var userMaxMessageIdDao = Object.create(baseDao);

userMaxMessageIdDao.db = "dianwutong";
userMaxMessageIdDao.table = "user_max_message_id";

userMaxMessageIdDao.selectAll = function(){
    var sql = "select * from `" +this.table+ "`";
    this.query(sql, function(ret,err){
      console.log("userMaxMessageId的所有数据：")
      console.log(JSON.stringify(ret));
      console.log(JSON.stringify(err));
    })
}

userMaxMessageIdDao.deleteTable = function(){
    var sql = "drop table `" +this.table+ "`";
    this.exec(sql, function(ret,err){
      console.log('删除表：userMaxMessage');
    })
}

//创建message表
userMaxMessageIdDao.initTable = function(callback) {
    var sql = " CREATE TABLE IF NOT EXISTS `" + this.table + "` ( " +
        " `msg_id` INT(11) NOT NULL, " +
        " `user_id` INT(11) NOT NULL" +
        " )";

    this.exec(sql, function(ret, err){

        if(callback){
          callback(ret, err);

        }
    });



}

userMaxMessageIdDao.insert = function( userId, msgId, callback){
  var sql = "insert into `" + this.table + "`(`user_id`, `msg_id`) values(" +userId+ "," +msgId+ ")";
  this.exec(sql, function(ret, err) {
    if(callback){
      callback();
    }
  })
}

userMaxMessageIdDao.update = function( userId, msgId, callback ){
  var sql = "update `" +this.table+ "` set `msg_id` = " + msgId +" where user_id = "+userId;
  this.exec(sql, function(ret, err) {
    if(callback){
      callback();
    }
  })
}

userMaxMessageIdDao.updateUserMessageId = function(userId, msgId, callback){
    //判断用户是否存在最大id 如果存在 则执行修改操作 否则执行插入操作
    var _this = this;
    _this.getMaxId(userId, function(maxId){
      if(maxId){

        _this.update(userId, msgId, function(){

          if(callback){ callback() }

        })

      }else{

        _this.insert(userId, msgId, function(){

          if(callback){ callback() }

        })

      }
    })
}

userMaxMessageIdDao.getMaxId = function(userId, callback) {
  var sql = "select max(msg_id) as max from `" + this.table +"` where user_id = "+userId;
  this.query(sql, function(ret,err){

    var max = 0;

    if(ret && ret.data &&ret.data[0] && ret.data[0].max){
        max = ret.data[0].max;
    }

    if(callback){
      callback(max);
    }

  })
}