/*
 * #%L
 * BroadleafCommerce Common Libraries
 * %%
 * Copyright (C) 2009 - 2013 Broadleaf Commerce
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *       http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */
package org.broadleafcommerce.common.security.service;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.broadleafcommerce.common.exception.ServiceException;
import org.broadleafcommerce.common.security.RandomGenerator;
import org.broadleafcommerce.common.util.BLCRequestUtils;
import org.owasp.validator.html.AntiSamy;
import org.owasp.validator.html.CleanResults;
import org.owasp.validator.html.Policy;
import org.springframework.stereotype.Service;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.context.request.ServletWebRequest;

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLStreamHandler;
import java.security.NoSuchAlgorithmException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

/**
 * @author jfischer
 */
@Service("blExploitProtectionService")
public class ExploitProtectionServiceImpl implements ExploitProtectionService {

    private static final String CSRFTOKEN = "csrfToken";
    private static final String CSRFTOKENPARAMETER = "csrfToken";
    private static final Log LOG = LogFactory.getLog(ExploitProtectionServiceImpl.class);

    private static class Handler extends URLStreamHandler {
        @Override
        protected URLConnection openConnection(URL u) throws IOException {
            URL resourceUrl = getClass().getClassLoader().getResource(u.getPath());
            return resourceUrl.openConnection();
        }
    }

    private static Policy getAntiSamyPolicy(String policyFileLocation) {
        try {
            URL url = new URL(null, policyFileLocation, new Handler());
            return Policy.getInstance(url);
        } catch (Exception e) {
            throw new RuntimeException("Unable to create URL", e);
        }
    }

    private static final String DEFAULTANTISAMYPOLICYFILELOCATION = "classpath:antisamy-myspace.xml";

    protected String antiSamyPolicyFileLocation = DEFAULTANTISAMYPOLICYFILELOCATION;
    //this is thread safe
    private Policy antiSamyPolicy = getAntiSamyPolicy(antiSamyPolicyFileLocation);
    //this is thread safe for the usage of scan()
    private final AntiSamy as = new AntiSamy();

    protected boolean xsrfProtectionEnabled = true;
    protected boolean xssProtectionEnabled = true;

    @Override
    public String cleanString(String string) throws ServiceException {
        if (!xssProtectionEnabled || StringUtils.isEmpty(string)) {
            return string;
        }
        try {
            CleanResults results = as.scan(string, antiSamyPolicy);
            return results.getCleanHTML();
        } catch (Exception e) {
            LOG.error("Unable to clean the passed in entity values", e);
            throw new ServiceException("Unable to clean the passed in entity values", e);
        }
    }

    @Override
    public String cleanStringWithResults(String string) throws ServiceException {
        if (!xssProtectionEnabled || StringUtils.isEmpty(string)) {
            return string;
        }
        try {
            CleanResults results = as.scan(string, antiSamyPolicy);
            if (results.getNumberOfErrors() > 0) {
                throw new CleanStringException(results);
            }
            return results.getCleanHTML();
        } catch (CleanStringException e) {
            throw e;
        } catch (Exception e) {
            StringBuilder sb = new StringBuilder();
            sb.append("Unable to clean the passed in entity values");
            sb.append("\nNote - ");
            sb.append(getAntiSamyPolicyFileLocation());
            sb.append(" policy in effect. Set a new policy file to modify validation behavior/strictness.");
            LOG.error(sb.toString(), e);
            throw new ServiceException(sb.toString(), e);
        }
    }

    @Override
    public void compareToken(String passedToken) throws ServiceException {
        if (xsrfProtectionEnabled) {
            if (!getCSRFToken().equals(passedToken)) {
                throw new ServiceException("XSRF token mismatch (" + passedToken + "). Session may be expired.");
            } else {
                LOG.debug("Validated CSRF token");
            }
        }
    }

    @Override
    public String getCSRFToken() throws ServiceException {
        HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();
        if (BLCRequestUtils.isOKtoUseSession(new ServletWebRequest(request))) {
            HttpSession session = request.getSession();
            String token = (String) session.getAttribute(CSRFTOKEN);
            if (StringUtils.isEmpty(token)) {
                try {
                    token = RandomGenerator.generateRandomId("SHA1PRNG", 32);
                } catch (NoSuchAlgorithmException e) {
                    LOG.error("Unable to generate random number", e);
                    throw new ServiceException("Unable to generate random number", e);
                }
                session.setAttribute(CSRFTOKEN, token);
            }
            return token;
        }
        return null;
    }

    @Override
    public String getAntiSamyPolicyFileLocation() {
        return antiSamyPolicyFileLocation;
    }

    @Override
    public void setAntiSamyPolicyFileLocation(String antiSamyPolicyFileLocation) {
        this.antiSamyPolicyFileLocation = antiSamyPolicyFileLocation;
        antiSamyPolicy = getAntiSamyPolicy(antiSamyPolicyFileLocation);
    }

    public boolean isXsrfProtectionEnabled() {
        return xsrfProtectionEnabled;
    }

    public void setXsrfProtectionEnabled(boolean xsrfProtectionEnabled) {
        this.xsrfProtectionEnabled = xsrfProtectionEnabled;
    }

    public boolean isXssProtectionEnabled() {
        return xssProtectionEnabled;
    }

    public void setXssProtectionEnabled(boolean xssProtectionEnabled) {
        this.xssProtectionEnabled = xssProtectionEnabled;
    }
    
    @Override
    public String getCsrfTokenParameter() {
        return CSRFTOKENPARAMETER;
    }
}