package cn.iocoder.dashboard.util.servlet;

import cn.hutool.core.io.IoUtil;
import cn.hutool.extra.servlet.ServletUtil;
import com.alibaba.fastjson.JSON;
import org.springframework.http.MediaType;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLEncoder;

/**
 * 客户端工具类
 *
 * @author 芋道源码
 */
public class ServletUtils {

    /**
     * 返回 JSON 字符串
     *
     * @param response 响应
     * @param object 对象，会序列化成 JSON 字符串
     */
    @SuppressWarnings("deprecation") // 必须使用 APPLICATION_JSON_UTF8_VALUE，否则会乱码
    public static void writeJSON(HttpServletResponse response, Object object) {
        String content = JSON.toJSONString(object);
        ServletUtil.write(response, content, MediaType.APPLICATION_JSON_UTF8_VALUE);
    }

    /**
     * 返回附件
     *
     * @param response 响应
     * @param filename 文件名
     * @param content 附件内容
     * @throws IOException
     */
    public static void writeAttachment(HttpServletResponse response, String filename, byte[] content) throws IOException {
        // 设置 header 和 contentType
        response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(filename, "UTF-8"));
        response.setContentType(MediaType.APPLICATION_OCTET_STREAM_VALUE);
        // 输出附件
        IoUtil.write(response.getOutputStream(), false, content);
    }

    /**
     * @param request 请求
     * @return ua
     */
    public static String getUserAgent(HttpServletRequest request) {
        String ua = request.getHeader("User-Agent");
        return ua != null ? ua : "";
    }

}