();
		uc.setHostnameVerifier(HOSTNAME_VERIFIER);
		uc.setDoOutput(true);
		uc.setRequestMethod("POST");
		uc.setRequestProperty("Content-Type",
				"application/x-www-form-urlencoded");
		uc.setUseCaches(false);
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(uc
				.getOutputStream()));
		bw.write(URLEncoder.encode("Email", "UTF-8") + "="
				+ URLEncoder.encode(mUsername, "UTF-8") + "&"
				+ URLEncoder.encode("Passwd", "UTF-8") + "="
				+ URLEncoder.encode(mPassword, "UTF-8") + "&"
				+ URLEncoder.encode("source", "UTF-8") + "="
				+ URLEncoder.encode("Tag-ToDo-List", "UTF-8") + "&"
				+ URLEncoder.encode("service", "UTF-8") + "="
				+ URLEncoder.encode("cl", "UTF-8"));
		bw.flush();
		bw.close();
		BufferedReader in = new BufferedReader(new InputStreamReader(uc
				.getInputStream()));
		if (uc.getResponseCode() == HttpsURLConnection.HTTP_FORBIDDEN) {
			return false;
		}
		// only the 3rd parameter (Auth) is of interest
		in.readLine();
		in.readLine();
		mAuthToken = in.readLine().substring(5);
		in.close();
		return true;
	}
}