package com.cjs.cms.util.lang;

import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.lang3.StringUtils;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.type.CollectionType;
import com.fasterxml.jackson.databind.util.JSONPObject;

/**
 * JSON转换工具类
 * 
 * @author trunks
 * @version $Id: JsonUtils.java, v 0.1 2014-5-27 trunks Exp $
 */
public class JsonUtil {

    private static Logger       logger = LogManager.getLogger();
    private static ObjectMapper mapper = null;

    static {
        mapper = new ObjectMapper();
        // 设置输入时忽略在JSON字符串中存在但Java对象实际没有的属性
        mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
        //允许key没有使用双引号的json
        mapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);

        //零时区
        DateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        //format.setTimeZone(TimeZone.getTimeZone("UTC"));
        mapper.setDateFormat(format);

        //输出格式化
        mapper.configure(SerializationFeature.INDENT_OUTPUT, false);
    }

    /**
     * 将对象转换成JSON字符串
     * @param obj 目标对象
     * @return 字符串，转换失败时返回null
     */
    public static String toJson(Object obj) {
        try {
            return mapper.writeValueAsString(obj);
        } catch (JsonProcessingException e) {
            logger.error("write to json string error:" + obj, e);
            return null;
        }
    }

    /**
     * 将单个键值对转换成JSON字符串，用于返回只有一个键值对json时的便捷方法
     * @param obj 目标对象
     * @return 字符串，转换失败时返回null
     */
    public static String toJson(Object key, Object value) {
        Map<Object, Object> map = new HashMap<Object, Object>();
        map.put(key, value);
        try {
            return mapper.writeValueAsString(map);
        } catch (JsonProcessingException e) {
            logger.error("write to json string error:" + map, e);
            return null;
        }
    }

    /**
     * 转换JSON对象为Ext表单提交成功的方式<br />
     * ex.{"success":"false","data":{"name":"名称已存在"}}
     * 
     * @param obj 错误信息，若用map，Key若为表单项的name，则会自动在对应表单项显示错误信息
     */
    public static String toFormJson(Object obj, boolean success) {
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("success", success);
        map.put("data", obj);
        try {
            return mapper.writeValueAsString(map);
        } catch (JsonProcessingException e) {
            logger.error("write to json string error:" + obj, e);
            return null;
        }
    }

    /**
     * 转换JSON对象为EasyUI GridView分页格式<br />
     * @param rows 记录集合
     * @param total 记录数
     * @param footer 页脚
     */
    public static String toPageJson(List<?> rows, int total, Object... footer) {
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("rows", rows);
        map.put("total", total);
        if (footer != null && footer.length > 0 && footer[0] != null) {
            map.put("footer", footer);
        }
        try {
            return mapper.writeValueAsString(map);
        } catch (JsonProcessingException e) {
            logger.error("write to json string error:" + rows, e);
            return null;
        }
    }

    /**
     * 转换分页查询结果
     * 
     * @param list 结果集
     * @param total 记录数
     */
    public static String writePageJson(Object list, Object total) {
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("list", list);
        map.put("total", total);
        try {
            return mapper.writeValueAsString(map);
        } catch (JsonProcessingException e) {
            logger.error("write to json string error:" + list, e);
            return null;
        }
    }

    /**
     * 反序列化POJO或简单Collection如List<String>.
     * 
     * 如果JSON字符串为Null或"null"字符串, 返回Null.
     * 如果JSON字符串为"[]", 返回空集合.
     * 
     * 如需反序列化复杂Collection如List<MyBean>, 请使用fromJson(String, JavaType)
     * 
     * @see #fromJson(String, JavaType)
     */
    public static <T> T fromJson(String jsonString, Class<T> clazz) {
        if (StringUtils.isBlank(jsonString)) {
            return null;
        }
        try {
            return mapper.readValue(jsonString, clazz);
        } catch (IOException e) {
            logger.error("parse json string error:" + jsonString, e);
            return null;
        }
    }

    /**
     * 反序列化复杂Collection如List<Bean>
     * @param jsonString 
     * @param collectionType 集合类型
     * @param elementType 集合内元素类型
     * @return 转换失败时返回 null
     */
    public static <L extends Collection<E>, E> L fromJson(String jsonString,
                                                          Class<L> collectionClass,
                                                          Class<E> elementClass) {
        if (StringUtils.isBlank(jsonString)) {
            return null;
        }
        try {
            CollectionType type = mapper.getTypeFactory().constructCollectionType(collectionClass,
                elementClass);
            return mapper.readValue(jsonString, type);
        } catch (Exception e) {
            logger.error("parse json string error:" + jsonString, e);
            return null;
        }
    }

    /**
     * 当JSON里只含有Bean的部分属性，更新一个已存在Bean，只覆盖该部分的属性.
     */
    public static void update(String jsonString, Object object) {
        try {
            mapper.readerForUpdating(object).readValue(jsonString);
        } catch (JsonProcessingException e) {
            logger.error("update json string:" + jsonString + " to object:" + object + " error.",
                e);
        } catch (IOException e) {
            logger.error("update json string:" + jsonString + " to object:" + object + " error.",
                e);
        }
    }

    /**
     * 输出JSONP格式数据
     */
    public static String toJsonP(String functionName, Object object) {
        return toJson(new JSONPObject(functionName, object));
    }

}