/*******************************************************************************
 * Copyright (c) 2005, 2014 springside.github.io
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 *******************************************************************************/
package org.springside.modules.web;

import java.util.Enumeration;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.StringTokenizer;
import java.util.TreeMap;

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

import org.apache.commons.lang3.Validate;
import org.springside.modules.utils.Collections3;
import org.springside.modules.utils.Encodes;

import com.google.common.base.Charsets;
import com.google.common.net.HttpHeaders;

/**
 * Http与Servlet工具类.
 * 
 * @author calvin
 */
public class Servlets {

	// -- 常用数值定义 --//
	public static final long ONE_YEAR_SECONDS = 60 * 60 * 24 * 365;

	/**
	 * 设置客户端缓存过期时间 的Header.
	 */
	public static void setExpiresHeader(HttpServletResponse response, long expiresSeconds) {
		// Http 1.0 header, set a fix expires date.
		response.setDateHeader(HttpHeaders.EXPIRES, System.currentTimeMillis() + (expiresSeconds * 1000));
		// Http 1.1 header, set a time after now.
		response.setHeader(HttpHeaders.CACHE_CONTROL, "private, max-age=" + expiresSeconds);
	}

	/**
	 * 设置禁止客户端缓存的Header.
	 */
	public static void setNoCacheHeader(HttpServletResponse response) {
		// Http 1.0 header
		response.setDateHeader(HttpHeaders.EXPIRES, 1L);
		response.addHeader(HttpHeaders.PRAGMA, "no-cache");
		// Http 1.1 header
		response.setHeader(HttpHeaders.CACHE_CONTROL, "no-cache, no-store, max-age=0");
	}

	/**
	 * 设置LastModified Header.
	 */
	public static void setLastModifiedHeader(HttpServletResponse response, long lastModifiedDate) {
		response.setDateHeader(HttpHeaders.LAST_MODIFIED, lastModifiedDate);
	}

	/**
	 * 设置Etag Header.
	 */
	public static void setEtag(HttpServletResponse response, String etag) {
		response.setHeader(HttpHeaders.ETAG, etag);
	}

	/**
	 * 根据浏览器If-Modified-Since Header, 计算文件是否已被修改.
	 * 
	 * 如果无修改, checkIfModify返回false ,设置304 not modify status.
	 * 
	 * @param lastModified 内容的最后修改时间.
	 */
	public static boolean checkIfModifiedSince(HttpServletRequest request, HttpServletResponse response,
			long lastModified) {
		long ifModifiedSince = request.getDateHeader(HttpHeaders.IF_MODIFIED_SINCE);
		if ((ifModifiedSince != -1) && (lastModified < (ifModifiedSince + 1000))) {
			response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
			return false;
		}
		return true;
	}

	/**
	 * 根据浏览器 If-None-Match Header, 计算Etag是否已无效.
	 * 
	 * 如果Etag有效, checkIfNoneMatch返回false, 设置304 not modify status.
	 * 
	 * @param etag 内容的ETag.
	 */
	public static boolean checkIfNoneMatchEtag(HttpServletRequest request, HttpServletResponse response, String etag) {
		String headerValue = request.getHeader(HttpHeaders.IF_NONE_MATCH);
		if (headerValue != null) {
			boolean conditionSatisfied = false;
			if (!"*".equals(headerValue)) {
				StringTokenizer commaTokenizer = new StringTokenizer(headerValue, ",");

				while (!conditionSatisfied && commaTokenizer.hasMoreTokens()) {
					String currentToken = commaTokenizer.nextToken();
					if (currentToken.trim().equals(etag)) {
						conditionSatisfied = true;
					}
				}
			} else {
				conditionSatisfied = true;
			}

			if (conditionSatisfied) {
				response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
				response.setHeader(HttpHeaders.ETAG, etag);
				return false;
			}
		}
		return true;
	}

	/**
	 * 设置让浏览器弹出下载对话框的Header.
	 * 
	 * @param fileName 下载后的文件名.
	 */
	public static void setFileDownloadHeader(HttpServletRequest request, HttpServletResponse response, String fileName) {
		// 中文文件名支持
		String encodedfileName = null;
		// 替换空格，否则firefox下有空格文件名会被截断,其他浏览器会将空格替换成+号
		encodedfileName = fileName.trim().replaceAll(" ", "_");
		String agent = request.getHeader("User-Agent");
		boolean isMSIE = (agent != null && agent.toUpperCase().indexOf("MSIE") != -1);
		if (isMSIE) {
			encodedfileName = Encodes.urlEncode(fileName);
		} else {
			encodedfileName = new String(fileName.getBytes(), Charsets.ISO_8859_1);
		}

		response.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + encodedfileName + "\"");

	}

	/**
	 * 取得带相同前缀的Request Parameters, copy from spring WebUtils.
	 * 
	 * 返回的结果的Parameter名已去除前缀.
	 */
	public static Map<String, Object> getParametersStartingWith(ServletRequest request, String prefix) {
		Validate.notNull(request, "Request must not be null");
		Enumeration paramNames = request.getParameterNames();
		Map<String, Object> params = new TreeMap<String, Object>();
		if (prefix == null) {
			prefix = "";
		}
		while ((paramNames != null) && paramNames.hasMoreElements()) {
			String paramName = (String) paramNames.nextElement();
			if ("".equals(prefix) || paramName.startsWith(prefix)) {
				String unprefixed = paramName.substring(prefix.length());
				String[] values = request.getParameterValues(paramName);
				if ((values == null) || (values.length == 0)) {
					// Do nothing, no values found at all.
				} else if (values.length > 1) {
					params.put(unprefixed, values);
				} else {
					params.put(unprefixed, values[0]);
				}
			}
		}
		return params;
	}

	/**
	 * 组合Parameters生成Query String的Parameter部分, 并在paramter name上加上prefix.
	 * 
	 * @see #getParametersStartingWith
	 */
	public static String encodeParameterStringWithPrefix(Map<String, Object> params, String prefix) {
		if (Collections3.isEmpty(params)) {
			return "";
		}

		if (prefix == null) {
			prefix = "";
		}

		StringBuilder queryStringBuilder = new StringBuilder();
		Iterator<Entry<String, Object>> it = params.entrySet().iterator();
		while (it.hasNext()) {
			Entry<String, Object> entry = it.next();
			queryStringBuilder.append(prefix).append(entry.getKey()).append('=').append(entry.getValue());
			if (it.hasNext()) {
				queryStringBuilder.append('&');
			}
		}
		return queryStringBuilder.toString();
	}

	/**
	 * 客户端对Http Basic验证的 Header进行编码.
	 */
	public static String encodeHttpBasic(String userName, String password) {
		String encode = userName + ":" + password;
		return "Basic " + Encodes.encodeBase64(encode.getBytes());
	}
}