//copyright by lanxyou lanxyou[at]gmail.com
var lanxDB=function(dbname){
  var db=openDatabase(dbname,\'1.0.0\',\'\',65536);
  return{
    //返回数据库名
    getDBName:function(){
      return dbname;
    },
    //初始化数据库，如果需要则创建表
    init:function(tableName,colums){
      this.switchTable(tableName);
      colums.length>0?this.createTable(colums):\'\';
      return this;
    },
    //创建表，colums:[name:字段名,type:字段类型]
    createTable:function(colums){
      var sql=\"CREATE TABLE IF NOT EXISTS \" + this._table ;
      var t;
      if (colums instanceof Array && colums.length>0){
        t=[];
        for (var i in colums){
          t.push(colums[i].name+\' \'+colums[i].type);
        }
        t=t.join(\', \');
      }else if(typeof colums==\"object\"){
        t+=colums.name+\' \'+colums.type;
      }
      sql=sql+\" (\"+t+\")\";
      var that=this;
      db.transaction(function (t) { 
        t.executeSql(sql) ;
   })
    },
    //切换表
    switchTable:function(tableName){
      this._table=tableName;
      return this;
    },
    //插入数据并执行回调函数，支持批量插入
    //data为Array类型，每一组值均为Object类型，每一个Obejct的属性应为表的字段名，对应要保存的值
    insertData:function(data,callback){
      var that=this;
      var sql=\"INSERT INTO \"+this._table;
      if (data instanceof Array && data.length>0){
        var cols=[],qs=[];
        for (var i in data[0]){
          cols.push(i);
          qs.push(\'?\');
        }
        sql+=\" (\"+cols.join(\',\')+\") Values (\"+qs.join(\',\')+\")\";
      }else{
        return false;
      }
      var p=[],
        d=data,
        pLenth=0,
        r=[];
      for (var i=0,dLength=d.length;i<dLength;i++){
        var k=[];
        for (var j in d[i]){
          k.push(d[i][j]);
        }
        p.push(k);
      }
      var queue=function(b,result){
        if (result){
          r.push(result.insertId ||result.rowsAffected);
        }
        if (p.length>0){
          db.transaction(function (t) { 
            t.executeSql(sql,p.shift(),queue,that.onfail);
          })
        }else{
          if (callback){
            callback.call(this,r);
          }
        }
      }
      queue();
    },
    _where:\'\',
    //where语句，支持自写和以对象属性值对的形式
    where:function(where){
      if (typeof where===\'object\'){
        var j=this.toArray(where);
        this._where=j.join(\' and \');
      }else if (typeof where===\'string\'){
        this._where=where;
      }
      return this;
    },
    //更新数据，data为属性值对形式
    updateData:function(data,callback){
      var that=this;
      var sql=\"Update \"+this._table;
      data=this.toArray(data).join(\',\');
      sql+=\" Set \"+data+\" where \"+this._where;
      this.doQuery(sql,callback);
    },
    //根据条件保存数据，如果存在则更新，不存在则插入数据
    saveData:function(data,callback){
      var sql=\"Select * from \"+this._table+\" where \"+this._where;
      var that=this;
      this.doQuery(sql,function(r){
        if (r.length>0){
          that.updateData(data,callback);
        }else{
          that.insertData([data],callback);
        }
      });
    },
    //获取数据
    getData:function(callback){
      var that=this;
      var sql=\"Select * from \"+that._table;
      that._where.length>0?sql+=\" where \"+that._where:\"\";
      that.doQuery(sql,callback);
    },
    //查询，内部方法
    doQuery:function(sql,callback){
      var that=this;
      var a=[];
      var bb=function(b,result){
        if (result.rows.length){
          for (var i=0;i<result.rows.length;i++){
            a.push(result.rows.item(i));
          }
        }else{
          a.push(result.rowsAffected);
        }
        if (callback){
          callback.call(that,a);
        }
      }
      db.transaction(function (t) { 
        t.executeSql(sql,[],bb,that.onfail) ;
      })
    },
    //根据条件删除数据
    deleteData:function(callback){
      var that=this;
      var sql=\"delete from \"+that._table;
      that._where.length>0?sql+=\" where \"+that._where:\'\';
      that.doQuery(sql,callback);
    },
    //删除表
    dropTable:function(){
      var sql=\"DROP TABLE IF EXISTS \"+this._table;
      this.doQuery(sql);
    },
    _error:\'\',
    onfail:function(t,e){
      this._error=e.message;
      console.log(\'----sqlite:\'+e.message);
    },
    toArray:function(obj){
      var t=[];
      obj=obj || {};
      if (obj){
        for (var i in obj){
          t.push(i+\"=\'\"+obj[i]+\"\'\");
        }
      }
      return t;
    }
  }
}
/*
examples:
var db=new lanxDB(\'testDB\');
db.init(\'channel_list\',[{name:\'id\',type:\'integer primary key autoincrement\'},{name:\'name\',type:\'text\'},{name:\'link\',type:\'text\'},{name:\'cover\',type:\'text\'},{name:\'updatetime\',type:\'integer\'},{name:\'orders\',type:\'integer\'}]);
db.init(\'feed_list\',[{name:\'parentid\',type:\'integer\'},{name:\'feed\',type:\'text\'}]);
db.switchTable(\'channel_list\').insertData([{name:\'aa\',link:\'ss\',updatetime:new Date().getTime()},{name:\'bb\',link:\'kk\',updatetime:new Date().getTime()}]);
db.where({name:\'aa\'}).getData(function(result){
  console.log(result);//result为Array
});
db.where({name:\'aa\'}).deleteData(function(result){
  console.log(result[0]);//删除条数
});
db.where({name:\'bb\'}).saveData({link:\'jj\'},function(result){
  console.log(result);//影响条数
})
})
*/