/*
 * Copyright 1999-2018 Alibaba Group Holding Ltd.
 *
 * 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.
 */
package com.alibaba.csp.sentinel.dashboard.auth;

import org.apache.commons.lang.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Component;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.util.List;

/**
 * <p>The Servlet filter for authentication.</p>
 *
 * <p>Note: some urls are excluded as they needn't auth, such as:</p>
 * <ul>
 * <li>index url: {@code /}</li>
 * <li>authentication request url: {@code /login}, {@code /logout}</li>
 * <li>machine registry: {@code /registry/machine}</li>
 * <li>static resources</li>
 * </ul>
 *
 * The excluded urls and urlSuffixes could be configured in {@code application.properties} file.
 *
 * @author cdfive
 * @since 1.6.0
 */
@Component
public class LoginAuthenticationFilter implements Filter {

    private static final String URL_SUFFIX_DOT = ".";

    /**
     * Some urls which needn't auth, such as /auth/login, /registry/machine and so on.
     */
    @Value("#{'${auth.filter.exclude-urls}'.split(',')}")
    private List<String> authFilterExcludeUrls;

    /**
     * Some urls with suffixes which needn't auth, such as htm, html, js and so on.
     */
    @Value("#{'${auth.filter.exclude-url-suffixes}'.split(',')}")
    private List<String> authFilterExcludeUrlSuffixes;

    /**
     * Authentication using AuthService interface.
     */
    @Autowired
    private AuthService<HttpServletRequest> authService;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
        throws IOException, ServletException {
        HttpServletRequest httpRequest = (HttpServletRequest) request;

        String servletPath = httpRequest.getServletPath();

        // Exclude the urls which needn't auth
        if (authFilterExcludeUrls.contains(servletPath)) {
            chain.doFilter(request, response);
            return;
        }

        // Exclude the urls with suffixes which needn't auth
        for (String authFilterExcludeUrlSuffix : authFilterExcludeUrlSuffixes) {
            if (StringUtils.isBlank(authFilterExcludeUrlSuffix)) {
                continue;
            }

            // Add . for url suffix so that we needn't add . in property file
            if (!authFilterExcludeUrlSuffix.startsWith(URL_SUFFIX_DOT)) {
                authFilterExcludeUrlSuffix = URL_SUFFIX_DOT + authFilterExcludeUrlSuffix;
            }

            if (servletPath.endsWith(authFilterExcludeUrlSuffix)) {
                chain.doFilter(request, response);
                return;
            }
        }

        AuthService.AuthUser authUser = authService.getAuthUser(httpRequest);

        HttpServletResponse httpResponse = (HttpServletResponse) response;
        if (authUser == null) {
            // If auth fail, set response status code to 401
            httpResponse.setStatus(HttpStatus.UNAUTHORIZED.value());
        } else {
            chain.doFilter(request, response);
        }
    }

    @Override
    public void destroy() {

    }
}
