package edu.kit.scc.dei.ecplean;

import java.io.IOException;
import java.net.URI;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathException;

import org.apache.http.HttpResponse;
import org.apache.http.ParseException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class ECPAuthenticator extends ECPAuthenticatorBase {

	public ECPAuthenticator(DefaultHttpClient client, String username, String password,
			URI idpEcpEndpoint, URI spUrl) {
		super(client);
		authInfo = new ECPAuthenticationInfo(username, password, idpEcpEndpoint, spUrl);
		authInfo.setAuthState(ECPAuthState.NOT_STARTED);
	}
	
	public ECPAuthenticator(String username, String password,
			URI idpEcpEndpoint, URI spUrl) {
		this(new DefaultHttpClient(), username, password, idpEcpEndpoint, spUrl);
	}
	
	public void authenticate() throws ECPAuthenticationException {
		logger.info("Starting authentication");

		logger.info("Contacting SP " + authInfo.getSpUrl());
		authInfo.setAuthState(ECPAuthState.INITIAL_PAOS_SP);
		setChanged();
		notifyObservers(authInfo);
		
		logger.info("Sending initial SP Request");
		
		HttpGet httpGet = new HttpGet(authInfo.getSpUrl().toString());
		httpGet.setHeader("Accept", "text/html; application/vnd.paos+xml");
		httpGet.setHeader("PAOS", "ver='urn:liberty:paos:2003-08';'urn:oasis:names:tc:SAML:2.0:profiles:SSO:ecp'");

		HttpResponse httpResponse;
		String responseBody;
		try {
			httpResponse = client.execute(httpGet);
			responseBody = EntityUtils.toString(httpResponse.getEntity());
		} catch (IOException | ParseException e) {
			logger.debug("Initial SP Request failed");
			throw new ECPAuthenticationException(e);
		}
		
		Document initResponse;
		try {
			initResponse = buildDocumentFromString(responseBody);
		} catch (IOException | SAXException | ParserConfigurationException e) {
			logger.debug("Parsing SP Request failed");
			throw new ECPAuthenticationException(e);
		}
		
		String relayState;
		try {
			relayState = (String) queryDocument(initResponse, "//ecp:RelayState", XPathConstants.STRING);
		} catch (XPathException e) {
			logger.debug("Could not find relay state in PAOS answer from SP");
			throw new ECPAuthenticationException(e);
		}
		logger.info("Got relayState: " + relayState);
		String responseConsumerUrl;
		try {
			responseConsumerUrl = (String) queryDocument(initResponse, "/S:Envelope/S:Header/paos:Request/@responseConsumerURL", XPathConstants.STRING);
		} catch (XPathException e) {
			logger.debug("Could not find response consumer url in PAOS answer from SP");
			throw new ECPAuthenticationException(e);
		}
		logger.info("Got responseConsumerUrl: " + responseConsumerUrl);

		Node firstChild = initResponse.getDocumentElement().getFirstChild();
		initResponse.getDocumentElement().removeChild(firstChild);
		
		Document idpResponse = authenticateIdP(initResponse);

		String statusCode = getStatusCode(idpResponse);

		if (statusCode == null)
			throw new ECPAuthenticationException("IdP returned no status code!!!x");
		if (!statusCode.endsWith(":Success") && !statusCode.endsWith(":success"))
			throw new ECPAuthenticationException("IdP Returned StatusCode " + statusCode);
		
		String assertionConsumerUrl;
		try {
			assertionConsumerUrl = (String) queryDocument(idpResponse, "/S:Envelope/S:Header/ecp:Response/@AssertionConsumerServiceURL", XPathConstants.STRING);
		} catch (Exception e) {
			logger.debug("Could not find assertion consumer url in answer from IdP");
			throw new ECPAuthenticationException(e);
		}
		logger.info("Got assertionConsumerUrl: " + assertionConsumerUrl);

		if (! assertionConsumerUrl.equals(responseConsumerUrl)) {
			throw new ECPAuthenticationException("Assertion- and ResponseConsumerURL don't match");
		}

		idpResponse.getDocumentElement().getFirstChild().getFirstChild().setTextContent(relayState);

		logger.info("Sending Assertion to SP");
		HttpPost httpPost = new HttpPost(assertionConsumerUrl);
		httpPost.setHeader("Content-Type", "application/vnd.paos+xml");
		httpPost.setHeader("PAOS", "ver='urn:liberty:paos:2003-08';'urn:oasis:names:tc:SAML:2.0:profiles:SSO:ecp'");
		try {
			httpPost.setEntity(new StringEntity(documentToString(idpResponse)));
			httpResponse = client.execute(httpPost);
			responseBody = EntityUtils.toString(httpResponse.getEntity());
		} catch (TransformerException | IOException e) {
			logger.debug("Could not post assertion back to SP");
			throw new ECPAuthenticationException(e);
		}
		
		logger.info("Requesting original URL");
		httpGet = new HttpGet(authInfo.getSpUrl().toString());
		try {
			httpResponse = client.execute(httpGet);
			responseBody = EntityUtils.toString(httpResponse.getEntity());
			
			logger.info(responseBody);
		} catch (IOException | ParseException e) {
			logger.debug("Could not request original URL");
			throw new ECPAuthenticationException(e);
		}
		
	}

	private String getStatusCode(Document idpResponse) {
		NodeList nl;
		try {
			nl = (NodeList) queryDocument(idpResponse, "//*", XPathConstants.NODESET);
		} catch (XPathException e) {
			return null;
		}
		if (nl == null)
			return null;
		for (int i = 0; i < nl.getLength(); ++i) {
			Node ns = nl.item(i);
			if (!ns.getLocalName().endsWith("StatusCode"))
				continue;
			if (!ns.hasAttributes())
				continue;
			Node val = ns.getAttributes().getNamedItem("Value");
			if (val == null)
				continue;
			return val.getNodeValue();
		}
		return null;
	}
}