import java.io.IOException;
import java.util.Map;

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

import org.apache.commons.lang.StringUtils;
import org.apache.struts2.ServletActionContext;
import org.json.JSONObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Struts2 Utils类.
 * 
 * 实现获取Request/Response/Session与绕过jsp/freemaker直接输出文本的简化函数.
 * 
 */
public class Struts2Utils {

        //header 常量定义
        private static final String ENCODING_PREFIX = "encoding:";
        private static final String NOCACHE_PREFIX = "no-cache:";
        private static final String ENCODING_DEFAULT = "UTF-8";
        private static final boolean NOCACHE_DEFAULT = true;

        private static Logger logger = LoggerFactory.getLogger(Struts2Utils.class);

        private Struts2Utils() {
        }

        // 取得Request/Response/Session的简化函数 //

        /**
         * 取得HttpSession的简化方法.
         */
        public static HttpSession getSession() {
                return ServletActionContext.getRequest().getSession();
        }

        /**
         * 取得HttpRequest的简化方法.
         */
        public static HttpServletRequest getRequest() {
                return ServletActionContext.getRequest();
        }

        /**
         * 取得HttpResponse的简化方法.
         */
        public static HttpServletResponse getResponse() {
                return ServletActionContext.getResponse();
        }

        /**
         * 取得Request Parameter的简化方法.
         */
        public static String getParameter(String name) {
                return getRequest().getParameter(name);
        }

        // 绕过jsp/freemaker直接输出文本的函数 //

        /**
         * 直接输出内容的简便函数.
          
         * eg.
         * render("text/plain", "hello", "encoding:GBK");
         * render("text/plain", "hello", "no-cache:false");
         * render("text/plain", "hello", "encoding:GBK", "no-cache:false");
         * 
         * @param headers 可变的header数组，目前接受的值为"encoding:"或"no-cache:",默认值分别为UTF-8和true.                 
         */
        public static void render(final String contentType, final String content, final String... headers) {
                try {
                        //分析headers参数
                        String encoding = ENCODING_DEFAULT;
                        boolean noCache = NOCACHE_DEFAULT;
                        for (String header : headers) {
                                String headerName = StringUtils.substringBefore(header, ":");
                                String headerValue = StringUtils.substringAfter(header, ":");

                                if (StringUtils.equalsIgnoreCase(headerName, ENCODING_PREFIX)) {
                                        encoding = headerValue;
                                } else if (StringUtils.equalsIgnoreCase(headerName, NOCACHE_PREFIX)) {
                                        noCache = Boolean.parseBoolean(headerValue);
                                } else
                                        throw new IllegalArgumentException(headerName + "不是一个合法的header类型");
                        }

                        HttpServletResponse response = ServletActionContext.getResponse();

                        //设置headers参数
                        String fullContentType = contentType + ";charset=" + encoding;
                        response.setContentType(fullContentType);
                        if (noCache) {
                                response.setHeader("Pragma", "No-cache");
                                response.setHeader("Cache-Control", "no-cache");
                                response.setDateHeader("Expires", 0);
                        }

                        response.getWriter().write(content);

                } catch (IOException e) {
                        logger.error(e.getMessage(), e);
                }
        }

        /**
         * 直接输出文本.
         */
        public static void renderText(final String text, final String... headers) {
                render("text/plain", text, headers);
        }

        /**
         * 直接输出HTML.
         */
        public static void renderHtml(final String html, final String... headers) {
                render("text/html", html, headers);
        }

        /**
         * 直接输出XML.
         */
        public static void renderXml(final String xml, final String... headers) {
                render("text/xml", xml, headers);
        }

        /**
         * 直接输出JSON.
         * 
         * @param string json字符串.
         */
        public static void renderJson(final String string, final String... headers) {
                render("application/json", string, headers);
        }

        /**
         * 直接输出JSON.
         * 
         * @param map Map对象,将被转化为json字符串.
         */
        @SuppressWarnings("unchecked")
        public static void renderJson(final Map map, final String... headers) {
                String jsonString = new JSONObject(map).toString();
                renderJson(jsonString, headers);
        }

        /**
         * 直接输出JSON.
         * 
         * @param object Java对象,将被转化为json字符串.
         */
        public static void renderJson(final Object object, final String... headers) {
                String jsonString = new JSONObject(object).toString();
                renderJson(jsonString, headers);
        }
}