package net.sourceforge.fenixedu.util;

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;

import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;

import net.sourceforge.fenixedu._development.LogLevel;
import net.sourceforge.fenixedu._development.PropertiesManager;

import org.apache.log4j.Logger;

import pt.ist.fenixWebFramework.servlets.filters.PathAccessControlFilter;

public class HostAccessControl {
    private static final Logger logger = Logger.getLogger(PathAccessControlFilter.class);

    private static final String HOST_CONTROL_PROPERTIES = "/.pathAccessControl.properties";
    private static final String HOST_CONTROL_NAME_PREFIX = "host.control.name.";

    private static HostAccessControl intance = new HostAccessControl();

    public static HostAccessControl getInstance() {
	return HostAccessControl.intance;
    }

    private Map<String, List<InetAddress>> configuration;

    public HostAccessControl() {
	super();

	setupConfiguration();
    }

    private void setupConfiguration() {
	this.configuration = new HashMap<String, List<InetAddress>>();

	try {
	    Properties properties = new Properties();
	    PropertiesManager.loadProperties(properties, HOST_CONTROL_PROPERTIES);

	    for (Object key : properties.keySet()) {
		String keyName = (String) key;

		if (keyName.startsWith(HOST_CONTROL_NAME_PREFIX)) {
		    String name = keyName.substring(HOST_CONTROL_NAME_PREFIX.length());
		    String[] hostList = properties.get(key).toString().split(",");

		    for (int i = 0; i < hostList.length; i++) {
			String host = hostList[i].trim();

			if (host.length() > 0) {
			    addEntry(name, host);
			}
		    }

		    // just for a cleaner message
		    if (LogLevel.DEBUG) {
			logger.debug("access for '" + name + "' limited to " + this.configuration.get(name));
		    }
		}
	    }
	} catch (IOException e) {
	    throw new RuntimeException("failed to read the host access control properties '" + HOST_CONTROL_PROPERTIES + "'", e);
	}
    }

    private void addEntry(String name, String host) {
	List<InetAddress> hostList = this.configuration.get(name);

	if (hostList == null) {
	    hostList = new ArrayList<InetAddress>();

	    this.configuration.put(name, hostList);
	}

	try {
	    InetAddress[] addresses = InetAddress.getAllByName(host);

	    for (int i = 0; i < addresses.length; i++) {
		hostList.add(addresses[i]);
	    }
	} catch (UnknownHostException e) {
	    if (LogLevel.WARN) {
		logger.warn("could not find host '" + host + "', host ignored.");
	    }
	}
    }

    public static boolean isAllowed(String name, ServletRequest request) {
	return getInstance().isAllowed(name, getRemoteAddress(request));
    }

    public static boolean isAllowed(Class type, ServletRequest request) {
	return isAllowed(type.getName(), request);
    }

    public static boolean isAllowed(Object object, ServletRequest request) {
	return isAllowed(object.getClass(), request);
    }

    private boolean isAllowed(String name, String address) {
	try {
	    InetAddress remoteAddress = InetAddress.getByName(address);

	    List<InetAddress> hostList = this.configuration.get(name);
	    if (hostList == null) {
		if (LogLevel.WARN) {
		    logger.warn(name + " denied[" + remoteAddress + "]: allowed hosts not defined");
		}
		return false;
	    }

	    for (InetAddress allowedHost : hostList) {
		if (remoteAddress.equals(allowedHost)) {
		    if (LogLevel.DEBUG) {
			logger.debug(name + " allowed[" + remoteAddress + "]: matches group " + hostList);
		    }

		    return true;
		}
	    }

	    if (LogLevel.WARN) {
		logger.warn(name + " denied[" + remoteAddress + "]: is not member of " + hostList);
	    }
	} catch (UnknownHostException e) {
	    if (LogLevel.WARN) {
		logger.warn(name + " denied[" + address + "]: could not find host");
	    }
	}

	return false;
    }

    public static String getRemoteAddress(ServletRequest request) {
	if (request instanceof HttpServletRequest) {
	    final HttpServletRequest httpServletRequest = (HttpServletRequest) request;
	    final String xForwardFor = httpServletRequest.getHeader("x-forwarded-for");
	    if (xForwardFor != null && xForwardFor.length() > 0) {
		return xForwardFor;
	    }
	}
	return request.getRemoteAddr();
    }

}